Age of Flexible Electronics: Emerging Trends in Soft Multifunctional Sensors

Universal Coating Strategy Breaks Stability-Performance Trade-Off in Macroscopic Graphene Films

Macroscopic graphene film (MGF), excelling in superior electric and thermal conductivities, holds great promise in energy storage, thermal management, and flexible electronics. However, the high graphitization of MGF leads to surface fragility because of the weak interlayer interaction, leading to severe performance limitations. Herein, we report an interface engineering strategy for the thinnest coating on MGF to date, significantly enhancing surface stability while preserving ultrahigh electric and thermal conductivities. With a surfactant-enhanced interface self-assembly strategy, we construct a 5 nm thick Triton X-100-enhanced graphene oxide coating on MGF (MGF@TGO). This modification increases the surface adhesion by 206.36% while maintaining over 99% of its electrical and thermal conductivities. MGF@TGO serves as an effective thermal management unit, exhibiting excellent stability without surface detachment under simulated operating conditions. Depth profiling characterizations reveal that hydrogen bonding and π-π stacking costrengthen the MGF@TGO surface. Notably, our strategy is universally applicable to multiple aromatic-polar amphiphilic surfactants. This work successfully balances surface stability with performance retention, offering a scalable solution for MGF applications in industry.

Natural Al2O3 Nanodielectric-Based Flexible Sensor with Triple Insensitivity for Healthcare and Robotics

Flexible pressure sensors are critical for advanced systems such as electronic skins and human-machine interaction. Among them, ionic capacitive pressure sensors have attracted widespread attention due to their exceptional flexibility and sensitivity. However, variations in ambient temperature, humidity, and operating circuit frequency significantly degrade the measurement accuracy of ionic capacitive pressure sensors and increase the complexity of subsequent signal processing. This paper proposes a capacitor structure based on the Al-Al2O3-CB interface, which achieves temperature insensitivity (-5 °C-45 °C), humidity insensitivity (20% RH-80% RH), and frequency insensitivity (volatility <3% within the range of 100 kHz-1 MHz), while maintaining high sensitivity (24.62 kPa-1) and fast response and recovery time (33 ms/16 ms), and this design can substantially reduce circuit calibration complexity for sensor systems. The sensor's performance has been validated in various application scenarios, including physiological signal monitoring, gesture recognition, and robotic tactile sensing. By further integrating communication electronic modules, the sensor system offers wheelchair control based on hand movement perception, providing enhanced accessibility and convenience for patients with muscular weakness and other special needs.

Superspreading-Based Fabrication of Poly(methyl methacrylate) Films with High Toughness for Ultra-Wideband Flexible Transparent Antenna

With the rapid advancement of Internet of Things (IoT) technology, ultra-wideband flexible transparent antennas have garnered substantial attention for their potential applications in wireless communication devices. Poly(methyl methacrylate) (PMMA), renowned for its exceptional optical properties and favorable processing characteristics, has been extensively utilized as a transparent substrate material for antennas. However, the intrinsic brittleness of transparent PMMA substrates poses a significant limitation in applications such as flexible antennas. In this study, we introduce a superspreading strategy to address the complex trade-off among transparency, toughness, and dielectric properties in flexible electronics through molecular disorder engineering. The PMMA films fabricated via this superspreading strategy exhibit a visible transmittance of 85-95% at 400 nm, a toughness of 9 × 10⁵ J/m3 (representing an enhancement of 150-225% compared to conventional methods), and a frequency-stable permittivity (εr = 3.6 ± 0.05) within the 9-12 GHz range. These films also feature a precisely tunable thickness range of 5.5-60 μm. The PMMA-based flexible transparent antenna demonstrates a gain of 2-4 dBi and a relative bandwidth of 40%, thereby confirming its suitability for ultra-wideband applications. Collectively, this research presents a promising candidate for the development of ultra-wideband flexible transparent antennas.

