Sang Woo Kim

We have developed a simple approach to high-performance, stretchable, and foldable integrated circuits. The systems integrate inorganic electronic materials, including aligned arrays of nanoribbons of single crystalline silicon, with ultrathin plastic and elastomeric substrates. The designs combine multilayer neutral mechanical plane layouts and “wavy” structural configurations in silicon complementary logic gates, ring oscillators, and differential amplifiers. We performed three-dimensional analytical and computational modeling of the mechanics and the electronic behaviors of these integrated circuits. Collectively, the results represent routes to devices, such as personal health monitors and other biomedical devices, that require extreme mechanical deformations during installation/use and electronic properties approaching those of conventional systems built on brittle semiconductor wafers.

Magnetic, fluorescent core–shell nanoparticles consist of a single Fe3O4 nanocrystal core and a dye-doped mesoporous silica shell with a poly(ethylene glycol) coating (see picture of TEM images and schematic depictions). These nanoparticles can be used as magnetic resonance and fluorescence imaging agents, and as drug delivery vehicles, thus making them novel candidates for simultaneous cancer diagnosis and therapy. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Flora & Fauna Resources of National Institute of Biological Resources

Clever combinations of different types of functional nanostructured materials will enable the development of multifunctional nanomedical platforms for multimodal imaging or simultaneous diagnosis and therapy. Mesoporous silica nanoparticles (MSNs) possess unique structural features such as their large surface areas, tunable nanometer-scale pore sizes, and well-defined surface properties. Therefore, they are ideal platforms for constructing multifunctional materials that incorporate a variety of functional nanostructured materials.In this Account, we discuss recent progress by our group and other researchers in the design and fabrication of multifunctional nanocomposite nanoparticles based on mesoporous silica nanostructures for applications to simultaneous diagnosis and therapy. Versatile mesoporous silica-based nanocomposite nanoparticles were fabricated using various methods. Here, we highlight two synthetic approaches: the encapsulation of functional nanoparticles within a mesoporous silica shell and the assembly of nanoparticles on the surface of silica nanostructures. Various nanoparticles were encapsulated in MSNs using surfactants as both phase transfer agents and pore-generating templates. Using MSNs as a scaffold, functional components such as magnetic nanoparticles and fluorescent dyes have been integrated within these systems to generate multifunctional nanocomposite systems that maintain their individual functional characteristics. For example, uniform mesoporous dye-doped silica nanoparticles immobilized with multiple magnetite nanocrystals on their surfaces have been fabricated for their use as a vehicle capable of simultaneous magnetic resonance (MR) and fluorescence imaging and drug delivery. The resulting nanoparticle-incorporated MSNs were then tested in mice with tumors. These in vivo experiments revealed that these multifunctional nanocomposite nanoparticles were delivered to the tumor sites via passive targeting. These nanocomposite nanoparticles served as successful multimodal imaging probes and also delivered anticancer drugs to the tumor site. With innumerable combinations of imaging modalities and drug delivery available within these vehicles, multifunctional nanocomposite nanoparticles provide new opportunities for clinical diagnostics and therapeutics.

Highly versatile nanocomposite nanoparticles were synthesized by decorating the surface of mesoporous dye-doped silica nanoparticles with multiple magnetite nanocrystals. The superparamagnetic property of the magnetite nanocrystals enabled the nanoparticles to be used as a contrast agent in magnetic resonance (MR) imaging, and the dye molecule in the silica framework imparted optical imaging modality. Integrating a multitude of magnetite nanocrystals on the silica surface resulted in remarkable enhancement of MR signal due to the synergistic magnetism. An anticancer drug, doxorubicin (DOX), could be loaded in the pores and induced efficient cell death. In vivo passive targeting and accumulation of the nanoparticles at the tumor sites was confirmed by both T2 MR and fluorescence imaging. Furthermore, apoptotic morphology was clearly detected in tumor tissues of mice treated with DOX loaded nanocomposite nanoparticles, demonstrating that DOX was successfully delivered to the tumor sites and its anticancer activity was retained.

Here we report a fully flexible, foldable nanopatterned wearable triboelectric nanogenerator (WTNG) with high power-generating performance and mechanical robustness. Both a silver (Ag)-coated textile and polydimethylsiloxane (PDMS) nanopatterns based on ZnO nanorod arrays on a Ag-coated textile template were used as active triboelectric materials. A high output voltage and current of about 120 V and 65 μA, respectively, were observed from a nanopatterned PDMS-based WTNG, while an output voltage and current of 30 V and 20 μA were obtained by the non-nanopatterned flat PDMS-based WTNG under the same compressive force of 10 kgf. Furthermore, very high voltage and current outputs with an average value of 170 V and 120 μA, respectively, were obtained from a four-layer-stacked WTNG under the same compressive force. Notably it was found there are no significant differences in the output voltages measured from the multilayer-stacked WTNG over 12 000 cycles, confirming the excellent mechanical durability of WTNGs. Finally, we successfully demonstrated the self-powered operation of light-emitting diodes, a liquid crystal display, and a keyless vehicle entry system only with the output power of our WTNG without any help of external power sources.

A major challenge for implantable medical systems is the inclusion or reliable delivery of electrical power. We use ultrasound to deliver mechanical energy through skin and liquids and demonstrate a thin implantable vibrating triboelectric generator able to effectively harvest it. The ultrasound can induce micrometer-scale displacement of a polymer thin membrane to generate electrical energy through contact electrification. We recharge a lithium-ion battery at a rate of 166 microcoulombs per second in water. The voltage and current generated ex vivo by ultrasound energy transfer reached 2.4 volts and 156 microamps under porcine tissue. These findings show that a capacitive triboelectric electret is the first technology able to compete with piezoelectricity to harvest ultrasound in vivo and to power medical implants.

Abstract Deformable full-colour light-emitting diodes with ultrafine pixels are essential for wearable electronics, which requires the conformal integration on curvilinear surface as well as retina-like high-definition displays. However, there are remaining challenges in terms of polychromatic configuration, electroluminescence efficiency and/or multidirectional deformability. Here we present ultra-thin, wearable colloidal quantum dot light-emitting diode arrays utilizing the intaglio transfer printing technique, which allows the alignment of red–green–blue pixels with high resolutions up to 2,460 pixels per inch. This technique is readily scalable and adaptable for low-voltage-driven pixelated white quantum dot light-emitting diodes and electronic tattoos, showing the best electroluminescence performance (14,000 cd m −2 at 7 V) among the wearable light-emitting diodes reported up to date. The device performance is stable on flat, curved and convoluted surfaces under mechanical deformations such as bending, crumpling and wrinkling. These deformable device arrays highlight new possibilities for integrating high-definition full-colour displays in wearable electronics.

Primates can develop a conditioned fear response by witnessing other primates being subjected to adverse stimuli. Jeon et al. report that mice are capable of this form of observational fear conditioning and that the medial pain system underlies the neural circuits mediating socially acquired fear. Fear can be acquired vicariously through social observation of others suffering from aversive stimuli. We found that mice (observers) developed freezing behavior by observing other mice (demonstrators) receive repetitive foot shocks. Observers had higher fear responses when demonstrators were socially related to themselves, such as siblings or mating partners. Inactivation of anterior cingulate cortex (ACC) and parafascicular or mediodorsal thalamic nuclei, which comprise the medial pain system representing pain affection, substantially impaired this observational fear learning, whereas inactivation of sensory thalamic nuclei had no effect. The ACC neuronal activities were increased and synchronized with those of the lateral amygdala at theta rhythm frequency during this learning. Furthermore, an ACC-limited deletion of Cav1.2 Ca2+ channels in mice impaired observational fear learning and reduced behavioral pain responses. These results demonstrate the functional involvement of the affective pain system and Cav1.2 channels of the ACC in observational social fear.

Hexagonal boron nitride (h-BN) has received a great deal of attention as a substrate material for high-performance graphene electronics because it has an atomically smooth surface, lattice constant similar to that of graphene, large optical phonon modes, and a large electrical band gap. Herein, we report the large-scale synthesis of high-quality h-BN nanosheets in a chemical vapor deposition (CVD) process by controlling the surface morphologies of the copper (Cu) catalysts. It was found that morphology control of the Cu foil is much critical for the formation of the pure h-BN nanosheets as well as the improvement of their crystallinity. For the first time, we demonstrate the performance enhancement of CVD-based graphene devices with large-scale h-BN nanosheets. The mobility of the graphene device on the h-BN nanosheets was increased 3 times compared to that without the h-BN nanosheets. The on–off ratio of the drain current is 2 times higher than that of the graphene device without h-BN. This work suggests that high-quality h-BN nanosheets based on CVD are very promising for high-performance large-area graphene electronics.

This research is concerned with the fungicidal properties of nano-size silver colloidal solution used as an agent for antifungal treatment ofvarious plant pathogens. We used WA-CV-WA13B, WA-AT-WB13R, and WA-PR-WB13R silver nanoparticles (AgNPs) at concentrations of 10, 25, 50, and 100 ppm. Eighteen different plant pathogenic fungi were treated with these AgNPs on potato dextrose agar (PDA), malt extract agar, and corn meal agar plates. We calculated fungal inhibition in order to evaluate the antifungal efficacy of silver nanoparticles against pathogens. The results indicated that AgNPs possess antifungal properties against these plant pathogens at various levels. Treatment with WA-CV-WB13R AgNPs resulted in maximum inhibition of most fungi. Results also showed that the most significant inhibition of plant pathogenic fungi was observed on PDA and 100 ppm of AgNPs.

We report a coaxial fiber supercapacitor, which consists of carbon microfiber bundles coated with multiwalled carbon nanotubes as a core electrode and carbon nanofiber paper as an outer electrode. The ratio of electrode volumes was determined by a half-cell test of each electrode. The capacitance reached 6.3 mF cm(-1) (86.8 mF cm(-2)) at a core electrode diameter of 230 μm and the measured energy density was 0.7 μWh cm(-1) (9.8 μWh cm(-2)) at a power density of 13.7 μW cm(-1) (189.4 μW cm(-2)), which were much higher than the previous reports. The change in the cyclic voltammetry characteristics was negligible at 180° bending, with excellent cycling performance. The high capacitance, high energy density, and power density of the coaxial fiber supercapacitor are attributed to not only high effective surface area due to its coaxial structure and bundle of the core electrode, but also all-carbon materials electrodes which have high conductivity. Our coaxial fiber supercapacitor can promote the development of textile electronics in near future.

Mesoporous silica-coated hollow manganese oxide (HMnO@mSiO2) nanoparticles were developed as a novel T1 magnetic resonance imaging (MRI) contrast agent. We hypothesized that the mesoporous structure of the nanoparticle shell enables optimal access of water molecules to the magnetic core, and consequently, an effective longitudinal (R1) relaxation enhancement of water protons, which value was measured to be 0.99 (mM−1s−1) at 11.7 T. Adipose-derived mesenchymal stem cells (MSCs) were efficiently labeled using electroporation, with much shorter T1 values as compared to direct incubation without electroporation, which was also evidenced by signal enhancement on T1-weighted MR images in vitro. Intracranial grafting of HMnO@mSiO2-labeled MSCs enabled serial MR monitoring of cell transplants over 14 days. These novel nanoparticles may extend the arsenal of currently available nanoparticle MR contrast agents by providing positive contrast on T1-weighted images at high magnetic field strengths.

Uniform 3 nm-sized ceria nanoparticles can protect against ischemic stroke by scavenging reactive oxygen species (ROS) and reducing apoptosis. PEGylated ceria nanoparticles showed protective effects against ROS-induced cell death in vitro. Optimal doses of ceria nanoparticles reduced infarct volumes and the rate of ischemic cell death in vivo.

A highly stretchable hybrid nanogenerator has been developed using a micro-patterned piezoelectric polymer P(VDF-TrFE), PDMS-CNT composite, and graphene nanosheets. Mechanical and thermal energies are simultaneously harvested from a single cell of the device. The hybrid nanogenerator exhibits high robustness behavior even after 30% stretching and generates very stable piezoelectric and pyroelectric power outputs due to micro-pattern designing.

Crohn's disease (CD) and ulcerative colitis (UC) are considered rare diseases in developing countries. We have evaluated the incidence and prevalence of CD and UC over time in a district of Seoul, Korea.A population-based study was performed from 1986 to 2005 in the Songpa-Kangdong district of Seoul. To recruit patients as completely as possible, multiple information sources, including all medical facilities in the study area and 3 referral centers nearby but outside the study area, were used.During the 20-year study period, 138 incident cases of CD (102 men, 36 women) and 341 incident cases of UC (170 men, 171 women) were identified. For the 20-year period, the adjusted mean annual incidence rates of CD and UC per 100,000 inhabitants were 0.53 (95% CI 0.44-0.62) and 1.51 (95% CI 1.34-1.67), respectively. When analyzed by 5-year intervals, the mean annual incidence rates of CD and UC increased significantly, from 0.05 and 0.34 per 100,000 inhabitants, respectively, in 1986-1990 to 1.34 and 3.08 per 100,000 inhabitants, respectively, in 2001-2005. The adjusted prevalence rates of CD and UC per 100,000 inhabitants on December 31, 2005, were 11.24 (95% CI 9.29-13.18) and 30.87 (95% CI 27.47-34.27), respectively.The incidence and prevalence of CD and UC in Seoul, Korea, are still low compared with those in Western countries, but are rapidly increasing.

