Moisture-Wicking, Breathable, and Intrinsically Antibacterial Electronic Skin Based on Dual-Gradient Poly(ionic liquid) Nanofiber Membranes

ε-Poly-L-lysine-graft-oligo(3-hexylthiophene) Copolymers as Antibacterial and Biodegradable Polymer Electronics

Biodegradable polymer electronics offer an innovative solution to the growing challenge of electronic waste, which are engineered to disintegrate after a defined functional period. Here, a new class of graft copolymer is presented, ε-poly-L-lysine-graft-oligo(3-hexylthiophene) (EPL-g-O3HTs), synthesized by covalently grafting oligo(3-hexylthiophene) onto the biopolymer ε-poly-L-lysine at three grafting densities, resulting in copolymers containing 43, 65 and 90 wt.% O3HT (EPL-g-O3HT-1, EPL-g-O3HT-2 and EPL-g-O3HT-3, respectively). Benefiting from the "guidance" of ε-poly-L-lysine on O3HT chains alignment, the graft copolymer with optimized grafting density exhibits an extended conjugation length and increased crystallite size of O3HT. Thin films of three copolymers, upon doping, demonstrate appreciable conductivity under ambient conditions. EPL-g-O3HT-1 could be fully break down over 12 days by enzymatic degradation. EPL-g-O3HT-1 also displays excellent broad-spectrum antibacterial activity against Gram-negative and Gram-positive bacteria, attributed to its high ɛ-poly-L-lysine content. It is further demonstrated the versatility of EPL-g-O3HTs in transient electronics for electromyography sensors for muscle signal acquisition and as the channel material in organic electrochemical transistors. Combining tunable conductivity, controlled biodegradability, and antimicrobial properties, EPL-g-O3HT copolymers hold significant potential for diverse transient electronic applications, including skin and implantable electronics, where degradable electronics with antimicrobial properties are highly desirable.

A Noninterfering Dual-Module E-Skin for Direction Strain and Pressure Sensing

Biomimetic electronic skins (e-skins) possessing strain-pressure sensing characteristics are widely applied in wearables for comprehensive mechanical stimuli sensing. However, dual-module e-skins with strain-pressure sensing performance show an innate defect that the strain causes interference with the accuracy of pressure sensing. Herein, a noninterfering dual-module e-skin (NIDM-skin) has been developed to achieve decoupled strain-pressure sensing via interlocked alteration of PDMS with different elastic moduli. In this research, a carbon nanotube-oriented thermoplastic polyurethane nanofiber membrane (CNT-OTPU) serves as a conductive network to realize direction strain sensing (gauge factor of 638 under 275% strain) and is encapsulated by low-modulus polydimethylsiloxane (LPDMS). High-modulus polydimethylsiloxane (HPDMS) is employed as a triboelectric material for pressure sensing, which is strain insensitive (under 200% strain) due to modulus mismatch. With the stable pressure sensing ability on the deformable surface, magnitude, and direction recognition capacity of strain, NIDM-skin displays great potential in soft robotics and medical rehabilitation for accurate identification.

Flexible iontronic sensing

The emerging flexible iontronic sensing (FITS) technology has introduced a novel modality for tactile perception, mimicking the topological structure of human skin while providing a viable strategy for seamless integration with biological systems. With research progress, FITS has evolved from focusing on performance optimization and structural enhancement to a new phase of integration and intelligence, positioning it as a promising candidate for next-generation wearable devices. Therefore, a review from the perspective of technological development trends is essential to fully understand the current state and future potential of FITS devices. In this review, we examine the latest advancements in FITS. We begin by examining the sensing mechanisms of FITS, summarizing research progress in material selection, structural design, and the fabrication of active and electrode layers, while also analysing the challenges and bottlenecks faced by different segments in this field. Next, integrated systems based on FITS devices are reviewed, highlighting their applications in human-machine interaction, healthcare, and environmental monitoring. Additionally, the integration of artificial intelligence into FITS is explored, focusing on optimizing front-end device design and improving the processing and utilization of back-end data. Finally, building on existing research, future challenges for FITS devices are identified and potential solutions are proposed.

