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Epidermal electronics utilize deformable devices that are seamlessly integrated into the body for various cutting‐edge applications. Stretchable conductors are essential for creating electrodes in these devices, allowing them to interface with the skin for sensing and stimulation. Despite considerable progress in improved deformability, these conductors may not easily adhere to the skin for long‐term use. There is a growing interest in imparting self‐adhesive properties to epidermal devices to ensure secure integration with the body. This article focuses on the emerging field of stretchable and self‐adhesive conductors. It explores the design strategy required to enable stretchability and conformability in these materials and discusses their pivotal applications in smart epidermal electronics. Additionally, this article also addresses the current challenges and future directions in this dynamic area of research. [ABSTRACT FROM AUTHOR]

In recent years, skin-mounted devices have gained prominence in personal wellness and remote patient care. However, the rigid components of many wearables often cause discomfort due to their mechanical mismatch with the skin. To address this, we extend the use of the solderable stretchable sensing system (S4) to develop a wireless skin temperature-sensing smart adhesive. This work introduces two novel types of progress in wearables: the first demonstration of Bluetooth-integration and development of a thin-film-based stretchable inverted-F antenna (SIFA). Characterized through RF simulations, vector network analysis under deformation, and anechoic chamber tests, SIFA demonstrated potential as a low-profile, on-body Bluetooth antenna with a resonant frequency of 2.45 GHz that helps S4 retain its thin overall profile. The final S4 system achieved high correlation (R = 0.95, p < 0.001, mean standard error = 0.04 °C) with commercial sensors during daily activities. These findings suggest that S4-based smart adhesives integrated with SIFAs could offer a promising platform for comfortable, efficient, and functional skin-integrated wearables, supporting a range of health monitoring applications. [ABSTRACT FROM AUTHOR]

Recent advancements in artificial intelligence (AI) technologies, particularly machine learning (ML) techniques, have opened up a promising frontier in the development of intelligent soft bioelectronics, demonstrating unparalleled performance in interfacing with the human body. Hydrogels, owing to their unique combination of biocompatibility, tunable mechanical properties, and high water content, have emerged as a versatile platform for constructing soft bioelectronic devices. Functionalized hydrogels, such as conductive hydrogels, can efficiently capture biosignals from various target tissues while seamlessly forming conformal and reliable interfaces. They can also function as an intermediary layer between biological tissues and soft bioelectronics for diagnosis and therapy purposes. Meanwhile, ML has demonstrated its efficacy in processing extensive datasets collected from the bioelectronics. The convergence of hydrogel‐based soft bioelectronics and ML has unlocked a myriad of possibilities in unprecedented diagnostics, therapeutics, and beyond. In this review, the latest advances in hydrogel‐based soft bioelectronics are introduced. After briefly describing the materials and device strategies for high‐performance hydrogel bioelectronics, how ML can be integrated to augment the functionalities is discussed. Recent examples of ML‐integrated hydrogel bioelectronics are then discussed. Finally, the review is concluded by introducing future potential applications of AI in hydrogel‐based bioelectronics, alongside inherent challenges in this interdisciplinary domain. [ABSTRACT FROM AUTHOR]

Metasurfaces have recently gained significant attention due to the strong capacity in light field manipulation. However, most traditional metasurfaces are fabricated on rigid substrates, which fix their functionality after fabrication and limit their applications in dynamic measurement fields. In this work, we designed and fabricated a silver metasurface embedded in a stretchable substrate for sensing applications. This metasurface can generate different point cloud patterns under varying stretch ratios when illuminated by a laser beam. By collecting and analyzing the patterns, we can precisely reconstruct the deformation of the metasurface. Furthermore, the sample exhibits excellent performance under incident light of various wavelengths. These results pave the way for developing microdevices with novel capabilities based on flexible metamaterials. [ABSTRACT FROM AUTHOR]

Motion is vital for life. Currently, the clinical assessment of motion abnormalities is largely qualitative. We previously developed methods to quantitatively assess motion using visual detection systems (around-body) and stretchable electronic sensors (on-body). Here we compare the efficacy of these methods across predefined motions, hypothesizing that the around-body system detects motion with similar accuracy as on-body sensors. Six human volunteers performed six defined motions covering three excursion lengths, small, medium, and large, which were analyzed via both around-body visual marker detection (MoCa version 1.0) and on-body stretchable electronic sensors (BioStamp version 1.0). Data from each system was compared as to the extent of trackability and comparative efficacy between systems. Both systems successfully detected motions, allowing quantitative analysis. Angular displacement between systems had the highest agreement efficiency for the bicep curl and body lean motion, with 73.24% and 65.35%, respectively. The finger pinch motion had an agreement efficiency of 36.71% and chest abduction/adduction had 45.55%. Shoulder abduction/adduction and shoulder flexion/extension motions had the lowest agreement efficiencies with 24.49% and 26.28%, respectively. MoCa was comparable to BioStamp in terms of angular displacement, though velocity and linear speed output could benefit from additional processing. Our findings demonstrate comparable efficacy for non-contact motion detection to that of on-body sensor detection, and offers insight as to the best system selection for specific clinical uses based on the use-case of the desired motion being analyzed. [ABSTRACT FROM AUTHOR]

The island‐bridge structural design is a common strategy for imparting stretchability to flexible electronic devices. In this structure, the low modulus regions bear most of the deformation, while the rigid islands, which house the electronic components, undergo minimal deformation. However, due to the modulus differences that can be several times or even several orders of magnitude larger, severe strain concentration occur at the edges of the rigid islands in high modulus regions. This strain concentration caused by rigid constraints not only reduces the stretchability of the soft substrate but also degrades the mechanical performance of the interconnected structures, thereby significantly affecting the overall stability of the device. Starting from finite element simulations, this paper introduces modulus gradient regions and optimizes geometric parameters, significantly alleviating the strain concentration at the edges of the rigid islands. Serpentine‐shaped circuits are then transferred to a substrate with strain isolation, which demonstrates better stretchability stability under 20% elongation compared to traditional strain isolation strategies. In addition, the stretchable light emitting diode (LED) system with gradient modulus has better stretchability compared to the system with conventional strategy. This suggests that this strategy has great potential in maintaining the stability of stretchable systems. [ABSTRACT FROM AUTHOR]