Monitoring of human activities can provide clinically relevant information pertaining to disease diagnostics, preventive medicine, care for patients with chronic diseases, rehabilitation, and prosthetics. The recognition of strains on human skin, induced by subtle movements of muscles in the internal organs, such as the esophagus and trachea, and the motion of joints, was demonstrated using a self-powered patchable strain sensor platform, composed on multifunctional nanocomposites of low-density silver nanowires with a conductive elastomer of poly(3,4-ethylenedioxythiophene):polystyrenesulfonate/polyurethane, with high sensitivity, stretchability, and optical transparency. The ultra-low-power consumption of the sensor, integrated with both a supercapacitor and a triboelectric nanogenerator into a single transparent stretchable platform based on the same nanocomposites, results in a self-powered monitoring system for skin strain. The capability of the sensor to recognize a wide range of strain on skin has the potential for use in new areas of invisible stretchable electronics for human monitoring. A new type of transparent, stretchable, and ultrasensitive strain sensor based on a AgNW/PEDOT:PSS/PU nanocomposite was developed. The concept of a self-powered patchable sensor system integrated with a supercapacitor and a triboelectric nanogenerator that can be used universally as an autonomous invisible sensor system was used to detect the wide range of strain on human skin.

Hydrophobic sponge structure-based triboelectric nanogenerators using an inverse opal structured film for sustainable energy harvesting over a wide range of humid atmosphere have been successfully demonstrated. The output voltage and current density reach a record value of 130 V and 0.10 mA cm−2, respectively, giving over 10-fold power enhancement, compared with the flat film-based triboelectric nanogenerator.

Transparent flexible charge-generating piezoelectric nanodevices are developed. The resulting integrated nanodevice generates a noticeable current when it is pushed by application of an external load. Piezoelectric ZnO nanorod-based nanodevices with embossed PdAu top electrodes produce the highest output current density of approximately 10 μA cm−2 at a load of 0.9 kgf.

Transparent flexible graphene triboelectric nanogenerators as new promising applications of chemical vapor deposition-grown graphene are successfully demonstrated. The work function and friction are decisive factors to understand the difference in output performance depending on the number of layers of graphene. In this work, we were able to power an LCD, LEDs, and an EL display using the electrical power output of the graphene triboelectric nanogenerator without any external energy source. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Abstract Recent technological advances in nanomaterials have driven the development of high‐performance light‐emitting devices with flexible and stretchable form factors. Deformability in such devices is mainly achieved by replacing the rigid materials in the device components with flexible nanomaterials and their assemblies (e.g., carbon nanotubes, silver nanowires, graphene, and quantum dots) or with intrinsically soft materials and their composites (e.g., polymers and elastomers). Downscaling the dimensions of the functional materials to the nanometer range dramatically decreases their flexural rigidity, and production of polymer/elastomer composites with functional nanomaterials provides light‐emitting devices with flexibility and stretchability. Furthermore, monolithic integration of these light‐emitting devices with deformable sensors furnishes the resulting display with various smart functions such as force/capacitive touch‐based data input, personalized health monitoring, and interactive human–machine interfacing. These ultrathin, lightweight, and deformable smart optoelectronic devices have attracted widespread interest from materials scientists and device engineers. Here, a comprehensive review of recent progress concerning these flexible and stretchable smart displays is presented with a focus on materials development, fabrication techniques, and device designs. Brief overviews of an integrated system of advanced smart displays and cutting‐edge wearable sensors are also presented, and, to conclude, a discussion of the future research outlook is given.

Perfluorocarbon nanoemulsions can deliver lipophilic therapeutic agents to solid tumors and simultaneously provide for monitoring nanocarrier biodistribution via ultrasonography and/or (19)F MRI. In the first generation of block copolymer stabilized perfluorocarbon nanoemulsions, perfluoropentane (PFP) was used as the droplet forming compound. Although manifesting excellent therapeutic and ultrasound imaging properties, PFP nanoemulsions were unstable at storage, difficult to handle, and underwent hard to control phenomenon of irreversible droplet-to-bubble transition upon injection. To solve the above problems, perfluoro-15-crown-5-ether (PFCE) was used as a core forming compound in the second generation of block copolymer stabilized perfluorocarbon nanoemulsions. PFCE nanodroplets manifest both ultrasound and fluorine ((19)F) MR contrast properties, which allows using multimodal imaging and (19)F MR spectroscopy for monitoring nanodroplet pharmacokinetics and biodistribution. In the present paper, acoustic, imaging, and therapeutic properties of unloaded and paclitaxel (PTX) loaded PFCE nanoemulsions are reported. As manifested by the (19)F MR spectroscopy, PFCE nanodroplets are long circulating, with about 50% of the injected dose remaining in circulation 2h after the systemic injection. Sonication with 1-MHz therapeutic ultrasound triggered reversible droplet-to-bubble transition in PFCE nanoemulsions. Microbubbles formed by acoustic vaporization of nanodroplets underwent stable cavitation. The nanodroplet size (200nm to 350nm depending on a type of the shell and conditions of emulsification) as well as long residence in circulation favored their passive accumulation in tumor tissue that was confirmed by ultrasonography. In the breast and pancreatic cancer animal models, ultrasound-mediated therapy with paclitaxel-loaded PFCE nanoemulsions showed excellent therapeutic properties characterized by tumor regression and suppression of metastasis. Anticipated mechanisms of the observed effects are discussed.

Multifunctional ZnO semiconductor is a potential candidate for electronics and optoelectronics applications and can be commercialized owing to its excellent electrical and optical properties, inexpensiveness, relative abundance, chemical stability towards air, and much simpler and wide range of crystal-growth technologies. The semiconducting and piezoelectric properties of environmental friendly ZnO are extremely important for energy harvesting devices. This article reviews the importance of energy harvesting using ZnO nanostructures, mainly focusing on ZnO nanostructure-based photovoltaics, piezoelectric nanogenerators, and the hybrid approach to energy harvesting. Several research and design efforts leading to commercial products in the field of energy harvesting are discussed. This paper discusses the future goals that must be achieved to commercialize these approaches for everyday use.

For existing triboelectric nanogenerators (TENGs), it is important to explore unique methods to further enhance the output power under realistic environments to speed up their commercialization. We report here a practical TENG composed of three layers, in which the key layer, an electric double layer, is inserted between a top layer, made of Al/polydimethylsiloxane, and a bottom layer, made of Al. The efficient charge separation in the middle layer, based on Volta's electrophorus, results from sequential contact configuration of the TENG and direct electrical connection of the middle layer to the earth. A sustainable and enhanced output performance of 1.22 mA and 46.8 mW cm-2 under low frequency of 3 Hz is produced, giving over 16-fold enhancement in output power and corresponding to energy conversion efficiency of 22.4%. Finally, a portable power-supplying system, which provides enough d.c. power for charging a smart watch or phone battery, is also successfully developed.

Piezomaterials are known to display enhanced energy conversion efficiency at nanoscale due to geometrical effect and improved mechanical properties. Although piezoelectric nanowires have been the most widely and dominantly researched structure for this application, there only exist a limited number of piezomaterials that can be easily manufactured into nanowires, thus, developing effective and reliable means of preparing nanostructures from a wide variety of piezomaterials is essential for the advancement of self-powered nanotechnology. In this study, we present nanoporous arrays of polyvinylidene fluoride (PVDF), fabricated by a lithography-free, template-assisted preparation method, as an effective alternative to nanowires for robust piezoelectric nanogenerators. We further demonstrate that our porous PVDF nanogenerators produce the rectified power density of 0.17 mW/cm3 with the piezoelectric potential and the piezoelectric current enhanced to be 5.2 times and 6 times those from bulk PVDF film nanogenerators under the same sonic-input.

Here micropatterned poly(vinylidenefluoride‐ co ‐trifluoroethylene) (P(VDF‐TrFE)) films‐based piezoelectric nanogenerators (PNGs) with high power‐generating performance for highly sensitive self‐powered pressure sensors are demonstrated. The microstructured P(VDF‐TrFE)‐based PNGs reveal nearly five times larger power output compared to a flat film‐based PNG. The micropatterning of P(VDF‐TrFE) polymer makes itself ultrasensitive in response to mechanical deformation. The application is demonstrated successfully as self‐powered pressure sensors in which mechanical energy comes from water droplet and wind. The mechanism of the high performance is intensively discussed and illustrated in terms of strain developed in the flat and micropatterned P(VDF‐TrFE) films. The impact derived from the patterning on the output performance is studied in term of effective pressure using COMSOL multiphysics software.

Soluble β-amyloid (Aβ) oligomers impair synaptic plasticity and cause synaptic loss associated with Alzheimer's disease (AD). We report that murine PirB (paired immunoglobulin-like receptor B) and its human ortholog LilrB2 (leukocyte immunoglobulin-like receptor B2), present in human brain, are receptors for Aβ oligomers, with nanomolar affinity. The first two extracellular immunoglobulin (Ig) domains of PirB and LilrB2 mediate this interaction, leading to enhanced cofilin signaling, also seen in human AD brains. In mice, the deleterious effect of Aβ oligomers on hippocampal long-term potentiation required PirB, and in a transgenic model of AD, PirB not only contributed to memory deficits present in adult mice, but also mediated loss of synaptic plasticity in juvenile visual cortex. These findings imply that LilrB2 contributes to human AD neuropathology and suggest therapeutic uses of blocking LilrB2 function.

The development of highly sensitive pressure sensors with a low-cost and facile fabrication technique is desirable for electronic skins and wearable sensing devices. Here a low-cost and facile fabrication strategy to obtain multiscale-structured elastomeric electrodes and a highly sensitive and robust flexible pressure sensor is presented. The principles of spontaneous buckle formation of the PDMS surface and the embedding of silver nanowires are used to fabricate the multiscale-structured elastomeric electrode. By laminating the multiscale-structured elastomeric electrode onto the dielectric layer/bottom electrode template, the pressure sensor can be obtained. The pressure sensor is based on the capacitive sensing mechanism and shows high sensitivity (>3.8 kPa(-1)), fast response and relaxation time (<150 ms), high bending stability and high cycle stability. The fabrication process can be easily scaled up to produce pressure sensor arrays and they can detect the spatial distribution of the applied pressure. It is also demonstrated that the fingertip pressure sensing device can sense the pressure distribution of each finger, when grabbing an object.

A facile synthesis of mesoporous films impregnated with Au nanoparticles as effective dielectrics for enhancing the TENG's performance based on vertical contact-separation mode is demonstrated.

Metal halide perovskites are attracting a lot of attention as next-generation light-emitting materials owing to their excellent emission properties, with narrow band emission1-4. However, perovskite light-emitting diodes (PeLEDs), irrespective of their material type (polycrystals or nanocrystals), have not realized high luminance, high efficiency and long lifetime simultaneously, as they are influenced by intrinsic limitations related to the trade-off of properties between charge transport and confinement in each type of perovskite material5-8. Here, we report an ultra-bright, efficient and stable PeLED made of core/shell perovskite nanocrystals with a size of approximately 10 nm, obtained using a simple in situ reaction of benzylphosphonic acid (BPA) additive with three-dimensional (3D) polycrystalline perovskite films, without separate synthesis processes. During the reaction, large 3D crystals are split into nanocrystals and the BPA surrounds the nanocrystals, achieving strong carrier confinement. The BPA shell passivates the undercoordinated lead atoms by forming covalent bonds, and thereby greatly reduces the trap density while maintaining good charge-transport properties for the 3D perovskites. We demonstrate simultaneously efficient, bright and stable PeLEDs that have a maximum brightness of approximately 470,000 cd m-2, maximum external quantum efficiency of 28.9% (average = 25.2 ± 1.6% over 40 devices), maximum current efficiency of 151 cd A-1 and half-lifetime of 520 h at 1,000 cd m-2 (estimated half-lifetime >30,000 h at 100 cd m-2). Our work sheds light on the possibility that PeLEDs can be commercialized in the future display industry.

Sound-driven power generation using nanogenerators based on piezoelectric ZnO nanowires has been demonstrated. Systematic investigations on the power-generating performance of sound-driven nanogenerators clearly support that the measured output voltage originated from the sound-driven nanogenerator. This study shows that sound can be one of promising energy sources when using highly efficient nanogenerators based on piezoelectric nanowires. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Highly stretchable 2D fabrics are prepared by weaving fibers for a fabric-structured triboelectric nanogenerator (FTENG). The fibers mainly consist of Al wires and polydimethylsiloxane (PDMS) tubes with a high-aspect-ratio nanotextured surface with vertically aligned nanowires. The fabrics were produced by interlacing the fibers, which was bonded to a waterproof fabric for all-weather use for fabric-structured triboelectric nanogenerator (FTENG). It showed a stable high-output voltage and current of 40 V and 210 μA, corresponding to an instantaneous power output of 4 mW. The FTENG also exhibits high robustness behavior even after 25% stretching, enough for use in smart clothing applications and other wearable electronics. For wearable applications, the nanogenerator was successfully demonstrated in applications of footstep-driven large-scale power mats during walking and power clothing attached to the elbow.

