Kewang Nan

Assembly of 3D micro/nanostructures in advanced functional materials has important implications across broad areas of technology. Existing approaches are compatible, however, only with narrow classes of materials and/or 3D geometries. This paper introduces ideas for a form of Kirigami that allows precise, mechanically driven assembly of 3D mesostructures of diverse materials from 2D micro/nanomembranes with strategically designed geometries and patterns of cuts. Theoretical and experimental studies demonstrate applicability of the methods across length scales from macro to nano, in materials ranging from monocrystalline silicon to plastic, with levels of topographical complexity that significantly exceed those that can be achieved using other approaches. A broad set of examples includes 3D silicon mesostructures and hybrid nanomembrane-nanoribbon systems, including heterogeneous combinations with polymers and metals, with critical dimensions that range from 100 nm to 30 mm. A 3D mechanically tunable optical transmission window provides an application example of this Kirigami process, enabled by theoretically guided design.

Three-dimensional (3D) structures capable of reversible transformations in their geometrical layouts have important applications across a broad range of areas. Most morphable 3D systems rely on concepts inspired by origami/kirigami or techniques of 3D printing with responsive materials. The development of schemes that can simultaneously apply across a wide range of size scales and with classes of advanced materials found in state-of-the-art microsystem technologies remains challenging. Here, we introduce a set of concepts for morphable 3D mesostructures in diverse materials and fully formed planar devices spanning length scales from micrometres to millimetres. The approaches rely on elastomer platforms deformed in different time sequences to elastically alter the 3D geometries of supported mesostructures via nonlinear mechanical buckling. Over 20 examples have been experimentally and theoretically investigated, including mesostructures that can be reshaped between different geometries as well as those that can morph into three or more distinct states. An adaptive radiofrequency circuit and a concealable electromagnetic device provide examples of functionally reconfigurable microelectronic devices.

Origami is a topic of rapidly growing interest in both the scientific and engineering research communities due to its promising potential in a broad range of applications. Previous assembly approaches of origami structures at the micro/nanoscale are constrained by the applicable classes of materials, topologies and/or capability of control over the transformation. Here, we introduce an approach that exploits controlled mechanical buckling for autonomic origami assembly of 3D structures across material classes from soft polymers to brittle inorganic semiconductors, and length scales from nanometers to centimeters. This approach relies on a spatial variation of thickness in the initial 2D structures as an effective strategy to produce engineered folding creases during the compressive buckling process. The elastic nature of the assembly scheme enables active, deterministic control over intermediate states in the 2D to 3D transformation in a continuous and reversible manner. Demonstrations include a broad set of 3D structures formed through unidirectional, bidirectional, and even hierarchical folding, with examples ranging from half cylindrical columns and fish scales, to cubic boxes, pyramids, starfish, paper fans, skew tooth structures, and to amusing system-level examples of soccer balls, model houses, cars, and multi-floor textured buildings.

With accelerating trends in miniaturization of semiconductor devices, techniques for energy harvesting become increasingly important, especially in wearable technologies and sensors for the internet of things. Although thermoelectric systems have many attractive attributes in this context, maintaining large temperature differences across the device terminals and achieving low-thermal impedance interfaces to the surrounding environment become increasingly difficult to achieve as the characteristic dimensions decrease. Here, we propose and demonstrate an architectural solution to this problem, where thin-film active materials integrate into compliant, open three-dimensional (3D) forms. This approach not only enables efficient thermal impedance matching but also multiplies the heat flow through the harvester, thereby increasing the efficiencies for power conversion. Interconnected arrays of 3D thermoelectric coils built using microscale ribbons of monocrystalline silicon as the active material demonstrate these concepts. Quantitative measurements and simulations establish the basic operating principles and the key design features. The results suggest a scalable strategy for deploying hard thermoelectric thin-film materials in harvesters that can integrate effectively with soft materials systems, including those of the human body.

Capabilities for assembly of three-dimensional (3D) micro/nanostructures in advanced materials have important implications across a broad range of application areas, reaching nearly every class of microsystem technology. Approaches that rely on the controlled, compressive buckling of 2D precursors are promising because of their demonstrated compatibility with the most sophisticated planar technologies, where materials include inorganic semiconductors, polymers, metals, and various heterogeneous combinations, spanning length scales from submicrometer to centimeter dimensions. We introduce a set of fabrication techniques and design concepts that bypass certain constraints set by the underlying physics and geometrical properties of the assembly processes associated with the original versions of these methods. In particular, the use of releasable, multilayer 2D precursors provides access to complex 3D topologies, including dense architectures with nested layouts, controlled points of entanglement, and other previously unobtainable layouts. Furthermore, the simultaneous, coordinated assembly of additional structures can enhance the structural stability and drive the motion of extended features in these systems. The resulting 3D mesostructures, demonstrated in a diverse set of more than 40 different examples with feature sizes from micrometers to centimeters, offer unique possibilities in device design. A 3D spiral inductor for near-field communication represents an example where these ideas enable enhanced quality (Q) factors and broader working angles compared to those of conventional 2D counterparts.

Abstract Efficient and highly functional three-dimensional systems that are ubiquitous in biology suggest that similar design architectures could be useful in electronic and optoelectronic technologies, extending their levels of functionality beyond those achievable with traditional, planar two-dimensional platforms. Complex three-dimensional structures inspired by origami, kirigami have promise as routes for two-dimensional to three-dimensional transformation, but current examples lack the necessary combination of functional materials, mechanics designs, system-level architectures, and integration capabilities for practical devices with unique operational features. Here, we show that two-dimensional semiconductor/semi-metal materials can play critical roles in this context, through demonstrations of complex, mechanically assembled three-dimensional systems for light-imaging capabilities that can encompass measurements of the direction, intensity and angular divergence properties of incident light. Specifically, the mechanics of graphene and MoS 2 , together with strategically configured supporting polymer films, can yield arrays of photodetectors in distinct, engineered three-dimensional geometries, including octagonal prisms, octagonal prismoids, and hemispherical domes.