Inorganic semiconductor‐based nano/micro‐membranes are of great interest and can be used as active materials for high‐performance and flexible electronics, due to their unique and stable physical or chemical properties. However, the creation of high‐quality and single‐crystalline semiconducting membranes, particularly germanium (Ge) membranes, remains a significant challenge. In this study, a wet etching approach is developed to thin bulk Ge into soft Ge membranes, which are further used to fabricate flexible and stretchable photodetectors. The thickness of the obtained Ge membranes can be precisely controlled, with a minimum thickness of ≈1.6 µm. Investigations on the surface morphology, surface chemical composition, and Raman shifts indicate that the prepared Ge membranes are single‐crystalline and suitable for the following device fabrication. As an example, flexible and stretchable Ge photodetectors, of which the stretchability is realized by a meshed‐structure design, are demonstrated. Bending (with a minimum radius of 4 mm and a bending cycle of 10 000 times) and stretching (with a stretching strain of up to 10%) tests result in negligible variations in the device performance, revealing good flexibility, and stretchability, as well as the significant potentials of the prepared Ge membranes as candidates for flexible electronics. [ABSTRACT FROM AUTHOR]

Skin‐like optoelectronic devices have progressed in leaps and bounds, permitting considerable applications such as remote medical diagnosis, optical communication, biometric authentication, and 3D vision imaging. However, achieving extendable imaging in such frontier detectors poses a formidable challenge for stretchable electronic materials and remains largely unexplored. Herein, an ultrasensitive intrinsically stretchable organic photodiode is configured by the spatially modularizable‐assembled elastic photoactive film for faint near‐infrared light detection and extendable imaging. The performance metrics of the stretchable organic photodiodes rival that of commercial photodetectors, including high specific detectivity (D*noise) over 1012 Jones at 850 nm, ultralow noise current of 4.1 × 10−15 A Hz−1/2 and high stretchability up to 100%. Furthermore, it is the first time to simultaneously achieve the extendable near‐infrared cryptographic imaging and stable photoplethysmography signal detection based on stretchable photodiodes. These results signify a significant advancement toward enabling practical scenarios for stretchable organic optoelectronics. [ABSTRACT FROM AUTHOR]

Autonomously self‐healing, reversible, and soft adhesive microarchitectures and structured electric elements could be important features in stable and versatile bioelectronic devices adhere to complex surfaces of the human body (rough, dry, wet, and vulnerable). In this study, we propose an autonomous self‐healing multi‐layered adhesive patch inspired by the octopus, which possess self‐healing and robust adhesion properties in dry/underwater conditions. To implement autonomously self‐healing octopus‐inspired architectures, a dynamic polymer reflow model based on structural and material design suggests criteria for three‐dimensional patterning self‐healing elastomers. In addition, self‐healing multi‐layered microstructures with different moduli endows efficient self‐healing ability, human‐friendly reversible bio‐adhesion, and stable mechanical deformability. Through programmed molecular behavior of microlevel hybrid multiscale architectures, the bioinspired adhesive patch exhibited robust adhesion against rough skin surface under both dry and underwater conditions while enabling autonomous adhesion restoring performance after damaged (over 95% healing efficiency under both conditions for 24 h at 30°C). Finally, we developed a self‐healing skin‐mountable adhesive electronics with repeated attachment and minimal skin irritation by laminating thin gold electrodes on octopus‐like structures. Based on the robust adhesion and intimate contact with skin, we successfully obtained reliable measurements during dynamic motion under dry, wet, and damaged conditions. [ABSTRACT FROM AUTHOR]

As continuous wearable physiological monitoring systems become more ubiquitous in healthcare, there is an increasing need for power sources that can sustainably power wireless sensors and electronics for long durations. Wearable energy harvesting with thermoelectric generators (TEGs), in which body heat is converted to electrical energy, presents a promising way to prolong wireless operation and address battery life concerns. In this work, high performance TEGs are introduced that combine 3D printed elastomers with liquid metal epoxy polymer composites and thermoelectric semiconductors to achieve elastic compliance and mechanical compatibility with the body. The thermoelectric properties are characterized in both energy harvesting (Seebeck) and active heating/cooling (Peltier) modes, and examine the performance of wearable energy harvesting under various conditions such as sitting, walking, and running. When worn on a user's forearm while walking outside, the TEG arrays are able to power circuitry to collect photoplethysmography (PPG) waveform data with a photonic sensor and wirelessly transmit the data to an external PC using an on‐board Bluetooth Low Energy (BLE) radio. This represents a significant step forward on the path to sustainable body‐worn smart electronics. [ABSTRACT FROM AUTHOR]

Advancements in biomedical research have spurred the development of stretchable electronic devices. While soft insulators are readily available, soft conductors with metal‐like electrical conductivity are rare. Gallium and its alloys, being nontoxic and intrinsically stretchable, are potentially ideal solutions. However, current additive liquid metal (LM) patterning methods face limitations in achieving high‐throughput, high‐resolution, and high‐density LM wiring. Here, a subtractive LM patterning method is developed to meet all these requirements simultaneously. The innovative method involves parallel filling a single continuous microfluidic mesh network with LM that short‐circuits all the pins and pads of a circuit, followed by parallel cutting of the unwanted short‐circuited interconnections using hydrochloric acid (HCl) vapor. Cutting locations are pre‐defined by designing narrower intersecting channels, leveraging capillary force for precise filling and cutting. The process is characterized using a multidimensional parametric study with varying LM line widths and HCl concentrations, and in situ impedance measurements to assess insulation performance. To showcase its high‐throughput capabilities, a mock circuit is used to successfully generate complex LM interconnects that connected hundreds of electrical pads. Finally, a stretchable LM circuit with a micro‐LED array is fabricated to demonstrate the practical application of this technology for massively parallel wiring in stretchable electronics. [ABSTRACT FROM AUTHOR]