Recently, sustainable green energy harvesting systems have been receiving great attention for their potential use in self-powered smart wireless sensor network (WSN) systems. In particular, though the developed WSN systems are able to advance public good, very high and long-term budgets will be required in order to use them to supply electrical energy through temporary batteries or connecting power cables. This report summarizes recent significant progress in the development of hybrid nanogenerators for a sustainable energy harvesting system that use natural and artificial energies such as solar, wind, wave, heat, machine vibration, and automobile noise. It starts with a brief introduction of energy harvesting systems, and then summarizes the different hybrid energy harvesting systems: integration of mechanical and photovoltaic energy harvesters, integration of mechanical and thermal energy harvesters, integration of thermal and photovoltaic energy harvesters, and others. In terms of the reported hybrid nanogenerators, a systematic summary of their structures, working mechanisms, and output performances is provided. Specifically, electromagnetic induction, triboelectric, piezoelectric, photovoltaic, thermoelectric, and pyroelectric effects are reviewed on the basis of the individual and hybrid power performances of hybrid nanogenerators and their practical applications with various device designs. Finally, the perspectives on and challenges in developing high performance and sustainable hybrid nanogenerator systems are presented.

Abstract The preparation of ferroelectric polymer–metallic nanowire composite nanofiber triboelectric layers is described for use in high‐performance triboelectric nanogenerators (TENGs). The electrospun polyvinylidene fluoride (PVDF)–silver nanowire (AgNW) composite and nylon nanofibers are utilized in the TENGs as the top and bottom triboelectric layers, respectively. The electrospinning process facilitates uniaxial stretching of the polymer chains, which enhances the formation of the highly oriented crystalline β‐phase that forms the most polar crystalline phase of PVDF. The addition of AgNWs further promotes the β‐phase crystal formation by introducing electrostatic interactions between the surface charges of the nanowires and the dipoles of the PVDF chains. The extent of β‐phase formation and the resulting variations in the surface charge potential upon the addition of nanowires are systematically analyzed using X‐ray diffraction (XRD) and Kelvin probe force microscopy techniques. The ability of trapping the induced tribocharges increases upon the addition of nanowires to the PVDF matrix. The enhanced surface charge potential and the charge trapping capabilities of the PVDF–AgNW composite nanofibers significantly enhance the TENG output performances. Finally, the mechanical stability of the electrospun nanofibers is dramatically enhanced while maintaining the TENG performances by applying thermal welding near the melting temperature of PVDF.

Low output current represents a critical challenge that has interrupted the use of triboelectric nanogenerators (TNGs) in a wide range of applications as sustainable power sources. Many approaches (e.g., operation at high frequency, parallel stacks of individual devices, and hybridization with other energy harvesters) remain limited in solving the challenge of low output current from TNGs. Here, a nanocomposite material system having a superior surface charge density as a triboelectric active material is reported. The nanocomposite material consists of a high dielectric ceramic material, barium titanate, showing great charge‐trapping capability, together with a ferroelectric copolymer matrix, Poly(vinylidenefluoride‐co‐trifluoroethylene) (P(VDF‐TrFE)), with electrically manipulated polarization with strong triboelectric charge transfer characteristics. Based on a contact potential difference study showing that poled P(VDF‐TrFE) has 18 times higher charge attracting properties, a fraction between two components is optimized. Boosting power‐generating performance is achieved for 1130 V of output voltage and 1.5 mA of output current with this ferroelectric composite‐based TNG, under 6 kgf of pushing force at 5 Hz. An enormously faster charging property than traditional polymer film‐based TNGs is demonstrated in this study. Finally, the charging of a self‐powering smartwatch with a charging management circuit system with no external power sources is demonstrated successfully.

Constitutive activation of the NF-κB pathway is associated with diffuse large B-cell lymphoma (DLBCL) pathogenesis, but whether microRNA dysfunction can contribute to these events remains unclear. Starting from an integrative screening strategy, we uncovered that the negative NF-κB regulator TNFAIP3 is a direct target of miR-125a and miR-125b, which are commonly gained and/or overexpressed in DLBCL. Ectopic expression of these microRNAs in multiple cell models enhanced K63-linked ubiquitination of proximal signaling complexes and elevated NF-κB activity, leading to aberrant expression of its transcriptional targets and the development of a proproliferative and antiapoptotic phenotype in malignant B cells. Concordantly, genetic inhibition of miR-125a/miR-125b blunted NF-κB signals, whereas rescue assays and genetic modulation of a TNFAIP3-null model defined the essential role of the TNFAIP3 targeting on miR-125a/miR-125b-mediated lymphomagenesis. Importantly, miR-125a/mir-125b effects on TNFAIP3 expression and NF-κB activity were confirmed in a well-characterized cohort of primary DLBCLs. Our data delineate a unique epigenetic model for aberrant activation of the NF-κB pathway in cancer and provide a coherent mechanism for the role of these miRNAs in immune cell activation and hematopoiesis. Further, as miR-125b is a direct NF-κB transcriptional target, our results suggest the presence of a positive self-regulatory loop whereby termination of TNFAIP3 function by miR-125 could strengthen and prolong NF-κB activity.

A piezopotential-powered active matrix strain sensor array based on a piezopotential-gated graphene transistor (GT) is demonstrated using a piezoelectric polymer. The strain sensor based on the piezopotential-gated GT exhibits excellent performance, including ultrahigh sensitivity (gauge factor = 389) and good durability (>3000 bending and releasing cycles) with a minimum detectable strain at 0.008%.

Fully rollable transparent nanogenerators have been developed using chemical vapor deposition-grown large-scale graphene sheets as transparent electrodes and piezoelectric ZnO-nanorod arrays. The electrical and structural stability of the nanogenerators with excellent charge scavenging performance under external mechanical loads such as bending and rolling shows that graphene-based nanogenerators are suitable for self-powered rollable transparent device applications. Detailed facts of importance to specialist readers are published as ”Supporting Information”. Such documents are peer-reviewed, but not copy-edited or typeset. They are made available as submitted by the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Impaired regulation of mitochondrial dynamics, which shifts the balance towards fission, is associated with neuronal death in age-related neurodegenerative diseases, such as Alzheimer's disease or Parkinson's disease. A role for mitochondrial dynamics in acute brain injury, however, has not been elucidated to date. Here, we investigated the role of dynamin-related protein 1 (Drp1), one of the key regulators of mitochondrial fission, in neuronal cell death induced by glutamate toxicity or oxygen-glucose deprivation (OGD) in vitro, and after ischemic brain damage in vivo. Drp1 siRNA and small molecule inhibitors of Drp1 prevented mitochondrial fission, loss of mitochondrial membrane potential (MMP), and cell death induced by glutamate or tBid overexpression in immortalized hippocampal HT-22 neuronal cells. Further, Drp1 inhibitors protected primary neurons against glutamate excitotoxicity and OGD, and reduced the infarct volume in a mouse model of transient focal ischemia. Our data indicate that Drp1 translocation and associated mitochondrial fission are key features preceding the loss of MMP and neuronal cell death. Thus, inhibition of Drp1 is proposed as an efficient strategy of neuroprotection against glutamate toxicity and OGD in vitro and ischemic brain damage in vivo.

This article introduces an international regional experiment, East Asian Regional Experiment 2005 (EAREX 2005), carried out in March–April 2005 in the east Asian region, as one of the first phase regional experiments under the UNEP Atmospheric Brown Cloud (ABC) project, and discusses some outstanding features of aerosol characteristics and its direct radiative forcing in the east Asian region, with some comparison with the results obtained in another ABC early phase regional experiment, ABC Maldives Monsoon Experiment (APMEX) conducted in the south Asian region. Time series of aerosol optical thickness (AOT), single scattering albedo (SSA), aerosol extinction cross section profile and CO concentration shows that air pollutants and mineral dust were transported every 5 to 7 days in the EAREX region to produce SSA values at wavelength of 700 nm from 0.86 to 0.96 and large clear‐sky shortwave forcing efficiency at 500 nm from 60 W m −2 to 90 W m −2 , though there are some unexplained inconsistencies depending on the evaluation method. The simulated whole‐sky total forcing in the EAREX region is −1 to −2 W m −2 at TOA and −2 to −10 W m −2 at surface in March 2005 which is smaller in magnitude than in the APMEX region, mainly because of large cloud fraction in this region (0.70 at Gosan versus 0.51 at Hanimadhoo in the ISCCP total cloud fraction). We suggest there may be an underestimation of the forcing due to overestimation of the simulated cloudiness and aerosol scale height. On the other hand, the possible error in the simulated surface albedo may cause an overestimation of the magnitude of the forcing over the land area. We also propose simple formulae for shortwave radiative forcing to understand the role of aerosol parameters and surface condition to determine the aerosol forcing. Such simple formulae are useful to check the consistency among the observed quantities.

Due to its superiority such as low access latency, low energy consumption, light weight, and shock resistance, the success of flash memory as a storage alternative for mobile computing devices has been steadily expanded into personal computer and enterprise server markets with ever increasing capacity of its storage. However, since flash memory exhibits poor performance for small-to-moderate sized writes requested in a random order, existing database systems may not be able to take full advantage of flash memory without elaborate flash-aware data structures and algorithms. The objective of this work is to understand the applicability and potential impact that flash memory SSD (Solid State Drive) has for certain type of storage spaces of a database server where sequential writes and random reads are prevalent. We show empirically that up to more than an order of magnitude improvement can be achieved in transaction processing by replacing magnetic disk with flash memory SSD for transaction log, rollback segments, and temporary table spaces.

Abstract The two oxidation states of ceria nanoparticles, Ce 3+ and Ce 4+ , play a pivotal role in scavenging reactive oxygen species (ROS). In particular, Ce 3+ is largely responsible for removing O 2 − and . OH that are associated with inflammatory response and cell death. The synthesis is reported of 2 nm ceria–zirconia nanoparticles (CZ NPs) that possess a higher Ce 3+ /Ce 4+ ratio and faster conversion from Ce 4+ to Ce 3+ than those exhibited by ceria nanoparticles. The obtained Ce 0.7 Zr 0.3 O 2 (7CZ) NPs greatly improve ROS scavenging performance, thus regulating inflammatory cells in a very low dose. Moreover, 7CZ NPs are demonstrated to be effective in reducing mortality and systemic inflammation in two representative sepsis models. These findings suggest that 7CZ NPs have the potential as a therapeutic nanomedicine for treating ROS‐related inflammatory diseases.

The extremely stable high‐power generation from hybrid piezoelectric nanogenerator (HP‐NG) based on a composite of single‐crystalline piezoelectric perovskite zinc stannate (ZnSnO 3 ) nanocubes and polydimethylsiloxane without any electrical poling treatment is reported. The HP‐NG generates large power output under only vertical compression, while there is negligible power generation with other configurations of applied strain, such as bending and folding. This unique high unidirectionality of power generation behavior of the HP‐NG provides desirable features for large‐area piezoelectric power generation based on vertical mechanical compression such as moving vehicles, railway transport, and human walking. The HP‐NGs of ZnSnO 3 nanocubes exhibit high mechanical durability, excellent robustness, and high power‐generation performance. A large recordable output voltage of about 20 V and an output current density value of about 1 μA cm −2 are successfully achived, using a single cell of HP‐NG obtained under rolling of a vehicle tire.

It is essential to control the electronic structure of graphene in order to apply graphene films for use in electrodes. We have introduced chemical dopants that modulate the electronic properties of few-layer graphene films synthesized by chemical vapor deposition. The work function, sheet carrier density, mobility, and sheet resistance of these films were systematically modulated by the reduction potential values of dopants. We further demonstrated that the power generation of a nanogenerator was strongly influenced by the choice of a graphene electrode with a modified work function. The off-current was well quenched in graphene films with high work functions (Au-doped) due to the formation of high Schottky barrier heights, whereas leakage current was observed in graphene films with low work functions (viologen-doped), due to nearly ohmic contact.

The recent development and perspectives of energy harvesting and storage devices including integration strategies are summarized and discussed.

Abstract Using an Al‐foil of thickness ≈18 μm as a substrate and electrode, a piezoelectric nanogenerator (NG) that is super‐flexible in responding to the wavy motion of a very light wind is fabricated using ZnO nanowire arrays. The NG is used to harvest the energy from a waving flag, demonstrating its high flexibility and excellent conformability to be integrated into fabric. The NG is applied to detect the wrinkling of a human face, showing its capability to serve as an active deformation sensor that needs no extra power supply. This strategy may provide a highly promising platform as energy harvesting devices and self‐powered sensors for practical use wherever movement is available.

Pepper anthracnose caused by Colletotrichum species is one of the most important limiting factors for pepper production in Korea, its management being strongly dependent on chemicals. The aim of this work was to evaluate the possibilities of using silver nanoparticles instead of commercial fungicides. In this study, we evaluated the effect of silver nanoparticles against pepper anthracnose under different culture conditions. Silver nanoparticles (WA-PR-WB13R) were applied at various concentrations to determine antifungal activities in vitro and in the field. The application of 100 ppm concentration of silver nanoparticles produced maximum inhibition of the growth of fungal hyphae as well as conidial germination in comparison to the control in vitro. In field trials, the inhibition of fungi was significantly high when silver nanoparticles were applied before disease outbreak on the plants. Scanning electron microscopy results indicated that the silver nanoparticles caused a detrimental effect on mycelial growth of Colletotrichum species.

