Fully Integrated Design of a Stretchable Solid‐State Lithium‐Ion Full Battery

A solid‐state lithium‐ion battery, in which all components (current collector, anode and cathode, electrolyte, and packaging) are stretchable, is introduced, giving rise to a battery design with mechanical properties that are compliant with flexible electronic devices and elastic wearable systems. By depositing Ag microflakes as a conductive layer on a stretchable carbon–polymer composite, a current collector with a low sheet resistance of ≈2.7 Ω □^?1 at 100% strain is obtained. Stretchable electrodes are fabricated by integrating active materials with the elastic current collector. A polyacrylamide–“water‐in‐salt” electrolyte is developed, offering high ionic conductivity of 10^?3 to 10^?2 S cm^?1 at room temperature and outstanding stretchability up to ≈300% of its original length. Finally, all these components are assembled into a solid‐state lithium‐ion full cell in thin‐film configuration. Thanks to the deformable individual components, the full cell functions when stretched, bent, or even twisted. For example, after stretching the battery to 50%, a reversible capacity of 28 mAh g^?1 and an average energy density of 20 Wh kg^?1 can still be obtained after 50 cycles at 120 mA g^?1, confirming the functionality of the battery under extreme mechanical stress.     

Bath Electrospinning of Continuous and Scalable Multifunctional MXene‐Infiltrated Nanoyarns

Electroactive yarns that are stretchable are desired for many electronic textile applications, including energy storage, soft robotics, and sensing. However, using current methods to produce these yarns, achieving high loadings of electroactive materials and simultaneously demonstrating stretchability is a critical challenge. Here, a one‐step bath electrospinning technique is developed to effectively capture Ti₃C₂T_x MXene flakes throughout continuous nylon and polyurethane (PU) nanofiber yarns (nanoyarns). With up to ≈90 wt% MXene loading, the resulting MXene/nylon nanoyarns demonstrate high electrical conductivity (up to 1195 S cm^?1). By varying the flake size and MXene concentration, nanoyarns achieve stretchability of up to 43% (MXene/nylon) and 263% (MXene/PU). MXene/nylon nanoyarn electrodes offer high specific capacitance in saturated LiClO₄ electrolyte (440 F cm^?3 at 5 mV s^?1), with a wide voltage window of 1.25 V and high rate capability (72% between 5 and 500 mV s^?1). As strain sensors, MXene/PU yarns demonstrate a wide sensing range (60% under cyclic stretching), high sensitivity (gauge factor of ≈17 in the range of 20–50% strain), and low drift. Utilizing the stretchability of polymer nanofibers and the electrical and electrochemical properties of MXene, MXene‐based nanoyarns demonstrate potential in a wide range of applications, including stretchable electronics and body movement monitoring.     

Highly Stretchable Metallic Nanowire Networks Reinforced by the Underlying Randomly Distributed Elastic Polymer Nanofibers via Interfacial Adhesion Improvement

On‐skin electronics require conductive, porous, and stretchable materials for a stable operation with minimal invasiveness to the human body. However, porous elastic conductors that simultaneously achieve high conductivity, good stretchability, and durability are rare owing to the lack of proper design for good adhesion between porous elastic polymer and conductive metallic networks. Here, a simple fabrication approach for porous nanomesh‐type elastic conductors is shown by designing a layer‐by‐layer structure of nanofibers/nanowires (NFs/NWs) via interfacial hydrogen bonding. The as‐prepared conductors, consisting of Ag NWs and polyurethane (PU) NFs, simultaneously achieve high conductivity (9190 S cm^?1), high stretchability (310%), and good durability (82% resistance increase after 1000 cycles of deformation at 70% tensile strain). The direct contact between the Ag NWs enables the high conductivity. The synergistic effect of the layer‐by‐layer structure and good adhesion between the Ag NWs and the PU NFs enables good mechanical properties. Furthermore, without any adhesive gel/tape, the conductors can be utilized as breathable strain sensors for precise joint motion monitoring, and as breathable sensing electrodes for continuous electrophysiological signal recording.     