Tissue-wide electrophysiology with single-cell and millisecond spatiotemporal resolution is critical for heart and brain studies. Issues arise, however, from the invasive, localized implantation of electronics that destroys well-connected cellular networks within matured organs. Here, we report the creation of cyborg organoids: the three-dimensional (3D) assembly of soft, stretchable mesh nanoelectronics across the entire organoid by the cell-cell attraction forces from 2D-to-3D tissue reconfiguration during organogenesis. We demonstrate that stretchable mesh nanoelectronics can migrate with and grow into the initial 2D cell layers to form the 3D organoid structure with minimal impact on tissue growth and differentiation. The intimate contact between the dispersed nanoelectronics and cells enables us to chronically and systematically observe the evolution, propagation, and synchronization of the bursting dynamics in human cardiac organoids through their entire organogenesis.

A composite material made of graphene nanoribbons and iron oxide nanoparticles provides a remarkable route to lithium‐ion battery anode with high specific capacity and cycle stability. At a rate of 100 mA/g, the material exhibits a high discharge capacity of ~910 mAh/g after 134 cycles, which is >90% of the theoretical li‐ion storage capacity of iron oxide. Carbon black, carbon nanotubes, and graphene flakes have been employed by researchers to achieve conductivity and stability in lithium‐ion electrode materials. Herein, the use of graphene nanoribbons as a conductive platform on which iron oxide nanoparticles are formed combines the advantages of long carbon nanotubes and flat graphene surfaces. The high capacity over prolonged cycling achieved is due to the synergy between an electrically percolating networks of conductive graphene nanoribbons and the high lithium‐ion storage capability of iron oxide nanoparticles.

Significance Exploiting advanced 3D designs in micro/nanomanufacturing inspires potential applications in various fields including biomedical engineering, metamaterials, electronics, electromechanical components, and many others. The results presented here provide enabling concepts in an area of broad, current interest to the materials community––strategies for forming sophisticated 3D micro/nanostructures and means for using them in guiding the growth of synthetic materials and biological systems. These ideas offer qualitatively differentiated capabilities compared with those available from more traditional methodologies in 3D printing, multiphoton lithography, and stress-induced bending––the result enables access to both active and passive 3D mesostructures in state-of-the-art materials, as freestanding systems or integrated with nearly any type of supporting substrate.

A conductive composite of graphene nanoribbon (GNR) stacks and epoxy is fabricated. The epoxy is filled with the GNR stacks, which serve as a conductive additive. The GNR stacks are on average 30 nm thick, 250 nm wide, and 30 μm long. The GNR-filled epoxy composite exhibits a conductivity >100 S/m at 5 wt % GNR content. This permits application of the GNR-epoxy composite for deicing of surfaces through Joule (voltage-induced) heating generated by the voltage across the composite. A power density of 0.5 W/cm2 was delivered to remove ∼1 cm-thick (14 g) monolith of ice from a static helicopter rotor blade surface in a −20 °C environment.

Capabilities for controlled formation of sophisticated 3D micro/nanostructures in advanced materials have foundational implications across a broad range of fields. Recently developed methods use stress release in prestrained elastomeric substrates as a driving force for assembling 3D structures and functional microdevices from 2D precursors. A limitation of this approach is that releasing these structures from their substrate returns them to their original 2D layouts due to the elastic recovery of the constituent materials. Here, a concept in which shape memory polymers serve as a means to achieve freestanding 3D architectures from the same basic approach is introduced, with demonstrated ability to realize lateral dimensions, characteristic feature sizes, and thicknesses as small as ≈500, 10, and 5 µm simultaneously, and the potential to scale to much larger or smaller dimensions. Wireless electronic devices illustrate the capacity to integrate other materials and functional components into these 3D frameworks. Quantitative mechanics modeling and experimental measurements illustrate not only shape fixation but also capabilities that allow for structure recovery and shape programmability, as a form of 4D structural control. These ideas provide opportunities in fields ranging from micro-electromechanical systems and microrobotics, to smart intravascular stents, tissue scaffolds, and many others.

Three-dimensional (3D) helical mesostructures are attractive for applications in a broad range of microsystem technologies, due to their mechanical and electromagnetic properties as stretchable interconnects, radio frequency antennas and others. Controlled compressive buckling of 2D serpentine-shaped ribbons provides a strategy to formation of such structures in wide ranging classes of materials (from soft polymers to brittle inorganic semiconductors) and length scales (from nanometer to centimeter), with an ability for automated, parallel assembly over large areas. The underlying relations between the helical configurations and fabrication parameters require a relevant theory as the basis of design for practical applications. Here, we present an analytic model of compressive buckling in serpentine microstructures, based on the minimization of total strain energy that results from various forms of spatially dependent deformations. Experiments at micro- and millimeter-scales, together with finite element analyses (FEA), were exploited to examine the validity of developed model. The theoretical analyses shed light on general scaling laws in terms of three groups of fabrication parameters (related to loading, material and 2D geometry), including a negligible effect of material parameters and a square root dependence of primary displacements on the compressive strain. Furthermore, analytic solutions were obtained for the key physical quantities (e.g., displacement, curvature and maximum strain). A demonstrative example illustrates how to leverage the analytic solutions in choosing the various design parameters, such that brittle fracture or plastic yield can be avoided in the assembly process.

Smart contact lenses have emerged as novel wearable devices. Due to their multifunctional biosensing capabilities and highly integrated performance, they provide a great platform for the diagnosis of eye diseases and the delivery of drugs. Herein, a brief history of the development of contact lenses is given. Then, the state‐of‐the‐art design and fabrication of smart contact lenses for biomedical applications, including contact lens materials, fabrication technologies, and integration, are presented. Furthermore, biosensors implemented in contact lenses to measure lactic acid, glucose, intraocular pressure, and other key metabolites in tears are highlighted. Applications of smart contact lenses in drug delivery are also described. These unique features make smart contact lenses promising diagnostic and treatment devices. Challenges and future opportunities for further applications of smart contact lenses in biomedicine are also discussed.