The rapid repurposing of antivirals is particularly pressing during pandemics. However, rapid assays for assessing candidate drugs typically involve in vitro screens and cell lines that do not recapitulate human physiology at the tissue and organ levels. Here we show that a microfluidic bronchial-airway-on-a-chip lined by highly differentiated human bronchial-airway epithelium and pulmonary endothelium can model viral infection, strain-dependent virulence, cytokine production and the recruitment of circulating immune cells. In airway chips infected with influenza A, the co-administration of nafamostat with oseltamivir doubled the treatment-time window for oseltamivir. In chips infected with pseudotyped severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), clinically relevant doses of the antimalarial drug amodiaquine inhibited infection but clinical doses of hydroxychloroquine and other antiviral drugs that inhibit the entry of pseudotyped SARS-CoV-2 in cell lines under static conditions did not. We also show that amodiaquine showed substantial prophylactic and therapeutic activities in hamsters challenged with native SARS-CoV-2. The human airway-on-a-chip may accelerate the identification of therapeutics and prophylactics with repurposing potential.

Conductive hydrogels are a class of composite materials that consist of hydrated and conducting polymers. Due to the mechanical similarity to biointerfaces such as human skin, conductive hydrogels have been primarily utilized as bioelectrodes, specifically neuroprosthetic electrodes, in an attempt to replace metallic electrodes by enhancing the mechanical properties and long-term stability of the electrodes within living organisms. Here, we report a conductive, smart hydrogel, which is thermoplastic and self-healing owing to its unique properties of reversible liquefaction and gelation in response to thermal stimuli. In addition, we demonstrated that our conductive hydrogel could be utilized to fabricate bendable, stretchable, and patternable electrodes directly on human skin. The excellent mechanical and thermal properties of our hydrogel make it potentially useful in a variety of biomedical applications such as electronic skin.

Direct chemical vapor deposition (CVD) growth of single-layer graphene on CVD-grown hexagonal boron nitride (h-BN) film can suggest a large-scale and high-quality graphene/h-BN film hybrid structure with a defect-free interface. This sequentially grown graphene/h-BN film shows better electronic properties than that of graphene/SiO2 or graphene transferred on h-BN film, and suggests a new promising template for graphene device fabrication.

<h2>Summary</h2> Huntington's disease is a genetic neurodegenerative disorder resulting from polyglutamine (polyQ) expansion (>36Q) within the first exon of Huntingtin (Htt) protein. We applied X-ray crystallography to determine the secondary structure of the first exon (EX1) of Htt17Q. The structure of Htt17Q-EX1 consists of an amino-terminal α helix, poly17Q region, and polyproline helix formed by the proline-rich region. The poly17Q region adopts multiple conformations in the structure, including α helix, random coil, and extended loop. The conformation of the poly17Q region is influenced by the conformation of neighboring protein regions, demonstrating the importance of the native protein context. We propose that the conformational flexibility of the polyQ region observed in our structure is a common characteristic of many amyloidogenic proteins. We further propose that the pathogenic polyQ expansion in the Htt protein increases the length of the random coil, which promotes aggregation and facilitates abnormal interactions with other proteins in cells.

A silk nanofiber-networked bio-triboelectric generator (Silk Bio-TEG) is developed using an eco-friendly and sustainable silk biomaterial with strong hydrogen bonding between peptide blocks. The electrospun Silk Bio-TEG shows highly durable and reliable energy harvesting performances due to its notably high surface-to-volume ratio, mechanically super-strong silk fibers, and fracture tolerant behavior of nanofiber-networks. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Repair of DNA interstrand crosslinks requires action of multiple DNA repair pathways, including homologous recombination. Here, we report a de novo heterozygous T131P mutation in RAD51/FANCR, the key recombinase essential for homologous recombination, in a patient with Fanconi anemia-like phenotype. In vitro, RAD51-T131P displays DNA-independent ATPase activity, no DNA pairing capacity, and a co-dominant-negative effect on RAD51 recombinase function. However, the patient cells are homologous recombination proficient due to the low ratio of mutant to wild-type RAD51 in cells. Instead, patient cells are sensitive to crosslinking agents and display hyperphosphorylation of Replication Protein A due to increased activity of DNA2 and WRN at the DNA interstrand crosslinks. Thus, proper RAD51 function is important during DNA interstrand crosslink repair outside of homologous recombination. Our study provides a molecular basis for how RAD51 and its associated factors may operate in a homologous recombination-independent manner to maintain genomic integrity.

Recently, as applications based on triboelectricity have expanded, understanding the triboelectric charging behavior of various materials has become essential. This study investigates the triboelectric charging behaviors of various 2D layered materials, including MoS2 , MoSe2 , WS2 , WSe2 , graphene, and graphene oxide in a triboelectric series using the concept of a triboelectric nanogenerator, and confirms the position of 2D materials in the triboelectric series. It is also demonstrated that the results are obviously related to the effective work functions. The charging polarity indicates the similar behavior regardless of the synthetic method and film thickness ranging from a few hundred nanometers (for chemically exfoliated and restacked films) to a few nanometers (for chemical vapor deposited films). Further, the triboelectric charging characteristics could be successfully modified via chemical doping. This study provides new insights to utilize 2D materials in triboelectric devices, allowing thin and flexible device fabrication.

Graphene tribotronics is introduced for touch-sensing applications such as electronic skins and touch screens. The devices are based on a coplanar coupling of triboelectrification and current transport in graphene transistors. The touch sensors are ultrasensitive, fast, and stable. Furthermore, they are transparent and flexible, and can spatially map touch stimuli such as movement of a ball, multi-touch, etc.

The piezoelectric effect, discovered in 1880 by Jacques and Pierre Curie, effectively allows to transduce signals from the mechanical domain to the electrical domain and vice versa. For this reason, piezoelectric devices are already ubiquitous, including, for instance, quartz oscillators, mechanical actuators with sub-atomic resolution and microbalances. However, the ability to synthesize two-dimensional (2D) materials may enable the fabrication of innovative devices with unprecedented performance. For instance, many materials which are not piezoelectric in their bulk form become piezoelectric when reduced to a single atomic layer; moreover, since all the atoms belong to the surface, piezoelectricity can be effectively engineered by proper surface modifications. As additional advantages, 2D materials are strong, flexible, easy to be co-integrated with conventional integrated circuits or micro-electromechanical systems and, in comparison with bulk or quasi-1D materials, easier to be simulated at the atomistic level. Here, we review the state of the art on 2D piezoelectricity, with reference to both computational predictions and experimental characterization. Because of their unique advantages, we believe 2D piezoelectric materials will substantially expand the applications of piezoelectricity.

Control of interfacial interactions leads to a dramatic change in shape and morphology for particles based on poly(styrene-b-2-vinylpyridine) diblock copolymers. Key to these changes is the addition of Au-based surfactant nanoparticles (SNPs) which are adsorbed at the interface between block copolymer-containing emulsion droplets and the surrounding amphiphilic surfactant to afford asymmetric, ellipsoid particles. The mechanism of formation for these novel nanostructures was investigated by systematically varying the volume fraction of SNPs, with the results showing the critical nature that the segregation of SNPs to specific interfaces plays in controlling structure. A theoretical description of the system allows the size distribution and aspect ratio of the asymmetric block copolymer colloidal particles to be correlated with the experimental results.

Recently, piezoelectric and triboelectric energy harvesting devices have been developed to convert mechanical energy into electrical energy. Especially, it is well known that triboelectric nanogenerators have a simple structure and a high output voltage. However, whereas nanostructures improve the output of triboelectric generators, its fabrication process is still complicated and unfavorable in term of the large scale and long-time durability of the device. Here, we demonstrate a hybrid generator which does not use nanostructure but generates much higher output power by a small mechanical force and integrates piezoelectric generator into triboelectric generator, derived from the simultaneous use of piezoelectric and triboelectric mechanisms in one press-and-release cycle. This hybrid generator combines high piezoelectric output current and triboelectric output voltage, which produces peak output voltage of ~370 V, current density of ~12 μA · cm(-2), and average power density of ~4.44 mW · cm(-2). The output power successfully lit up 600 LED bulbs by the application of a 0.2 N mechanical force and it charged a 10 μF capacitor to 10 V in 25 s. Beyond energy harvesting, this work will provide new opportunities for developing a small, built-in power source in self-powered electronics such as mobile electronics.

We propose a HfZrO <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>x</i></sub> (HZO)-based ferroelectric synapse device with multi-levels states of remnant polarization that is equivalent to multi-levels conductance states. By optimizing the pulse condition, we obtained 32 levels of remnant polarization states for both potentiation and depression. Furthermore, a ferroelectric field-effect transistor is simulated using the obtained multiple remnant polarization states. The simulation results show that linear and symmetric conductance states can be obtained by applying optimum potentiation and depression pulse conditions. A neural network was simulated using the proposed devices for pattern recognition. Using synapse parameters of the HZO-based ferroelectric device and a neural network simulator, we have confirmed that the pattern recognition accuracy of the MNIST data set is 84%. It shows that the HZO-based synapse device has potential for future high-density neuromorphic systems.

We introduce a new smart SMP–TENG structure and studied its degradation and healing process. The SMP improves the endurance and lifetime, and thus demonstrates the huge potential of self-healing SMP–TENGs.

A fully packaged hemispheres-array-structured triboelectric nanogenerator (H-TENG) that can endure severe environments is reported. The hemispheres-array-structure plays a dual role as the triboelectric material and an elastic “spring” to keep the two opposite materials separated for inducing the electrostatic effect during contact-separation cycle. H-TENGs can be applicable as an active self-powered sensor array to detect the distribution of external pressure.

A robust nanogenerator based on poly(tert-butyl acrylate) (PtBA)-grafted polyvinylidene difluoride (PVDF) copolymers via dielectric constant control through an atom-transfer radical polymerization technique, which can markedly increase the output power, is demonstrated. The copolymer is mainly composed of α phases with enhanced dipole moments due to the π-bonding and polar characteristics of the ester functional groups in the PtBA, resulting in the increase of dielectric constant values by approximately twice, supported by Kelvin probe force microscopy measurements. This increase in the dielectric constant significantly increased the density of the charges that can be accumulated on the copolymer during physical contact. The nanogenerator generates output signals of 105 V and 25 μA/cm2, a 20-fold enhancement in output power, compared to pristine PVDF-based nanogenerator after tuning the surface potential using a poling method. The markedly enhanced output performance is quite stable and reliable in harsh mechanical environments due to the high flexibility of the films. On the basis of these results, a much faster charging characteristic is demonstrated in this study.

Transparent flexible and stretchable nanogenerators (NGs) that harvest various types of mechanical energy exhibit a great potential for powering low-power portable devices and self-powered electronic systems. Integration of transparency, flexibility and stretchability to NGs has gained a lot of interest for realizing the energy harvesting systems in practical life. Flexible piezoelectric nanostructures, which can generate electrical signal when mechanically deformed, are the most promising candidates for piezoelectric NGs, which offer sufficient power to drive portable electronics and cardiac pacemakers. Moreover, triboelectric NGs enlighten a new technique to harvest mechanical energies with high conversion efficiency. This review highlights the recent research progress of transparent and flexible ZnO nanorods/nanowires, two-dimensional ZnO nanosheets, stretchable micro-patterned P(VDF-TrFE) polymer, ZnSnO3 nanocubes-based piezoelectric NGs along with graphene and hydrophobic sponge structure-based triboelectric NGs, and their potential applications in powering portable electronics are summarized and presented. Finally, the power generation under different modes of pressure/friction such as vertical compressive, bending, contact-separation and stretching are collected and the involved future challenges are discussed in terms of device configuration and efficiency.