Printable Superelastic Conductors with Extreme Stretchability and Robust Cycling Endurance Enabled by Liquid‐Metal Particles

Stretchable conductors are vital and indispensable components in soft electronic systems. The development for stretchable conductors has been highly motivated with different approaches established to address the dilemma in the conductivity and stretchability trade‐offs to some extent. Here, a new strategy to achieve superelastic conductors with high conductivity and stable electrical performance under stretching is reported. It is demonstrated that by electrically anchoring conductive fillers with eutectic gallium indium particles (EGaInPs), significant improvement in stretchability and durability can be achieved in stretchable conductors. Different from the strategy of modulating the chemical interactions between the conductive fillers and host polymers, the EGaInPs provide dynamic and robust electrical anchors between the conductive fillers. A superelastic conductor which can achieve a high stretchability with 1000% strain at initial conductivity of 8331 S cm^?1 and excellent cycling durability with about eight times resistance change (compared to the initial resistance at 0% strain before stretching) after reversibly stretching to 800% strain for 10 000 times is demonstrated. Applications of the superelastic conductor in an interactive soft touch device and a stretchable light‐emitting system are also demonstrated, featuring its promising applications in soft robotics or soft and interactive human–machine interfaces.     

Editable Supercapacitors with Customizable Stretchability Based on Mechanically Strengthened Ultralong MnO2 Nanowire Composite

Although some progress has been made on stretchable supercapacitors, traditional stretchable supercapacitors fabricated by predesigning structured electrodes for device assembling still lack the device‐level editability and programmability. To adapt to wearable electronics with arbitrary configurations, it is highly desirable to develop editable supercapacitors that can be directly transferred into desirable shapes and stretchability. In this work, editable supercapacitors for customizable shapes and stretchability using electrodes based on mechanically strengthened ultralong MnO₂ nanowire composites are developed. A supercapacitor edited with honeycomb‐like structure shows a specific capacitance of 227.2 mF cm^?2 and can be stretched up to 500% without degradation of electrochemical performance, which is superior to most of the state‐of‐the‐art stretchable supercapacitors. In addition, it maintains nearly 98% of the initial capacitance after 10 000 stretch‐and‐release cycles under 400% tensile strain. As a representative of concept for system integration, the editable supercapacitors are integrated with a strain sensor, and the system exhibits a stable sensing performance even under arm swing. Being highly stretchable, easily programmable, as well as connectable in series and parallel, an editable supercapacitor with customizable stretchability is promising to produce stylish energy storage devices to power various portable, stretchable, and wearable devices.     

Tunable Piezoelectricity of Multifunctional Boron Nitride Nanotube/Poly(dimethylsiloxane) Stretchable Composites

Boron nitride nanotubes (BNNT) uniformly dispersed in stretchable materials, such as poly(dimethylsiloxane) (PDMS), could create the next generation of composites with augmented mechanical, thermal, and piezoelectric characteristics. This work reports tunable piezoelectricity of multifunctional BNNT/PDMS stretchable composites prepared via co-solvent blending with tetrahydrofuran (THF) to disperse BNNTs in PDMS while avoiding sonication or functionalization. The resultant stretchable BNNT/PDMS composites demonstrate augmented Young's modulus (200% increase at 9 wt% BNNT) and thermal conductivity (120% increase at 9 wt% BNNT) without losing stretchability. Furthermore, BNNT/PDMS composites demonstrate piezoelectric responses that are linearly proportional to BNNT wt%, achieving a piezoelectric constant (|d₃₃|) of 18 pmV⁻¹ at 9 wt% BNNT without poling, which is competitive with commercial piezoelectric polymers. Uniquely, BNNT/PDMS accommodates tensile strains up to 60% without plastic deformation by aligning BNNTs, which enhances the composites’ piezoelectric response approximately five times. Finally, the combined stretchable and piezoelectric nature of the composite was exploited to produce a vibration sensor sensitive to low-frequency (≈1 kHz) excitation. This is the first demonstration of multifunctional, stretchable BNNT/PDMS composites with enhanced mechanical strength and thermal conductivity and furthermore tunable piezoelectric response by varying BNNT wt% and applied strain, permitting applications in soft actuators and vibration sensors.     