Multi-bioinspired electronic skins with on-demand adhesion and opto-electronic synergistic display capabilities

Flexible electronic skins hold great promise for biomedical applications, although challenges remain in achieving controllable interactions with the biological interface and accurate signal collection. Inspired by octopuses and chameleons, we propose a novel electronic skin paradigm with on-demand adhesion and opto-electronic synergistic display capabilities. Our electronic skins are composed of a stretchable polyurethane (PU) inverse opal film integrated with a carbon nanotube (CNT)-hybridized polyacrylamide (PAAm)-gelatin double-network-hydrogel conductive flexible substrate and a temperature-responsive poly(N-isopropylacrylamide) (PNIPAm) octopus-inspired hemispherical adhesive array. The device's CNT hybrid double-network provides robust and sensitive monitoring of temperature and motion. Meanwhile, its flexible PU layer with an inverse opal structure allows for visual motion color sensing. Integrated neural network processing ensures accurate, wide-range, and independent multimodal display. Additionally, the integration of the photothermal effect of CNTs and the temperature-sensitive octopus-inspired PNIPAm adhesive array enables on-demand adhesion. The sensing and adhesion demonstrations ex vivo and in vivo showcase the proposed flexible electronic skin's inspirational design and functional utilities. The potential applications of such a versatile device are vast, ranging from healthcare to human-machine interactions.

Smart Dust for Chemical Mapping

This review article explores the transformative potential of smart dust systems by examining how existing chemical sensing technologies can be adapted and advanced to realize their full capabilities. Smart dust, characterized by submillimeter-scale autonomous sensing platforms, offers unparalleled opportunities for real-time, spatiotemporal chemical mapping across diverse environments. This article introduces the technological advancements underpinning these systems, critically evaluates current limitations, and outlines new avenues for development. Key challenges, including multi-compound detection, system control, environmental impact, and cost, are discussed alongside potential solutions. By leveraging innovations in miniaturization, wireless communication, AI-driven data analysis, and sustainable materials, this review highlights the promise of smart dust to address critical challenges in environmental monitoring, healthcare, agriculture, and defense sectors. Through this lens, the article provides a strategic roadmap for advancing smart dust from concept to practical application, emphasizing its role in transforming the understanding and management of complex chemical systems.

A Review on Multifunctional Polymer-MXene Hybrid Materials for Electronic Applications

MXenes, a family of two-dimensional (2D) transition metal carbides, carbonitrides, and nitrides, have emerged as a promising class of nanomaterials for interdisciplinary applications due to their unique physiochemical properties. The large surface area, excellent electrical conductivity, superior mechanical properties, and abundant possible functional groups make this layered nanomaterial an ideal candidate for multifunctional hybrid materials for electronic applications. This review highlights recent progress in MXene-based hybrid materials, focusing on their electrical, dielectric, and electromagnetic interference (EMI) shielding properties, with an emphasis on the development of multifunctionality required for advanced electronic devices. The review explores the multifunctional nature of MXene-based polymer nanocomposites and hybrid materials, covering the coexistence of a diverse range of properties, including sensory capabilities, electromagnetic interference shielding, energy storage, and the Joule heating phenomenon. Finally, the future outlook and key challenges are summarized, offering insights to guide future research aimed at improving the performance and functionality of MXene-polymer nanocomposites.

Leveraging bound states in the continuum for advanced ultra-sensitive sensing technologies

Traditional sensing methods, such as ELISA, PCR, and electrochemical sensors, face challenges like limited sensitivity, high costs and complex sample preparation. In contrast, optical sensors, particularly surface plasmon resonance (SPR) and dielectric-based guided-mode resonance (GMR) sensors have emerged as promising alternatives. These sensors offer non-invasive measurements, remote readouts, and enhanced sensitivity. While SPR sensors benefit from high local sensitivity, they are limited by energy losses in the metal, reducing the overall quality-factor (Q). On the other hand, GMR sensors, which use low-loss dielectric materials, achieve higher Q factors but are constrained by their inability to effectively detect biomolecules located farther from the sensor surface. Recently, materials that support bound states in the continuum (BICs) have attracted attention for their potential to achieve infinite Q factors, resulting in ultra-narrow resonance linewidths, exceptional precision, and enhanced light-matter interaction. These features make BICs highly promising for sensing applications. This review offers an in-depth understanding of BICs, explaining their principles, including the topological nature of BICs, and exploring recent advancements in BIC-based refractive index sensing technologies. It focuses on material platforms such as dielectric, plasmonic, and hybrid materials that host BICs. Additionally, the review addresses challenges in the field and suggests potential solutions.