Organic transistors with elastic conductors and dielectrics can be stretched up to 250% strain while maintaining the transistor characteristics. Strain-independent properties can be achieved after an initial “programming” cycle that causes the formation of microcracks in the semiconductor. The change in mobility with strain follows the same trend in different stretching directions. Liberating electronic devices from the confines of traditional rigid substrates can improve mechanical robustness and enable new applications and manufacturing methods. Stretchability facilitates electronics that can be mounted on unconventional substrates,1 such as lenses and human bodies,2 and allows dynamic tuning of devices such as electronic eye cameras3 and lasers.4 Accommodating complex movements of supporting structures facilitates integration with moving entities and is critical for biointerfacing applications5 and electronic skins6-10 for prosthetics and robotics. Arrays of electronic devices often include transistors as active addressing elements in order to improve the signal collection process.5, 8 Furthermore, many applications, including sensor arrays6, 11 and displays,12 require large area coverage and therefore benefit from low-cost, high-throughput fabrication methods. In this communication, we report a stretchable organic transistor that maintains transistor behavior to >250% strain, which is several times larger than previous reports.13-16 Strain-independent characteristics are achieved by “programming” the device with an initial strain that causes the formation of microcracks in the semiconductor layer. Crack formation accommodates strain, while maintaining a percolating pathway. Similar microcracking17, 18 or void formation19 strategies have been employed successfully in stretchable conductors used in applications such as strain sensors19 and neuroprosthetic devices.20 The fabrication process involves cost efficient solution methods including spraycoating and spincoating. Stretchable electronics can be fabricated using two main methods. The first involves geometrical patterning of conventional electronic materials such as metals and inorganic semiconductors into meandering patterns or buckles in order to reduce deformation in the active material.21-24 Stiff islands connected with stretchable conductors have produced arrays of high-performance devices including transistors,25 photodetectors,3 and LEDs.12 However, because stretchability is imparted by the regions between islands, there is a trade-off between device density and stretchability. Buckling involves the formation of wavy structures that flatten out to accommodate applied strain. The optical properties of these wavy structures could benefit the performance of stretchable solar cells,2, 24 but may be undesirable for other optoelectronic applications,26 or for devices that require planar interfaces. The second method of imparting stretchability is to fabricate devices composed of elastic materials. Because elastomers are typically insulators, electronic functionality is often imparted by blending with electronic materials12, 26 or applying thin films of compliant electronic materials.15 Several intrinsically stretchable electronic devices have been reported, including stretchable light emitters based on electrochemical active layers26, 27 and graphene-13 and MoS2-based14 transistors that stretch to 5%. A hybrid method was reported by Chae et al. in which an intrinsically stretchable graphene-based gate electrode was combined with a buckled inorganic dielectric layer to make high-performance transistors that could sustain repeated strain cycles to 20%.15 Inorganic semiconductors with proper fabrication schemes and device design can provide exceptional performance in stretchable electronic devices,3, 28 but their high processing costs limit implementation in applications where devices need to be disposable, cheap, or cover large areas. Organic semiconductors (OS) are an alternative that have been touted for their materials availability and compatibility with high-throughput, room-temperature deposition methods such as slot die coating29 and inkjet printing.30 While the performance of OS has traditionally lagged behind that of their inorganic counterparts, their electrical characteristics have been steadily improving,31 and their mechanical properties may be more suitable for compliant electronics. The strain tolerance of OS can vary; research by O'Connor et al. suggests that a rigid, 3D packing structure results in a very low strain at fracture, while the 2D packing structure of a common polymeric semiconductor poly(3-hexylthiophene) (P3HT) allows deformation to greater than 150%.32 Consequently, P3HT was chosen as the semiconductor in our stretchable transistors due to favorable mechanical characteristics, well-characterized properties,33 and ready availability. Devices were fabricated in a bottom contact, top gate architecture, as depicted in the schematic in Figure 1a. The source and drain (S/D) electrodes were composed of carbon nanotubes embedded in a polyurethane elastomer (PU), similar to electrodes first published by Pei and coworkers.27 The sheet resistance of the electrodes before and after embedding in PU was ∼155 Ω/sq and 945 Ω/sq, respectively. P3HT films were transferred from a wafer coated with a hydrophobic silane monolayer34 onto the embedded CNT electrodes, and a 4 μm thick PU dielectric layer (Figure S1) was spincoated on top. The device was completed by applying eutectic gallium indium (EGaIn), a liquid metal, as the gate electrode. Figure S2 provides microscope images of a device at different stages throughout the fabrication process, and a more thorough description is given in the experimental section. Figure 1b and 1c depict the device at 0% and 150% strain. The electrical characteristics of the assembled transistors were collected using a probe station in a nitrogen environment, and a typical transfer curve is provided in Figure 1d. The average and standard deviation of the transistor characteristics include mobility (μ) values of μ = 3.4•10−2 ± 1.63•10−2 cm2/Vs and an on/off ratio of 591 ± 461. The large variation in device characteristics was a consequence of the manual fabrication processes, which included transferring the semiconductor, spincoating the dielectric, and applying the top gate. The device performance is expected to be closely related to the nature of the dielectric. A large dielectric thickness and concomitant low capacitance (∼1 nF/cm2) can lead to impaired mobility values, due to a lower applied electrical field. Correspondingly, the on/off ratio was also lower than some other reports.35 Transfer characteristics of a device stretched to 160% and released back to 20% are provided in Figure 1d. Additionally, exposure to air is known to result in a lower on/off ratio for P3HT transistors due to oxygen and water doping.36 Furthermore, the loose packing and flexibility of PU results in a tendency to absorb polar solvents, which can have several potential effects on the device performance: (1) solvents can disrupt charge transport, reducing charge mobility13 (2) absorbed water increases the polarization in the dielectric and consequently the measured on current (ION), distorting mobility values,37 and (3) polar groups can increase leakage, off currents (IOFF), and hysteresis.38 While there is much room for improvement in dielectric selection, the main purpose of this report is to analyze the relative performance of the device with applied strain. The changes in P3HT morphology with strain were investigated using three structures: (1) P3HT transferred onto a PU substrate (PU/P3HT-t) (Figure 2a-c), (2) PU Spincoated onto P3HT and then transferred onto a PU substrate (PU/P3HT-s) (Figure 2d-f) and (3) (PU/P3HT-t) with a dielectric spincoated on top (PU/P3HT/PU) (Figure 2g-i). In the PU/P3HT-t structure, optical microscopy revealed that cracking started in the semiconductor at strains less than 15% strain. At 65% strain, large cracks with widths in the range of 10 μm were observed (Figure 2b). In addition to the microscale cracks observable with optical microscopy, smaller nanoscale crack-like defects could be resolved using AFM (Figure S3). Continued stretching increased the crack width (Figure 2c). With PU/P3HT-s, the onset of observable microscale cracking occurred between 40% and 65% (Figure 2e). Similar to the PU/P3HT-t structure, the crack length and width increased with strain (Figure 2f). However, the widths of the cracks in the PU/P3HT-s structure were in the range of hundreds of nanometers to several microns. The improved stretchability may be due to a better adhesion of P3HT on the spin coated PU inhibiting crack formation in the semiconductor. Observations for PU/P3HT/PU were similar to those from PU/P3HT-s. The crack size in this structure is much smaller than the device dimensions, indicating that crack formation does not induce substantial variability between devices. The orientation of polymer backbones can be investigated using UV-Vis measurements polarized perpendicular and parallel to the stretching directions. The dichroic ratio (R) is defined as the ratio of the peak intensity of the absorption polarized parallel to the stretching direction divided by the peak intensity of the perpendicular absorption (R = A∥/A⊥). When strain is accommodated by continuous plastic deformation in P3HT, alignment of the polymer chains in the direction of stretching causes anisotropy in the optical absorption, resulting in a dichroic ratio larger than 1.39 The trend in R with strain displayed key differences between the different structures with P3HT (Figure 2j). The PU/P3HT-t sample exhibited a slight increase in R at small strains followed by a gradual return to 1. This suggests that a small amount of plastic deformation is accommodated before cracking occurs. Subsequent stretching resulted in misorientation of the partially-aligned domains, causing R to approach 1. In contrast, the PU/P3HT-s and PU/P3HT/PU structures exhibited a linear increase in R up to ∼1.3 at 50% strain, followed by a region with relatively little change in R. The UV-Vis observations are consistent with those from optical microscopy; both characterization methods indicate that large-scale cracking begins below 15% strain for P3HT transferred onto PU (PU/P3HT-t) and in the range of 50% strain for the systems in which spincoating was used (PU/P3HT-s and PU/P3HT/PU). Adhesion of a plastic material to a deformable substrate improves ductility by limiting the localization of strain that is responsible for crack formation.40 The spincoating process may facilitate excellent adhesion by conformally coating the P3HT, limiting delamination. UV-Vis spectra collected before and after spincoating the dielectric (Figure S4) suggest that the semiconductor film is largely unchanged. Several reports have described the continuous deformation of P3HT to large strain values without the formation of cracks. However, these reports used high temperatures during stretching41 or higher molecular weight P3HT with improved adhesion promoted by UV/Ozone treatments.39 UV/Ozone treatments were detrimental to the device performance in this work because of doping effects that increased IOFF. Electrical measurements were collected while stretching the devices both perpendicular and parallel to the direction of current flow in the channel (Figure 3a). When stretching was undertaken parallel to the charge transport direction (perpendicular to the orientation of the S-D electrodes), the ION decreased rapidly. The experiment was concluded at 140% strain when the On/Off ratio reached below 10. Compared to the parallel direction, the ION decreased more slowly while stretching in the perpendicular direction, and the devices exhibited transistor characteristics to ∼265% strain (Figure 3a). These uniaxial strain values are significantly larger than reported in previous work.13-16 The output characteristics displayed in Figure S6 showed that there is little contact resistance in the measured strain range. Contact resistance is discussed more thoroughly in the supplementary. The gauge factor (GF) is a parameter that is commonly used to quantify the sensitivity of strain sensors. GF is defined as (ΔR/R0)/ε, where ΔR is the change in resistance, R0 is the initial resistance, and ε is the strain. A small GF is sought for application in stretchable active matrices. In the parallel stretching direction, the GF began at ∼7 at low strains, and slightly decreased before increasing at high strains (Figure 3b). In contrast, devices stretched in the perpendicular direction exhibited a GF close to 2 throughout the measured strain range. These values compare favorably to a GF of >10 estimated from published data on stretchable graphene transistors.13 The mobility of the devices decrease at a similar rate for both the perpendicular and parallel stretching directions (Figure 3c). The method of calculating mobility is included in the supplementary information. The increase in leakage current (Figure 3d) is consistent with a reduction in the dielectric thickness. The threshold voltage does not show a stable trend with strain (Figure S7). A strain series was conducted in the parallel direction (Figure 3e), which shows reversible characteristics at small strains, with the degree of irreversible changes increasing with strain. Strain-independent ION was achieved during multiple perpendicular stretching cycles (Figure 3f); ION decreased by ∼50% during the first cycle and remained relatively constant throughout the subsequent cycles. Similar strain-independent properties after an initial prestretch have been observed in CNT-based stretchable electrodes6 and in pentacene transistors.42 Reversible changes in OS transistors have been observed only at low strains,43, 44 which is consistent with our observations. In both stretching directions, IOFF was limited by leakage through the dielectric, which changed modestly with strain (Figure 3c). Consequently, the trend in the on/off ratio followed ION. The collected data facilitate the consideration of possible mechanisms for strain-dependence in the electrical properties. Microscale cracking was not observed until ∼50% strain, indicating that the rapid reduction in ION at low strain values must be attributed to other processes. One possible process could be the formation of nanoscale cracks observed by AFM in Figure S3, which could not be resolved using optical micro­scopy. Alternatively, work on flexible devices has suggested that strain sensitivity can arise from both changes in the separation between molecules44, 45 and changes in the separation between crystallites.43, 46 The relatively constant shape of the UV-Vis spectra with strain (Figure S9) suggests that increased separation between crystallites is more likely than changes in intermolecular distance. At larger strain values, irreversible characteristics begin to be observed (Figure 3b), which we attribute to the onset of cracking. The irreversible behavior associated with crack formation allows the devices to be “programmed” to have strain-independent properties within a chosen strain range (Figure 3d), providing a method to create reliable stretchable transistors consisting of conventional organic semiconductors. Despite the formation of cracks, the change in mobility shows the same trend in the perpendicular and parallel stretching directions. This is contrary to the findings of O'Connor et al.,39 who found that the mobility increases in the perpendicular direction and decreases in the parallel stretching direction. However, it is consistent with some studies on strained pentacene devices.45 Additional considerations include the role of the electrodes and dielectric. While the conductivity of the S/D electrodes decreased with strain (Figure S10), this is not expected to significantly affect the device performance due to the small currents extracted from the device. The strain-induced changes in dielectric capacitance were consistent with what would be expected based on a Poisson ratio of 0.5 (Figure S11). While increasing capacitance should improve device performance, the effect was evidently overshadowed by changes in the semiconductor layer. The cycling stability of the electrical characteristics was investigated by repeatedly applying 40% strain perpendicular to the charge transport direction. The device characteristics were measured in the unstretched state ∼5 min after completing 1, 10, and 100 cycles, and the transfer curves are depicted in Figure 4a. IOFF remained constant throughout the cycling measurements. After the first cycle (initial programming), ION decreased by 17% after cycle 10 and 28% after cycle 100. This cycling performance could be related to the changes in P3HT morphology and the viscoelastic properties of the substrate. R decreased from ∼1.3 after one cycle to ∼1.2 after 300 cycles, indicating some reorganization of the P3HT (Figure 4b). Observations from AFM (Figure S12) provide support for the morphology change with increased cycle number. In addition to the changes in semiconductor morphology, the viscoelastic properties of the substrate can affect cycling results. Physical crosslinking elastomers, such as the thermoplastic PU used in this work, are known to exhibit large mechanical hysteresis,47 and the stress-strain behavior of the substrate (Figure S13) indicated that viscous deformation increases with increasing cycles. The extension ratio (λ) at zero stress was taken as a measure of the extent of viscous deformation. A plot of 1/λ vs strain displays a similar trend as the normalized ION (Figure 4c), providing support for a relationship between the substrate viscosity and the cycling performance. To further characterize the effect of substrate viscosity, transfer characteristics were collected at different times after the completion of 100 cycles to 40% strain (Figure 4d). Over a 40 minute period, ION increased from 0.65 μA to 0.80 μA, which can be attributed to the continued contraction of the substrate toward its initial dimensions. In contrast, pentacene devices operated within the elastic strain range of the substrate (2.6%) have shown no cycling dependence.42 The observation of a significant time-dependence in the electrical properties emphasizes the importance of elastomer viscoelastic properties in stretchable devices. Chemical crosslinking elastomers, which typically display less viscous response,48 may be more appropriate for compliant electronics. In summary, stretchable transistors have been fabricated that exhibit transistor characteristics to large strains. Embedding the semiconductor between two elastomer layers was found to modify the deformation processes and suppress the formation of cracks. Strain-independent characteristics were achieved by programming microcracks with an initial strain. Subsequently, measurements within the range up to the initial strain were relatively constant (Figure 1d). The cycling performance of the device is related to both the change in P3HT morphology and the viscous deformation in the substrate, highlighting the importance of implementing elastomers with minimal viscous response. Further work is required to gain a complete understanding of the origin of the strain-dependent electrical properties of the devices. While the described devices provide an initial platform to study several phenomena in stretchable electronics, there are many potential avenues for improvement. Replacing the dielectric with a more resistive elastomer that absorbs fewer solvents could improve the device characteristics. Furthermore, the stretching performance could be improved by implementing a more elastic semiconducting film. Lastly, for practical applications, the liquid metal electrodes must be replaced with a solid state conductor. All solvents were purchased from commercial sources and used as received. P3HT (Sepiolid P200, MW = 20 to 30 K, ave PDI = 2.0) and soluble polyurethane (Tecoflex SG80A) were kindly donated by BASF and Lubrizol, respectively. Device Fabrication: Polyurethane (PU) substrates were created by dissolving PU in dimethylformamide (DMF) at a concentration of 50 mg/mL. The solution was cast into a glass petri dish and the solvent was evaporated at 120 °C. The final substrate thickness was 500 μm. Arc-discharge CNTs (Hanwaha Nanotech Corp.) in N-methylpyrrolidinone (NMP) at a concentration of 0.165 mg/mL were ultrasonicated (Cole Parmer ultrasonic processor 750 W) for 30 min at 30% power. The resulting dispersion was centrifuged at 8000 RPM for 30 min to remove bundles and contaminants, and the top 75% of the supernatant was retained for spraycoating. Si wafers were cleaned in UV/Ozone for 20 min prior to deposition. The substrates were heated at 200 °C on a hotplate and a commercial airbrush (Master Airbrush, Model SB844-SET) was used to spraycoat the CNT/NMP dispersion through a magnetic shadow mask to define the source and drain electrodes. Due to limitations in the spraycoating process, the channel length was 400 μm. PU in tetrahydrofuran (THF) (10 mg/mL) was cast on the electrodes and the solvent was allowed to evaporate while covered with a glass dish. The electrodes were transferred onto a 500 μm thick PU substrate for easy handling. Silicon wafers treated with a self-assembled layer of octadecyltrimethoxysilane (OTS) were prepared by spincoating a solution of OTS in trichloroethylene followed by a vapour treatment in ammonium hydroxide. P3HT in chloroform (10 mg/mL) was spincoated onto the OTS-coated wafers using a two-step program: (1) 0 RPM for 30 s, and (2) 1000 RPM with 500 RPM s−1 acceleration for 1 min. The resulting P3HT films were manually transferred onto the CNT/PU electrodes at 60 °C by applying gentle pressure for 2 min. The PU dielectric was deposited by spincoating from THF (40 mg/mL) at 1000 RPM. During the spincoating process, the device was placed off-center from the spincoater chuck to ensure that a portion of the electrodes remained exposed. To complete the device, eutectic gallium indium (EGaIn) liquid metal was applied as a top gate using a syringe and needle. The manual process of applying the EGaIn resulted in variation in the W/L of the devices, and the channel width was later measured using optical microscopy. The W/L ratio was ∼12. Capacitors used to measure the dielectric properties of the elastomer with strain were fabricated by spraycoating CNTs onto Si without a shadow mask and then embedding them in PU. PU was spincoated on top from THF (40 mg/mL), and EGaIn was used as the top electrode. Characterization: The sheet resistance of the CNT electrodes was measured using a four point probe setup connected to a Keithley 2400 sourcemeter. The resistance of the CNT electrodes was investigated by securing the film into a linear actuator (Newmark Systems) that had been modified in lab to include clamps. EGaIn was used to make electrical contact to the clamped sections of the conductor. For the PU capacitors, EGaIn was again used to make contact to the clamped, bottom CNT electrode, and a micromanipulator was used to make contact to the top EGaIn electrode. The electrical characteristics were collected using an LCR (inductance, capacitance, resistance) meter (Agilent E498E precision LCR meter) controlled with a LabView Script. To collect UV-Vis and optical microscope images, thin PU substrates (∼80 μm) were used to facilitate easy deformation. Strain was applied by stretching the substrate and applying Kapton tape to secure it to a glass slide. Microscope images were collected using a Leica DM4000 M microscope equipped with a digital camera and operated in Differential Interference Contrast (DIC) mode. UV-Vis spectra were collected using a Cary 6000i UV/Vis/NIR Spectrometer equipped with a polarizer that could be rotated relative to the sample. Electrical characteristics of the transistors were collected using a probe station in a nitrogen environment connected to a Keithley 4200. The source and drain electrodes were probed using 50 μm gold wire attached to the tungsten probes of the micromanipulators, while contact to the EGaIn gate was made using a tungsten probe. Stretching measurements were facilitated by a homemade, hand operated stretching apparatus. The engineering strain in the device was measured directly using digital calipers. Cycling measurements were conducted in a nitrogen environment by hand using a second stretching apparatus. Electrical measurements were collected in the released state after completing the designated number of cycles. Mechanical properties of the PU substrate were collected using an Instron 5565 with a 5 kN load cell. 100 cycles were completed at a strain rate of 1 mm s−1. This work is partially supported by the Samsung Advanced Instituted of Technology and Air Force Office of Scientific Research (FA9550–12–1–0190). This research was partially supported by the MSIP (Ministry of Science, ICT and Future Planning), Korea, under the “IT Consilience Creative Program” (NIPA-2014-H0201–14–1001) supervised by the NIPA (National IT Industry Promotion Agency). As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Due to the interesting semiconducting and optical properties of transition metal dichalcogenides, they have received particular attention for novel electronics and optoelectronics. In addition it is expected that piezoelectric properties of two-dimensional (2D) layered materials are very useful to realize next generation mechanically powered transparent flexible charge-generating devices. Here we report directional dependent piezoelectric effects in chemical vapor deposition grown monolayer MoS2 for flexible piezoelectric nanogenerators (NGs). It was found that the output power obtained from the NG with the armchair direction of MoS2 is about two times higher than that from the NG with the zigzag direction of MoS2 under the same strain of 0.48% and the strain velocity of 70 mm/s. This study provides a new way to effectively harvest mechanical energy using novel flexible piezoelectric NGs based on 2D semiconducting piezoelectric MoS2 for powering low power-consuming electronics and realizing self-powered sensors.