The surface mucosa that lines many of our organs houses myriad biometric signals and, therefore, has great potential as a sensor–tissue interface for high-fidelity and long-term biosensing. However, progress is still nascent for mucosa-interfacing electronics owing to challenges with establishing robust sensor–tissue interfaces; device localization, retention and removal; and power and data transfer. This is in sharp contrast to the rapidly advancing field of skin-interfacing electronics, which are replacing traditional hospital visits with minimally invasive, real-time, continuous and untethered biosensing. This Review aims to bridge the gap between skin-interfacing electronics and mucosa-interfacing electronics systems through a comparison of the properties and functions of the skin and internal mucosal surfaces. The major physiological signals accessible through mucosa-lined organs are surveyed and design considerations for the next generation of mucosa-interfacing electronics are outlined based on state-of-the-art developments in bio-integrated electronics. With this Review, we aim to inspire hardware solutions that can serve as a foundation for developing personalized biosensing from the mucosa, a relatively uncharted field with great scientific and clinical potential. The surface mucosa that lines many of our organs hosts a diverse set of biometric signals. This Review compares present skin-interfacing and mucosa-interfacing electronics to inspire hardware solutions for developing devices for personalized biosensing from the mucosa.

Actively triggerable materials, which break down upon introduction of an exogenous stimulus, enable precise control over the lifetime of biomedical technologies, as well as adaptation to unforeseen circumstances, such as changes to an established treatment plan. Yet, most actively triggerable materials are low-strength polymers and hydrogels with limited long-term durability. By contrast, metals possess advantageous functional properties, including high mechanical strength and conductivity, that are desirable across several applications within biomedicine. To realize actively triggerable metals, a mechanism called liquid metal embrittlement is leveraged, in which certain liquid metals penetrate the grain boundaries of certain solid metals and cause them to dramatically weaken or disintegrate. In this work, it is demonstrated that eutectic gallium indium (EGaIn), a biocompatible alloy of gallium, can be formulated to reproducibly trigger the breakdown of aluminum within different physiologically relevant environments. The breakdown behavior of aluminum after triggering can further be readily controlled by manipulating its grain structure. Finally, three possible use cases of biomedical devices constructed from actively triggerable metals are demonstrated.

Nearly all micro/nanosystems found in biology have function that is intrinsically enabled by hierarchical, three-dimensional (3D) designs. Compelling opportunities exist in exploiting similar 3D architectures in man-made devices for applications in biomedicine, sensing, energy storage and conversion, electronics and many other areas of advanced technology. Although a lack of practical routes to the required 3D layouts has hindered progress to date, recent advances in mechanically-guided 3D assembly have the potential to provide the required access to wide-ranging structural geometries, across a broad span of length scales, in a way that leverages the most sophisticated materials and design concepts that exist in state-of-the-art 2D microsystems. This review summaries the key concepts and illustrates their use in four major categories of 3D mesostructures: open filamentary frameworks, mixed structures of membranes/filaments (Kirigami-inspired structures), folded constructs (Origami-inspired structures) and overlapping, nested and entangled networks. The content includes not only previously published examples, but also several additional illustrative cases. A collection of 3D starfish-like and jellyfish-like structures with critical dimensions that span nearly a factor of ten million, from one hundred nanometers to nearly one meter, demonstrates the scalability of the process.

Approaches capable of creating three-dimensional (3D) mesostructures in advanced materials (device-grade semiconductors, electroactive polymers etc.) are of increasing interest in modern materials research. A versatile set of approaches exploits transformation of planar precursors into 3D architectures through the action of compressive forces associated with release of prestrain in a supporting elastomer substrate. Although a diverse set of 3D structures can be realized in nearly any class of material in this way, all previously reported demonstrations lack the ability to vary the degree of compression imparted to different regions of the 2D precursor, thus constraining the diversity of 3D geometries. This paper presents a set of ideas in materials and mechanics in which elastomeric substrates with engineered distributions of thickness yield desired strain distributions for targeted control over resultant 3D mesostructures geometries. This approach is compatible with a broad range of advanced functional materials from device-grade semiconductors to commercially available thin films, over length scales from tens of microns to several millimeters. A wide range of 3D structures can be produced in this way, some of which have direct relevance to applications in tunable optics and stretchable electronics.

Abstract 3D structures that incorporate high‐performance electronic materials and allow for remote, on‐demand 3D shape reconfiguration are of interest for applications that range from ingestible medical devices and microrobotics to tunable optoelectronics. Here, materials and design approaches are introduced for assembly of such systems via controlled mechanical buckling of 2D precursors built on shape‐memory polymer (SMP) substrates. The temporary shape fixing and recovery of SMPs, governed by thermomechanical loading, provide deterministic control over the assembly and reconfiguration processes, including a range of mechanical manipulations facilitated by the elastic and highly stretchable properties of the materials. Experimental demonstrations include 3D mesostructures of various geometries and length scales, as well as 3D aquatic platforms that can change trajectories and release small objects on demand. The results create many opportunities for advanced, programmable 3D microsystem technologies.

Engineered bacteria can be leveraged for in situ tumor vaccinations with their tumor-targeting ability and adjuvanticity. Engineering strategies like chemical modification, nanotechnology, and genetic engineering improve their safety and efficacy.