Microtopography‐Guided Conductive Patterns of Liquid‐Driven Graphene Nanoplatelet Networks for Stretchable and Skin‐Conformal Sensor Array

Flexible thin‐film sensors have been developed for practical uses in invasive or noninvasive cost‐effective healthcare devices, which requires high sensitivity, stretchability, biocompatibility, skin/organ‐conformity, and often transparency. Graphene nanoplatelets can be spontaneously assembled into transparent and conductive ultrathin coatings on micropatterned surfaces or planar substrates via a convective Marangoni force in a highly controlled manner. Based on this versatile graphene assembled film preparation, a thin, stretchable and skin‐conformal sensor array (144 pixels) is fabricated having microtopography‐guided, graphene‐based, conductive patterns embedded without any complicated processes. The electrically controlled sensor array for mapping spatial distributions (144 pixels) shows high sensitivity (maximum gauge factor ≈1697), skin‐like stretchability (<48%), high cyclic stability or durability (over 10⁵ cycles), and the signal amplification (≈5.25 times) via structure‐assisted intimate‐contacts between the device and rough skin. Furthermore, given the thin‐film programmable architecture and mechanical deformability of the sensor, a human skin‐conformal sensor is demonstrated with a wireless transmitter for expeditious diagnosis of cardiovascular and cardiac illnesses, which is capable of monitoring various amplified pulse‐waveforms and evolved into a mechanical/thermal‐sensitive electric rubber‐balloon and an electronic blood‐vessel. The microtopography‐guided and self‐assembled conductive patterns offer highly promising methodology and tool for next‐generation biomedical devices and various flexible/stretchable (wearable) devices.     

A Highly Stretchable Transparent Self‐Powered Triboelectric Tactile Sensor with Metallized Nanofibers for Wearable Electronics

Recently, the quest for new highly stretchable transparent tactile sensors with large‐scale integration and rapid response time continues to be a great impetus to research efforts to expand the promising applications in human–machine interactions, artificial electronic skins, and smart wearable equipment. Here, a self‐powered, highly stretchable, and transparent triboelectric tactile sensor with patterned Ag‐nanofiber electrodes for detecting and spatially mapping trajectory profiles is reported. The Ag‐nanofiber electrodes demonstrate high transparency (>70%), low sheet resistance (1.68–11.1 Ω □^?1), excellent stretchability, and stability (>100% strain). Based on the electrode patterning and device design, an 8 × 8 triboelectric sensor matrix is fabricated, which works well under high strain owing to the effect of the electrostatic induction. Using cross‐locating technology, the device can execute more rapid tactile mapping, with a response time of 70 ms. In addition, the object being detected can be made from any commonly used materials or can even be human hands, indicating that this device has widespread potential in tactile sensing and touchpad technology applications.     

Stretchable Conductive Polymers and Composites Based on PEDOT and PEDOT:PSS

The conductive polymer poly(3,4‐ethylenedioxythiophene) (PEDOT), and especially its complex with poly(styrene sulfonate) (PEDOT:PSS), is perhaps the most well‐known example of an organic conductor. It is highly conductive, largely transmissive to light, processible in water, and highly flexible. Much recent work on this ubiquitous material has been devoted to increasing its deformability beyond flexibility—a characteristic possessed by any material that is sufficiently thin—toward stretchability, a characteristic that requires engineering of the structure at the molecular‐ or nanoscale. Stretchability is the enabling characteristic of a range of applications envisioned for PEDOT in energy and healthcare, such as wearable, implantable, and large‐area electronic devices. High degrees of mechanical deformability allow intimate contact with biological tissues and solution‐processable printing techniques (e.g., roll‐to‐roll printing). PEDOT:PSS, however, is only stretchable up to around 10%. Here, the strategies that have been reported to enhance the stretchability of conductive polymers and composites based on PEDOT and PEDOT:PSS are highlighted. These strategies include blending with plasticizers or polymers, deposition on elastomers, formation of fibers and gels, and the use of intrinsically stretchable scaffolds for the polymerization of PEDOT.     