Stretchable organic photovoltaics (OPVs) are pivotal for advancing conformable electronics, yet achieving both efficient and intrinsically stretchable OPVs remains a significant challenge. The main issue is maintaining electronic and mechanical properties under deformation. Here, a ternary blend system, PTzBI‐oF:PYIT:EVA is presented, incorporating ethylene‐vinyl acetate (EVA) to establish a conjugated and elastomeric dual‐network morphology. The elastomer network dissipates applied stress, preserving the crystalline packing of the conjugated network and enabling improved mechanical stability of charge carrier generation and transport. Specifically, with 15% EVA content, the ternary blend achieved a power conversion efficiency (PCE) of 15.28% in rigid devices and exhibited a crack onset strain of 17.23%. Notably, the stretchable OPVs retained over 80% of their initial PCE under 30% strain. These findings underscore the potential of conjugated and elastomeric dual‐network morphology in developing high‐performance stretchable electronics for various applications. [ABSTRACT FROM AUTHOR]

The roll‐to‐roll (R2R) process for fabricating elastic substrates is essential for the social implementation of next‐generation stretchable devices with soft interfaces. In recent years, there is a growing demand for soft heterostructures with multiple monolithically patterned organic materials. However, a continuous processing technique for substrates with heterostructures patterned using highly stretchable wiring has not yet been developed. Conventional manufacturing methods for stretchable electronics lack production capacity. This study introduces an R2R‐based method for the continuous production of multilayered substrates composed of various elastic materials, integrated with liquid metal (LM) wiring, suitable for stretchable electronics. Continuous fabrication of polymer films is achieved with pattern areas as small as 0.78 mm2, using three different polymers varying in hardness. The R2R coating process, paired with liquid metal wiring dispensing printing, allows for the creation of lines as fine as 140 microns. This process supports the batch production of 15 stretchable hybrid devices at a time and enables the creation of large‐area devices up to 400 cm2. The fabrication technique developed herein holds promise for the future manufacturing of not only stretchable electronics but also cutting‐edge soft electronics like smart packaging. This is expected to be a factor leading to the commercialization of stretchable electronics. [ABSTRACT FROM AUTHOR]

The rapid development of stretchable electronics made by circuits, microchips, and encapsulation elastomers has caused the production of a large amount of electronic waste (e‐waste). The degradation of elastomers can highly minimize the negative effects of e‐wastes. However, chemicals that included acid, alkali, and organics were repeatedly used during the recycling process, which were environmentally unfriendly. Here, a water‐modulation‐degradation‐reconstruction (WDR) polyvinylpyrrolidone (PVP)‐honey composite (PHC) polymer‐gel was developed and could be regarded as encapsulation elastomers to realize a fully recyclable water‐degradable stretchable (WS) electronics with multi‐functions. The stretchability of the PHC polymer‐gel could be modulated by the change of its water retention. The Chip‐integrated liquid metal (LM) circuits encapsulated with the modulated PHC encapsulation elastomer could withstand a strain value of ~3000%. Moreover, we developed a WS biomedical sensor composed of PHC encapsulation elastomer, LM circuits, and microchips, which could be fully recycled by biodegrading it in water to reconstruct a new one. As before, the reconstructed WS biomedical sensor could still simultaneously realize the combination of ultra‐stretchability, recycling, self‐healing, self‐adhesive, and self‐conformal abilities. The results revealed that this study exercises a profound influence on the rational design of multi‐functional WS electronics. [ABSTRACT FROM AUTHOR]

In this paper, we present an optimization of the planar manufacturing scheme for stretch-free, shape-induced metal interconnects to simplify fabrication with the aim of maximizing the flexibility in a structure regarding stress and strain. The formation of trenches between silicon islands is actively used in the lithographic process to create arc shape structures by spin coating resists into the trenches. The resulting resist form is used as a template for the metal lines, which are structured on top. Because this arc shape is beneficial for the flexibility of these bridges. The trench depth as a key parameter for the stress distribution is investigated by applying numerical simulations. The simulated results show that the increase in penetration depth of the metal bridge into the trench increases the tensile load which is converted into a shear force Q(x), that usually leads to increased strains the structure can generate. For the fabrication, the filling of the trenches with resists is optimized by varying the spin speed. Compared to theoretical resistance, the current–voltage measurements of the metal bridges show a similar behavior and almost every structural variation is capable of functioning as a flexible electrical interconnect in a complete island-bridge array. [ABSTRACT FROM AUTHOR]

Current stretchable conductors, often composed of elastomeric composites infused with rigid conductive fillers, suffer from limited stretchability and durability, and declined conductivity with stretching. These limitations hinder their potential applications as essential components such as interconnects, sensors, and actuators in stretchable electronics and soft machines. In this context, an innovative elastomeric composite that incorporates a 3D network of liquid metal (LM), offering exceptional stretchability, durability, and conductivity, is introduced. The mechanics model elucidates how the interconnected 3DLM architecture imparts softness and stretchability to the composites, allowing them to withstand tensile strains of up to 500% without rupture. The relatively low surface‐to‐volume ratio of the 3DLM network limits the reforming of the oxide layer during cyclic stretch, thereby contributing to low permanent strain and enhanced durability. Additionally, the 3D architecture facilitates crack blunting and stress delocalization, elevating fracture resistance, while simultaneously establishing continuous conductive pathways that result in high conductivity. Notably, the conductivity of the 3DLM composite increases with strain during substantial stretching, highlighting its strain‐enhanced conductivity. In comparison to other LM‐based composites featuring 0D LM droplets, the 3DLM composite stands out with superior properties. [ABSTRACT FROM AUTHOR]

Liquid metal composites are promising soft conductors for applications in soft electronics, sensors, and soft robotics. Existing liquid metal composites usually have a high‐volume fraction of liquid metal, which not only increases the density but also the material cost. Future applications in soft electronics and robotics highly demand liquid metal composites with low density and high conductivity for large‐scale, low‐cost, lightweight, and more sustainable applications. In this work, lightweight and highly conductive composites embedded with liquid metal fiber networks are synthesized. This new paradigm of liquid metal composites consists of an interconnected liquid metal fiber network embedded in a compliant rubber matrix. The liquid metal fiber network serves as an ultra‐lightweight conductive pathway for electrons. Experiments indicate that this soft conductive composite also possesses nearly strain‐insensitive conductance and superior cyclic stability. Potential applications of the composite films as stretchable interconnects, electrodes, and sensors are demonstrated. [ABSTRACT FROM AUTHOR]