Gastrointestinal (GI) residence systems that integrate functions such as sensing, stimulation, and drug delivery hold promise for intervening in and treating chronic GI conditions. However, extending device retention beyond 24 h remains challenging. In this review, we present current engineering approaches that extend GI retention across various spatiotemporal scales. We then summarize their applications in drug delivery, sensing, and stimulation within the GI tract that benefit from prolonged device residency. Finally, we outline emerging strategies that leverage breakthroughs in materials, mechanics, and robotics to enable the development of next-generation GI residence systems. This review aims to present a future of GI residence systems that enable long-term, autonomous, and closed-loop therapies and are thus indispensable in next-generation healthcare.

Abstract Silver‐graphene nanoribbons (Ag‐GNRs) were prepared from the chemical unzipping of multiwalled carbon nanotubes (MWCNTs) by reaction with Na/K alloy, Ag(O 2 CCH 3 ) and then CH 3 OH. Ag‐GNRs exhibited improved electrocatalytic ability for the oxygen reduction reaction (ORR) in 0.1 M KOH as compared to the underlying GNR substrate alone and displayed an earlier onset and higher currents than a commercial Ag/Carbon (Ag/C) catalyst. The Ag‐GNR hybrid demonstrates an outstanding tolerance to CH 3 OH crossover which exceeds that of the commercial benchmark, 20 % Pt/C.

Development of origami-inspired routes to assembly of three dimensional structures is an area of growing activity in scientific and engineering research communities due to fundamental interest in mathematical topics in topology and to the potential for practical applications in areas ranging from advanced surgical tools to systems for space exploration. Recently reported approaches that exploit the controlled, compressive buckling of 2D precursors induced by dimensional change in an underlying elastomer support offer broad versatility in material selection (from polymers to device grade semiconductors), feature sizes (from centimeters to nanometers), topological forms (open frameworks to closed form polyhedra) and shape controllability (dynamic tuning of shape), thereby establishing a promising avenue to autonomic assembly of complex 3D systems. Localization of origami-like folding deformations at targeted regions can be achieved through the use of engineered, spatial variations in the thicknesses of the 2D precursors. While this approach offers high levels of control in the targeted formation of creases, creating the necessary thickness variations requires a set of additional processing steps in the fabrication. This paper presents an alternative, and complementary, approach that exploits controlled plastic deformation in the precursors, as validated in a comprehensive set of experimental and theoretical studies. Specifically, plasticity and strain localization can be used to dramatically reduce the bending stiffness at targeted regions, to form well-defined creases as mountain or valley folds during the 2D to 3D geometrical transformation process. The content begins with studies of a model system that consists of a 2D precursor in the form of a straight ribbon with reduced widths at certain sections. The results illustrate the important role of plasticity in the course of folding, in such a manner that dictates the final 3D layouts. A broad range of complex 3D shapes, achieved in both the millimeter-scale and the mesoscale structures (i.e. micron to sub-millimeter), demonstrate the power of these ideas.

Microelectromechanical systems remain an area of significant interest in fundamental and applied research due to their wide ranging applications. Most device designs, however, are largely 2D and constrained to only a few simple geometries. Achieving tunable resonant frequencies or broad operational bandwidths requires complex components and/or fabrication processes. The work presented here reports unusual classes of 3D micromechanical systems in the form of vibratory platforms assembled by controlled compressive buckling. Such 3D structures can be fabricated across a broad range of length scales and from various materials, including soft polymers, monocrystalline silicon, and their composites, resulting in a wide scope of achievable resonant frequencies and mechanical behaviors. Platforms designed with multistable mechanical responses and vibrationally decoupled constituent elements offer improved bandwidth and frequency tunability. Furthermore, the resonant frequencies can be controlled through deformations of an underlying elastomeric substrate. Systematic experimental and computational studies include structures with diverse geometries, ranging from tables, cages, rings, ring‐crosses, ring‐disks, two‐floor ribbons, flowers, umbrellas, triple‐cantilever platforms, and asymmetric circular helices, to multilayer constructions. These ideas form the foundations for engineering designs that complement those supported by conventional, micro‐electromechanical systems, with capabilities that could be useful in systems for biosensing, energy harvesting, and others.

The creation of highly effective oral drug delivery systems (ODDSs) has long been the main objective of pharmaceutical research. Multidisciplinary efforts involving materials, electronics, control, and pharmaceutical sciences encourage the development of robot-enabled ODDSs. Compared with conventional rigid robots, soft robots potentially offer better mechanical compliance and biocompatibility with biological tissues, more versatile shape control and maneuverability, and multifunctionality. In this paper, we first describe and highlight the importance of manipulating drug release kinetics, i.e. pharmaceutical kinetics. We then introduce an overview of state-of-the-art soft robot-based ODDSs comprising resident, shape-programming, locomotive, and integrated soft robots. Finally, the challenges and outlook regarding future soft robot-based ODDS development are discussed.

Engineered bacteria are increasingly recognized as sustained and intelligent sources for sensing and therapeutics due to their unique capabilities such as in situ multiplication, tissue targeting, and genetic editability. However, the clinical applications of these living agents are hindered by the ineffective immunoisolation, residency, and removal against the complex and dynamic in vivo environment. Existing approaches focus on surface decoration and encapsulation of engineered bacteria, or "microencapsulation," but there are limits to what can be achieved with modifications of bacteria themselves. An emerging strategy combines millimeter- to centimeter-scale engineered devices and systems with bacteria, or "macroencapsulation," offering unique advantages such as extending the in vivo lifetime and engraftment of bacteria, enhancing immunoisolation, and enabling real-time signal readouts via wireless electronic technologies. In this review, the design rationales for macroencapsulated bacteria toward in vivo applications are discussed, and examples in bacterial devices for transdermal and oral applications are highlighted. Since the gastrointestinal tract represents a major site for engineered bacteria, we also summarize and compare various strategies for synthetic engraftment of orally administered encapsulated bacteria.

