A high performance wearable strain sensor with advanced thermal management for motion monitoring

From MXene Trash to Ultraflexible Composites for Multifunctional Electromagnetic Interference Shielding

The development of flexible composites based on the transition metal carbides/nitrides (MXenes) is gaining popularity because of MXenes' high application potentials for electromagnetic interference (EMI) shields. Here, we prepare a new type of ultraflexible composite films composed of "trashed" MXene sediment (MS) and waterborne polyurethane using a simple, facile solution casting approach. In addition to the outstanding mechanical strength and electrical conductivity, an extremely wide-range of MS contents can be achieved for the composites, resulting in EMI shielding effectiveness (SE) that may be controlled over a wide range. The X-band EMI SE of the flexible, low-density composites containing 70 wt % MS reaches 45.3 dB at a thickness of merely 0.51 mm. Moreover, the SE values of more than 34.5 dB in the ultrabroadband gigahertz frequency range including X-band, P-band, K-band, and R-band, are accomplished for the thin composites. Furthermore, the MS/WPU composite films show excellent electrothermal and photothermal performance, demonstrating the multifunctionalities of the MS-based EMI shields. Combined with the cost-efficient, sustainable, and scalable preparation approach, the ultraflexible, multifunctional composites from "trashed MXene" show great potentials for next-generation electronics. This work also opens a new avenue for the creation of innovative, high-performance, multifunctional flexible composites.

AWI-Assembled TPU-BNNS Composite Films with High In-Plane Thermal Conductivity for Thermal Management of Flexible Electronics

Thermal management of flexible/stretchable electronics has been a crucial issue. Mass supernumerary thermal heat is created in the repetitive course of deformation because of the large nanocontact resistance between electric conductive fillers, as well as the interfacial resistance between fillers and the polymer matrix. Here, we report a stretchable thermoplastic polyurethane (TPU)-boron nitride nanosheet (BNNS) composite film with a high in-plane thermal conductivity based on an air/water interfacial (AWI) assembly method. In addition to rigid devices, it was capable for thermal management of flexible electronics. During more than 2000 cycles of the bending-releasing process, the average saturated surface temperature of the flexible conductor covered with composite film with 30 wt % BNNSs was approximately 40.8 ± 1 °C (10.5 °C lower than that with pure TPU). Moreover, the thermal dissipating property of the composite under stretching was measured. All the results prove that this TPU-BNNS composite film is a candidate for thermal management of next-generation flexible/stretchable electronics with high power density.

Printable Aligned Single-Walled Carbon Nanotube Film with Outstanding Thermal Conductivity and Electromagnetic Interference Shielding Performance

Ultrathin, lightweight, and flexible aligned single-walled carbon nanotube (SWCNT) films are fabricated by a facile, environmentally friendly, and scalable printing methodology. The aligned pattern and outstanding intrinsic properties render "metal-like" thermal conductivity of the SWCNT films, as well as excellent mechanical strength, flexibility, and hydrophobicity. Further, the aligned cellular microstructure promotes the electromagnetic interference (EMI) shielding ability of the SWCNTs, leading to excellent shielding effectiveness (SE) of ~ 39 to 90 dB despite a density of only ~ 0.6 g cm^-3 at thicknesses of merely 1.5-24 µm, respectively. An ultrahigh thickness-specific SE of 25 693 dB mm^-1 and an unprecedented normalized specific SE of 428 222 dB cm² g^-1 are accomplished by the freestanding SWCNT films, significantly surpassing previously reported shielding materials. In addition to an EMI SE greater than 54 dB in an ultra-broadband frequency range of around 400 GHz, the films demonstrate excellent EMI shielding stability and reliability when subjected to mechanical deformation, chemical (acid/alkali/organic solvent) corrosion, and high-/low-temperature environments. The novel printed SWCNT films offer significant potential for practical applications in the aerospace, defense, precision components, and smart wearable electronics industries.

The Potential of Electrical Stimulation and Smart Textiles for Patients with Diabetes Mellitus

Diabetes mellitus is one of the most frequent diseases in the general population. Electrical stimulation is a treatment modality based on the transmission of electrical pulses into the body that has been widely used for improving wound healing and for managing acute and chronic pain. Here, we discuss recent advancements in electroceuticals and haptic/smart devices for quality of life and present in which patients and how electrical stimulation may prove to be useful for the treatment of diabetes-related complications.

Superhydrophobic conductive rubber band with synergistic dual conductive layer for wide-range sensitive strain sensor

Wearable electronic devices have received increasing interests because of their excellent flexibility, stretchability, and human friendliness. As the core components, flexible strain sensors integrated with wide working range, high sensitivity, and environment stability, especially in moisture or corrosive environments, remain a huge challenge. Herein, synergistic carbon nanotubes (CNTs)/reduced graphene oxide (rGO) dual conductive layer decorated elastic rubber band (RB) was successfully developed and treated with hydrophobic fumed silica (Hf-SiO₂) for preparing superhydrophobic strain sensor. As expected, stable entangled CNTs layer and ultrasensitive microcracked rGO layer endow the sensor with extremely low detection limit (0.1%), high sensitivity (gauge factor is 685.3 at 482% strain), wide workable strain range (0-482%), fast response/recovery (200 ms/200 ms) and favorable reliability and reproducibility over 1000 cycles. Besides, the constructed Hf-SiO₂ coating also makes the sensor exhibit excellent superhydrophobicity, self-cleaning property, and corrosion-resistance. As a proof of concept, our prepared high-performance strain sensor can realize the full-range monitoring of human motions and physiological signals even in the water environment, including pulse, vocalization, joint bending, running, and gesture recognition. Interestingly, it can also be knitted into a tactile electronic textile for spatial pressure distribution measurement. Thus, this study provides a universal technique for the preparation of high-performance strain sensors with great potential applications in the field of next-generation intelligent wearable electronics.

Ionic conductive hydroxypropyl methyl cellulose reinforced hydrogels with extreme stretchability, self-adhesion and anti-freezing ability for highly sensitive skin-like sensors

Ionically-conductive hydrogels are attracting increasing interest as skin-like sensors, however, the fabrication of ion-conductive hydrogels with excellent mechanical properties, high conductivity, self-adhesion and anti-freezing ability for high-performance sensors remains a challenge. Herein, a highly ion-conductive hydrogel is prepared by introducing LiCl into polyacrylamide/hydroxypropyl methyl cellulose (PAM/HPMC) composite hydrogel. The introduction of LiCl simultaneously endows the PAM/HPMC/LiCl hydrogel with outstanding stretchability (1453 %), high tensile strength (135 kPa), skin-like elasticity (9.18 kPa), high conductivity (7.85 S/m), good adhesiveness and wide operating temperature range. Impressively, this ion-conductive hydrogel can be utilized in skin-like sensor, which achieves high strain sensitivity (GF = 11.19) with wide sensing ranges (up to 600 %), and excellent endurance over 250 consecutive stretching. As a result, the wearable sensor assembled from the hydrogels can be used to detect complex human activities with high stability even at -40 °C. This work promotes the development of ion-conductive hydrogels with broad operating temperature in advanced sensory platform.