Multifunctional Cooling Textiles with Enhanced Radiative and Moisture Management by One-Step Phase Separation

The development of multifunctional cooling textiles has become crucial in addressing global warming and the increasing need for personal thermal management. Developing textiles with integrated unidirectional moisture transport and radiative cooling functionalities through a simple fabrication method has become a critical challenge in addressing thermal and moisture management under high-temperature conditions. This study presents the development of a radiative cooling and unidirectional moisture-wicking textile (RCUM-Textile) through one-step phase separation method. By employing evaporation-induced phase separation (EIPS) and non-solvent-induced phase separation (NIPS) mechanisms, the RCUM-Textile achieves a trilayer structure comprising a hydrophobic SiO2/PVDF-HFP upper layer and a hydrophilic cotton lower layer. This innovative structure integrates radiative cooling and efficient sweat evaporation, enabling a solar reflectance of 89.7%, a mid-infrared emissivity of 94.9%, and a cooling effect of 8.7°C under direct sunlight. The SiO2/PVDF-HFP solution, utilized as a cotton finishing agent, simplifies the functionalization process, ensuring uniform coating and structural stability while reducing processing complexity. Additionally, its enhanced sweat evaporation rate (0.029 g·m-2·s-1) and reduced evaporation enthalpy (2084 J/g) significantly improve thermal regulation and wearer comfort. This study provides a cost-effective and practical approach to fabricating high-performance textiles, paving the way for applications in personal cooling devices, wearable electronics, and industrial-scale cooling systems.

Emerging Multifunctional Wearable Sensors: Integrating Multimodal Sweat Analysis and Advanced Material Technologies for Next-Generation Health Monitoring

Sweat, a noninvasive and readily accessible biofluid, offers significant potential in health monitoring through its diverse biomarker profile, including electrolytes, metabolites, and hormones, which reflect physiological states in real time. Multimodal wearable sensors, integrating chemical, physical, and thermal sensing capabilities, have emerged as transformative tools for capturing these biomarkers alongside additional physiological signals. By combining advanced materials such as hydrogels, MXenes, and graphene with innovative structural designs, these sensors enable simultaneous monitoring of biomarkers (e.g., glucose, sodium, and cortisol) alongside parameters like movement and temperature. This Review systematically explores the classification and design of multimodal sensors, emphasizing their ability to address health monitoring challenges across applications including metabolic health management, stress detection, and hydration assessment. Key innovations in functional materials, such as conductive hydrogels and biomimetic structures, are discussed alongside challenges in signal integration, data processing, and power management. Additionally, advancements in self-powered systems and energy harvesting technologies have been highlighted as critical enablers for continuous, real-time monitoring. The Review concludes with a perspective on future directions, emphasizing the need for scalable manufacturing techniques, artificial intelligence integration, and standardized frameworks to enhance sensor functionality and adoption. Multimodal wearable sensors, by seamlessly integrating health data into daily life, hold the promise of transforming personalized healthcare, enabling proactive management of health and wellness through noninvasive, comprehensive, and real-time monitoring.

Intrinsically Conductive, Optical Transparent, and Underwater Self-healing Ionogel with On-Demand Bonding Triggered by Skin Temperature