An Underwater Robust-Adhesion Triboelectric Ion-Gel Enabled by Amphiphilic Copolymer Encapsulation and Water-Induced Interfacial Rearrangement

Water drives the electronic device adhesion interface to debonding, leading to attenuation or distortion of signals and limiting the potential for underwater applications. Here, a hydrophobic ion-gel (HIG) modeled on barnacle gum was developed by encapsulating the ionic liquid [BMIm]Cl in a copolymer formed by free radical quenching of a lignin-carbohydrate complex (LCC) and polythioctic acid (PTA). Due to the dynamic bonding and hydrophobic action to promote the strong underwater adhesion, and a hydrophobic lining hydration structure that improves the underwater stability, the resulting HIG exhibits superextensibility (maximum 10,286%), stable underwater conductivity (180 mS m-1), strong underwater adhesion (maximum 15 N/cm2), and rapid underwater self-healing. It can be used as a single-electrode triboelectric sensor without the need for additional adhesives and encapsulation design and simply adheres to the glove, enabling durable sensing and communication under water. The proposed strategy offers a novel possibility for the material design of flexible and wearable underwater electronics.

3D Integrated Physicochemical-Sensing Electronic Skin

The integration of physical and chemical signal sensing is of great significance to bridge the gap between electronic skin (e-skin) and natural skin. However, the existing method of integrating physical and chemical signal sensing units in two dimensions is not conducive to the development of e-skin in multifunctionality and miniaturization. Herein, a new three-dimensional (3D) integrated physicochemical-sensing e-skin (TDPSES) is developed by integrating a piezoresistive sensing unit, a biochemical signal sensing electrode, and a microfluidic system in a 3D superposition mode. For pressure sensing, TDPSES demonstrates an ultra-high sensitivity of 208.6 kPa-1 in 0-15 kPa and excellent stability of 8000 cycles. For glucose sensing in sweat, TDPSES has a sensitivity of 3.925 µA mm-1 and a detection limit of 29.1 µm. Meanwhile, TDPSES can not only continuously detect biological fluids, but also self-monitor its fluid-driving behavior, demonstrating its intelligent fluid-driving characteristics. Furthermore, TDPSES is applied to monitor a variety of physiological signals such as sweat, pulse, and voice, demonstrating its multifunctional sensing capabilities and application potential in health care. In conclusion, the implementation of TDPSES provides a new idea for constructing miniaturized and multifunctional e-skin, which helps to narrow the gap between e-skin and natural skin.

Lignocellulose-Mediated Functionalization of Liquid Metals toward the Frontiers of Multifunctional Materials

Lignocellulose-mediated liquid metal (LM) composites, as emerging functional materials, show tremendous potential for a variety of applications. The abundant hydroxyl, carboxyl, and other polar groups in lignocellulose facilitate the formation of strong chemical bonds with LM surfaces, enhancing wettability and adhesion for improved interface compatibility. Beyond serving as a supportive matrix, lignocellulose can be tailored to optimize the microstructure of the composites, adapting them for diverse applications. This review comprehensively summarizes the fundamental principles and recent advancements in lignocellulose-mediated LM composites, highlighting the advantages of lignocellulose in composite fabrication, including facile synthesis, versatile interactions, and inherent functionalities. Key modulation strategies for LMs and innovative synthesis methods for functionalized lignocellulose composites are discussed. Furthermore, the roles and structure-performance relationships of these composites in electromagnetic shielding, flexible sensors, and energy storage devices are systematically summarized. Finally, the obstacles and prospective advancements pertaining to lignocellulose-mediated LM composites are thoroughly scrutinized and deliberated upon. This review is expected to provide basic guidance for researchers to boost the popularity of LMs in diverse applications and provide useful references for design strategies of state-of-the-art LMs.

Scalable Integration of High Sensitivity Strain Sensors Based on Silicon Nanowire Spring Array Directly Grown on Flexible Polyimide Films

The growth and integration of position-controlled, morphology-programmable silicon nanowires (SiNWs), directly upon low-cost polymer substrates instead of postgrowth transferring, is attractive for developing advanced flexible sensors and logics. In this work, a low temperature growth of SiNWs at only 200 °C has been demonstrated, for the first time, upon flexible polyimide (PI) films, via a planar solid-liquid-solid (IPSLS) growth mechanism. The SiNWs with diameter of ∼146 nm can be grown into precise locations on PI as orderly array and with preferred elastic geometry. Strain sensor array, built upon these spring-shape SiNWs integrated on PI, achieves a gauge factor (GF) of ∼90, sustains large stretching strains up to 3.3% (with 1.5 mm radius) and endures over 30,000 cycles. Strain sensors attached to the finger to monitor movements are also successfully demonstrated, showing high sensitivity and superior mechanical reliability, particularly suited for wearable health applications.