Invariable resistance of conductive nanocomposite over 30% strain

The dependence of the electrical resistance on materials' geometry determines the performance of conductive nanocomposites. Here, we report the invariable resistance of a conductive nanocomposite over 30% strain. This is enabled by the in situ-generated hierarchically structured silver nanosatellite particles, realizing a short interparticle distance (4.37 nm) in a stretchable silicone rubber matrix. Furthermore, the barrier height is tuned to be negligible by matching the electron affinity of silicone rubber to the work function of silver. The stretching results in the electron flow without additional scattering in the silicone rubber matrix. The transport is changed to quantum tunneling if the barrier height is gradually increased by using different matrix polymers with smaller electron affinities, such as ethyl vinyl acetates and thermoplastic polyurethane. The tunneling current decreases with increasing strain, which is accurately described by the Simmons approximation theory. The tunable transport in nanocomposites provides an advancement in the design of stretchable conductors.

Fluidic phase-change materials with continuous latent heat from theoretically tunable ternary metals for efficient thermal management

Phase-change materials (PCMs), as important energy storage materials (ESMs), have been widely used in heat dissipation for electronics. However, PCMs are encountering huge challenges since the extremely limited space in microelectronics largely suppresses the applied volume of PCMs, which demands excellent PCMs that can fully utilize the valuable latent heat. This work successfully found a universal strategy toward powerful ESMs from fluidic ternary metals (TMs, GaInSn as a representative TM in this work). TMs exhibit high thermal conductivity (20.3 W m-1 K-1) and significantly effective latent heat (115 J/cm3) and, more important, show continuous phase transition and full utilization of the valuable latent heat. Interestingly, theoretical prediction through ternary phase diagram is carried out to easily tune the melting range, latent heat, and fluidity (viscosity) of TMs to adapt with different service conditions. As a result, thermally conductive silicone grease can be conveniently fabricated via simple shear mixing of TM and polymers. Such thermally conductive TM grease inherits the merits of TM, exhibiting continuous thermal control over daily electronics according to thermal shock performance.

Self-Cooling Gallium-Based Transformative Electronics with a Radiative Cooler for Reliable Stiffness Tuning in Outdoor Use

Reconfigurability of a device that allows tuning of its shape and stiffness is utilized for personal electronics to provide an optimal mechanical interface for an intended purpose. Recent approaches in developing such transformative electronic systems (TES) involved the use of gallium liquid metal, which can change its liquid-solid phase by temperature to facilitate stiffness control of the device. However, the current design cannot withstand excessive heat during outdoor applications, leading to undesired softening of the device when the rigid mode of operation is favored. Here, a gallium-based TES integrated with a flexible and stretchable radiative cooler is presented, which offers zero-power thermal management for reliable rigid mode operation in the hot outdoors. The radiative cooler can both effectively reflect the heat transfer from the sun and emit thermal energy. It, therefore, allows a TES-in-the-air to maintain its temperature below the melting point of gallium (29.8 ℃) under hot weather with strong sun exposure, thus preventing unwanted softening of the device. Comprehensive studies on optical, thermal, and mechanical characteristics of radiative-cooler-integrated TES, along with a proof-of-concept demonstration in the hot outdoors verify the reliability of this design approach, suggesting the possibility of expanding the use of TES in various environments.

High-Stretchability, Ultralow-Hysteresis ConductingPolymer Hydrogel Strain Sensors for Soft Machines

Highly stretchable strain sensors based on conducting polymer hydrogel are rapidly emerging as a promising candidate toward diverse wearable skins and sensing devices for soft machines. However, due to the intrinsic limitations of low stretchability and large hysteresis, existing strain sensors cannot fully exploit their potential when used in wearable or robotic systems. Here, a conducting polymer hydrogel strain sensor exhibiting both ultimate strain (300%) and negligible hysteresis (<1.5%) is presented. This is achieved through a unique microphase semiseparated network design by compositing poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) nanofibers with poly(vinyl alcohol) (PVA) and facile fabrication by combining 3D printing and successive freeze-thawing. The overall superior performances of the strain sensor including stretchability, linearity, cyclic stability, and robustness against mechanical twisting and pressing are systematically characterized. The integration and application of such strain sensor with electronic skins are further demonstrated to measure various physiological signals, identify hand gestures, enable a soft gripper for objection recognition, and remote control of an industrial robot. This work may offer both promising conducting polymer hydrogels with enhanced sensing functionalities and technical platforms toward stretchable electronic skins and intelligent robotic systems.

End-to-end design of wearable sensors

Wearable devices provide an alternative pathway to clinical diagnostics by exploiting various physical, chemical and biological sensors to mine physiological (biophysical and/or biochemical) information in real time (preferably, continuously) and in a non-invasive or minimally invasive manner. These sensors can be worn in the form of glasses, jewellery, face masks, wristwatches, fitness bands, tattoo-like devices, bandages or other patches, and textiles. Wearables such as smartwatches have already proved their capability for the early detection and monitoring of the progression and treatment of various diseases, such as COVID-19 and Parkinson disease, through biophysical signals. Next-generation wearable sensors that enable the multimodal and/or multiplexed measurement of physical parameters and biochemical markers in real time and continuously could be a transformative technology for diagnostics, allowing for high-resolution and time-resolved historical recording of the health status of an individual. In this Review, we examine the building blocks of such wearable sensors, including the substrate materials, sensing mechanisms, power modules and decision-making units, by reflecting on the recent developments in the materials, engineering and data science of these components. Finally, we synthesize current trends in the field to provide predictions for the future trajectory of wearable sensors.

Binary Co-Gelator Strategy: Toward Highly Deformable Ionic Conductors for Wearable Ionoskins

Stretchable ionic conductors have been actively developed due to the increasing demand for wearable electrochemical platforms. Herein, we propose a convenient and effective strategy for tailoring the mechanical deformability of ionic conductors. The mixing of poly(methyl methacrylate) (PMMA, polymer gelator) and 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide ([BMI][TFSI], ionic liquid) produces mechanically stiff ionic conductors. To reduce the chain entanglement of polymer gelators and induce effective dissipation of applied stresses, flexible poly(butyl acrylate) (PBA) with a low glass-transition temperature is additionally doped into the ionic conductor. An extremely stretchable (∼1500%) homogeneous ternary ionic conductor is obtained without a notable change in electrochemical characteristics, unless the content of PBA exceeds the macrophase separation limit of 3 wt %. In addition, the mechanical elasticity (1.8 × 10⁵ Pa) and durability (e.g., recovery ratio of ∼86.3% after 1000 stretching/releasing cycles) of the conductor further support its suitability as a strain sensory platform. In contrast to conventional ionoskins that have to fit the area of target body parts, even a small piece of the ternary ionic conductor successfully monitors human motion over large areas by taking advantage of its superior deformability.