Implantable endovascular devices such as bare metal, drug eluting, and bioresorbable stents have transformed interventional care by providing continuous structural and mechanical support to many peripheral, neural, and coronary arteries affected by blockage. Although effective in achieving immediate restoration of blood flow, the long-term re-endothelialization and inflammation induced by mechanical stents are difficult to diagnose or treat. Here we present nanomaterial designs and integration strategies for the bioresorbable electronic stent with drug-infused functionalized nanoparticles to enable flow sensing, temperature monitoring, data storage, wireless power/data transmission, inflammation suppression, localized drug delivery, and hyperthermia therapy. In vivo and ex vivo animal experiments as well as in vitro cell studies demonstrate the previously unrecognized potential for bioresorbable electronic implants coupled with bioinert therapeutic nanoparticles in the endovascular system.

Powdery mildew is one of the most devastating diseases in cucurbits. Crop yield can decline as the disease severity increases. In this study, we evaluated the effect of silver nanoparticles against powdery mildew under different cultivation conditions in vitro and in vivo . Silver nanoparticles (WA-CV-WA13B) at various concentrations were applied before and after disease outbreak in plants to determine antifungal activities. In the field tests, the application of 100 ppm silver nanoparticles showed the highest inhibition rate for both before and after the outbreak of disease on cucumbers and pumpkins. Also, the application of 100 ppm silver nanoparticles showed maximum inhibition for the growth of fungal hyphae and conidial germination in in vivo tests. Scanning electron microscope results indicated that the silver nanoparticles caused detrimental effects on both mycelial growth and conidial germination.

Here we report a new type of stretchable transparent piezoelectric nanogenerator (NG) using an organic piezoelectric material consisting of poly(vinylidene fluoride trifluoroethylene) [P(VDF-TrFE)] sandwiched with mobility-modified chemical vapor deposition-grown graphene electrodes by ferroelectric polarization into P(VDF-TrFE). This new type of NG has a very high sensitivity and mechanical durability with fully flexible, rollable, stretchable, foldable, and twistable properties. We also investigated the mobility-modified graphene electrodes with ferroelectric P(VDF-TrFE) remnant polarization, and a mechanism is proposed for switching the mobility of the carriers by the ferroelectric remnant polarization. Upon exposure to the same input sound pressure, the measured output performance of the stretchable NG with a thin polydimethylsiloxane stretchable rubber template is up to 30 times that of a normal NG with a plastic substrate. Upon exposure to an air flow at the same speed, the measured output voltage from the stretchable NG is about 8 times larger than that of the normal NG.

Blue energy in the form of ocean waves offers an enormous energy resource. However, it has yet to be fully exploited in order to make it available for the use of mankind. Blue energy harvesting is a challenging task as the kinetic energy from ocean waves is irregular in amplitude and is at low frequencies. Though electromagnetic generators (EMGs) are well-known for harvesting mechanical kinetic energies, they have a crucial limitation for blue energy conversion. Indeed, the output voltage of EMGs can be impractically low at the low frequencies of ocean waves. In contrast, triboelectric nanogenerators (TENGs) are highly suitable for blue energy harvesting as they can effectively harvest mechanical energies from low frequencies (<1 Hz) to relatively high frequencies (∼kHz) and are also low-cost, lightweight, and easy to fabricate. Several important steps have been taken by Wang’s group to develop TENG technology for blue energy harvesting. In this Perspective, we describe some of the recent progress and also address concerns related to durable packaging of TENGs in consideration of harsh marine environments and power management for an efficient power transfer and distribution for commercial applications.

Harvesting human-motion energy for power-integrated wearable electronics could be a promising way to extend the battery-operation time of small low-power-consumption electronics such as various sensors. For this purpose, a fully stretchable triboelectric nanogenerator (S-TENG) that has been fabricated with knitted fabrics and has been integrated with the directly available materials and techniques of the textile industry is introduced. This device has been adapted to cloth movement and can generate electricity under compression and stretching. We investigated plain-, double-, and rib-fabric structures and analyzed their potentials for textile-based energy harvesting. The superior stretchable property of the rib-knitted fabric contributed to a dramatic enhancement of the triboelectric power-generation performance owing to the increased contact surface. The present study shows that, under stretching motions of up to 30%, the S-TENG generates a maximum voltage and a current of 23.50 V and 1.05 μA, respectively, depending on the fabric structures. Under compressions at 3.3 Hz, the S-TENG generated a constant average root-mean square power of up to 60 μW. The results of this work show the feasibility of a cloth-integrated and industrial-ready TENG for the harvesting of energy from human biomechanical movements in cloth and garments.

Enhancing the output power of a nanogenerator is essential in applications as a sustainable power source for wireless sensors and microelectronics. We report here a novel approach that greatly enhances piezoelectric power generation by introducing a p-type polymer layer on a piezoelectric semiconducting thin film. Holes at the film surface greatly reduce the piezoelectric potential screening effect caused by free electrons in a piezoelectric semiconducting material. Furthermore, additional carriers from a conducting polymer and a shift in the Fermi level help in increasing the power output. Poly(3-hexylthiophene) (P3HT) was used as a p-type polymer on piezoelectric semiconducting zinc oxide (ZnO) thin film, and phenyl-C61-butyric acid methyl ester (PCBM) was added to P3HT to improve carrier transport. The ZnO/P3HT:PCBM-assembled piezoelectric power generator demonstrated 18-fold enhancement in the output voltage and tripled the current, relative to a power generator with ZnO only at a strain of 0.068%. The overall output power density exceeded 0.88 W/cm3, and the average power conversion efficiency was up to 18%. This high power generation enabled red, green, and blue light-emitting diodes to turn on after only tens of times bending the generator. This approach offers a breakthrough in realizing a high-performance flexible piezoelectric energy harvester for self-powered electronics.

This paper reports highly bright and efficient CsPbBr 3 perovskite light‐emitting diodes (PeLEDs) fabricated by simple one‐step spin‐coating of uniform CsPbBr 3 polycrystalline layers on a self‐organized buffer hole injection layer and stoichiometry‐controlled CsPbBr 3 precursor solutions with an optimized concentration. The PeLEDs have maximum current efficiency of 5.39 cd A −1 and maximum luminance of 13752 cd m −2 . This paper also investigates the origin of current hysteresis, which can be ascribed to migration of Br − anions. Temperature dependence of the electroluminescence (EL) spectrum is measured and the origins of decreased spectrum area, spectral blue‐shift, and linewidth broadening are analyzed systematically with the activation energies, and are related with Br − anion migration, thermal dissociation of excitons, thermal expansion, and electron–phonon interaction. This work provides simple ways to improve the efficiency and brightness of all‐inorganic polycrystalline PeLEDs and improves understanding of temperature‐dependent ion migration and EL properties in inorganic PeLEDs.