Stretchable electronic fibers are essential for soft electronics because of their small footprint, light weight, high compliance, and ease of integration. To date, the majority of stretchable electronic fibers are fabricated with solidly filled fiber substrates where the exchange of gas or liquid between the outer environment and the inner part of the fiber is largely inhibited, if not impossible. The nonpermeability largely wastes the inner volume of the fiber, especially for those sensor fibers. Here, a continuous fabrication of permeable and super‐stretchable liquid metal fibers for constructing high‐integration‐density and multifunctional electronic fibers are reported. The electronic fiber is comprised of self‐assembled porous elastomer fibers and multilayers of coaxially arranged liquid metal circuits patterned in the three‐dimensional space of the fiber matrix. The micron‐scale porous structure of the fiber matrix enables high permeability for effective materials/energy exchange between the surrounding environment and the components in different layers of the fiber. As a proof of concept, a stretchable multifunctional electronic fiber incorporated with three individual layers responsible for lighting, data transmission, and biochemical sensing, as well as an artificial neuron integrating multi‐modal sensing and electrical signal transmission capabilities, illustrating the potential of the fiber fabrication strategy for stretchable electronics applications is demonstrated. [ABSTRACT FROM AUTHOR]

Stretchable electronics have found widespread applications in various fields such as wearable electronics, soft robots, and bioelectronics. As an important promising alternative of traditional rigid conductors, liquid metals have demonstrated immense potential to provide high conductivity and stretchability for the stretchable electronic systems. However, limited by their fluidity and high surface tension, challenges remain in achieving liquid metal patterns with low-cost, high-precision, large-scale, and complex geometry. Here, a fabrication technique was proposed based on laser-induced graphene (LIG) stamps to enable liquid metal self-selectively adhere to substrates. Liquid metal patterns could thus be achieved in different designed geometries and could be transferred onto stretchable substrates. The liquid metal patterns exhibit exceptional electrical conductivity (3.24 × 106 S/m even under 1000% strain), high stretchability (1000% strain, maximum of 2500%), small resistance changes under significant deformations (with a quality factor of 62.5 under 1000% strain), and high resolution (down to 50 µm). Utilizing the patterned liquid metals, a stretchable integrated multifunctional optoelectronic system was demonstrated, encompassing a stretchable display matrix, a pressure sensor array, a wireless powering coil, and cardiovascular sensors, which further highlight the remarkable application potential of liquid metals in optoelectronic user-interaction and advanced physiological monitoring. [ABSTRACT FROM AUTHOR]

Integrating liquid metal (LM) particles into compliant polymers presents an innovative approach for developing intelligent and adaptable systems in stretchable electronics, wearable devices, soft robotics, and other emerging technologies. However, the inherent electrically insulative nature of these solid‐liquid composites, compounded by the gallium oxide shell surrounding LM droplets, poses a significant challenge in establishing conductive pathways, especially for small droplet sizes and ultrasoft elastomers. Here, an interface modification approach that addresses this bottleneck and enables the synthesis of highly stretchable and printable composites with LM microparticles (<2 µm) is presented. Polyvinylpyrrolidone (PVP) is used to functionalize these small LM inclusions, weakening the particle‐matrix interface, and facilitating the formation of a conductive percolating network under tensile strain. Optimized synthesis parameters result in printed conductive traces with excellent electrical conductivity (0.2 Ω cm−1), ultra‐high elongation at break (>900% strain), and minimal resistance change (≈131%). Furthermore, this comprehensive study of the electromechanical response of these stretchable conductors under various strain rates reveals their exceptional stability under dynamic loading conditions, surpassing the performance of conductive traces composed of sprayed liquid metal. Finally, the potential application of these multifunctional materials in stretchable circuitry, addressing the demand for high stretchability and stability in wearable electronics, is demonstrated. [ABSTRACT FROM AUTHOR]

Stretchable electronics have experienced remarkable progress, especially in sensors and wireless communication systems, attributed to their ability to conformably contact with rough or uneven surfaces. However, the development of complex, multifunctional, and high‐precision stretchable electronics faces substantial challenges, including instability at rigid‐soft interfaces and incompatibility with traditional high‐precision patterning technologies. Metallized electrospun nanofibers emerge as a promising conductive filler, offering exceptional stretchability, electrical conductivity, transparency, and compatibility with existing patterning technologies. Here, this review focuses on the fundamental properties, preparation processes, patterning technologies, and application scenarios of conductive stretchable composites based on metallized nanofibers. Initially, it introduces the fabrication processes of metallized electrospun nanofibers and their advantages over alternative materials. It then highlights recent progress in patterning technologies, including collector collection, vapor deposition with masks, and lithography, emphasizing their role in enhancing precision and integration. Furthermore, the review shows the broad applicability and potential influence of metallized electrospun nanofibers in various fields through their use in sensors, wireless systems, semiconductor devices, and intelligent healthcare solutions. Ultimately, this review seeks to spark further innovation and address the prevailing challenges in stretchable electronics, paving the way for future breakthroughs in this dynamic field. [ABSTRACT FROM AUTHOR]

The concept of polyrotaxane comes from the rotaxane structure in the supramolecular field. It is a mechanically interlocked supramolecular assembly composed of linear polymer chains and cyclic molecules. Over recent decades, the synthesis and application of polyrotaxanes have seen remarkable growth. Particularly, cyclodextrin‐based polyrotaxanes have been extensively reported due to the low‐price raw materials, good biocompatibility, and ease of modification. Hence, it is also one of the most promising mechanically interlocking supramolecules for wide industrialization in the future. Polyrotaxanes are widely introduced into materials such as elastomers, hydrogels, and engineering polymers to improve their mechanical properties or impart functionality to the materials. In these materials, polyrotaxane acts as a slidable cross‐linker to dissipate energy through sliding or assist in dispersing stress concentration in the cross‐linked network, thereby enhancing the toughness of the materials. Further, the unique sliding‐ring effect of cyclodextrin‐based polyrotaxanes has pioneered advancements in stretchable electronics and energy storage materials. This includes their innovative use in stretchable conductive composite and binders for anodes, addressing critical challenges in these fields. In this mini‐review, our focus is to highlight the current progress and potential wider applications in the future, underlining their transformative impact across various domains of material science. [ABSTRACT FROM AUTHOR]