Interfacial Coordination Interaction Enables Soft Elastomer Composites High Thermal Conductivity and High Toughness

Soft elastomers have attracted wide applications, such as soft electronic devices and soft robotics, due to their ability to undergo large deformation with a small external force. Most elastomers suffer from poor toughness and thermal conductivity, which limits their use. The addition of inorganic fillers can enhance the thermal conductivity and toughness, but it deteriorates the softness (low Young's modulus and high stretchability). Integrating thermal conductivity, toughness, and softness into one elastomer is still a challenge. Here, we report a strategy of interfacial coordination interaction to achieve soft elastomer composites with high thermal conductivity and high toughness. We demonstrate the strategy by using poly(lipoic acid) elastomer and silver-coated aluminum filler as model, where silver-sulfur coordination cross-links are formed at the interface. The resultant elastomer composite shows high streachability (450%), high thermal conductivity (2.35 W m-1 K-1), low modulus (321 kPa), and high toughness (3496 J m-2), which cannot be achieve in existing elastomers. The time domain thermoreflectance technique demonstrates that the silver-sulfur coordination interaction lowers the interfacial thermal resistance, resulting in enhanced thermal conductivity of the elastomer composites. The excellent softness stems from lower bonding energy of the silver-sulfur coordination cross-links compared with covalent chemical cross-links. The high toughness also benefits from the interfacial silver-sulfur coordination interaction that can dissipate more energy upon deformation. We further demonstrate the potential application of the thermally conductive, tough, and soft elastomer composites for thermal management of chip and soft electronic devices.

All-Nanofibrous Ionic Capacitive Pressure Sensor for Wearable Applications

Currently, with the development of electronic skins (e-skins), wearable pressure sensors with low energy consumption and excellent wearability for long-term physiological signal monitoring are urgently desired but remain a challenge. Capacitive-type devices are desirable candidates for wearable applications, but traditional capacitive pressure sensors are limited by low capacitance and sensitivity. In this study, an all-nanofibrous ionic pressure sensor (IPS) is developed, and the formation of an electrical double layer at the electrode/electrolyte contact interface significantly enhances the capacitance and sensing properties. The IPS is fabricated by sandwiching a nanofibrous ionic gel sensing layer between two thermoplastic polyurethane nanofibrous membranes with graphene electrodes. The IPS has a high sensitivity of 217.5 kPa^-1 in the pressure range of 0-5 kPa, which is much higher than that of conventional capacitive pressure sensors. Combined with the rapid response and recovery speed (30 and 60 ms), the IPS is suitable for real-time monitoring of multiple physiological signals. Moreover, the nanofiber network endows the IPS with excellent air permeability and heat dissipation, which guarantees comfort during long-term wearing. This work provides a viable strategy to improve the wearability of wearable sensors, which can promote healthcare and human-machine interaction applications.

Bending Sensor Based on Controlled Microcracking Regions for Application toward Wearable Electronics and Robotics

A soft bending sensor based on the inverse pyramid structure is demonstrated, revealing that it can effectively suppress microcrack formation in designated regions, thus allowing the cracks to open gradually with bending in a controlled manner. Such a feature enabled the bending sensor to simultaneously have a wide dynamic range of bending strain (0.025-5.4%), high gauge factor (∼74), and high linearity (R² ∼ 0.99). Furthermore, the bending sensor can capture repeated instantaneous changes in strain and various types of vibrations, owing to its fast response time. Moreover, the bending direction can be differentiated with a single layer of the sensor, and using an array of sensors integrated on a glove, object recognition was demonstrated via machine learning. Finally, a self-monitoring proprioceptive ionic electroactive polymer (IEAP) actuator capable of operating in liquid was demonstrated. Such features of our bending sensor will enable a simple and effective way of detecting sophisticated motion, thus potentially advancing wearable healthcare monitoring electronics and enabling proprioceptive soft robotics.

Nanocage Ferritin Reinforced Polyacrylamide Hydrogel for Wearable Flexible Strain Sensors

Biocomposite hydrogels are promising for applications in wearable flexible strain sensors. Nevertheless, the existing biocomposite hydrogels are still hard to meet all requirements, which limits the practical application. Here, inspired by the structure and composition of natural ferritin, we design a PAAm-Ferritin hybrid hydrogel through a facile method. Ferritin is uniformly distributed in the cross-linking networks and acts as a nanocage spring model, leading to the enhanced tensile strength of the hydrogel. The fracture stress is 99 kPa at 1400% maximum elongation. As fabricated PAAm-Ferritin hybrid hydrogels exhibit high toughness and low elastic modulus (21 kPa). The PAAm-Ferritin hybrid hydrogels present excellent biocompatibility and increased conductivity compared with PAAm hydrogel. Impressively, as a wearable flexible strain sensor, the PAAm-Ferritin hybrid hydrogels have high sensitivity (gauge factor = 2.06), excellent reliability, and cycling stability. This study indicates the feasibility of utilizing ferritin to synthesize functional materials, which is conducive to expanding the use of protein synthesis of materials technology and application fields.

High-Performance Liquid Metal/Polyborosiloxane Elastomer toward Thermally Conductive Applications

With the combination of high flexibility and thermal property, thermally conductive elastomers have played an important role in daily life. However, traditional thermally conductive elastomers display limited stretchability and toughness, seriously restricting their further development in practical applications. Herein, a high-performance composite is fabricated by dispersing room-temperature liquid metal microdroplets (LM) into a polyborosiloxane elastomer (PBSE). Due to the unique solid-liquid coupling mechanism, the LM can deform with the PBSE matrix, achieving higher fracture strain (401%) and fracture toughness (2164 J/m²). Meanwhile, the existence of LM microdroplets improves the thermal conductivity of the composite. Interestingly, the LM/PBSE also exhibits remarkable anti-impact, adhesion capacities under complex loading environments. As a novel stretchable elastomer with enhanced mechanical and thermal behavior, the LM/PBSE shows good application prospects in the fields of thermal camouflages, stretchable heat-dissipation matrixes, and multifunctional shells for electronic devices.