Abstract Hedgehog (Hh) signalling regulates hepatic fibrogenesis. MicroRNAs (miRNAs) mediate various cellular processes; however, their role in liver fibrosis is unclear. Here we investigate regulation of miRNAs in chronically damaged fibrotic liver. MiRNA profiling shows that expression of miR-378 family members (miR-378a-3p, miR-378b and miR-378d) declines in carbon tetrachloride (CCl 4 )-treated compared with corn-oil-treated mice. Overexpression of miR-378a-3p, directly targeting Gli3 in activated hepatic stellate cells (HSCs), reduces expression of Gli3 and profibrotic genes but induces gfap , the inactivation marker of HSCs, in CCl 4 -treated liver. Smo blocks transcriptional expression of miR-378a-3p by activating the p65 subunit of nuclear factor-κB (NF-κB). The hepatic level of miR-378a-3p is inversely correlated with the expression of Gli3 in tumour and non-tumour tissues in human hepatocellular carcinoma. Our results demonstrate that miR-378a-3p suppresses activation of HSCs by targeting Gli3 and its expression is regulated by Smo-dependent NF-κB signalling, suggesting miR-378a-3p has therapeutic potential for liver fibrosis.

Abstract Wearable smart electronic devices based on wireless systems use batteries as a power source. However, recent miniaturization and various functions have increased energy consumption, resulting in problems such as reduction of use time and frequent charging. These factors hinder the development of wearable electronic devices. In order to solve this energy problem, research studies on triboelectric nanogenerators (TENGs) are conducted based on the coupling of contact‐electrification and electrostatic induction effects for harvesting the vast amounts of biomechanical energy generated from wearer movement. The development of TENGs that use a variety of structures and materials based on the textile platform is reviewed, including the basic components of fibers, yarns, and fabrics made using various weaving and knitting techniques. These textile‐based TENGs are lightweight, flexible, highly stretchable, and wearable, so that they can effectively harvest biomechanical energy without interference with human motion, and can be used as activity sensors to monitor human motion. Also, the main application of wearable self‐powered systems is demonstrated and the directions of future development of textile‐based TENG for harvesting biomechanical energy presented.

Recently, several reports have demonstrated that a moving droplet of seawater or ionic solution over monolayer graphene produces an electric power of about 19 nW, and this has been suggested to be a result of the pseudocapacitive effect between graphene and the liquid droplet. Here, we show that the change in the triboelectrification-induced pseudocapacitance between the water droplet and monolayer graphene on polytetrafluoroethylene (PTFE) results in a large power output of about 1.9 μW, which is about 100 times larger than that presented in previous research. During the graphene transfer process, a very strong negative triboelectric potential is generated on the surface of the PTFE. Positive and negative charge accumulation, respectively, occurs on the bottom and the top surfaces of graphene due to the triboelectric potential, and the negative charges that accumulate on the top surface of graphene are driven forward by the moving droplet, charging and discharging at the front and rear of the droplet.

We report on ferroelectric polarization behavior in CH3NH3PbI3 perovskite in the dark and under illumination. Perovskite crystals with three different sizes of 700, 400, and 100 nm were prepared for piezoresponse force microscopy (PFM) measurements. PFM results confirmed the formation of spontaneous polarization in CH3NH3PbI3 in the absence of electric field, where the size dependency to polarization was not significant. Whereas the photoinduced stimulation was not significant without an external electric field, the stimulated polarization by poling was further enhanced under illumination. The retention of ferroelectric polarization was also observed after removal of the electric field, in which larger crystals showed longer retention behavior compared to the smaller sized one. Additionally, we suggest the effect of perovskite crystal size (morphology) on charge collection at the interface of the ferroelectric material even though insignificant size dependency in electric polarization was observed.

Abstract During fasting and vigorous exercise, a shift of brain cell energy substrate utilization from glucose to the ketone 3‐hydroxybutyrate (3 OHB ) occurs. Studies have shown that 3 OHB can protect neurons against excitotoxicity and oxidative stress, but the underlying mechanisms remain unclear. Neurons maintained in the presence of 3 OHB exhibited increased oxygen consumption and ATP production, and an elevated NAD + / NADH ratio. We found that 3 OHB metabolism increases mitochondrial respiration which drives changes in expression of brain‐derived neurotrophic factor ( BDNF ) in cultured cerebral cortical neurons. The mechanism by which 3 OHB induces Bdnf gene expression involves generation of reactive oxygen species, activation of the transcription factor NF ‐κB, and activity of the histone acetyltransferase p300/ EP 300. Because BDNF plays important roles in synaptic plasticity and neuronal stress resistance, our findings suggest cellular signaling mechanisms by which 3 OHB may mediate adaptive responses of neurons to fasting, exercise, and ketogenic diets. image

The growth of one metal-organic framework (MOF) on another MOF for constructing a heterocompositional hybrid MOF is an interesting research topic because of the curiosity regarding the occurrence of this phenomenon and the value of hybrid MOFs as multifunctional materials or routes for fine-tuning MOF properties. In particular, the anisotropic growth of MOF on MOF is fascinating for the development of MOFs possessing atypical shapes and heterostructures or abnormal properties. Herein, we clarify the understanding of growth behavior of a secondary MOF on an initial MOF template, such as isotropic or anisotropic ways associated with their cell parameters. The isotropic growth of MIL-68-Br on the MIL-68 template results in the formation of core-shell-type MIL-68@MIL-68-Br. However, the unique anisotropic growth of a secondary MOF (MOF-NDC) on the MIL-68 template results in semitubular particles, and structural features of this unknown secondary MOF are successfully speculated for the first time on the basis of its unique growth behavior and morphological characteristics. Finally, the validation of this structural speculation is verified by the powder X-ray diffraction and the selected area electron diffraction studies. The results suggests that the growth behavior and morphological features of MOFs should be considered to be important factors for understanding the MOFs' structures.

Here, we report the synthesis of lead-free single-crystalline two-dimensional (2D) vanadium(V)-doped ZnO nanosheets (NSs) and their application for high-performance flexible direct current (DC) power piezoelectric nanogenerators (NGs). The vertically aligned ZnO nanorods (NRs) converted to NS networks by V doping. Piezoresponse force microscopy studies reveal that vertical V-doped ZnO NS exhibit typical ferroelectricity with clear phase loops, butterfly, and well-defined hysteresis loops with a piezoelectric charge coefficient of up to 4 pm/V, even in 2D nanostructures. From pristine ZnO NR-based NGs, alternating current (AC)-type output current was observed, while from V-doped ZnO NS-based NGs, a DC-type output current density of up to 1.0 μAcm–2 was surprisingly obtained under the same vertical compressive force. The growth mechanism, ferroelectric behavior, charge inverted phenomena, and high piezoelectric output performance observed from the V-doped ZnO NS are discussed in terms of the formation of an ionic layer of [V(OH)4–], permanent electric dipole, and the doping-induced resistive behavior of ZnO NS.

The Geostationary Environment Monitoring Spectrometer (GEMS) is scheduled for launch in February 2020 to monitor air quality (AQ) at an unprecedented spatial and temporal resolution from a geostationary Earth orbit (GEO) for the first time. With the development of UV–visible spectrometers at sub-nm spectral resolution and sophisticated retrieval algorithms, estimates of the column amounts of atmospheric pollutants (O3, NO2, SO2, HCHO, CHOCHO, and aerosols) can be obtained. To date, all the UV–visible satellite missions monitoring air quality have been in low Earth orbit (LEO), allowing one to two observations per day. With UV–visible instruments on GEO platforms, the diurnal variations of these pollutants can now be determined. Details of the GEMS mission are presented, including instrumentation, scientific algorithms, predicted performance, and applications for air quality forecasts through data assimilation. GEMS will be on board the Geostationary Korea Multi-Purpose Satellite 2 (GEO-KOMPSAT-2) satellite series, which also hosts the Advanced Meteorological Imager (AMI) and Geostationary Ocean Color Imager 2 (GOCI-2). These three instruments will provide synergistic science products to better understand air quality, meteorology, the long-range transport of air pollutants, emission source distributions, and chemical processes. Faster sampling rates at higher spatial resolution will increase the probability of finding cloud-free pixels, leading to more observations of aerosols and trace gases than is possible from LEO. GEMS will be joined by NASA’s Tropospheric Emissions: Monitoring of Pollution (TEMPO) and ESA’s Sentinel-4 to form a GEO AQ satellite constellation in early 2020s, coordinated by the Committee on Earth Observation Satellites (CEOS).

Our study shows that the surface energy of all 2D layered materials is undoubtedly dominated by London–van der Waals forces with little contribution from dipole–dipole interactions.

Abstract Recent findings demonstrate that cellulose, a highly abundant, versatile, sustainable, and inexpensive material, can be used in the preparation of very stable and flexible electrochemical energy storage devices with high energy and power densities by using electrodes with high mass loadings, composed of conducting composites with high surface areas and thin layers of electroactive material, as well as cellulose‐based current collectors and functional separators. Close attention should, however, be paid to the properties of the cellulose (e.g., porosity, pore distribution, pore‐size distribution, and crystallinity). The manufacturing of cellulose‐based electrodes and all‐cellulose devices is also well‐suited for large‐scale production since it can be made using straightforward filtration‐based techniques or paper‐making approaches, as well as utilizing various printing techniques. Herein, the recent development and possibilities associated with the use of cellulose are discussed, regarding the manufacturing of electrochemical energy storage devices comprising electrodes with high energy and power densities and lightweight current collectors and functional separators.

Recently, smart systems have met with large success. At the origin of the internet of things, they are a key driving force for the development of wireless, sustainable, and independent autonomous smart systems. In this context, autonomy is critical, and despite all the progress that has been made in low-power electronics and batteries, energy harvesters are becoming increasingly important. Thus, harvesting mechanical energy is essential, as it is widespread and abundant in our daily life environment. Among harvesters, flexible triboelectric nanogenerators (TENGs) exhibit good performance, and they are easy to integrate, which makes them perfect candidates for many applications and, therefore, crucial to develop. In this review paper, we first introduce the fundamentals of TENGs, including their four basic operation modes. Then, we discuss the different improvement parameters. We review some progress made in terms of performance and integration that have been possible through the understanding of each operation mode and the development of innovative structures. Finally, we present the latest trends, structures, and materials in view of future improvements and applications.

Recently, piezoelectricity has been observed in 2D atomically thin materials, such as hexagonal-boron nitride, graphene, and transition metal dichalcogenides (TMDs). Specifically, exfoliated monolayer MoS2 exhibits a high piezoelectricity that is comparable to that of traditional piezoelectric materials. However, monolayer TMD materials are not regarded as suitable for actual piezoelectric devices due to their insufficient mechanical durability for sustained operation while Bernal-stacked bilayer TMD materials lose noncentrosymmetry and consequently piezoelectricity. Here, it is shown that WSe2 bilayers fabricated via turbostratic stacking have reliable piezoelectric properties that cannot be obtained from a mechanically exfoliated WSe2 bilayer with Bernal stacking. Turbostratic stacking refers to the transfer of each chemical vapor deposition (CVD)-grown WSe2 monolayer to allow for an increase in degrees of freedom in the bilayer symmetry, leading to noncentrosymmetry in the bilayers. In contrast, CVD-grown WSe2 bilayers exhibit very weak piezoelectricity because of the energetics and crystallographic orientation. The flexible piezoelectric WSe2 bilayers exhibit a prominent mechanical durability of up to 0.95% of strain as well as reliable energy harvesting performance, which is adequate to drive a small liquid crystal display without external energy sources, in contrast to monolayer WSe2 for which the device performance becomes degraded above a strain of 0.63%.

Abstract. Recent observations suggest that a certain fraction of organic carbon (OC) aerosol effectively absorbs solar radiation, which is also known as brown carbon (BrC) aerosol. Despite much observational evidence of its presence, very few global modelling studies have been conducted because of poor understanding of global BrC emissions. Here we present an explicit global simulation of BrC in a global 3-D chemical transport model (GEOS-Chem), including global BrC emission estimates from primary (3.9 ± 1.7 and 3.0 ± 1.3 TgC yr−1 from biomass burning and biofuel) and secondary (5.7 TgC yr−1 from aromatic oxidation) sources. We evaluate the model by comparing the results with observed absorption by water-soluble OC in surface air in the United States, and with single scattering albedo observations at Aerosol Robotic Network (AERONET) sites all over the globe. The model successfully reproduces the seasonal variations of observed light absorption by water-soluble OC, but underestimates the magnitudes, especially in regions with high secondary source contributions. Our global simulations show that BrC accounts for 21 % of the global mean surface OC concentration, which is typically assumed to be scattering. We find that the global direct radiative effect of BrC is nearly zero at the top of the atmosphere, and consequently decreases the direct radiative cooling effect of OC by 16 %. In addition, the BrC absorption leads to a general reduction of NO2 photolysis rates, whose maximum decreases occur in Asia up to −8 % (−17 %) on an annual (spring) mean basis. The resulting decreases of annual (spring) mean surface ozone concentrations are up to −6 % (−13 %) in Asia, indicating a non-negligible effect of BrC on photochemistry in this region.