Photonic Nanomaterials for Wearable Health Solutions

This review underscores the transformative potential of photonic nanomaterials in wearable health technologies, driven by increasing demands for personalized health monitoring. Their unique optical and physical properties enable rapid, precise, and sensitive real-time monitoring, outperforming conventional electrical-based sensors. Integrated into ultra-thin, flexible, and stretchable formats, these materials enhance compatibility with the human body, enabling prolonged wear, improved efficiency, and reduced power consumption. A comprehensive exploration is provided of the integration of photonic nanomaterials into wearable devices, addressing material selection, light-matter interaction principles, and device assembly strategies. The review highlights critical elements such as device form factors, sensing modalities, and power and data communication, with representative examples in skin patches and contact lenses. These devices enable precise monitoring and management of biomarkers of diseases or biological responses. Furthermore, advancements in materials and integration approaches have paved the way for continuum of care systems combining multifunctional sensors with therapeutic drug delivery mechanisms. To overcome existing barriers, this review outlines strategies of material design, device engineering, system integration, and machine learning to inspire innovation and accelerate the adoption of photonic nanomaterials for next-generation of wearable health, showcasing their versatility and transformative potential for digital health applications.

Bionic Recognition Technologies Inspired by Biological Mechanosensory Systems

Mechanical information is a medium for perceptual interaction and health monitoring of organisms or intelligent mechanical equipment, including force, vibration, sound, and flow. Researchers are increasingly deploying mechanical information recognition technologies (MIRT) that integrate information acquisition, pre-processing, and processing functions and are expected to enable advanced applications. However, this also poses significant challenges to information acquisition performance and information processing efficiency. The novel and exciting mechanosensory systems of organisms in nature have inspired us to develop superior mechanical information bionic recognition technologies (MIBRT) based on novel bionic materials, structures, and devices to address these challenges. Herein, first bionic strategies for information pre-processing are presented and their importance for high-performance information acquisition is highlighted. Subsequently, design strategies and considerations for high-performance sensors inspired by mechanoreceptors of organisms are described. Then, the design concepts of the neuromorphic devices are summarized in order to replicate the information processing functions of a biological nervous system. Additionally, the ability of MIBRT is investigated to recognize basic mechanical information. Furthermore, further potential applications of MIBRT in intelligent robots, healthcare, and virtual reality are explored with a view to solve a range of complex tasks. Finally, potential future challenges and opportunities for MIBRT are identified from multiple perspectives.

Multi-Level High Entropy-Dissipative Structure Enables Efficient Self-Decoupling of Triple Signals

The theory of high entropy-dissipative structure is confined to high-entropy alloys and their oxide materials under harsh conditions, but it is very difficult to obtain high entropy-dissipative structure for smart sensors based on polymers and metal oxides under mild conditions. Moreover, multiple signal coupling effect heavily hinder the sensor applications, and current multimodal integrated devices can solve two signal-decoupling, but need very complicated process way. In this work, new synthesis concept is the first time to fabricate high entropy-dissipative conductive layer of smart sensors with triple-signal response and self-decoupling ability within poly-pyrrole/zinc oxide (PPy/ZnO) system. The sensor (SPZ20) amplifies pressure (17.54%/kPa) and gas (0.37%/ppm), reduces humidity (0.41%/% RH) and temperature (0.12%/°C) signals, simultaneously achieving the triple self-decoupling effect of pressure and gas in the complex temperature-humidity field because of the enlarged pressure-contact area, enhanced gas-responsive sites, altered vapor path and its own heat insulation function. Additionally, it inherits the strong robustness (500 rubbing, washing, and heating or freezing cycles) and endurance (10 000 photo-purification cycles) of traditional high-entropy materials for information transmission and smart alarms in emergencies or harsh environments. This work gives a new insight into the multiple-signal response and smart flexible electronic design from natural fibers.