Abstract Autonomously self‐healing, reversible, and soft adhesive microarchitectures and structured electric elements could be important features in stable and versatile bioelectronic devices adhere to complex surfaces of the human body (rough, dry, wet, and vulnerable). In this study, we propose an autonomous self‐healing multi‐layered adhesive patch inspired by the octopus, which possess self‐healing and robust adhesion properties in dry/underwater conditions. To implement autonomously self‐healing octopus‐inspired architectures, a dynamic polymer reflow model based on structural and material design suggests criteria for three‐dimensional patterning self‐healing elastomers. In addition, self‐healing multi‐layered microstructures with different moduli endows efficient self‐healing ability, human‐friendly reversible bio‐adhesion, and stable mechanical deformability. Through programmed molecular behavior of microlevel hybrid multiscale architectures, the bioinspired adhesive patch exhibited robust adhesion against rough skin surface under both dry and underwater conditions while enabling autonomous adhesion restoring performance after damaged (over 95% healing efficiency under both conditions for 24 h at 30°C). Finally, we developed a self‐healing skin‐mountable adhesive electronics with repeated attachment and minimal skin irritation by laminating thin gold electrodes on octopus‐like structures. Based on the robust adhesion and intimate contact with skin, we successfully obtained reliable measurements during dynamic motion under dry, wet, and damaged conditions.

Abstract Because of the weak interfacial bonding between the substrates and active materials, most stretchable electronics often face the problem of performance destabilization and functional failure, especially under large strains. Herein, a super‐elastic, high conductive and core‐shell nanofibrous helix based on polyurethane (PU), silk fibroin (SF) and liquid metal (LM) is fabricated. Compared with traditional membrane, that the LM@PU/SF fibrous helix shows a wider range of workable strain (1500%) and reversible elasticity (600%) accompany with high conductivity is found. SF is acted as “glue” to strengthen the interfacial bonding between the PU and LM. The good elasticity of the helical structure and PU polymer as well as the fluidity of LM improve the stretchability, reversible elasticity and conductivity of the fibrous helix conductor. Furthermore, an alarming and monitoring apparatus using LM@PU/SF helix as the conductive unit based on multiscale fracture is engineered. This composite nanofibrous helix with ultra‐high conductivity and elasticity, making it a promising candidate for stretchable electronic devices.

Abstract Inorganic semiconductor‐based nano/micro‐membranes are of great interest and can be used as active materials for high‐performance and flexible electronics, due to their unique and stable physical or chemical properties. However, the creation of high‐quality and single‐crystalline semiconducting membranes, particularly germanium (Ge) membranes, remains a significant challenge. In this study, a wet etching approach is developed to thin bulk Ge into soft Ge membranes, which are further used to fabricate flexible and stretchable photodetectors. The thickness of the obtained Ge membranes can be precisely controlled, with a minimum thickness of ≈1.6 µm. Investigations on the surface morphology, surface chemical composition, and Raman shifts indicate that the prepared Ge membranes are single‐crystalline and suitable for the following device fabrication. As an example, flexible and stretchable Ge photodetectors, of which the stretchability is realized by a meshed‐structure design, are demonstrated. Bending (with a minimum radius of 4 mm and a bending cycle of 10 000 times) and stretching (with a stretching strain of up to 10%) tests result in negligible variations in the device performance, revealing good flexibility, and stretchability, as well as the significant potentials of the prepared Ge membranes as candidates for flexible electronics.

Mechanically flexible and stretchable inductive coils are critical for enabling communication, sensing, and wireless power transfer capabilities in wearable electronics that conform to the body for healthcare and Internet of Things (IoT) applications. Leading stretchable conductors such as liquid metals (LMs) offer conformability but sacrifice electromagnetic performance compared with Cu wires, leading to lossy radio‐frequency (RF) characteristics. Here, a strategy leveraging multistranded 3D woven 'litz' transmission lines is presented to amplify the resonant RF performance of LM inductors. Through comprehensive simulations and experiments, it is discovered that interwoven LM litz wires boost the Quality Factor (Q) by 80% compared to standard liquid metal wires. A fabrication methodology is also demonstrated for stretchable coils that retain high Q (>30), outperforming the previously reported LM coils and maintaining 98% of their wireless transmission efficiency under up to 30% biaxial strain. Moreover, the versatility of this approach is showcased by 3D printing four‐terminal 'choke' inductors optimized for RF filtering and inductance tunability, overcoming the fabrication limitations of traditional planar printed electronics. These results offer valuable insights into the design and implementation of 3D‐printed inductors for a diverse suite of electromagnetic device applications. [ABSTRACT FROM AUTHOR]

This article demonstrates scalable production of liquid metal (LM)-based microwires through the thermal drawing of extrudates. These extrudates were first co-extruded using a eutectic alloy of gallium and indium (EGaIn) as a core element and a thermoplastic elastomer, styrene–ethylene/butylene–styrene (SEBS), as a shell material. By varying the feed speed of the co-extruded materials and the drawing speed of the extrudate, it was possible to control the dimensions of the microwires, such as core diameter and shell thickness. How the extrusion temperature affects the dimensions of the microwire was also analyzed. The smallest microwire (core diameter: 52 ± 14 μm and shell thickness: 46 ± 10 μm) was produced from a drawing speed of 300.1 mm s−1 (the maximum attainable speed of the apparatus used), SEBS extrusion speed of 1.50 mm3 s−1, and LM injection rate of 5 × 105 μL s−1 at 190 °C extrusion temperature. The same extrusion condition without thermal drawing generated significantly large extrudates with a core diameter of 278 ± 26 μm and shell thickness of 430 ± 51 μm. The electrical properties of the microwires were also characterized under different degrees of stretching and wire kinking deformation which proved that these LM-based microwires change electrical resistance as they are deformed and fully self-heal once the load is removed. Finally, the sewability of these microwires was qualitatively tested by using a manual sewing machine to pattern microwires on a traditional cotton fabric. [ABSTRACT FROM AUTHOR]

Stretchable displays represent a cutting‐edge technology for creating novel freeform deformable displays. In this study, we developed a highly stretchable liquid metal‐based stretchable backplane technology for deformable micro‐LED displays. We developed a fine liquid metal patterning process and highly stretchable backplane fabrication technology to implement micro‐LED stretchable displays utilizing liquid metal electrodes. The developed stretchable display demonstrated exceptional flexibility allowing it to transition from planar to hemispherical shapes with up to 50% stretchability without disconnection of lines. Even when subjected to dome‐shaped deformation under 50% strain, the developed stretchable display utilizing liquid metal electrodes exhibited stable electrical characteristics, showcasing its practical applicability. [ABSTRACT FROM AUTHOR]