Wires with Continuous Sabal Leaf-Patterned Micropores Constructed by Freeze Printing for a Wearable Sensor Responsible to Multiple Deformations

The design of porous structure in wearable sensors is very important for the detection of mechanical signals. However, it remains challenging to construct a porous structure capable of detecting all kinds of mechanical signals. Here, round wire with long-range orientated micropores (RW-LOM) is fabricated by a newly established freeze printing technique and constructed into a wearable sensor by the incorporation of carbon nanotubes and polydimethylsiloxane. The Sabal leaf-like lamellar structure in RW-LOM is realized and can be tuned by the proper coordination of slurry concentration and the printing parameters. The fine structures in RW-LOM allow the wearable sensor to detect compression, stretching, twisting, and bending with a high sensitivity, stability, and broad detecting range. This work not only provides a wearable sensor with high stability and high sensitivity but also establishes a technique to construct porous wires that could find applications in the fields like intelligent industry and healthcare.

A 3D-printed neuromorphic humanoid hand for grasping unknown objects

Compared with conventional von Neumann's architecture-based processors, neuromorphic systems provide energy-saving in-memory computing. We present here a 3D neuromorphic humanoid hand designed for providing an artificial unconscious response based on training. The neuromorphic humanoid hand system mimics the reflex arc for a quick response by managing complex spatiotemporal information. A 3D structural humanoid hand is first integrated with 3D-printed pressure sensors and a portable neuromorphic device that was fabricated by the multi-axis robot 3D printing technology. The 3D neuromorphic robot hand provides bioinspired signal perception, including detection, signal transmission, and signal processing, together with the biomimetic reflex arc function, allowing it to hold an unknown object with an automatically increased gripping force without a conventional controlling processor. The proposed system offers a new approach for realizing an unconscious response with an artificially intelligent robot.

Flexible pressure sensors via engineering microstructures for wearable human-machine interaction and health monitoring applications

Flexible pressure sensors capable of transducing pressure stimuli into electrical signals have drawn extensive attention owing to their potential applications for human-machine interaction and healthcare monitoring. To meet these application demands, engineering microstructures in the pressure sensors are an efficient way to improve key sensing performances, such as sensitivity, linear sensing range, response time, hysteresis, and durability. In this review, we provide an overview of the recent advances in the fabrication and application of high-performance flexible pressure sensors via engineering microstructures. The implementation mechanisms and fabrication strategies of microstructures including micropatterned, porous, fiber-network, and multiple microstructures are systematically summarized. The applications of flexible pressure sensors with microstructures in the fields of wearable human-machine interaction, and ex vivo and in vivo healthcare monitoring are comprehensively discussed. Finally, the outlook and challenges in the future improvement of flexible pressure sensors toward practical applications are presented.

Wireless graphene-based thermal patch for obtaining temperature distribution and performing thermography

Thermal imaging provides information regarding the general condition of the human body and facilitates the diagnosis of various diseases. Heat therapy or thermotherapy can help in the treatment of injuries to the skin tissue. Here, we report a wearable thermal patch with dual functions of continuous skin temperature sensing and thermotherapy for effective self-care treatment. This system consists of a graphene-based capacitive sensor, a graphene thermal pad, and a flexible readout board with a wireless communication module. The wearable sensor continuously monitors the temperature variation over a large area of the skin (3 × 3cm²) with high resolution and sensitivity and performs thermotherapy via the graphene-based heater mounted at the bottom of the device. Animal studies prove that the proposed system can be used to diagnose various diseases. This technology could be useful in the development of convenient and wearable health care devices.

Materials, Preparation Strategies, and Wearable Sensor Applications of Conductive Fibers: A Review

The recent advances in wearable sensors and intelligent human-machine interfaces have sparked a great many interests in conductive fibers owing to their high conductivity, light weight, good flexibility, and durability. As one of the most impressive materials for wearable sensors, conductive fibers can be made from a variety of raw sources via diverse preparation strategies. Herein, to offer a comprehensive understanding of conductive fibers, we present an overview of the recent progress in the materials, the preparation strategies, and the wearable sensor applications related. Firstly, the three types of conductive fibers, including metal-based, carbon-based, and polymer-based, are summarized in terms of their principal material composition. Then, various preparation strategies of conductive fibers are established. Next, the primary wearable sensors made of conductive fibers are illustrated in detail. Finally, a robust outlook on conductive fibers and their wearable sensor applications are addressed.

Skin bioelectronics towards long-term, continuous health monitoring

Skin bioelectronics are considered as an ideal platform for personalised healthcare because of their unique characteristics, such as thinness, light weight, good biocompatibility, excellent mechanical robustness, and great skin conformability. Recent advances in skin-interfaced bioelectronics have promoted various applications in healthcare and precision medicine. Particularly, skin bioelectronics for long-term, continuous health monitoring offer powerful analysis of a broad spectrum of health statuses, providing a route to early disease diagnosis and treatment. In this review, we discuss (1) representative healthcare sensing devices, (2) material and structure selection, device properties, and wireless technologies of skin bioelectronics towards long-term, continuous health monitoring, (3) healthcare applications: acquisition and analysis of electrophysiological, biophysical, and biochemical signals, and comprehensive monitoring, and (4) rational guidelines for the design of future skin bioelectronics for long-term, continuous health monitoring. Long-term, continuous health monitoring of advanced skin bioelectronics will open unprecedented opportunities for timely disease prevention, screening, diagnosis, and treatment, demonstrating great promise to revolutionise traditional medical practices.

Fully Printed Stretchable and Multifunctional E-Textiles for Aesthetic Wearable Electronic Systems

Electronic textiles (e-textiles) that combine the wearing comfort of textiles and the functionality of soft electronics are highly demanded in wearable applications. However, fabricating robust high-performance stretchable e-textiles with good abrasion resistance and high-resolution aesthetic patterns for high-throughput manufacturing and practical applications remains challenging. Herein, the authors report a new multifunctional e-textile fabricated via screen printing of the water-based silver fractal dendrites conductive ink. The as-fabricated e-textiles spray-coated with the invisible waterproofing agent exhibit superior flexibility, water resistance, wearing comfort, air permeability, and abrasion resistance, achieving a low sheet resistance of 0.088 Ω sq^-1 , high stretchability of up to 154%, and excellent dynamic stability for over 1000 cyclic testing (ε = 100%). The printed e-textiles can be explored as strain sensors and ultralow voltage-driven Joule heaters driven for personalized thermal management. They finally demonstrate an integrated aesthetic smart clothing made of their multifunctional e-textiles for human motion detection and body-temperature management. The printed e-textiles provide new opportunities for developing novel wearable electronics and smart clothing for future commercial applications.

Improving thermal conductivities of textile materials by nanohybrid approaches

The thermal transfer between individual body and the surroundings occurs by several paths such as radiation, evaporation, conduction, and convection. Thermal management is related with the heat transfer between the human body and the surroundings, which aims to keep the body temperature in the comfort range either via preserving or via emitting the body heat. The essential duty of clothing is to contribute to the thermal balance of the human body by regulating the heat and moisture transfer. In the case of poorly controlled body heat, health problems such as hyperthermia and heatstroke along with environmental problems due to higher energy consumption can occur. Recently, research has been focused on advanced textiles with novel approaches on materials synthesis and structure design, which can provide thermal comfort together with energy saving. This review article focuses on the innovative strategies basically on the passive textile models for improved thermal conductivity. We will discuss both the fabrication techniques and the inclusion of carbon-based and boron-based fillers to form nano-hybrid textile solutions, which are used to improve the thermal conductivity of the materials.