In the field of ionogels, reversible bonding-debonding triggered by mild and accessible stimuli is highly demanded especially for the use of bioelectric electrodes. In addition, the consistent stability of ionogels in underwater conditions are also needed to deal with complex practical scenarios. Herein, an intrinsically conductive, transparent, and underwater self-healing ionogel with on-demand bonding triggered by skin temperature is proposed. The ionogel is designed by incorporating long alkyl side chains into a chemically-physically crosslinked fluorine-rich elastomer with ionic liquid (IL) encapsulated as the conductive media. The long alkyl side chains undergo a semicrystalline-to-amorphous transition between 20 and 32 °C, resulting in large conductivity and adhesion variation of the ionogel. It can be reversibly bonding and debonding with the skin for more than 500 cycles without electrical/mechanical property degradation. The unique morphology with adaptive, conductive IL islands and ion shuttles ensure a high conductivity (1.3 × 10-2 S m-1) above the skin temperature even under 800% deformations. When utilized as bioelectric electrodes, the ionogel exhibits long-term stability, reusability, and high precision for electromyography and electrocardiogram signal collecting. This study proposes a new design of reversible bonding-debonding ionogel, which can be used in wet environments such as sweaty bodies and underwater conditions.

Adaptive All-Fiber Actuator for Human-Environment Interaction

A closed-loop pathway of "efficient actuation-synchronous sensing-multimodal feedback" is crucial for actuators to adapt to complex scenarios and human-environment interactions. Strategies to reconcile mechanics-guaranteed adaptive actuation with multimodal responses and perceptivity remain challenging. Through a continuous electrospinning strategy to construct a reinforced fiber-interlocked interface, a bilayer fiber membrane (TCTR) actuator composed of highly aligned fiber and hierarchical structures is developed to obtain efficient photothermal performance (22.9 °C min-1), excellent mechanical toughness (17.9 MJ m-3), and intuitive color changes (dark purple red to bright pale yellow with lightness variation of 68). This humidity-dominated and photothermal-assisted-responsive actuator demonstrates superior actuation response (0.67 cm-1 s-1) and bending curvature (7.37 cm-1) with electro-visual cooperative perceptivity. Integrated with the actuation-triggered triboelectric self-powered sensing and synchronous thermochromic effect, the TCTR actuator can be differentially programmed to perceive material types and object temperature (with a sensitivity of 99.5%), and visualize writing paths. By optimizing fiber alignment and assembly pattern, TCTR demonstrates utility as filter material, smart mask, and electronic textile, which can sense and visualize air contamination degrees, environmental temperature, and respiratory status, as well as achieve thermal management/alarming. This work proposes materials with mechano-electrical-optical cooperation and inspires a facile strategy for human-environment interactive actuators with multiscenario adaptivity.

Recent advances and challenges in metal-based antimicrobial materials: a review of strategies to combat antibiotic resistance

Despite the availability of a series of classical antibiotic drugs, bacterial infections continue to represent a significant and urgent threat to global human health. The emergence of drug-resistant bacteria and the slow pace of antibiotic development have rendered current treatment methods inadequate in meeting the clinical demands of bacterial infections. Consequently, there is an increasingly urgent and vital need for the development of safe, efficient, and alternative novel antimicrobial agents in the medical and healthcare field. Over the past five years, there has been a notable expansion in the field of nanomedicine with regard to the prevention and control of infectious diseases. The objective of this article is to provide a comprehensive review of the latest research developments in the field of metal nanomaterials for medical antimicrobial therapy. We begin by delineating the gravity of the bacterial infection crisis, subsequently undertaking a comprehensive examination of the potential mechanisms through which nanoparticles may combat bacterial infections and the specific applications of these nanomaterials in the treatment of diverse infectious diseases. In conclusion, we eagerly anticipate the future development directions of metal nanomaterials in the field of antimicrobial therapy. We believe that with continuous technological advancements and innovations, this field will make even more outstanding contributions to safeguarding human health and well-being.