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Solution‐processable organic conductor–supramolecular elastomer blends are emerging materials for intrinsically stretchable and autonomously self‐healing organic electronics. Herein, the feasibility of a heterogenous multiphase polymer blend is demonstrated for soft, ultraflexible, self‐adhesive, and self‐healing multilayered film structures for electromagnetic interference (EMI) shielding and microwave absorber (MWA) purposes. The developed soft multilayered films achieve a 5–40 fold improvement in the thickness of the MWA compared to the current state‐of‐the‐art. The thickness normalized reflection loss (RL) is up to 65.26 dB mm−1 with 8.5 GHz bandwidth at 18–26.5 GHz. The maximum thickness normalized EMI shielding effectiveness peaks at up to 175 dB mm−1. The EMI shielding and MWA properties are maintainable up to 150% tensile strain with only a small decrease in the overall attenuation and RL. Furthermore, the developed films are capable of fully autonomously self‐healing and achieve a tough adhesion in temperatures of −30–145 °C, and underwater with maximum single‐lap shear adhesion strength of ≈481.5 kPa to soft thermoplastic polyurethane films. Thus, the developed multilayered films can be utilized for absorption‐dominant EMI shielding or MWA purposes as stretchable coatings. The developed materials also show considerable potential for emerging damage and puncture‐resistant organic soft electronics with autonomous material‐level self‐healing. [ABSTRACT FROM AUTHOR]

Stretchable electronics have the unique capability of 3D (three dimensional) deformation, overcoming the brittleness of traditional inorganic electronics. However, during large deformations, different scale strains between the rigid and stretchable components lead to mismatch, causing interconnect failures. Therefore, the development of the rigidity‐programmable substrate with effective strain shielding capabilities has become a research hotspot. Furthermore, the exponential growth in electronic density presents challenges in the circuit design of stretchable electronics. The urgent need is to develop highly integrated stretchable electronic systems. In this study, a highly integrated stretchable pulse sensor with effective strain shielding capabilities using hybrid 3D printing technology is developed, which comprises electronic chips, a rigidity‐programmable substrate/encapsulation layer printed by using PSC (polydimethylsiloxane/silica‐nanoparticles composite)‐based ink, and LM (liquid metal)‐based 3D circuits. First, the PSC‐based ink is optimized to enhance the strain shielding effectiveness of the rigidity‐programmable substrate. Meanwhile, 3D printing parameters are optimized to achieve high printing precision with minimum line widths below 100 µm. The resulting stretchable pulse sensor demonstrated good mechanical and electrical stability under complex 3D deformations, including bending, twisting, and stretching. The PSC region strain of the sensor is only ≈2% when the global strain is up to ≈65%, which exhibited effective strain shielding capabilities. [ABSTRACT FROM AUTHOR]

The rapid advancements in artificial intelligence, particularly in the domains of robotics, prosthetics, and virtual and augmented reality (VR/AR), have driven an escalating demand for intuitive and effective human-machine interactions. Consequently, haptic devices, being electronic displays for the sense of touch, have drawn increasing attention. More efforts are in demand to develop stretchable and lightweight haptic devices that can trigger multiple mechanical cutaneous receptors using a single device. This work presents a new 3-modal 5-DOF stretchable haptic interface that is enabled by electromagnetic actuators and high-fidelity multi-layer metal printing. The haptic device renders rich haptic sensations (i.e., normal force, vibration, angular force, skin dragging) in one device, allowing for the comprehensive delivery of tactile information through the excitation of multiple cutaneous receptors. Additionally, haptic devices are designed to be compact, lightweight, and skin-compatible. The skin-like softness and stretchability enable intimate skin contact, which is crucial for efficient haptic information delivery. This feature prevents the impediment to natural movements of the skin and ensures the functional integrity of the device during daily deformations of the skin. Finally, three proof-of-concept demonstrations illustrate the potential of the reported multimodal haptic devices for advanced haptic interactions across various domains. [ABSTRACT FROM AUTHOR]

Metallic nanowires have a wide range of potential applications as interconnects in next-generation electronic devices, such as flexible electronics, due to their excellent electrical and mechanical properties. However, for their successful application, it is necessary to assess their electrical reliability, namely, their behavior under electromigration, a common failure mode for electronic interconnects. Here, for the first time, we have experimentally characterized the electromigration reliability of individual penta-twinned gold nanowires, conducting time-to-failure tests for 30 samples as a function of temperature. At each temperature, the distribution of results was modeled with a log-normal distribution to find the median time to failure (MTTF), an important metric for interconnects. The electromigration activation energy and other relevant constants were then determined by fitting the MTTF results to the classic Black's electromigration model. The activation energy found (0.47–0.58 eV) suggests that surface diffusion is a significant contributor to electromigration, which indicates that further improvements in lifetime and reliability could be obtained by surface passivation of the nanowires' surface. [ABSTRACT FROM AUTHOR]

Abstract Flexible and stretchable tactile sensors are attracted in the fields of soft robotics, wearable electronics, and healthcare monitoring. The sensing performance of tactile sensors is commonly affected by external deformations like stretching, bending, and twisting, thus they may fail to function on deformable object surfaces. This paper presents a stretchable tactile sensor array using kirigami‐patterned structural design and soft hinges to reduce the influences of deformation. The kirigami pattern of sensor array is parametrically studied to achieve the required expansion patterns. Laser engraving is employed to modify the micropillars on the force‐sensitive rubber surface to increase the sensitivity. Characterization tests show that the sensor array has high sensitivity (≈1.49 × 10−1 kPa−1) for force sensing, and the stretching and bending deformation have almost negligible effects on sensing performance. Under 40% stretching or 180° bending conditions, the measured resistance changes (ΔR/R0) is ≈0.03 and 0.06, respectively. To demonstrate the capability of developed sensor array, it is mounted on an expandable balloon surface for force detection. The recorded signals changed less than 1.5% during expanding process while rapidly rose under applied force, which indicated that the sensor array has the potential to effectively function on complex and deforming surfaces.