PF-00547659 is a fully human monoclonal antibody that binds to human mucosal addressin cell adhesion molecule-1 (MAdCAM-1) to selectively reduce lymphocyte homing to the intestinal tract. We aimed to assess the efficacy and safety of PF-00547659 in patients with moderate to severe ulcerative colitis.This phase 2, randomised, double-blind, placebo-controlled clinical trial recruited patients aged 18-65 years from 105 centres in 21 countries, with a history (≥3 months) of active ulcerative colitis extending more than 15 cm beyond the anal verge (with a total Mayo score ≥6 and a Mayo endoscopic subscore ≥2) who had failed or were intolerant to at least one conventional therapy. Patients were stratified by previous anti-TNFα treatment, and randomly assigned by a computer-generated randomisation schedule to receive a subcutaneous injection of 7·5 mg, 22·5 mg, 75 mg, or 225 mg PF-00547659 or placebo at baseline, then every 4 weeks. Patients, investigators, and sponsors were blinded to the treatment. The primary endpoint was the proportion of patients achieving remission (total Mayo score ≤2 with no individual subscore >1 and rectal bleeding subscore ≤1) at week 12. The efficacy analysis included all patients who received at least one dose of the randomised treatment; the safety analysis was done according to treatment received. All p values were one-sided and multiplicity-adjusted. This study is registered with ClinicalTrials.gov, number NCT01620255.Between Nov 2, 2012, and Feb 4, 2016, we screened 587 patients; 357 were eligible and randomly assigned to receive placebo (n=73) or PF-00547659 at doses of 7·5 mg (n=71), 22·5 mg (n=72), 75 mg (n=71), or 225 mg (n=70). Remission rates at week 12 were significantly greater in three of four active-treatment groups than in the placebo group (2·7% [two of 73]): 7·5 mg (11·3% [eight of 71]), 22·5 mg (16·7% [12 of 72]), 75 mg (15·5% [11 of 71]), and 225 mg (5·7% [four of 70]). These rates corresponded to a stratum-adjusted (anti-TNFα-naive and anti-TNFα-experienced) risk difference versus placebo of 8·0% for 7·5 mg (90% CI 1·9 to 14, p=0·0425), 12·8% for 22·5 mg (5·6 to 19·9, p=0·0099), 11·8% for 75 mg (4·8 to 18·8, p=0·0119), and 2·6% for 225 mg (-1·2 to 6·4, p=0·1803). Four of 73 (5·5%) patients had a serious adverse event in the placebo group, ten of 71 (14·1%) in the 7·5 mg group, one of 70 (1·4%) in the 22·5 mg group, three of 73 (4·1%) in the 75 mg group, and three of 70 (4·3%) in the 225 mg group. No safety signal was observed for the study drug.PF-00547659 was safe and well tolerated in this patient population, and better than placebo for induction of remission in patients with moderate to severe ulcerative colitis. The greatest clinical effects were observed with the 22·5 mg and 75 mg doses.Pfizer.

Butyrate is a bacterial metabolite of dietary fiber in the colon that has been used to treat inflammatory disease. However, the effect of oral supplementation with butyrate on colitis has not been fully explored. We evaluated the effects of and mechanisms underlying oral supplementation with butyrate on experimental murine colitis. In an in vitro study, we found that LPS induced the secretion of cytokines (i.e., IL-8 in COLO 205; TNF-α, IL-6, IL-12, and IL-10 in RAW 264.7; and TNF-α, IL-6 and IL-12 in peritoneal macrophages obtained from IL-10-deficient [IL-10−/−] mice). Butyrate (100 μM and 500 μM) inhibited pro-inflammatory cytokine production (i.e., IL-8 in COLO205 and TNF-α, IL-6 and IL-12 in macrophages) but promoted anti-inflammatory cytokine (i.e., IL-10) production in RAW264.7 cells. Butyrate attenuated both the LPS-induced degradation/phosphorylation of IκBα and DNA binding of NF-κB and enhanced histone H3 acetylation. To confirm that butyrate played a protective role in colitis, an acute colitis model was induced using dextran sulfate sodium (DSS) and a chronic colitis model was induced in IL-10−/− mice. The administration of oral butyrate (100 mg/kg) significantly improved histological scores in both colitis models, including the IL-10−/− mice. In immunohistochemical staining, IκBα phosphorylation was attenuated, and histone H3 acetylation was reversed in the treated colons of both colitis models. Our results indicate that oral supplementation with butyrate attenuates experimental murine colitis by blocking NF-κB signaling and reverses histone acetylation. These anti-colitic effects of butyrate were IL-10-independent. Butyrate may therefore be a therapeutic agent for colitis.

Focal cortical dysplasia (FCD) is a major cause of the sporadic form of intractable focal epilepsies that require surgical treatment. It has recently been reported that brain somatic mutations in <i>MTOR</i> account for 15%–25% of FCD type II (FCDII), characterized by cortical dyslamination and dysmorphic neurons. However, the genetic etiologies of FCDII-affected individuals who lack the <i>MTOR</i> mutation remain unclear. Here, we performed deep hybrid capture and amplicon sequencing (read depth of 100×–20,012×) of five important mTOR pathway genes—<i>PIK3CA, PIK3R2, AKT3, TSC1,</i> and <i>TSC2</i>—by using paired brain and saliva samples from 40 FCDII individuals negative for <i>MTOR</i> mutations. We found that 5 of 40 individuals (12.5%) had brain somatic mutations in <i>TSC1</i> (c.64C>T [p.Arg22Trp] and c.610C>T [p.Arg204Cys]) and <i>TSC2</i> (c.4639G>A [p.Val1547Ile]), and these results were reproducible on two different sequencing platforms. All identified mutations induced hyperactivation of the mTOR pathway by disrupting the formation or function of the TSC1-TSC2 complex. Furthermore, in utero CRISPR-Cas9-mediated genome editing of <i>Tsc1</i> or <i>Tsc2</i> induced the development of spontaneous behavioral seizures, as well as cytomegalic neurons and cortical dyslamination. These results show that brain somatic mutations in <i>TSC1</i> and <i>TSC2</i> cause FCD and that in utero application of the CRISPR-Cas9 system is useful for generating neurodevelopmental disease models of somatic mutations in the brain.

Multi-phase rotation-type triboelectric nanogenerators generate an almost constant direct current output, which overcomes the typical limitation of triboelectric nanogenerators.

Abstract Biomolecular piezoelectric materials are considered a strong candidate material for biomedical applications due to their robust piezoelectricity, biocompatibility, and low dielectric property. The electric field has been found to affect tissue development and regeneration, and the piezoelectric properties of biological materials in the human body are known to provide electric fields by pressure. Therefore, great attention has been paid to the understanding of piezoelectricity in biological tissues and its building blocks. The aim herein is to describe the principle of piezoelectricity in biological materials from the very basic building blocks (i.e., amino acids, peptides, proteins, etc.) to highly organized tissues (i.e., bones, skin, etc.). Research progress on the piezoelectricity within various biological materials is summarized, including amino acids, peptides, proteins, and tissues. The mechanisms and origin of piezoelectricity within various biological materials are also covered.

An artificial ionic mechanotransducer skin with an unprecedented sensitivity over a wide spectrum of pressure by fabricating visco-poroelastic nanochannels and microstructured features, directly mimicking the physiological tactile sensing mechanism of Piezo2 protein is demonstrated. This capability enables voice identification, health monitoring, daily pressure measurements, and even measurements of a heavy weight beyond capabilities of human skin. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Abstract In recent years, 2-dimensional (2D) materials such as graphene and h-BN have been spotlighted, because of their unique properties and high potential applicability. Among these 2D materials, transition metal dichalcogenides (TMDs) have attracted a lot of attention due to their unusual electrical, optical, and mechanical properties. Also, TMDs have virtually unlimited potential in various fields, including electronic, optoelectronic, sensing, and energy storage applications. For these various applications, there are many methods for sample preparation, such as the mechanical, liquid exfoliation and chemical vapor deposition techniques. In this review, we introduce the properties, preparation methods and various applications of TMDs materials.

<h3>Background</h3> The optimal technique for removal of diminutive or small colorectal polyps is debatable. <h3>Objective</h3> To compare the complete resection rates of cold snare polypectomy (CSP) and cold forceps polypectomy (CFP) for the removal of adenomatous polyps ≤7 mm. <h3>Design</h3> Prospective randomized controlled study. <h3>Setting</h3> A university hospital. <h3>Patients</h3> A total of 139 patients who were found to have ≥1 colorectal adenomatous polyps ≤7 mm. <h3>Interventions</h3> Polyps were randomized to be treated with either CSP or CFP. After the initial polypectomy, additional EMR was performed at the polypectomy site to assess the presence of residual polyp tissue. <h3>Main Outcome Measurements</h3> Absence of residual polyp tissue in the EMR specimen of the polypectomy site was defined as complete resection. <h3>Results</h3> Among a total of 145 polyps, 128 (88.3%) were adenomatous polyps. The overall complete resection rate for adenomatous polyps was significantly higher in the CSP group compared with the CFP group (57/59, 96.6% vs 57/69, 82.6%; <i>P</i> = .011). Although the complete resection rates for adenomatous polyps ≤4 mm were not different (27/27, 100% vs 31/32, 96.9%; <i>P</i> = 1.000), the complete resection rates for adenomatous polyps sized 5 to 7 mm was significantly higher in the CSP group compared with the CFP group (30/32, 93.8% vs 26/37, 70.3%; <i>P</i> = .013). <h3>Limitations</h3> Single-center study. <h3>Conclusion</h3> CSP is recommended for the complete resection of colorectal adenomatous polyps ≤7 mm. (Clinical trial registration number: NCT01665898.)

Biological cellular structures have inspired many scientific disciplines to design synthetic structures that can mimic their functions. Here, we closely emulate biological cellular structures in a rationally designed synthetic multicellular hybrid ion pump, composed of hydrogen-bonded [EMIM+][TFSI-] ion pairs on the surface of silica microstructures (artificial mechanoreceptor cells) embedded into thermoplastic polyurethane elastomeric matrix (artificial extracellular matrix), to fabricate ionic mechanoreceptor skins. Ionic mechanoreceptors engage in hydrogen bond-triggered reversible pumping of ions under external stimulus. Our ionic mechanoreceptor skin is ultrasensitive (48.1-5.77 kPa-1) over a wide spectrum of pressures (0-135 kPa) at an ultra-low voltage (1 mV) and demonstrates the ability to surpass pressure-sensing capabilities of various natural skin mechanoreceptors (i.e., Merkel cells, Meissner's corpuscles, Pacinian corpuscles). We demonstrate a wearable drone microcontroller by integrating our ionic skin sensor array and flexible printed circuit board, which can control directions and speed simultaneously and selectively in aerial drone flight.

The effect of visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) area on metabolic syndrome (MS) has been debated. We aimed to evaluate the effects of VAT and SAT on the incidence of MS and its components in a large and apparently healthy Asian population. We performed a longitudinal cohort study of 1,964 subjects who received health screenings over a 5-year follow-up period; 317 incidents of MS (16.1%) were observed during a median follow-up of 4.5 years. The VAT area was significantly associated with a higher incidence of MS; the adjusted HR for incident MS per 1 SD of VAT was 1.50 (95% CI 1.29-1.74), and the adjusted HR of the 5th VAT quintile compared with the 1st quintile was 3.73 (95% CI 2.22-6.28). However, the SAT area was not associated with incident MS. Although the VAT area was longitudinally associated with the incidence of each component of MS, the SAT area was inversely associated with the risk of high blood pressure, fasting blood sugar, and triglycerides, with marginal significance. In conclusion, the VAT area is longitudinally associated with an increased risk of incident MS, while SAT may have a protective effect against the incidence of individual MS components.

Abstract Ionic tactile sensors (ITS) represent a new class of deformable sensory platforms that mimic not only the tactile functions and topological structures but also the mechanotransduction mechanism across the biological ion channels in human skin, which can demonstrate a more advanced biological interface for targeting emerging human‐interactive technologies compared to conventional e‐skin devices. Recently, flexible and even stretchable ITS have been developed using novel structural designs and strategies in materials and devices. These skin‐like tactile sensors can effectively sense pressure, strain, shear, torsion, and other external stimuli with high sensitivity, high reliability, and rapid response beyond those of human perception. In this review, the recent developments of the ITS based on the novel concepts, structural designs, and strategies in materials innovation are entirely highlighted. In particular, biomimetic approaches have led to the development of the ITS that extend beyond the tactile sensory capabilities of human skin such as sensitivity, pressure detection range, and multimodality. Furthermore, the recent progress in self‐powered and self‐healable ITS, which should be strongly required to allow human‐interactive artificial sensory platforms is reviewed. The applications of ITS in human‐interactive technologies including artificial skin, wearable medical devices, and user‐interactive interfaces are highlighted. Last, perspectives on the current challenges and the future directions of this field are presented.

Utilization of ubiquitous low-grade waste heat constitutes a possible avenue towards soft matter actuation and energy recovery opportunities. While most soft materials are not all that smart relying on power input of some kind for continuous response, we conceptualize a self-locked thermo-mechano feedback for autonomous motility and energy generation functions. Here, the low-grade heat usually dismissed as 'not useful' is used to fuel a soft thermo-mechano-electrical system to perform perpetual and untethered multimodal locomotions. The innately resilient locomotion synchronizes self-governed and auto-sustained temperature fluctuations and mechanical mobility without external stimulus change, enabling simultaneous harvesting of thermo-mechanical energy at the pyro/piezoelectric mechanistic intersection. The untethered soft material showcases deterministic motions (translational oscillation, directional rolling, and clockwise/anticlockwise rotation), rapid transitions and dynamic responses without needing power input, on the contrary extracting power from ambient. This work may open opportunities for thermo-mechano-electrical transduction, multigait soft energy robotics and waste heat harvesting technologies.