Ti3C2Tx MXene-Based Flexible Piezoresistive Physical Sensors

MXenes have received increasing attention due to their two-dimensional layered structure, high conductivity, hydrophilicity, and large specific surface area. Because of these distinctive advantages, MXenes are considered as very competitive pressure-sensitive materials in applications of flexible piezoresistive sensors. This work reviews the preparation methods, basic properties, and assembly methods of MXenes and their recent developments in piezoresistive sensor applications. The recent developments of MXene-based flexible piezoresistive sensors can be categorized into one-dimensional fibrous, two-dimensional planar, and three-dimensional sensors according to their various structures. The trends of multifunctional integration of MXene-based pressure sensors are also summarized. Finally, we end this review by describing the opportunities and challenges for MXene-based pressure sensors and the great prospects of MXenes in the field of pressure sensor applications.

Functionalized Fiber-Based Strain Sensors: Pathway to Next-Generation Wearable Electronics

Wearable strain sensors are arousing increasing research interests in recent years on account of their potentials in motion detection, personal and public healthcare, future entertainment, man-machine interaction, artificial intelligence, and so forth. Much research has focused on fiber-based sensors due to the appealing performance of fibers, including processing flexibility, wearing comfortability, outstanding lifetime and serviceability, low-cost and large-scale capacity. Herein, we review the latest advances in functionalization and device fabrication of fiber materials toward applications in fiber-based wearable strain sensors. We describe the approaches for preparing conductive fibers such as spinning, surface modification, and structural transformation. We also introduce the fabrication and sensing mechanisms of state-of-the-art sensors and analyze their merits and demerits. The applications toward motion detection, healthcare, man-machine interaction, future entertainment, and multifunctional sensing are summarized with typical examples. We finally critically analyze tough challenges and future remarks of fiber-based strain sensors, aiming to implement them in real applications.

Porous and Ultra-Flexible Crosslinked MXene/Polyimide Composites for Multifunctional Electromagnetic Interference Shielding

Lightweight, ultra-flexible, and robust crosslinked transition metal carbide (Ti₃C₂ MXene) coated polyimide (PI) (C-MXene@PI) porous composites are manufactured via a scalable dip-coating followed by chemical crosslinking approach. In addition to the hydrophobicity, anti-oxidation and extreme-temperature stability, efficient utilization of the intrinsic conductivity of MXene, the interfacial polarization between MXene and PI, and the micrometer-sized pores of the composite foams are achieved. Consequently, the composites show a satisfactory X-band electromagnetic interference (EMI) shielding effectiveness of 22.5 to 62.5 dB at a density of 28.7 to 48.7 mg cm^-3, leading to an excellent surface-specific SE of 21,317 dB cm² g^-1. Moreover, the composite foams exhibit excellent electrothermal performance as flexible heaters in terms of a prominent, rapid reproducible, and stable electrothermal effect at low voltages and superior heat performance and more uniform heat distribution compared with the commercial heaters composed of alloy plates. Furthermore, the composite foams are well attached on a human body to check their electromechanical sensing performance, demonstrating the sensitive and reliable detection of human motions as wearable sensors. The excellent EMI shielding performance and multifunctionalities, along with the facile and easy-to-scalable manufacturing techniques, imply promising perspectives of the porous C-MXene@PI composites in next-generation flexible electronics, aerospace, and smart devices.

Liquid metal-polymer conductor-based wireless, battery-free epidermal patch

Wearable epidermal patch can seamlessly monitor biological signals in real-time. Here, we report a liquid metal-polymer conductor-based wireless epidermal patch. The epidermal patch is made of a new conductive material called liquid metal-polymer conductors (LMPC). LMPC is made by casting and peeling off polymers from patterned liquid metal particles. Our printable conductors present good stretchability, repeatability, and biocompatibility. We fabricate LMPC-based antenna and wire, which achieves wireless signal communication and power supply. To demonstrate the capability of our LMPC-based antenna and wire, we fabricate an epidermal patch to analyze metabolites, electrolytes, and urea in sweat. When a portable device is close to the epidermal sensor, the device can power and read the sensor through LMPC-based antenna. The epidermal patch exhibited good analytical performance for sweat analysis with a low limit of detection, fast response time, and multiplex detection capabilities. This epidermal patch opens the possibility for a broad range of non-invasive diagnostic tools that can be used for health monitoring in the general population.

Wearable Triboelectric Sensors Enabled Gait Analysis and Waist Motion Capture for IoT-Based Smart Healthcare Applications

Gait and waist motions always contain massive personnel information and it is feasible to extract these data via wearable electronics for identification and healthcare based on the Internet of Things (IoT). There also remains a demand to develop a cost-effective human-machine interface to enhance the immersion during the long-term rehabilitation. Meanwhile, triboelectric nanogenerator (TENG) revealing its merits in both wearable electronics and IoT tends to be a possible solution. Herein, the authors present wearable TENG-based devices for gait analysis and waist motion capture to enhance the intelligence and performance of the lower-limb and waist rehabilitation. Four triboelectric sensors are equidistantly sewed onto a fabric belt to recognize the waist motion, enabling the real-time robotic manipulation and virtual game for immersion-enhanced waist training. The insole equipped with two TENG sensors is designed for walking status detection and a 98.4% identification accuracy for five different humans aiming at rehabilitation plan selection is achieved by leveraging machine learning technology to further analyze the signals. Through a lower-limb rehabilitation robot, the authors demonstrate that the sensory system performs well in user recognition, motion monitoring, as well as robot and gaming-aided training, showing its potential in IoT-based smart healthcare applications.

Recent Advances in Wearable Optical Sensor Automation Powered by Battery versus Skin-like Battery-Free Devices for Personal Healthcare-A Review

Currently, old-style personal Medicare techniques rely mostly on traditional methods, such as cumbersome tools and complicated processes, which can be time consuming and inconvenient in some circumstances. Furthermore, such old methods need the use of heavy equipment, blood draws, and traditional bench-top testing procedures. Invasive ways of acquiring test samples can potentially cause patient discomfort and anguish. Wearable sensors, on the other hand, may be attached to numerous body areas to capture diverse biochemical and physiological characteristics as a developing analytical tool. Physical, chemical, and biological data transferred via the skin are used to monitor health in various circumstances. Wearable sensors can assess the aberrant conditions of the physical or chemical components of the human body in real time, exposing the body state in time, thanks to unintrusive sampling and high accuracy. Most commercially available wearable gadgets are mechanically hard components attached to bands and worn on the wrist, with form factors ultimately constrained by the size and weight of the batteries required for the power supply. Basic physiological signals comprise a lot of health-related data. The estimation of critical physiological characteristics, such as pulse inconstancy or variability using photoplethysmography (PPG) and oxygen saturation in arterial blood using pulse oximetry, is possible by utilizing an analysis of the pulsatile component of the bloodstream. Wearable gadgets with “skin-like” qualities are a new type of automation that is only starting to make its way out of research labs and into pre-commercial prototypes. Flexible skin-like sensing devices have accomplished several functionalities previously inaccessible for typical sensing devices due to their deformability, lightness, portability, and flexibility. In this paper, we studied the recent advancement in battery-powered wearable sensors established on optical phenomena and skin-like battery-free sensors, which brings a breakthrough in wearable sensing automation.