Stretchable Electronic Sensors of Nanocomposite Network Films for Ultrasensitive Chemical Vapor Sensing

A stretchable, transparent, and body‐attachable chemical sensor is assembled from the stretchable nanocomposite network film for ultrasensitive chemical vapor sensing. The stretchable nanocomposite network film is fabricated by in situ preparation of polyaniline/MoS₂ (PANI/MoS₂) nanocomposite in MoS₂ suspension and simultaneously nanocomposite deposition onto prestrain elastomeric polydimethylsiloxane substrate. The assembled stretchable electronic sensor demonstrates ultrasensitive sensing performance as low as 50 ppb, robust sensing stability, and reliable stretchability for high‐performance chemical vapor sensing. The ultrasensitive sensing performance of the stretchable electronic sensors could be ascribed to the synergistic sensing advantages of MoS₂ and PANI, higher specific surface area, the reliable sensing channels of interconnected network, and the effectively exposed sensing materials. It is expected to hold great promise for assembling various flexible stretchable chemical vapor sensors with ultrasensitive sensing performance, superior sensing stability, reliable stretchability, and robust portability to be potentially integrated into wearable electronics for real‐time monitoring of environment safety and human healthcare.     

Fabrication of Highly Stretchable Conductors via Morphological Control of Carbon Nanotube Network

Stretchable conductors, which can keep their excellent electrical conductivity while highly stretched, have been investigated extensively due to their wide range of applications in flexible and stretchable electronics, wearable displays, etc.; however, their preparation is often complicated and expensive. Herein, an efficient method to prepare high performance stretchable conductors through morphological control of conductive networks formed with carbon nanotubes (CNTs) in an elastomer matrix is reported. It is observed that an interface‐mediated method could be used to align randomly oriented filler during stretching and to induce buckling of CNTs during relaxation. Further morphological studies indicate the possible formation of a wavy CNT structure induced by cyclic pre‐straining. Subsequent thermal annealing is observed to collapse the oriented network and improve the local contacts between conductive networks. Through such a simple procedure, a conductivity of nearly 1000 S m^?1 and a stretchability of 200% can be achieved for composites containing 20 wt% CNTs. CNTs are observed to buckle over a large area in polymer bulk, and the combination of pre‐straining and thermal annealing modifies the conductive network in the elastomer matrix. As a general method, this could be used for easy fabrication of high‐performance stretchable conductors for arbitrary‐shaped objects on a large scale.     

A Freestanding Stretchable and Multifunctional Transistor with Intrinsic Self‐Healing Properties of all Device Components

A flexible and stretchable field‐effect transistor (FET) is an essential element in a number of modern electronics. To realize the potential of this device in harsh real‐world conditions and to extend its application spectrum, new functionalities are needed to be introduced into the device. Here, solution‐processable elements based on carbon nanotubes that empower flexible and stretchable FET with high hole‐mobility (µ_h ≈ 10 cm² V^?1 s^?1) and relatively low operating voltages (<8 V) and that retain self‐healing properties of all FET components are reported. The device has repeatable intrinsic and autonomic self‐healing ability, namely without use of any external trigger, enabling the restoration of its electrical and mechanical properties, both after microscale damage or complete cut of the device—for example by a scissor. The device can be repeatedly stretched for >200 cycles of up to 50% strain without a significant loss in its electrical properties. The device is applicable in the form of a ≈3 µm thick freestanding skin tattoo and has multifunctional sensing properties, such as detection of temperature and humidity. With this unprecedented biomimetic transistor, highly sustainable and reliable soft electronic applications can be introduced.     

A Highly Stretchable and Real‐Time Healable Supercapacitor

In addition to a high specific capacitance, a large stretchability and self‐healing properties are also essential to improve the practicality and reliability of supercapacitors in portable and wearable electronics. However, the integration of multiple functions into one device remains challenging. Here, the construction of a highly stretchable and real‐time omni‐healable supercapacitor is demonstrated by sandwiching the polypyrrole‐incorporated gold nanoparticle/carbon nanotube (CNT)/poly(acrylamide) (GCP@PPy) hydrogel electrodes with a CNT‐free GCP (GP) hydrogel as the electrolyte and chemically soldering an Ag nanowire film to the hydrogel electrode as the current collector. The newly developed dynamic metal‐thiolate (M‐SR, M = Au, Ag) bond‐induced integrated configuration, with an intrinsically powerful electrode and electrolyte, enables the assembled supercapacitor to deliver an areal capacitance of 885 mF cm^?2 and an energy density of 123 µWh cm^?2, which are among the highest‐reported values for stretchable supercapacitors. Notably, the device exhibits a superhigh stretching strain of 800%, rapid optical healing capability, and significant real‐time healability during the charge–discharge process. The exceptional performance combined with the facile assembly method confirms this multifunctional device as the best performer among all the flexible supercapacitors reported to date.     