Abstract Stretchable electronics have experienced remarkable progress, especially in sensors and wireless communication systems, attributed to their ability to conformably contact with rough or uneven surfaces. However, the development of complex, multifunctional, and high‐precision stretchable electronics faces substantial challenges, including instability at rigid‐soft interfaces and incompatibility with traditional high‐precision patterning technologies. Metallized electrospun nanofibers emerge as a promising conductive filler, offering exceptional stretchability, electrical conductivity, transparency, and compatibility with existing patterning technologies. Here, this review focuses on the fundamental properties, preparation processes, patterning technologies, and application scenarios of conductive stretchable composites based on metallized nanofibers. Initially, it introduces the fabrication processes of metallized electrospun nanofibers and their advantages over alternative materials. It then highlights recent progress in patterning technologies, including collector collection, vapor deposition with masks, and lithography, emphasizing their role in enhancing precision and integration. Furthermore, the review shows the broad applicability and potential influence of metallized electrospun nanofibers in various fields through their use in sensors, wireless systems, semiconductor devices, and intelligent healthcare solutions. Ultimately, this review seeks to spark further innovation and address the prevailing challenges in stretchable electronics, paving the way for future breakthroughs in this dynamic field.

Objective: We propose a modular stretchable coil design using conductive threads and commercially available embroidery machines. The coil design increases customizability of coil arrays for individual patients and each body part. Methods: Eight rectangular coils were constructed with custom-fabricated stretchable tinsel copper threads incorporated onto textile. Tune, match, and detune circuits were incorporated on the coil. A hook-and-loop mechanism was used to attach and decouple the modular coils. Phantom and in vivo scans at various anatomical flexion angles were acquired to highlight performance, and a temperature test was performed to verify safety. Results: In vivo MRI experiments demonstrate high sensitivity and coverage of each anatomy. As the coils are stretched, the sensitive volume increases at a rate of 10.93 mL/cm2. The SNR reduction of a single coil was greater during compression than when stretched, but this did not affect image quality for the array. The modularity of the array allows for adaptability for any anatomy with simple on-demand adjustment to the number and position of coil elements. Conclusion: The images demonstrated high sensitivity and coverage of the stretchable array for various anatomies and flexion angles. Stretching the coils increases the sensitive volume, allowing for a larger region to be effectively imaged. The resonance shift and SNR decrease during stretch and compression support further investigation of methods to reduce frequency shift in stretchable coils. Significance: The proposed array design allows for highly stretchable, flexible, modular, and conformal patient-centered coils that allow for increased imaging quality, greater comfort, and rapid production.

Abstract Metamaterials and metasurfaces of artificial micro-/nano- structures functioning from microwave, terahertz, to infrared regime have enabled numerous applications from bioimaging, cancer detection and immunoassay to on-body health monitoring systems in the past few decades. Recently, the trend of turning metasurface devices flexible and stretchable has arisen in that the flexibility and stretchability not only makes the device more biocompatible and wearable, but also provides unique control and manipulation of the structural and geometrical reconfiguration of the metasurface in a creative manner, resulting in an extraordinary tunability for biomedical sensing and detection purposes. In this Review, we summarize recent advances in the design and fabrication techniques of stretchable reconfigurable metasurfaces and their applications to date thereof, and put forward a perspective for future development of stretchable reconfigurable metamaterials and metasurfaces.

Stretchable power sources, especially stretchable lithium-ion batteries (LIBs), have attracted increasing attention due to their enormous prospects for powering flexible/wearable electronics. Despite recent advances, it is still challenging to develop ultra-stretchable LIBs that can withstand large deformation. In particular, stretchable LIBs require an elastic electrolyte as a basic component, while the conductivity of most elastic electrolytes drops sharply during deformation, especially during large deformations. This is why highly stretchable LIBs have not yet been realized until now. As a proof of concept, a super-stretchable LIB with strain up to 1200% is created based on an intrinsically super-stretchable polymer electrolyte as the lithium-ion conductor. The super-stretchable conductive system is constructed by an effective diblock copolymerization strategy via photocuring of vinyl functionalized 2-ureido-4-pyrimidone (VFUpy), an acrylic monomer containing succinonitrile and a lithium salt, achieving high ionic conductivity (3.5 × 10−4 mS cm−1 at room temperature (RT)) and large deformation (the strain can reach 4560%). The acrylic elastomer containing Li-ion conductive domains can strongly increase the compatibility between the neighboring elastic networks, resulting in high ionic conductivity under ultra-large deformation, while VFUpy increases elasticity modulus (over three times) and electrochemical stability (voltage window reaches 5.3 V) of the prepared polymer conductor. At a strain of up to 1200%, the resulting stretchable LIBs are still sufficient to power LEDs. This study sheds light on the design and development of high-performance intrinsically super-stretchable materials for the advancement of highly elastic energy storage devices for powering flexible/wearable electronics that can endure large deformation.

Highlights Nanocomposite/hydrogel hybrid electrodes are created with high interfacial toughness by introducing soft microfoams as the mechanically interlocking layer. In the hybrid electrodes, silver nanowires and hydrogels are electrically connected through the porous microfoams, achieving high conductivity and low contact impedance for high-quality biopotential recordings. The microfoam-enabled bonding strategy is generally applicable to diverse polymer substrates.

Motion is vital for life. Currently, the clinical assessment of motion abnormalities is largely qualitative. We previously developed methods to quantitatively assess motion using visual detection systems (around-body) and stretchable electronic sensors (on-body). Here we compare the efficacy of these methods across predefined motions, hypothesizing that the around-body system detects motion with similar accuracy as on-body sensors. Six human volunteers performed six defined motions covering three excursion lengths, small, medium, and large, which were analyzed via both around-body visual marker detection (MoCa version 1.0) and on-body stretchable electronic sensors (BioStamp version 1.0). Data from each system was compared as to the extent of trackability and comparative efficacy between systems. Both systems successfully detected motions, allowing quantitative analysis. Angular displacement between systems had the highest agreement efficiency for the bicep curl and body lean motion, with 73.24% and 65.35%, respectively. The finger pinch motion had an agreement efficiency of 36.71% and chest abduction/adduction had 45.55%. Shoulder abduction/adduction and shoulder flexion/extension motions had the lowest agreement efficiencies with 24.49% and 26.28%, respectively. MoCa was comparable to BioStamp in terms of angular displacement, though velocity and linear speed output could benefit from additional processing. Our findings demonstrate comparable efficacy for non-contact motion detection to that of on-body sensor detection, and offers insight as to the best system selection for specific clinical uses based on the use-case of the desired motion being analyzed.