Super Bending-Stable Flexible Colloidal QD Photodetector with Fast Response and Near-Unity Carrier Extraction Efficiency

Flexible colloidal quantum dot (QD) optoelectronics apply the superior properties of colloidal QDs to flexible devices, exhibiting unique advantages in the fields of imagers, solar cells, displays, wearable sensors, on-skin electronics, robotics, and bioimaging. Here, we show that colloidal QD photodiodes (QDPDs) with an ultrathin QD absorber layer have record bending stability with 100,000 repetitive bending cycles in QD devices. The QDPDs obtained a high-quality p-n junction with a 1700 rectification ratio. The formation of a Fabry-Pérot cavity by the layered stack results in a 3.4-fold enhanced light absorption, while the ultrathin structure ensures a near-unity efficient extraction (97%) of photogenerated charge carriers from the PbS QD film upon illumination with 1330 nm short-wavelength infrared light. Finally, upon suppression of the capacitance effect, the response time of this QDPD can be as short as 20 ns, which is the fastest response for flexible colloidal QDPDs.

Directional Liquid Transport in Thin Fibrous Matrices: Enhancement of Advanced Applications

Directional liquid transport fibrous matrices (DLTFMs) have the unique ability to direct liquid movement in a single direction through their thickness. Beyond their inherent liquid transport function, DLTFMs can also enhance the effectiveness of additional functionalities. This review focuses on recent advances in DLTFMs, particularly the role of DLTs in enhancing secondary functions. We begin with a brief overview of the historical development and major achievements in DLTFM research, followed by an outline of the classification, fabrication techniques, and basic functions derived from their natural liquid transport properties. The integration of DLT to enhance secondary functionalities such as responsiveness, thermal regulation, and wearable technology for innovative applications in various sectors is then discussed. The review concludes with a discussion of key challenges and prospects in the field, including the durability and reliability of DLT performance, the precise regulation of fluid transport rates, the resilience and longevity of DLTFMs in harsh environments, and the impact of DLT variations on performance enhancement. The goal of this review is to stimulate further innovative studies on DLTFMs and to promote their practical implementation in a variety of industries.

Bioinspired Intelligent Electronic Skin for Medicine and Healthcare

Intelligent electronic skin aims to mimic, enhance, and even surpass the functions of biological skin, enabling artificial systems to sense environmental stimuli and interact more naturally with humans. In healthcare, intelligent electronic skin is revolutionizing diagnostics and personalized medicine by detecting early signs of diseases and programming exogenous stimuli for timely intervention and on-demand treatment. This review discusses latest progress in bioinspired intelligent electronic skin and its application in medicine and healthcare. First, strategies for the development of intelligent electronic skin to simulate or even surpass human skin are discussed, focusing on its basic characteristics, as well as sensing and regulating functions. Then, the applications of electronic skin in health monitoring and wearable therapies are discussed, illustrating its potential to provide early warning and on-demand treatment. Finally, the significance of electronic skin in bridging the gap between electronic and biological systems is emphasized and the challenges and future perspectives of intelligent electronic skin are summarized.

Electrospun multifunctional nanofibers for advanced wearable sensors

The multifunctional extension of fiber-based wearable sensors determines their integration and sustainable development, with electrospinning technology providing reliable, efficient, and scalable support for fabricating these sensors. Despite numerous studies on electrospun fiber-based wearable sensors, further attention is needed to leverage composite structural engineering for functionalizing electrospun fibers. This paper systematically reviews the research progress on fiber-based multifunctional wearable sensors in terms of design concept, device fabrication, mechanism exploration, and application potential. Firstly, the basics of electrospinning are briefly introduced, including its development, principles, parameters, and material selection. Tactile sensors, as crucial components of wearable sensors, are discussed in detail, encompassing their performance parameters, transduction mechanisms, and preparation strategies for pressure, strain, temperature, humidity, and bioelectrical signal sensors. The main focus of the article is on the latest research progress in multifunctional sensing design concepts, multimodal decoupling mechanisms, sensing mechanisms, and functional extensions. These extensions include multimodal sensing, self-healing, energy harvesting, personal thermal management, EMI shielding, antimicrobial properties, and other capabilities. Furthermore, the review assesses existing challenges and outlines future developments for multifunctional wearable sensors, highlighting the need for continued research and innovation.