Improvement in Strain Sensor Stability by Adapting the Metal Contact Layer

Research on stretchable strain sensors is actively conducted due to increasing interest in wearable devices. However, typical studies have focused on improving the elasticity of the electrode. Therefore, methods of directly connecting wire or attaching conductive tape to materials to detect deformation have been used to evaluate the performance of strain sensors. Polyaniline (PANI), a p-type semiconductive polymer, has been widely used for stretchable electrodes. However, conventional procedures have limitations in determining an appropriate metal for ohmic contact with PANI. Materials that are generally used for connection with PANI form an undesirable metal-semiconductor junction and have significant contact resistance. Hence, they degrade sensor performance. This study secured ohmic contact by adapting Au thin film as the metal contact layer (the MCL), with lower contact resistance and a larger work function than PANI. Additionally, we presented a buffer layer using hard polydimethylsiloxane (PDMS) and structured it into a dumbbell shape to protect the metal from deformation. As a result, we enhanced steadiness and repeatability up to 50% strain by comparing the gauge factors and the relative resistance changes. Consequently, adapting structural methods (the MCL and the dumbbell shape) to a device can result in strain sensors with promising stability, as well as high stretchability.

Moisture-resistant, stretchable NOx gas sensors based on laser-induced graphene for environmental monitoring and breath analysis

The accurate, continuous analysis of healthcare-relevant gases such as nitrogen oxides (NO_x) in a humid environment remains elusive for low-cost, stretchable gas sensing devices. This study presents the design and demonstration of a moisture-resistant, stretchable NO_x gas sensor based on laser-induced graphene (LIG). Sandwiched between a soft elastomeric substrate and a moisture-resistant semipermeable encapsulant, the LIG sensing and electrode layer is first optimized by tuning laser processing parameters such as power, image density, and defocus distance. The gas sensor, using a needlelike LIG prepared with optimal laser processing parameters, exhibits a large response of 4.18‰ ppm^-1 to NO and 6.66‰ ppm^-1 to NO₂, an ultralow detection limit of 8.3 ppb to NO and 4.0 ppb to NO₂, fast response/recovery, and excellent selectivity. The design of a stretchable serpentine structure in the LIG electrode and strain isolation from the stiff island allows the gas sensor to be stretched by 30%. Combined with a moisture-resistant property against a relative humidity of 90%, the reported gas sensor has further been demonstrated to monitor the personal local environment during different times of the day and analyze human breath samples to classify patients with respiratory diseases from healthy volunteers. Moisture-resistant, stretchable NO_x gas sensors can expand the capability of wearable devices to detect biomarkers from humans and exposed environments for early disease diagnostics.

Programmable Sensitivity Screening of Strain Sensors by Local Electrical and Mechanical Properties Coupling

Owing to the canonical trade-off between the gauge factor and the working range, there is an emergent need for strain sensors with customizable sensitivity for various applications of different deformation ranges. However, current optimization strategies typically allow possessing either, not both, high-sensing performance or customizable sensing performance. Here, a laser-programmed heterogeneous strain sensor featured locally coupled electrical and mechanical properties (named an LCoup sensor) is developed to access customized sensor performance. Coupled electromechanical properties enable the applied strain to be mainly experienced by the higher sensitivity regions when stretched. By optimizing the parameters of laser processes, the gauge factor can systematically screen within 2 orders of magnitude (from 7.8 to 266.6) while maintaining good stretchability (50%). To prove the potential in human-machine interaction, the real-time monitoring and recognition of set hand gestures (left-click, right-click, and double-click) are demonstrated, representing the traditional input patterns of the computer mouse. Multiscale programming of material properties can further achieve excellent and tailored device performances, offering more opportunities for the design of a broad range of flexible electronics.

Highly Stretchable and Sensitive Single-Walled Carbon Nanotube-Based Sensor Decorated on a Polyether Ester Urethane Substrate by a Low Hydrothermal Process

We report a highly stretchable sensor with low-concentration (1.5 wt %) single-walled carbon nanotubes (SWCNTs) on flexible polyether ester urethane (PEEU) yarn, fabricated using a low hydrothermal process at 90 °C. Although SWCNTs restrict the PEEU polymer chain mobility, the resulting ductility of our nanocomposites reduces only by 16.5% on average, initially from 667.3% elongation at break to 557.2%. The resulting electrical resistivity of our nanocomposites can be controlled systematically by the number of hydrothermal cycles. A high gauge factor value of 4.84 is achieved at a tensile strain below 100%, and it increases up to 28.5 with applying a tensile strain above 450%. We find that the piezoresistivity of our nanocomposite is sensitive to temperature variations of 25-85 °C due to the hopping effect, which promotes more charge transport at elevated temperatures. Our nanocomposites offer both a high sensitivity and a large strain sensing range, which is achieved with a relatively simple fabrication technique and low concentration of SWCNTs.

Hierarchically Multifunctional Polyimide Composite Films with Strongly Enhanced Thermal Conductivity

The development of lightweight and integration for electronics requires flexible films with high thermal conductivity and electromagnetic interference (EMI) shielding to overcome heat accumulation and electromagnetic radiation pollution. Herein, the hierarchical design and assembly strategy was adopted to fabricate hierarchically multifunctional polyimide composite films, with graphene oxide/expanded graphite (GO/EG) as the top thermally conductive and EMI shielding layer, Fe3O4/polyimide (Fe3O4/PI) as the middle EMI shielding enhancement layer and electrospun PI fibers as the substrate layer for mechanical improvement. PI composite films with 61.0 wt% of GO/EG and 23.8 wt% of Fe3O4/PI exhibits high in-plane thermal conductivity coefficient (95.40 W (m K)-1), excellent EMI shielding effectiveness (34.0 dB), good tensile strength (93.6 MPa) and fast electric-heating response (5 s). The test in the central processing unit verifies PI composite films present broad application prospects in electronics fields.