In recent years, skin-mounted devices have gained prominence in personal wellness and remote patient care. However, the rigid components of many wearables often cause discomfort due to their mechanical mismatch with the skin. To address this, we extend the use of the solderable stretchable sensing system (S4) to develop a wireless skin temperature-sensing smart adhesive. This work introduces two novel types of progress in wearables: the first demonstration of Bluetooth-integration and development of a thin-film-based stretchable inverted-F antenna (SIFA). Characterized through RF simulations, vector network analysis under deformation, and anechoic chamber tests, SIFA demonstrated potential as a low-profile, on-body Bluetooth antenna with a resonant frequency of 2.45 GHz that helps S4 retain its thin overall profile. The final S4 system achieved high correlation (R = 0.95, p < 0.001, mean standard error = 0.04 °C) with commercial sensors during daily activities. These findings suggest that S4-based smart adhesives integrated with SIFAs could offer a promising platform for comfortable, efficient, and functional skin-integrated wearables, supporting a range of health monitoring applications.

The booming development of wearable devices has aroused increasing interests in flexible and stretchable devices. With mechanosensory functionality, these devices are highly desirable on account of their wide range of applications in electronic skin, personal healthcare, human–machine interfaces and beyond. However, they are mostly limited by single electrical signal feedback, restricting their diverse applications in visualized mechanical sensing. Inspired by the mechanochromism of structural color materials, interactively stretchable electronics with optical and electrical dual-signal feedbacks are recently emerged as novel sensory platforms, by combining both of their sensing mechanisms and characteristics. Herein, recent studies on interactively stretchable electronics based on structural color materials are reviewed. Following a brief introduction of their basic components (i.e., stretchable electronics and mechanochromic structural color materials), two types of interactively stretchable electronics with respect to the nanostructures of mechanochromic materials are outlined, focusing primarily on their design considerations and fabrication strategies. Finally, the main challenges and future perspectives of these emerging devices are discussed. [ABSTRACT FROM AUTHOR]

Conventional wearable bio-integrated electronics predominantly utilize materials such as silicon, which possess rigid and flat characteristics, in contrast to the flexible and curved nature of the human skin. This mismatch poses challenges in developing wearable devices specifically engineered to monitor electrophysiological signals, deliver therapeutic stimulations, convert biomechanical energy, and, most importantly, establish high-quality interfaces between biological tissues and devices. An effective strategy includes incorporating innovative materials that possess mechanical properties like skin with high biocompatibility. Through material processing with design and engineering strategies, the fabrication of ultrathin and stretchable devices that can completely attach to the contour of the skin is possible. This review highlights the importance of materials that possess both mechanical compatibility with the skin and established biocompatibility. Furthermore, the design strategy and engineering of the materials allow devices to encompass stretchability and form conformal contact with the skin. Then, we explore a range of devices, including sensors, stimulators, and energy harvesters, specifically designed for optimal integration with the skin. Lastly, the conclusion offers insights into potential prospects. [ABSTRACT FROM AUTHOR]

Stretchable photovoltaics have garnered increasing attention due to their adaptability to various surfaces and applications, meeting the rising demands for portable and flexible power sources. Herein, stretchable solar modules are demonstrated by sandwiching electrically connected rigid solar cells between top and bottom polydimethylsiloxane (PDMS) layers, which are then attached onto an elastomer with an island and trench structure. The electrical connection of solar cells is achieved by dispenser printing of electrically conductive adhesive (ECA). The fabricated stretchable solar modules have a maximum biaxial elongation of 75%, and the electrical connection of the solar cells using ECA results in a negligible efficiency loss of 1.6%. In particular, embedding of solar cells and interconnects between PDMS layers enhances mechanical stability by placing these key components at the mechanical neutral plane and the long‐term stability against humidity due to the encapsulation role of the PDMS layer. The module demonstrates only a 5% of efficiency drop after 1000 hours in the dump‐heat test (85°C/85%). The results in this study are not limited to solar cells but can be applied to various types of rigid devices, paving the way for the commercialization of stretchable electronics. [ABSTRACT FROM AUTHOR]

A stretchable electronic facial mask (SEFM) for skin electroporation by transdermal drug delivery is introduced. The SEFM exhibits characteristics of reusability, water‐resistant, low cost, and portability. To achieve these objectives while maintaining satisfactory mechanical and electrical performance of the device, two main areas are innovated: (1) Grinding and doping modification of conductive ink to enhance its adhesion to silicone and increase conductivity through material research, as well as mechanical structure design for stretching stability of conductive ink electrodes. (2) Doping modification of high‐temperature vulcanizes silicone to address the issue of increased resistance during encapsulation due to the swell of conductive ink. The SEFM designed with these innovations, is validated in rat experiments, demonstrating a 3–4 times increase in drug intake compared to the control group without skin electroporation. Safety is confirmed, and the promotion of niacinamide drug delivery is verified in human volunteers. The materials‐modified conductive ink and conductive silicone proposed in SEFM can be employed in other flexible wearable devices, and this platform has the potential for future integration of additional components to achieve expanded functionality and productization. [ABSTRACT FROM AUTHOR]

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Soft robots are characterized by their mechanical compliance, making them well-suited for various bio-inspired applications. However, the challenge of preserving their flexibility during deployment has necessitated using soft sensors which can enhance their mobility, energy efficiency, and spatial adaptability. Through emulating the structure, strategies, and working principles of human senses, soft robots can detect stimuli without direct contact with soft touchless sensors and tactile stimuli. This has resulted in noteworthy progress within the field of soft robotics. Nevertheless, soft, touchless sensors offer the advantage of non-invasive sensing and gripping without the drawbacks linked to physical contact. Consequently, the popularity of soft touchless sensors has grown in recent years, as they facilitate intuitive and safe interactions with humans, other robots, and the surrounding environment. This review explores the emerging confluence of touchless sensing and soft robotics, outlining a roadmap for deployable soft robots to achieve human-level dexterity. [ABSTRACT FROM AUTHOR]