Whisker-Implanted Biomimetic Electronic Skin for Tactile Sensing and Blind Perception

Rodent whiskers are a distinct class of tactile sensors that work in conjunction with the biological skin to discern airstreams and obstacles with remarkable sensitivity, facilitating navigation around proximate objects. In this study, a flexible artificial skin is developed comprising sensory active units, including electronic skin (e-skin) and an artificial whisker, inspired by the sensory capabilities of rodent skin and whiskers. As a novel strategy, unique congruent air pockets are introduced within the e-skin to enhance the sensitivity. Mechanical stimuli applied to the artificial whisker are efficiently transmitted to the active e-skin, which generates a sensitive tactile perception response. The developed artificial skin exhibits high sensitivity, a wide sensing range, high flexibility, superior stability, and tensile strength. The artificial whisker facilitates the sensitive detection of a broad range of applied mechanical forces. Therefore, the artificial skin can sense subtle and vigorous tactile stimuli including airstreams and field obstacles. The ability to sense, discriminate, and decipher the airstreams and obstacles imparts outstanding tactile sensing and blind perception characteristics to the artificial skin. This artificial skin is a promising platform for the development of sensitive e-skins suitable for a broad range of applications, such as human-machine interfaces, robotics, and wearable electronics.

Advances in flexible ionic thermal sensors: present and perspectives

Ionic thermal sensors (ITSs) represent a promising frontier in sensing technology, offering unique advantages over conventional electronic sensors. Comprising a polymer matrix and electrolyte, these sensors possess inherent flexibility, stretchability, and biocompatibility, allowing them to establish stable and intimate contact with soft surfaces without inducing mechanical or thermal stress. Through an ion migration/dissociation mechanism similar to biosensing, ITSs ensure low impedance contact and high sensitivity, especially in physiological monitoring applications. This review provides a comprehensive overview of ionic thermal sensing mechanisms, contrasting them with their electronic counterparts. Additionally, it explores the intricacy of the sensor architecture, detailing the roles of active sensing elements, stretchable electrodes, and flexible substrates. The decoupled sensing mechanisms for skin-inspired multimodal sensors are also introduced based on several representative examples. The latest applications of ITS are categorized into ionic skin (i-skin), healthcare, spatial thermal perception, and environment detection, regarding their materials, structures, and operation modes. Finally, the perspectives of ITS research are presented, emphasizing the significance of standardized sensing parameters and emerging requirements for practical applications.

Silylated Carbon Nanofiber/Polydimethylsiloxane Based Printable Electrorheological and Sensor Inks for Flexible Electronics

Electrorheological fluids (ERF) have garnered significant attention for their potential to provide actuation on demand. Similarly, developing stimuli-responsive printable inks for flexible electronics is also gaining antecedence. However, developing a material that demonstrates both functionalities is far and few. Accordingly, a printable ink is made using silylated carbon nanofiber (SiCNF)-polydimethylsiloxane (PDMS). The viscosity of the ink increased by 43%, when subjected to an electric field (E). Robust stability for 20 cycles under E = 300 V mm-1 is noted. The yield stress (τy) value increased by 1600% (E = 600 V mm-1) compared to zero-field yield stress. Applying temperature with E further increased the τy. In the absence of E, applying temperature not only slowed down the relaxation modulus but also counterintuitively augmented the extent of sluggishness with an increase in temperature. A comprehensive study on the waiting time also indicated a structure build-up within the ink composition happening as the waiting time increases. Accordingly, the time-temperature and time-waiting time superposition principle is applied to predict the long-term behavior of the inks. Further, the printability index of the ink check is studied and used for printing designs using direct ink writing. The printed ink demonstrated pressure sensing capability with a sensitivity of 6.3%/kPa and is stable over 60 cycles.

Breathable and Stretchable Epidermal Electronics for Health Management: Recent Advances and Challenges

Advanced epidermal electronic devices, capable of real-time monitoring of physical, physiological, and biochemical signals and administering appropriate therapeutics, are revolutionizing personalized healthcare technology. However, conventional portable electronic devices are predominantly constructed from impermeable and rigid materials, which thus leads to the mechanical and biochemical disparities between the devices and human tissues, resulting in skin irritation, tissue damage, compromised signal-to-noise ratio (SNR), and limited operational lifespans. To address these limitations, a new generation of wearable on-skin electronics built on stretchable and porous substrates has emerged. These substrates offer significant advantages including breathability, conformability, biocompatibility, and mechanical robustness, thus providing solutions for the aforementioned challenges. However, given their diverse nature and varying application scenarios, the careful selection and engineering of suitable substrates is paramount when developing high-performance on-skin electronics tailored to specific applications. This comprehensive review begins with an overview of various stretchable porous substrates, specifically focusing on their fundamental design principles, fabrication processes, and practical applications. Subsequently, a concise comparison of various methods is offered to fabricate epidermal electronics by applying these porous substrates. Following these, the latest advancements and applications of these electronics are highlighted. Finally, the current challenges are summarized and potential future directions in this dynamic field are explored.