Formation of 3D mesostructures in advanced functional materials is of growing interest due to the widespread envisioned applications of devices that exploit 3D architectures. Mechanically guided assembly based on compressive buckling of 2D precursors represents a promising method, with applicability to a diverse set of geometries and materials, including inorganic semiconductors, metals, polymers, and their heterogeneous combinations. This paper introduces ideas that extend the levels of control and the range of 3D layouts that are achievable in this manner. Here, thin, patterned layers with well-defined residual stresses influence the process of 2D to 3D geometric transformation. Systematic studies through combined analytical modeling, numerical simulations, and experimental observations demonstrate the effectiveness of the proposed strategy through ≈20 example cases with a broad range of complex 3D topologies. The results elucidate the ability of these stressed layers to alter the energy landscape associated with the transformation process and, specifically, the energy barriers that separate different stable modes in the final 3D configurations. A demonstration in a mechanically tunable microbalance illustrates the utility of these ideas in a simple structure designed for mass measurement.

Actively multiplexed, flexible electronic devices represent the most sophisticated forms of technology for high-speed, high-resolution spatiotemporal mapping of electrophysiological activity on the surfaces of the brain, heart, and other organ systems. Materials that simultaneously serve as long-lived, defect-free biofluid barriers and sensitive measurement interfaces are essential for chronically stable, high-performance operation. Recent work demonstrates that conductively coupled electrical interfaces of this type can be achieved based on the use of highly doped monocrystalline silicon electrical “via” structures embedded in insulating nanomembranes of thermally grown silica. A limitation of this approach is that dissolution of the silicon in biofluids limits the system lifetimes to 1–2 years, projected based on accelerated testing. Here, we introduce a construct that extends this time scale by more than a factor of 20 through the replacement of doped silicon with a metal silicide alloy (TiSi2). Systematic investigations and reactive diffusion modeling reveal the details associated with the materials science and biofluid stability of this TiSi2/SiO2 interface. An integration scheme that exploits ultrathin, electronic microcomponents manipulated by the techniques of transfer printing yields high-performance active systems with excellent characteristics. The results form the foundations for flexible, biocompatible electronic implants with chronic stability and Faradaic biointerfaces, suitable for a broad range of applications in biomedical research and human healthcare.

Incorporation of elastomers into bioelectronics that reduces the mechanical mismatch between electronics and biological systems could potentially improve the long-term electronics–tissue interface. However, the chronic stability of elastomers in physiological conditions has not been systematically studied. Here, using electrochemical impedance spectrum we find that the electrochemical impedance of dielectric elastomers degrades over time in physiological environments. Both experimental and computational results reveal that this phenomenon is due to the diffusion of ions from the physiological solution into elastomers over time. Their conductivity increases by 6 orders of magnitude up to 10–8 S/m. When the passivated conductors are also composed of intrinsically stretchable materials, higher leakage currents can be detected. Scaling analyses suggest fundamental limitations to the electrical performances of interconnects made of stretchable materials.

Vibrational resonances of microelectromechanical systems (MEMS) can serve as means for assessing physical properties of ultrathin coatings in sensors and analytical platforms. Most such technologies exist in largely two-dimensional configurations with a limited total number of accessible vibration modes and modal displacements, thereby placing constraints on design options and operational capabilities. This study presents a set of concepts in three-dimensional (3D) microscale platforms with vibrational resonances excited by Lorentz-force actuation for purposes of measuring properties of thin-film coatings. Nanoscale films including photodefinable epoxy, cresol novolak resin, and polymer brush with thicknesses as small as 270 nm serve as the test vehicles for demonstrating the advantages of these 3D MEMS for detection of multiple physical properties, such as modulus and density, within a single polymer sample. The stability and reusability of the structure are demonstrated through multiple measurements of polymer samples using a single platform, and via integration with thermal actuators, the temperature-dependent physical properties of polymer films are assessed. Numerical modeling also suggests the potential for characterization of anisotropic mechanical properties in single or multilayer films. The findings establish unusual opportunities for interrogation of the physical properties of polymers through advanced MEMS design.

Glycemic control through titration of insulin dosing remains the mainstay of diabetes mellitus treatment. Insulin therapy is generally divided into dosing with long- and short-acting insulin, where long-acting insulin provides basal coverage and short-acting insulin supports glycemic excursions associated with eating. The dosing of short-acting insulin often involves several steps for the user including blood glucose measurement and integration of potential carbohydrate loads to inform safe and appropriate dosing. The significant burden placed on the user for blood glucose measurement and effective carbohydrate counting can manifest in substantial effects on adherence. Through the application of computer vision, we have developed a smartphone-based system that is able to detect the carbohydrate load of food by simply taking a single image of the food and converting that information into a required insulin dose by incorporating a blood glucose measurement. Moreover, we report the development of comprehensive all-in-one insulin delivery systems that streamline all operations that peripheral devices require for safe insulin administration, which in turn significantly reduces the complexity and time required for titration of insulin. The development of an autonomous system that supports maximum ease and accuracy of insulin dosing will transform our ability to more effectively support patients with diabetes.

Complex 3D organizations of materials represent ubiquitous structural motifs found in the most sophisticated forms of matter, the most notable of which are in life‐sustaining hierarchical structures found in biology, but where simpler examples also exist as dense multilayered constructs in high‐performance electronics. Each class of system evinces specific enabling forms of assembly to establish their functional organization at length scales not dissimilar to tissue‐level constructs. This study describes materials and means of assembly that extend and join these disparate systems—schemes for the functional integration of soft and biological materials with synthetic 3D microscale, open frameworks that can leverage the most advanced forms of multilayer electronic technologies, including device‐grade semiconductors such as monocrystalline silicon. Cellular migration behaviors, temporal dependencies of their growth, and contact guidance cues provided by the nonplanarity of these frameworks illustrate design criteria useful for their functional integration with living matter (e.g., NIH 3T3 fibroblast and primary rat dorsal root ganglion cell cultures).