Multidimensional Force Sensors Based on Triboelectric Nanogenerators for Electronic Skin

The ability to detect multidimensional forces is highly desired for electronic skin (E-skin) sensors. Here, based on single-electrode-mode triboelectric nanogenerators (S-TENGs), fully elastic E-skin that can simultaneously sense normal pressure and shear force has been proposed. With the hemispherical curve-structure design and further structural optimization, the pressure sensor exhibits a high linearity and sensitivity of 144.8 mV/kPa in the low-pressure region. By partitioning the lower tribolayer into two symmetric parts, a multidimensional force sensor has been fabricated in which the output voltage sum and ratio of the two S-TENGs can be used for normal pressure and shear force sensing, respectively. When the multidimensional force sensors are mounted at a two-fingered robotic manipulator, the change of the grabbing state can be recognized, indicating that the sensor may have great application potential in tactile sensing for robotic manipulation, human-robot interactions, environmental awareness, and object recognition.

Smart Textile Based on 3D Stretchable Silver Nanowires/MXene Conductive Networks for Personal Healthcare and Thermal Management

Wearable electronics have enriched daily lives by providing smart functions as well as monitoring body health conditions. However, the realization of wearable electronics with personal healthcare and thermal comfort management of the human body is still a great challenge. Furthermore, manufacturing such on-skin wearable electronics on traditional thin-film substrates results in limited gas permeability and inflammation. Herein, we proposed a personal healthcare and thermal management smart textile with a three-dimensional (3D) interconnected conductive network, formed by silver nanowires (AgNWs) bridging lamellar structured transition-metal carbide/carbonitride (MXene) nanosheets deposited on nonwoven fabrics. Benefiting from the interconnected conductive network synergistic effect of one-dimensional (1D) AgNWs bridging two-dimensional (2D) MXene, the strain sensor exhibits excellent durability (>1500 stretching cycles) and high sensitivity (gauge factor (GF) = 1085) with a wide strain range limit (∼100%), and the details of human body activities can be accurately recognized and monitored. Moreover, thanks to the excellent Joule heating and photothermal effect endowed by AgNWs and MXene, the multifunctional smart textile with direct temperature visualization and solar-powered temperature regulation functions was successfully developed, after further combination of thermochromic and phase-change functional layers, respectively. The smart textiles with a stretchable AgNW-MXene 3D conductive network hold great promise for next-generation personal healthcare and thermal management wearable systems.

Smart Materials Enabled with Artificial Intelligence for Healthcare Wearables

Contemporary medicine suffers from many shortcomings in terms of successful disease diagnosis and treatment, both of which rely on detection capacity and timing. The lack of effective, reliable, and affordable detection and real‐time monitoring limits the affordability of timely diagnosis and treatment. A new frontier that overcomes these challenges relies on smart health monitoring systems that combine wearable sensors and an analytical modulus. This review presents the latest advances in smart materials for the development of multifunctional wearable sensors while providing a bird's eye‐view of their characteristics, functions, and applications. The review also presents the state‐of‐the‐art on wearables fitted with artificial intelligence (AI) and support systems for clinical decision in early detection and accurate diagnosis of disorders. The ongoing challenges and future prospects for providing personal healthcare with AI‐assisted support systems relating to clinical decisions are presented and discussed.

An Efficient Strategy for Reinforcing Flexible Ceramic Membranes

Herein, we present a facile reinforcement method for the large-scale fabrication of highly flexible, mechanically stable, temperature-resistant ceramic lightweight membranes based on the cross-linked assembly of zirconia-silica (ZrO₂-SiO₂) nanofibrous and montmorillonite (MMT) nanosheets through electrospinning and a subsequent calcination process. The resulting MMT@ZrO₂-SiO₂ membranes exhibit high flexibility with a bending rigidity of 0.2 cN mm^-1, robust mechanical performance with a tensile strength of up to 1.83 MPa, robust fire resistance, and temperature-invariant mechanical stability from -196 to 1000 °C. The thermal superinsulation with a thermal conductivity as low as 0.026 W m^-1 K^-1 and the improved mechanical strength can be attributed to the cross-linked interfacial interaction between the ZrO₂-SiO₂ nanofibers and the MMT nanosheets. Additionally, a firefighter uniform with MMT@ZrO₂-SiO₂ membranes inside features a superior thermal protective property up to the A2 level (combined flame and radiant exposure) and an excellent fire resistance of up to 1000 °C, which is ideal for next-generation firefighter uniform manufacturing.

Flexible and Stable Carbon Nanotube Film Strain Sensors with Self-Derived Integrated Electrodes

The development of flexible and wearable electronic devices has put an increasing demand on electrode systems with seamless connection and high compatibility with the main device, in order to accommodate complex deformation conditions and maintain stable performance. Here, we present a carbon nanotube-integrated electrode (CNTIE) by wet-pulling the ends of a carbon nanotube (CNT) film to form condensed thin fibers that resemble conventional conducting wire electrodes. A flexible strain sensor was constructed consisting of the middle CNT film as the main functional part and the CNTIE as self-derived electrodes, with inherent CNT connection between the two parts. The sensor can be transferred to versatile substrates (e.g., balloon surface) or encapsulated in thermoplastic polymers, exhibiting a large linear response range (up to 1000% in tensile strain), excellent durability and repeatability over 5000 cycles, and the ability to detect small- to large-degree human body motions. In addition, the strain sensor based on the CNTIE hybrid film (MXene/CNT and graphene/CNT) also shows superior linearity and stability at a strain range of 0-800%. Compared with the sensors using traditional silver wire electrodes and separately fabricated CNT fiber electrodes, our CNTIE plays an important role in achieving highly stable performance in the strain cycles. Our self-derived integrated electrodes provide a potential route to solve the incompatibility issues of conventional electrodes and to develop high-performance flexible and wearable systems based on CNTs and other nanomaterials.

Wearable Assistive Robotics: A Perspective on Current Challenges and Future Trends

Wearable assistive robotics is an emerging technology with the potential to assist humans with sensorimotor impairments to perform daily activities. This assistance enables individuals to be physically and socially active, perform activities independently, and recover quality of life. These benefits to society have motivated the study of several robotic approaches, developing systems ranging from rigid to soft robots with single and multimodal sensing, heuristics and machine learning methods, and from manual to autonomous control for assistance of the upper and lower limbs. This type of wearable robotic technology, being in direct contact and interaction with the body, needs to comply with a variety of requirements to make the system and assistance efficient, safe and usable on a daily basis by the individual. This paper presents a brief review of the progress achieved in recent years, the current challenges and trends for the design and deployment of wearable assistive robotics including the clinical and user need, material and sensing technology, machine learning methods for perception and control, adaptability and acceptability, datasets and standards, and translation from lab to the real world.