Liquid Metal-Enabled Epidermal Interfaces

Soft materials are crucial for epidermal interfaces in biomedical devices due to their capability to conform to the body compared to rigid inorganic materials. Gels, liquids, and polymers have been extensively explored, but they lack sufficient electrical and thermal conductivity required for many application settings. Gallium-based alloys are molten metals at room temperature with exceptional electrical and thermal conductivity. These liquid metals and their composites can be directly applied onto the skin as interface materials. In this Spotlight on Applications, we focus on the rapidly evolving field of liquid metal-enabled epidermal interfaces featuring unique physical properties beyond traditional gels and polymers. We delve into the role of liquid metal in electrical and thermal biointerfaces in various epidermal applications. Current challenges and future directions in this active area are also discussed.

Study of Electrode Design and Inclination Angle for Superior Droplet-Driven TENG Performance

The urgent need for efficient water energy harvesting has led to the development of triboelectric nanogenerators (TENGs). In this study, considering the droplet spreading dynamics and the capacitive effects in a droplet-driven TENG (DD-TENG) device, an inverse relationship between the width of the top electrode and the output voltage was derived for the first time through a circuit model and was experimentally verified. Additionally, key performance parameters were optimized, including the types and widths of top electrodes, dropping height, inclination angle of the device, and solution types. A nonmonotonic relationship between the inclination angle of the device and the output voltage was established. Under optimal conditions, the output voltage of the DD-TENG achieved a 1133% increase compared to that of the device without a top electrode. The power density reached 1265 mW·m-2, which is among the state-of-the-art DD-TENG devices. These findings provide valuable insights for the performance improvement of DD-TENGs.

Customized surface adhesive and wettability properties of conformal electronic devices

Conformal and body-adaptive electronics have revolutionized the way we interact with technology, ushering in a new era of wearable devices that can seamlessly integrate with our daily lives. However, the inherent mismatch between artificially synthesized materials and biological tissues (caused by irregular skin fold, skin hair, sweat, and skin grease) needs to be addressed, which can be realized using body-adaptive electronics by rational design of their surface adhesive and wettability properties. Over the past few decades, various approaches have been developed to enhance the conformability and adaptability of bioelectronics by (i) increasing flexibility and reducing device thickness, (ii) improving the adhesion and wettability between bioelectronics and biological interfaces, and (iii) refining the integration process with biological systems. Successful development of a conformal and body-adaptive electronic device requires comprehensive consideration of all three aspects. This review starts with the design strategies of conformal electronics with different surface adhesive and wettability properties. A series of conformal and body-adaptive electronics used in the human body under both dry and wet conditions are systematically discussed. Finally, the current challenges and critical perspectives are summarized, focusing on promising directions such as telemedicine, mobile health, point-of-care diagnostics, and human-machine interface applications.

Multifunctional Porous Soft Composites for Bimodal Wearable Cardiac Monitors

Wearable heart monitors are crucial for early diagnosis and treatment of heart diseases in non-clinical settings. However, their long-term applications require skin-interfaced materials that are ultrasoft, breathable, antibacterial, and possess robust, enduring on-skin adherence-features that remain elusive. Here, we have developed multifunctional porous soft composites that meet all these criteria for skin-interfaced bimodal cardiac monitoring. The composite consists of a bilayer structure featuring phase-separated porous elastomer and slot-die-coated biogel. The porous elastomer ensures ultrasoftness, breathability, ease of handling, and mechanical integrity, while the biogel enables long-term on-skin adherence. Additionally, we incorporated ε-polylysine in the biogel to offer antibacterial properties. Also, the conductive biogel embedded with silver nanowires was developed for use in electrocardiogram sensors to reduce contact impedance and ensure high-fidelity recordings. Furthermore, we assembled a bimodal wearable cardiac monitoring system that demonstrates high-fidelity recordings of both cardiac electrical (electrocardiogram) and mechanical (seismocardiogram) signals over a 14-day testing period.