Shape transformation in three dimensional (3D) structures is of interest in the design of engineered systems capable of accomplishing particular tasks that are unachievable by two dimensional (2D) architectures or static 3D ones. One approach involves the incorporation of stimuli responsive materials into the structural assembly to induce such transformations. In this work, we investigate the transformation of a curved bilayer ribbon supported by a flexible assembly that belongs to a family of complex three dimensional architectures. Through finite element analysis, we identified key design parameters and their effects on the deformation behavior of the assembly when it is subjected to an external stimuli in the form of a mismatch strain. Our results show that the behavior of the curved bilayer in response to the stimuli could be tuned by controlling the structural properties of the assembly. Our calculations also reveal a diverse set of deformation mechanisms including gradual flipping, snapping and creasing of the curved bilayer under specific circumstances. The design principles established in this work could be used to engineer 3D sensors, actuators for traditional and soft robotics, electronic device components, metamaterials, energy storage and harvesting devices with on-demand functional capabilities enabled by 3D transformations.

MicroRNA (miRNA) is demonstrated to be associated with the occurrence and development of various diseases including cancer. Currently, most miRNA detection methods are confined to in vitro detection and cannot obtain information on the temporal and spatial expression of miRNA in relevant tissues and cells. In this work, we established a novel enzyme-free method that can be applied to both in vitro detection and in situ imaging of miRNA by integrating DNAzyme and catalytic hairpin assembly (CHA) circuits. This developed CHA-Amplified DNAzyme miRNA (CHAzymi) detection system can realize the quantitively in vitro detection of miR-146b (the biomarker of papillary thyroid carcinoma, PTC) ranging from 25 fmol to 625 fmol. This strategy has also been successfully applied to in situ imaging of miR-146b both in human PTC cell TPC-1 and clinical samples, showing its capacity as an alternative diagnostic method for PTC. Furthermore, this CHAzymi system can be employed as a versatile sensing platform for various miRNAs by revising the relevant sequences. The results imply that this system may expand the modality of miRNA detection and show promise as a novel diagnostic tool in clinical settings, providing valuable insights for effective treatment and management of the disease.

Ingestible electronics have the capacity to transform our ability to effectively diagnose and potentially treat a broad set of conditions. Current applications could be significantly enhanced by addressing poor electrode-tissue contact, lack of navigation, short dwell time, and limited battery life. Here we report the development of an ingestible, battery-free, and tissue-adhering robotic interface (IngRI) for non-invasive and chronic electrostimulation of the gut, which addresses challenges associated with contact, navigation, retention, and powering (C-N-R-P) faced by existing ingestibles. We show that near-field inductive coupling operating near 13.56 MHz was sufficient to power and modulate the IngRI to deliver therapeutically relevant electrostimulation, which can be further enhanced by a bio-inspired, hydrogel-enabled adhesive interface. In swine models, we demonstrated the electrical interaction of IngRI with the gastric mucosa by recording conductive signaling from the subcutaneous space. We further observed changes in plasma ghrelin levels, the "hunger hormone," while IngRI was activated in vivo, demonstrating its clinical potential in regulating appetite and treating other endocrine conditions. The results of this study suggest that concepts inspired by soft and wireless skin-interfacing electronic devices can be applied to ingestible electronics with potential clinical applications for evaluating and treating gastrointestinal conditions.