Flexible Pressure, Humidity, and Temperature Sensors for Human Health Monitoring

The rapid advancements in artificial intelligence, micro-nano manufacturing, and flexible electronics technology have unleashed unprecedented innovation and opportunities for applying flexible sensors in healthcare, wearable devices, and human-computer interaction. The human body's tactile perception involves physical parameters such as pressure, temperature, and humidity, all of which play an essential role in maintaining human health. Inspired by the sensory function of human skin, many bionic sensors have been developed to simulate human skin's perception to various stimuli and are widely applied in health monitoring. Given the urgent requirements for sensing performance and integration of flexible sensors in the field of wearable devices and health monitoring, here is a timely overview of recent advances in pressure, humidity, temperature, and multi-functional sensors for human health monitoring. It covers the fundamental components of flexible sensors and categorizes them based on different response mechanisms, including resistive, capacitive, voltage, and other types. Specifically, the application of these flexible tactile sensors in the area of human health monitoring is highlighted. Based on this, an extended overview of recent advances in dual/triple-mode flexible sensors integrating pressure, humidity, and temperature tactile sensing is presented. Finally, the challenges and opportunities of flexible sensors are discussed.

Flexible Triboelectric Nanogenerators Based on Cadmium Metal-Organic Framework/Eethyl Cellulose Composites as Energy Harvesters for Selective Photoinduced Bromination Reaction

The fabrication of self-driven systems with flexibility and tunable output for organic photoinduction is highly desirable but challenging. In this study, a 3D cadmium metal-organic framework (Cd-MOF) is synthesized and used as a filler for ethyl cellulose (EC) to create mechanically durable and flexible Cd-MOF@EC composite films. Due to its well-established platform with periodically precise structure nature, the outputs of Cd-MOF-based TENG are much higher than those of ligand-based TENGs. Furthermore, composite films with different doping ratios of Cd-MOF are employed to assemble Cd-MOF@EC-based triboelectric nanogenerators (TENGs). The results reveal that a doping ratio of 10 wt.% Cd-MOF in Cd-MOF@EC provides the highest TENG output. Subsequently, a flexible 10 wt.% Cd-MOF@EC-based TENG (FCEC-TENG), working in the contact-separation model, is constructed to harvest mechanical energy from the human body, demonstrating excellent output performance and stability. The energy harvested from FCEC-TENG can directly illuminate 14 commercial white light-emitting diodes (LEDs), providing visible light for the photoinduction of the bromination reaction, and generating bromide with good yield and tolerance. This study presents an effective method for constructing flexible MOF-based TENG for self-powered photoinduced organic transformation systems.

Oriented Alginate-Poly(vinyl alcohol) Electrospun Nanofibers for Multimodal Sensing and Gesture Language Recognition

Flexible nanofiber sensors have gained substantial attention in extending application scenarios owing to their desirable lightweight, comfort, and breathability. Nevertheless, disorder and uneven dimension issues of nanofibers are the leading concerns in their multifunctional response, which often leads to erratic response signals as well as poor linearity. In this work, a high-performance oriented nanofiber film with a three-dimensional network consisting of alginate sodium, poly(vinyl alcohol), and poly(ethylene oxide) was successfully fabricated by a controllable directional electrospinning technique. The main properties of the nanofibers are capable of being regulated intentionally by varying the electrospinning temperature, collector rotation speed, and polymer concentrations. Based on the favorable structure orientation, the nanofiber film displays satisfied biodegradability and high mechanical strength (575.1 MPa). Being integrated with modified magnetic particles, the sensors not only display a fast response speed, high magnetic sensitivity, and exceptional recoverability in response to magnetic fields but also show favorable sensitivities and reliable long-term durability under mechanical excitations. As a wearable sensor, it can accurately perceive the physiological signals generated by the human body in real-time. Furthermore, with the assistance of a convolutional neural network model, a gesture language recognition system is developed by integrating multiple sensors to realize a high recognition accuracy (∼99.08%). This study provides a feasible strategy to manufacture high-performance multimodal sensors for wearable human-machine interaction applications.