Strong, Spontaneous, and Self-Healing Poly(Ionic Liquid) Elastomer Underwater Adhesive with Borate Ester Dynamic Crosslinking

Adhesion in aqueous environments is often hindered by the water layer on the surface of the substrate due to the water sensitivity of the adhesive, greatly limiting the application environment. Here, a borate ester dynamically crosslinked poly(ionic liquid) elastomer adhesive (PIEA) with high strength, toughness, self-healing abilities, and ionic conductivity is synthesized by copolymerizing hydrophobic ionic liquid monomer ([HPVIm][TFSI]) and 2-methoxyethyl acrylate (MEA). The adhesion strength of PIEA can increase spontaneously from almost no adhesion to 314 kPa after 12 h without any external preloading due to the dissociation of the borate ester in water, leading to noncovalent interactions between the hydroxyl groups of PIEA and the substrate. Additionally, PIEA can be developed for soft sensors or ion electrodes to enable underwater detection and communication. This strategy offers broad application potential for the development of novel underwater smart adhesives.

Research Progress of Flexible Electronic Devices Based on Electrospun Nanofibers

Electrospun nanofibers have become an important component in fabricating flexible electronic devices because of their permeability, flexibility, stretchability, and conformability to three-dimensional curved surfaces. This review delves into the advancements in adaptable and flexible electronic devices using electrospun nanofibers as the substrates and explores their diverse and innovative applications. The primary development of key substrates for flexible devices is summarized. After briefly discussing the principle of electrospinning, process parameters that affect electrospinning, and two major electrospinning techniques (i.e., single-fluid electrospinning and multifluid electrospinning), the review shines a spotlight on the recent breakthroughs in multifunctional and stretchable electronic devices that are based on electrospun substrates. These advancements include flexible sensors, flexible energy harvesting and storage devices, flexible accessories for electronic devices, and flexible environmental monitoring devices. In particular, the review outlines the challenges and potential solutions of developing electrospun nanofibers for flexible electronic devices, including overcoming the incompatibility of multiple interfaces, developing 3D microstructure sensor arrays with gradient geometry for various imperceptible on-skin devices, etc. This review may provide a comprehensive understanding of the rational design of application-oriented flexible electronic devices based on electrospun nanofibers.

Optically transparent and mechanically tough glass with impact resistance and flame retardancy enabled by covalent/supramolecular interactions

Exploring glass materials beyond inorganic components represents a new direction in the development of artificial transparent materials. Inspired by the successes of polymeric and supramolecular glasses, we shifted our attention to the preparation of a transparent glass through the polymerization of low-molecular-weight monomers that are naturally tailored with noncovalent recognition motifs. In this work, an imidazolium unit bearing a vinyl group and a tetrafluoroborate counter anion was selected to construct an artificial glass. Experimental and theoretical investigations revealed that the cross-linking behavior of anions effectively transformed linear polymeric chains into three-dimensional networks. The polymeric-supramolecular glass exhibits a tough tensile strength (61.31 MPa), high Young's modulus (1.17 GPa), and good optical transparency (>90%), which are comparable to those of polymethyl methacrylate. Moreover, the obtained glass maintains excellent mechanical toughness and optical transparency over a wide temperature range (from -150 to 150 °C). The material shows a superior impact resistance (18.34 kJ m-2) and flame retardancy (V0 rating), which are barely achieved by supramolecular materials.

Sustainable Nanofibril Interfaces for Strain-Resilient and Multimodal Porous Bioelectronics

Porous soft bioelectronics have attracted significant attention due to their high breathability, long-term biocompatibility, and other unique features inaccessible in nonporous counterparts. However, fabricating high-quality multimodal bioelectronic components that operate stably under strain on porous substrates, along with integrating microfluidics for sweat management, remains challenging. In this study, cellulose nanofibrils (CNF) are explored, biomass-derived sustainable biomaterials, as nanofibril interfaces with unprecedented interfacial robustness to enable high-quality printing of strain-resilient bioelectronics on porous substrates by reducing surface roughness and creating mechanical heterogeneity. Also, CNF-based microfluidics can provide continuous sweat collection and refreshment, crucial for accurate biochemical sensing. Building upon these advancements, a multimodal porous wearable bioelectronic system is further developed capable of simultaneously detecting electrocardiograms and glucose and beta-hydroxybutyrate in sweat for monitoring energy metabolism and consumption. This work introduces novel strategies for fabricating high-quality, strain-resilient porous bioelectronics with customizable multimodalities to meet arising personalized healthcare needs.