Advanced Intelligent SystemsVolume 3, Issue 5 2170047 Back CoverOpen Access Smart Contact Lenses for Biosensing Applications Xin Ma, Xin Ma School of Computer Science and Technology, Tiangong University, Tianjin, 300387 China School of Textile Science and Engineering, Tiangong University, Tianjin, 300387 China Department of Bioengineering, University of California – Los Angeles, Los Angeles, CA, 90095 USASearch for more papers by this authorSamad Ahadian, Corresponding Author Samad Ahadian sahadian@terasaki.org Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorSong Liu, Song Liu School of Computer Science and Technology, Tiangong University, Tianjin, 300387 ChinaSearch for more papers by this authorJingwen Zhang, Jingwen Zhang Faculty of Life Sciences and Medicine, King's College London, London, SE1 0NR UKSearch for more papers by this authorShengnan Liu, Shengnan Liu School of Computer Science and Technology, Tiangong University, Tianjin, 300387 ChinaSearch for more papers by this authorTeng Cao, Teng Cao School of Computer Science and Technology, Tiangong University, Tianjin, 300387 ChinaSearch for more papers by this authorWenbin Lin, Wenbin Lin School of Computer Science and Technology, Tiangong University, Tianjin, 300387 ChinaSearch for more papers by this authorDong Wu, Dong Wu School of Computer Science and Technology, Tiangong University, Tianjin, 300387 ChinaSearch for more papers by this authorNatan Roberto de Barros, Natan Roberto de Barros Bioprocess and Biotechnology Department, São Paulo State University (Unesp), Araraquara, 14801-902 Brazil Institute of Chemistry, São Paulo State University (Unesp), Araraquara, 14800-060 BrazilSearch for more papers by this authorMohammad Reza Zare, Mohammad Reza Zare Department of Chemical Engineering, Shiraz University, Shiraz, 71348 IranSearch for more papers by this authorSibel Emir Diltemiz, Sibel Emir Diltemiz Department of Chemistry, Eskisehir Technical University, Eskisehir, 26470 TurkeySearch for more papers by this authorVadim Jucaud, Vadim Jucaud Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorYangzhi Zhu, Yangzhi Zhu Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorShiming Zhang, Shiming Zhang Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorEthan Banton, Ethan Banton Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorYue Gu, Yue Gu Materials Science and Engineering Program, University of California San Diego, La Jolla, CA, 92093 USA Department of NanoEngineering, University of California San Diego, La Jolla, CA, 92093 USASearch for more papers by this authorKewang Nan, Kewang Nan Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorSheng Xu, Sheng Xu Materials Science and Engineering Program, University of California San Diego, La Jolla, CA, 92093 USA Department of Bioengineering, University of California San Diego, La Jolla, CA, 92093 USA Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, CA, 92093 USASearch for more papers by this authorMehmet Remzi Dokmeci, Mehmet Remzi Dokmeci Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorAli Khademhosseini, Corresponding Author Ali Khademhosseini khademh@terasaki.org orcid.org/0000-0002-2692-1524 Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this author Xin Ma, Xin Ma School of Computer Science and Technology, Tiangong University, Tianjin, 300387 China School of Textile Science and Engineering, Tiangong University, Tianjin, 300387 China Department of Bioengineering, University of California – Los Angeles, Los Angeles, CA, 90095 USASearch for more papers by this authorSamad Ahadian, Corresponding Author Samad Ahadian sahadian@terasaki.org Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorSong Liu, Song Liu School of Computer Science and Technology, Tiangong University, Tianjin, 300387 ChinaSearch for more papers by this authorJingwen Zhang, Jingwen Zhang Faculty of Life Sciences and Medicine, King's College London, London, SE1 0NR UKSearch for more papers by this authorShengnan Liu, Shengnan Liu School of Computer Science and Technology, Tiangong University, Tianjin, 300387 ChinaSearch for more papers by this authorTeng Cao, Teng Cao School of Computer Science and Technology, Tiangong University, Tianjin, 300387 ChinaSearch for more papers by this authorWenbin Lin, Wenbin Lin School of Computer Science and Technology, Tiangong University, Tianjin, 300387 ChinaSearch for more papers by this authorDong Wu, Dong Wu School of Computer Science and Technology, Tiangong University, Tianjin, 300387 ChinaSearch for more papers by this authorNatan Roberto de Barros, Natan Roberto de Barros Bioprocess and Biotechnology Department, São Paulo State University (Unesp), Araraquara, 14801-902 Brazil Institute of Chemistry, São Paulo State University (Unesp), Araraquara, 14800-060 BrazilSearch for more papers by this authorMohammad Reza Zare, Mohammad Reza Zare Department of Chemical Engineering, Shiraz University, Shiraz, 71348 IranSearch for more papers by this authorSibel Emir Diltemiz, Sibel Emir Diltemiz Department of Chemistry, Eskisehir Technical University, Eskisehir, 26470 TurkeySearch for more papers by this authorVadim Jucaud, Vadim Jucaud Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorYangzhi Zhu, Yangzhi Zhu Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorShiming Zhang, Shiming Zhang Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorEthan Banton, Ethan Banton Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorYue Gu, Yue Gu Materials Science and Engineering Program, University of California San Diego, La Jolla, CA, 92093 USA Department of NanoEngineering, University of California San Diego, La Jolla, CA, 92093 USASearch for more papers by this authorKewang Nan, Kewang Nan Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorSheng Xu, Sheng Xu Materials Science and Engineering Program, University of California San Diego, La Jolla, CA, 92093 USA Department of Bioengineering, University of California San Diego, La Jolla, CA, 92093 USA Department of Electrical and Computer Engineering, University of California San Diego, La Jolla, CA, 92093 USASearch for more papers by this authorMehmet Remzi Dokmeci, Mehmet Remzi Dokmeci Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this authorAli Khademhosseini, Corresponding Author Ali Khademhosseini khademh@terasaki.org orcid.org/0000-0002-2692-1524 Terasaki Institute for Biomedical Innovation, Los Angeles, CA, 90024 USASearch for more papers by this author First published: 24 May 2021 https://doi.org/10.1002/aisy.202170047AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Abstract Smart Contact Lenses Smart contact lenses are highly integrated devices with multifunctional capabilities for the diagnosis of eye diseases and the delivery of drugs. In article number 2000263, Samad Ahadian, Ali Khademhosseini, and co-workers present a brief history of the development of contact lenses and the state-of-the-art design and fabrication of smart contact lenses for biomedical applications. Challenges and future opportunities for further applications of smart contact lenses are also discussed. Volume3, Issue5May 20212170047 RelatedInformation

Adv. Funct. Mater. 2016, 26, 2629 Guided Formation of 3D Helical Mesostructures by Mechanical Buckling: Analytical Modeling and Experimental Validation Yuan Liu, Zheng Yan, Qing Lin, Xuelin Guo, Mengdi Han, Kewang Nan, Keh-Chih Hwang, Yonggang Huang, Yihui Zhang,* and John A. Rogers* Adv. Funct. Mater. 2016, 26, 2909 Engineered Elastomer Substrates for Guided Assembly of Complex 3D Mesostructures by Spatially Nonuniform Compressive Buckling Kewang Nan, Haiwen Luan, Zheng Yan, Xin Ning, Yiqi Wang, Ao Wang, Juntong Wang, Mengdi Han, Matthew Chang, Kan Li, Yutong Zhang, Wen Huang, Yeguang Xue, Yonggang Huang, Yihui Zhang,* and John A. Rogers* Adv. Funct. Mater. 2017, 27, 1604281 3D Tunable, Multiscale, and Multistable Vibrational Micro-Platforms Assembled by Compressive Buckling Xin Ning, Heling Wang, Xinge Yu, Julio A. N. T. Soares, Zheng Yan, Kewang Nan, Gabriel Velarde, Yeguang Xue, Rujie Sun, Qiyi Dong, Haiwen Luan, Chan Mi Lee, Aditya Chempakasseril, Mengdi Han, Yiqi Wang, Luming Li, Yonggang Huang, Yihui Zhang,* and John A. Rogers* Adv. Funct. Mater. 2017, 14, 1605914 All four above mentioned manuscripts contain the following funding statement in the acknowledgements section: “Y.H. and J.A.R. acknowledge the support from the NSF (Grant No. CMMI1400169) and the NIH (Grant No. R01EB019337).” The authors wish to correct this funding statement to read as follows: ““Y.H. acknowledges the support from the NSF (Grant No. CMMI1400169) and the NIH (Grant No. R01EB019337).” The authors apologize for any inconvenience or misunderstanding that these errors may have caused.