Abrasion tolerant, non-stretchable and super-water-repellent conductive & ultrasensitive pattern for identifying slow, fast, weak and strong human motions under diverse conditions

The conversion of mechanical deformation into electrical signals is a widely used principle for various relevant applications. Facile & scalable fabrication, ultrahigh-sensitivity, low-response time and uninterrupted performance under severe conditions are hallmarks of an efficient strain-sensor that would be suitable for realistic application. In the past, various approaches were introduced to achieve high gauge factor-mainly associated with a large tensile deformation. But, in reality, a flexible strain sensor that displays a high gauge factor at low applied strain and remains efficient under practically relevant diverse and challenging conditions would be more appropriate for unambiguous and effective monitoring of human motions and other relevant applications. But, a low-strain sensor with ultrahigh sensitivity and durability is yet to be introduced in the literature. Here, a metal-free, chemically reactive and conductive ink is unprecedentedly introduced following a 1,4-conjugate addition reaction. Furthermore, a strategic integration of a chemically reactive porous paper with the prepared conductive ink allowed the development of a chemically reactive and conductive interface that allowed desired post covalent modification with selected alkylamines under ambient conditions. Taking advantage of the spatially selective deposition of the prepared ink on chemically recative paper and the ability of post covalent modification of the prepared ink, an abrasion tolerant superhydrophobic & conductive patterned interface was developed for achieving a low-strain (below 0.2%) based flexible strain sensor with an ultrahigh sensitivity (gauge factor ∼18 300) and low response time (8 ms). The external low-strain induced cracks on the flexible & durable superhydrophobic and conductive patterned interface provided a facile basis for real-time & wireless monitoring of slow, fast, weak and strong human motions & expressions-under diverse conditions, including continuous aqueous exposures, physical abrasions etc.

Designing New-Generation Piezoelectric Transducers by Embedding Superior Graphene-Based Thermal Regulators

Cascaded-piezoelectric-transducers (CPETs) is a key component in modern energy-conversion fields, possessing versatile applications in ultrasonic scalpels, acoustic levitation, and sonar. However, serious self-heating inevitably occurs inside high-power CPETs, severely limiting their practical applications in broader fields. To tackle this, multidirectional heat-escape channels of multidimensional (multi-D, 3D/2D) graphene films are introduced in designing new-type thermal regulators. A porous AlN-ceramic thermal-sink is creatively selected as a template for directly synthesizing graphene via a two-step chemical vapor deposition strategy. This perfect combination of 3D/2D-graphene and the AlN ceramic can integrate their complementary advantages in uniformizing, transmitting, and releasing heat. Amazingly, in the new-generation CPETs embedded with these graphene-based thermal regulators, the self-heating-induced temperature rise can be substantially reduced by ≈60% (far exceeding actual demand standard). As another kernel parameter, electroacoustic-energy-conversion efficiency is dramatically improved in the new-generation CPETs. Briefly, this research realizes the first synthesis of a novel multi-D-graphene/AlN-ceramic hybrid, and propels its brand-new application directions in new-generation energy-conversion- and thermal-management-related territories.

Flexible Sandwich-Structured Electromagnetic Interference Shielding Nanocomposite Films with Excellent Thermal Conductivities

With the rapid development and popularization of smart, portable, and wearable flexible electronic devices, urgent demands have been raised for flexible electromagnetic interference (EMI) shielding films to solve related electromagnetic pollution problems. With polyvinyl alcohol (PVA) as polymer matrix, the sandwich-structured EMI shielding nanocomposite films are prepared via electrospinning-laying-hot pressing technology, where Fe₃ O₄ /PVA composite electrospun nanofibers in the top and bottom layers and Ti₃ C₂ T_x /PVA composite electrospun nanofibers in the middle layer. Owing to the electrospinning process and the successful construction of the sandwich structure, when the amounts of Ti₃ C₂ T_x and Fe₃ O₄ are respectively only 13.3 and 26.7 wt%, the EMI shielding effectiveness (EMI SE) of the sandwich-structured EMI shielding nanocomposite films reach 40 dB with the thickness of 75 µm, higher than that of (Fe₃ O₄ /Ti₃ C₂ T_x )/PVA EMI shielding nanocomposite films (21 dB) prepared based on blending-electrospinning-hot pressing process under the same amounts of fillers. Furthermore, the prepared sandwich-structured EMI shielding nanocomposite films possess excellent thermal conductivities and mechanical properties. This novel kind of flexible sandwich-structured EMI shielding nanocomposite films with excellent EMI shielding performances, thermal conductivities, and mechanical properties presents broad application prospects in the fields of EMI shielding and protection for high-power, portable, and wearable flexible electronic devices.

AI enabled sign language recognition and VR space bidirectional communication using triboelectric smart glove

Sign language recognition, especially the sentence recognition, is of great significance for lowering the communication barrier between the hearing/speech impaired and the non-signers. The general glove solutions, which are employed to detect motions of our dexterous hands, only achieve recognizing discrete single gestures (i.e., numbers, letters, or words) instead of sentences, far from satisfying the meet of the signers' daily communication. Here, we propose an artificial intelligence enabled sign language recognition and communication system comprising sensing gloves, deep learning block, and virtual reality interface. Non-segmentation and segmentation assisted deep learning model achieves the recognition of 50 words and 20 sentences. Significantly, the segmentation approach splits entire sentence signals into word units. Then the deep learning model recognizes all word elements and reversely reconstructs and recognizes sentences. Furthermore, new/never-seen sentences created by new-order word elements recombination can be recognized with an average correct rate of 86.67%. Finally, the sign language recognition results are projected into virtual space and translated into text and audio, allowing the remote and bidirectional communication between signers and non-signers.

Suppressing Thermal Negative Effect and Maintaining High-Temperature Steady Electrical Performance of Triboelectric Nanogenerators by Employing Phase Change Material

Triboelectric nanogenerators (TENGs) are newly developed energy-harvesting mechanisms, which can efficiently transmute irregular mechanical energy into scarce electrical energy. However, the electrical performance of TENGs shows a decreasing tendency with the increase in temperature, and the negative effect caused by friction heat and operating environmental thermal stresses for the output performance, durability, and reliability are still a bottleneck, restricting the practical application of TENG electronic devices. Especially for wearable TENG devices, the heat-induced temperature rise evokes extreme discomfort and even hazards to human health. To effectively suppress the thermal negative effect and maintain the high-temperature steady electrical performance of TENGs, a novel thermo-regulating TENG (Tr-TENG) based on phase change materials (PCMs) is designed. The results state clearly that the Tr-TENG can maintain steady output performance without deterioration by the introduction of PCMs, during continuous heating and natural cooling, while the output performance of conventional TENG is decayed by 18.33%. More importantly, the Tr-TENG possesses high-efficiency thermal management ability, resulting in its improved durability, reliability, and thermal comfort. This study creates new possibilities for the development of advanced multifunctional TENGs with attractive characteristics and desirable performances and promotes the application of TENG electronic devices in harsh environments.