A Highly Sensitive Strain Sensor with Self-Assembled MXene/Multi-Walled Carbon Nanotube Sliding Networks for Gesture Recognition

Flexible electronics is pursuing a new generation of electronic skin and human-computer interaction. However, effectively detecting large dynamic ranges and highly sensitive human movements remains a challenge. In this study, flexible strain sensors with a self-assembled PDMS/MXene/MWCNT structure are fabricated, in which MXene particles are wrapped and bridged by dense MWCNTs, forming complex sliding conductive networks. Therefore, the strain sensor possesses an impressive sensitivity (gauge factor = 646) and 40% response range. Moreover, a fast response time of 280 ms and detection limit of 0.05% are achieved. The high performance enables good prospects in human detection, like human movement and pulse signals for healthcare. It is also applied to wearable smart data gloves, in which the CNN algorithm is utilized to identify 15 gestures, and the final recognition rate is up to 95%. This comprehensive performance strain sensor is designed for a wide array of human body detection applications and wearable intelligent systems.

A Double-Layer Polyurethane Electrospun Membrane with Directional Sweat Transport Ability for Use as a Soft Strain Sensor

Wearable electronics for long-term monitoring of physiological signals should be capable of removing sweat generated during daily motion, which significantly impacts signal stability, human comfort, and safety of the electronics. In this study, we developed a double-layer polyurethane (PU) membrane with sweat-directional transport ability that can be applied for monitoring strain signals. The PU membrane was composed of a hydrophilic, conductive layer and a relatively hydrophobic layer. The double-layer PU composite membrane exhibited varied pore size and opposite hydrophilicity on its two sides, enabling the spontaneous pumping of sweat from the hydrophobic side to the hydrophilic side, i.e., the directional transport of sweat. The membrane can be used as a strain sensor to monitor motion strain over a broad working range of 0% to 250% with high sensitivity (GF = 4.11). The sensor can also detect simple human movements even under sweating conditions. We believe that the strategy demonstrated here will provide new insights into the design of next-generation strain sensors.

High-Performance Sensing Platform Based on Morphology/Lattice Collaborative Control of Femtosecond-Laser-Induced MXene-Composited Graphene

Flexible sensors based on laser-induced graphene (LIG) are widely used in wearable personal devices, with the morphology and lattice arrangement of LIG the key factors affecting their performance in various applications. In this study, femtosecond-laser-induced MXene-composited graphene (LIMG) is used to improve the electrical conductivity of graphene by incorporating MXene, a 2D material with a high concentration of free electrons, into the LIG structure. By combining pump-probe detection, laser-induced breakdown spectroscopy (LIBS), and density functional theory (DFT) calculations, the morphogenesis and lattice structuring principles of LIMG is explored, with the results indicating that MXene materials are successfully embedded in the graphene lattice, altering both their morphology and electrical properties. The structural sparsity and electrical conductivity of LIMG composites (up to 3187 S m-1) are significantly enhanced compared to those of LIG. Based on these findings, LIMG has been used in wearable electronics. LIMG electrodes are used to detect uric acid, with a minimum detection limit of 2.48 µM. Additionally, LIMG-based pressure and bending sensors have been successfully used to monitor human limb movement and pulse. The direct in situ femtosecond laser patterning synthesis of LIMG has significant implications for developing flexible wearable electronic sensors.

A Suspended, 3D Morphing Sensory System for Robots to Feel and Protect

Artificial sensory systems with synergistic touch and pain perception hold substantial promise for environment interaction and human-robot communication. However, the realization of biological skin-like functional integration of sensors with sensitive touch and pain perception still remains a challenge. Here, a concept is proposed of suspended electronic skins enabling 3D deformation-mechanical contact interactions for achieving synergetic ultrasensitive touch and adjustable pain perception. The suspended sensory system can sensitively capture tiny touch stimuli as low as 0.02 Pa and actively perceive pain response with reliable 5200 cycles via 3D deformation and mechanical contact mechanism, respectively. Based on the touch-pain effect, a visualized feedback demo with miniaturized sensor arrays on artificial fingers is rationally designed to give a pain perception mapping on sharp surfaces. Furthermore, the capability is shown of the suspended electronic skin serving as a safe human-robot communication interface from active and passive view through a feedback control system, demonstrating potential in bionic electronics and intelligent robotics.