Millimeter-scale animals such as Caenorhabditis elegans, Drosophila larvae, zebrafish, and bees serve as powerful model organisms in the fields of neurobiology and neuroethology. Various methods exist for recording large-scale electrophysiological signals from these animals. Existing approaches often lack, however, real-time, uninterrupted investigations due to their rigid constructs, geometric constraints, and mechanical mismatch in integration with soft organisms. The recent research establishes the foundations for 3-dimensional flexible bioelectronic interfaces that incorporate microfabricated components and nanoelectronic function with adjustable mechanical properties and multidimensional variability, offering unique capabilities for chronic, stable interrogation and stimulation of millimeter-scale animals and miniature tissue constructs. This review summarizes the most advanced technologies for electrophysiological studies, based on methods of 3-dimensional flexible bioelectronics. A concluding section addresses the challenges of these devices in achieving freestanding, robust, and multifunctional biointerfaces.

Ingestible electronics are promising platforms for on-demand health monitoring and drug delivery. However, these devices and their actuators must operate in the gastrointestinal (GI) environment, which has a pH range of 1 to 8. Drug delivery systems using electrochemical dissolution of metal films are particularly susceptible to pH changes. Optimal operation in this dynamic environment stands to transform our capacity to help patients across a range of conditions. Here we present an energy-efficient ingestible electronic electrochemical drug delivery system to support subjects through operation in this dynamic environment. The proposed system consists of a drug reservoir sealed with an electrochemically dissolvable gold membrane and an electronic subsystem. An electronic subsystem controls the rate of gold dissolution by sensing and adapting to the pH of the GI environment and provides an option for energy-efficient drug delivery, reducing energy consumption by up to 42.8 %. Integrating the electronics with electrochemical drug delivery enables the proposed system to adapt to the dynamic physiological environments which makes it suitable for drug and/or therapeutic delivery at different locations in the GI tract.

Abstract Establishing a robust and intimate mucosal interface that allows medical devices to remain within lumen-confined organs for extended periods has valuable applications, particularly for gastrointestinal (GI) theranostics. Here, we report the development of e-GLUE , an e lectroadhesive hydro g e l interface for robust and prolonged m u cosal r e tention following electrical activation. Notably, this novel mucosal adhesion mechanism can increase the adhesion energy of hydrogels on the mucosa by up to 30-fold and enable in vivo GI retention of e-GLUE devices for up to 30 days. Strong mucosal adhesion occurs within one minute of electrical activation, despite the presence of luminal fluid, mucus exposure, and organ motility, thereby ensuring compatibility with complex in vivo environments. In swine studies, we demonstrate the utility of e-GLUE for mucosal hemostasis, sustained local delivery of therapeutics, and intimate biosensing in the GI tract. This system can enable improved treatments for various health conditions, including gastrointestinal bleeding, inflammatory bowel disease, and diagnostic applications in the GI tract and beyond.

In article number 1700068, John A. Rogers, Ralph G. Nuzzo, and co-workers present direct ink write (DIW)-assisted integration of soft and cellular materials onto compressively buckled microframeworks that are constructed using polymer or high performance silicon semiconductor membranes. These scaffolds provide unique 3D environments upon which to study cellular migration and hydrogel integration. The cover was designed by Joselle M. McCracken.

ABSTRACT Tissue-wide electrophysiology with single-cell and millisecond spatiotemporal resolution is critical for heart and brain studies, yet issues arise from invasive, localized implantation of electronics that destructs the well-connected cellular networks within matured organs. Here, we report the creation of cyborg organoids: the three-dimensional (3D) assembly of soft, stretchable mesh nanoelectronics across the entire organoid by cell-cell attraction forces from 2D-to-3D tissue reconfiguration during organogenesis. We demonstrate that stretchable mesh nanoelectronics can grow into and migrate with the initial 2D cell layers to form the 3D structure with minimal interruptions to tissue growth and differentiation. The intimate contact of nanoelectronics to cells enables us to chronically and systematically observe the evolution, propagation and synchronization of the bursting dynamics in human cardiac organoids through their entire organogenesis.

On page 2629, Y. Zhang, J. A. Rogers, and co-workers introduce an approach that exploits controlled mechanical buckling for reversible, autonomic origami assembly of 3D structures across material classes from soft polymers to brittle inorganic semiconductors, and length scales from nanometers to centimeters. This approach provides access to 3D architectures with a broad range of topologies.

This chapter focuses on semiconductor nanomembranes (NMs) in general, and silicon NMs in particular, as a class of electronic material for devices that can bend, fold, and stretch without significant change in properties. The content begins with procedures for creating such materials, and for manipulating them using the techniques of transfer printing. Compressive buckling of NMs on elastomeric supports creates composite structures that can accommodate large strain deformations with reversible responses and without fracture. Examples of applications based on these ideas range from water-soluble, “transient” electronics to unusual optoelectronic systems for biointegration or for bio-inspired engineering. The results foreshadow a future for electronic devices that offer characteristics and features radically different from those that exist today.

The Martlets Society (www.martlets-society.com) is an independent non-profit organization found and run by young scholars. It aims to build a free and equal community for young scholars to build connections and have interdisciplinary exchanges. It currently holds talks and events with diverse topics to show young scholars the world of academia and beyond. It is also planning more events for the equality in education and academia. The Martlets Society (www.martlets-society.com) is an independent non-profit organization found and run by young scholars. It aims to build a free and equal community for young scholars to build connections and have interdisciplinary exchanges. It currently holds talks and events with diverse topics to show young scholars the world of academia and beyond. It is also planning more events for the equality in education and academia.