Mesoporous Silica Supported Silver–Bismuth Nanoparticles as Photothermal Agents for Skin Infection Synergistic Antibacterial Therapy

The emergence of multidrug resistant bacteria has resulted in plenty of stubborn nosocomial infections and severely threatens human health. Developing novel bactericide and therapeutic strategy is urgently needed. Herein, mesoporous silica supported silver–bismuth nanoparticles (Ag‐Bi@SiO₂ NPs) are constructed for synergistic antibacterial therapy. In vitro experiments indicate that the hyperthermia originating from Bi NPs can disrupt cell integrity and accelerate the Ag ions release, further exhibiting an excellent antibacterial performance toward methicillin‐resistant Staphylococcus aureus (MRSA). Besides, under laser irradiation, Ag‐Bi@SiO₂ NPs at 100 µg mL^?1 can effectively obliterate mature MRSA biofilm and cause a 69.5% decrease in the biomass, showing a better therapeutic effect than Bi@SiO₂ NPs with laser (26.8%) or Ag‐Bi@SiO₂ NPs without laser treatment (30.8%) groups. More importantly, in vivo results confirm that ≈95.4% of bacteria in abscess are killed and the abscess ablation is accelerated using the Ag‐Bi@SiO₂ NPs antibacterial platform. Therefore, Ag‐Bi@SiO₂ NPs with photothermal‐enhanced antibacterial activity are a potential nano‐antibacterial agent for the treatment of skin infections.     

Highly Sensitive and Stretchable Resistive Strain Sensors Based on Microstructured Metal Nanowire/Elastomer Composite Films

High sensitivity and high stretchability are two conflicting characteristics that are difficult to achieve simultaneously in elastic strain sensors. A highly sensitive and stretchable strain sensor comprising a microstructured metal nanowire (mNW)/elastomer composite film is presented. The surface structure is easily prepared by combining an mNW coating and soft‐lithographic replication processes in a simple and reproducible manner. The densely packed microprism‐array architecture of the composite film leads to a large morphological change in the mNW percolation network by efficiently concentrating the strain in the valley regions upon stretching. Meanwhile, the percolation network comprising mNWs with a high aspect ratio is stable enough to prevent electrical failure, even under high strains. This enables the sensor to simultaneously satisfy high sensitivity (gauge factor ≈81 at >130% strain) and high stretchability (150%) while ensuring long‐term reliability (10 000 cycles at 150% strain). The sensor can also detect strain induced by bending and pressure, thus demonstrating its potential as a versatile sensing tool. The sensor is successfully utilized to monitor a wide range of human motions in real time. Furthermore, the unique sensing mechanism is easily extended to detect more complex multiaxial strains by optimizing the surface morphology of the device.     

Kirigami‐Inspired Nanoconfined Polymer Conducting Nanosheets with 2000% Stretchability

Stretchable conductors are essential components of wearable electronics. However, such materials typically sacrifice their electronic conductivity to achieve mechanical stretchability and elasticity. Here, the nanoconfinement and air/water interfacial assembly is explored to grow freestanding mechanical endurance conducting polymer nanosheets that can be stretched up to 2000% with simultaneously high electrical conductivity, inspired by kirigami. Such stretchable conductors show remarkable electronic and mechanical reversibility and reproducibility under more than 1000 cycle durability tests with 2000% deformability, which can be accurately predicted using finite element modeling. The conductivity of nanoconfined freestanding conductor nanosheets increases by three orders of magnitude from 2.2 × 10^?3 to 4.002 S cm^?1 is shown, due to the charge‐transfer complex formation between polymer chain and halogen, while the electrical conductance of the stretchable kirigami nanosheets can be maintained over the entire strain regime. The nanoconfined polymer nanosheets can also act as a sensor capable of sensing the pressure with high durability and real‐time monitoring.     