Unique framework effect induced by uniform silk fibroin dynamic nanospheres enables multiscale hydrogel with outstanding elastic resilience and strain sensing performance

It is a significant challenge to obtain hydrogels simultaneously with low tensile energy dissipation, high compressive resilience and long durability. Herein, the uniform dynamic nanospheres (Sil-4H0.75) derived from 4-Hydroxybutyl acrylate glycidyl ether grafted silk fibroin is designed to overcome this issue. Due to its uniform and dynamic characteristic, Sil-4H0.75 could endow hydrogel with homogeneous multiscale structure and produce unique framework effect. Thus, transparent Sil-4H0.75 crosslinked acrylamide hydrogel doped with Ag nanowires APS3.75%/AgNW0.1 exhibits a high stretchability (1260 %) and outstanding elastic resilience. The tensile energy dissipation ratio maintains a low value of 9 % across a wide 800 % strain range. A high compression resilience ratio of 92.2 % is kept after ten compression cycles under 90 % compressive strain. The orderly AgNWs motion guided by framework effect also make it be used as both tensile and compressive sensors and exhibits high gauge factor of 7.35, outstanding compression sensitivity of 30.379 kPa-1 and excellent durability (up to 2000 cycles). The detection or other applications based on both two sensing modes are also demonstrated. In a word, this work affords a general strategy to achieve high-performance hydrogel based on uniform dynamic nanospheres which exhibits great potential in the applications of flexible wearable strain sensors.

E-Skin and Its Advanced Applications in Ubiquitous Health Monitoring

E-skin is a bionic device with flexible and intelligent sensing ability that can mimic the touch, temperature, pressure, and other sensing functions of human skin. Because of its flexibility, breathability, biocompatibility, and other characteristics, it is widely used in health management, personalized medicine, disease prevention, and other pan-health fields. With the proposal of new sensing principles, the development of advanced functional materials, the development of microfabrication technology, and the integration of artificial intelligence and algorithms, e-skin has developed rapidly. This paper focuses on the characteristics, fundamentals, new principles, key technologies, and their specific applications in health management, exercise monitoring, emotion and heart monitoring, etc. that advanced e-skin needs to have in the healthcare field. In addition, its significance in infant and child care, elderly care, and assistive devices for the disabled is analyzed. Finally, the current challenges and future directions of the field are discussed. It is expected that this review will generate great interest and inspiration for the development and improvement of novel e-skins and advanced health monitoring systems.

MXene-Fiber Composite Membranes for Permeable and Biocompatible Skin-Interfaced Iontronic Mechanosensing

Artificial ionic sensory systems, bridging the divide between biological systems and electronics, mimic human skin functions but face critical challenges with biocompatibility, comfort, signal stability, and simplifying packaging. Here, we present a simple and permeable skin-interfaced iontronic mechanosensing (SIIM) architecture that integrates human skin as natural ionic material and hierarchically porous MXene-fiber composite membranes as sensing electrodes. The SIIM system eliminates complex ionic material design and multilayer matrix, exhibiting ultrahigh pressure sensitivities (5.4 kPa-1, <75 Pa), a low detection limit (6 Pa), excellent output stability along with high permeability to minimize the impact of sweating on sensing. The noncytotoxic nature of SIIM electrodes ensures excellent biocompatibility (>97% cell coincubational viability), facilitating long-term wearability and high biosafety. Furthermore, the scalable SIIM configuration integrated with matrix smart gloves, effectively monitors human physical movements. This SIIM-based sensor with marked sensing capabilities, structural simplicity, and scalability, holds promising potential in diverse wearable applications.