Biofriendly,Stretchable, and Reusable Hydrogel Electronics as Wearable Force Sensors

The ever‐growing overlap between stretchable electronic devices and wearable healthcare applications is igniting the discovery of novel biocompatible and skin‐like materials for human‐friendly stretchable electronics fabrication. Amongst all potential candidates, hydrogels with excellent biocompatibility and mechanical features close to human tissues are constituting a promising troop for realizing healthcare‐oriented electronic functionalities. In this work, based on biocompatible and stretchable hydrogels, a simple paradigm to prototype stretchable electronics with an embedded three‐dimensional (3D) helical conductive layout is proposed. Thanks to the 3D helical structure, the hydrogel electronics present satisfactory mechanical and electrical robustness under stretch. In addition, reusability of stretchable electronics is realized with the proposed scenario benefiting from the swelling property of hydrogel. Although losing water would induce structure shrinkage of the hydrogel network and further undermine the function of hydrogel in various applications, the worn‐out hydrogel electronics can be reused by simply casting it in water. Through such a rehydration procedure, the dehydrated hydrogel can absorb water from the surrounding and then the hydrogel electronics can achieve resilience in mechanical stretchability and electronic functionality. Also, the ability to reflect pressure and strain changes has revealed the hydrogel electronics to be promising for advanced wearable sensing applications.     

Advances in Rational Design and Materials of High‐Performance Stretchable Electromechanical Sensors

Stretchable and wearable sensor technology has attracted significant interests and created high technological impact on portable healthcare and smart human–machine interfaces. Wearable electromechanical systems are an important part of this technology that has recently witnessed tremendous progress toward high‐performance devices for commercialization. Over the past few years, great attention has been paid to simultaneously enhance the sensitivity and stretchability of the electromechanical sensors toward high sensitivity, ultra‐stretchability, low power consumption or self‐power functionalities, miniaturisation as well as simplicity in design and fabrication. This work presents state‐of‐the‐art advanced materials and rational designs of electromechanical sensors for wearable applications. Advances in various sensing concepts and structural designs for intrinsic stretchable conductive materials as well as advanced rational platforms are discussed. In addition, the practical applications and challenges in the development of stretchable electromechanical sensors are briefly mentioned and highlighted.     

Stretchable Light‐Emitting Diodes with Organometal‐Halide‐Perovskite–Polymer Composite Emitters

Intrinsically stretchable light‐emitting diodes (LEDs) are demonstrated using organometal‐halide‐perovskite/polymer composite emitters. The polymer matrix serves as a microscale elastic connector for the rigid and brittle perovskite and induces stretchability to the composite emissive layers. The stretchable LEDs consist of poly(ethylene oxide)‐modified poly(3,4‐ethylenedioxythiophene) polystyrene sulfonate as a transparent and stretchable anode, a perovskite/polymer composite emissive layer, and eutectic indium–gallium as the cathode. The devices exhibit a turn‐on voltage of 2.4 V, and a maximum luminance intensity of 15 960 cd m^?2 at 8.5 V. Such performance far exceeds all reported intrinsically stretchable LEDs based on electroluminescent polymers. The stretchable perovskite LEDs are mechanically robust and can be reversibly stretched up to 40% strain for 100 cycles without failure.     

Surface Engineering of Spherical Metal Nanoparticles with Polymers toward Selective Asymmetric Synthesis of Nanobowls and Janus‐Type Dimers

New synthetic methods capable of controlling structural and compositional complexities of asymmetric nanoparticles (NPs) are very challenging but highly desired. A simple and general synthetic approach to designing sophisticated asymmetric NPs by anisotropically patterning the surface of isotropic metallic NPs with amphiphilic block copolymers (BCPs) is reported. The selective galvanic replacement and seed‐mediated growth of a second metal can be achieved on the exposed surface of metal NPs, resulting in the formation of nanobowls and Janus‐type metal–metal dimers, respectively. Using Ag and Au NPs tethered with amphiphilic block copolymers of poly(ethylene oxide)‐block‐polystyrene (PEO‐b‐PS), anisotropic surface patterning of metallic NPs (e.g., Ag and Au) is shown to be driven by thermodynamical phase segregation of BCP ligands on isotropic metal NPs. Two proof‐of‐concept experiments are given on, i) synthesis of Au nanobowls by a selective galvanic replacement reaction on Janus‐type patched Ag/polymer NPs; and ii) preparation of Au–Pd heterodimers and Au–Au homodimers by a seed‐mediated growth on Janus‐type patched Au/polymer NPs. The method shows remarkable versatility; and it can be easily handled in aqueous solution. This synthetic strategy stands out as the new methodology to design and synthesis asymmetric metal NPs with sophisticated topologies.