Self-Adhesive and Self-Sustainable Bioelectronic Patch for Physiological Feedback Electronic Modulation of Soft Organs

Bionic electrical stimulation (Bio-ES) aims to achieve personalized therapy and proprioceptive adaptation by mimicking natural neural signatures of the body, while current Bio-ES devices are reliant on complex sensing and computational simulation systems, thus often limited by the low-fidelity of simulated electrical signals, and failure of interface information interaction due to the mechanical mismatch between soft tissues and rigid electrodes. Here, the study presents a flexible and ultrathin self-sustainable bioelectronic patch (Bio-patch), which can self-adhere to the lesion area of organs and generate bionic electrical signals synchronized vagal nerve envelope in situ to implement Bio-ES. It allows adaptive adjustment of intensity, frequency, and waveform of the Bio-ES to fully meet personalized needs of tissue regeneration based on real-time feedback from the vagal neural controlled organs. With this foundation, the Bio-patch can effectively intervene with excessive fibrosis and microvascular stasis during the natural healing process by regulating the polarization time of macrophages, promoting the reconstruction of the tissue-engineered structure, and accelerating the repair of damaged liver and kidney. This work develops a practical approach to realize biomimetic electronic modulation of the growth and development of soft organs only using a multifunctional Bio-patch, which establishes a new paradigm for precise bioelectronic medicine.

Core-Shell Gel Nanofiber Scaffolds Constructed by Microfluidic Spinning toward Wound Repair and Tissue Regeneration

Growing demand for wound care resulting from the increasing chronic diseases and trauma brings intense pressure to global medical health service system. Artificial skin provides mechanical and microenvironmental support for wound, which is crucial in wound healing and tissue regeneration. However, challenges still remain in the clinical application of artificial skin since the lack of the synergy effect of necessary performance. In this study, a multi-functional artificial skin is fabricated through microfluidic spinning technology by using core-shell gel nanofiber scaffolds (NFSs). This strategy can precisely manipulate the microstructure of artificial skin under microscale. The as-prepared artificial skin demonstrates superior characteristics including surface wettability, breathability, high mechanical strength, strain sensitivity, biocompatibility and biodegradability. Notably, this artificial skin has the capability to deliver medications in a controlled and sustained manner, thereby accelerating the wound healing process. This innovative approach paves the way for the development of a new generation of artificial skin and introduces a novel concept for the structural design of the unique core-shell gel NFSs.

Flexible electronics for cardiovascular monitoring on complex physiological skins

Cardiovascular diseases (CVDs) pose a significant global health threat, responsible for a considerable portion of worldwide mortality. Flexible electronics enable continuous, noninvasive, real-time, and portable monitoring, providing an ideal platform for personalized healthcare. Nevertheless, challenges persist in sustaining stable adherence across diverse and intricate skin environments, hindering further advancement toward clinical applications. Strategies such as structural design and chemical modification can significantly enhance the environmental adaptability and monitoring performance of flexible electronics. This review delineates processing techniques, including structural design and chemical modification, to mitigate signal interference from sebaceous skin, motion artifacts from the skin in motion, and infection risks from fragile skin, thereby enabling the accurate monitoring of key cardiovascular indicators in complex physiological environments. Moreover, it delves into the potential for the strategic development and improvement of flexible electronics to ensure their alignment with complex physiological environment requirements, facilitating their transition to clinical applications.

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.

Micropatterned Polymer Nanoarrays with Distinct Superwettability for a Highly Efficient Sweat Collection and Sensing Patch

Wearable sweat sensor offers a promising means for noninvasive real-time health monitoring, but the efficient collection and accurate analysis of sweat remains challenging. One of the obstacles is to precisely modulate the surface wettability of the microfluidics to achieve efficient sweat collection. Here a facile initiated chemical vapor deposition (iCVD) method is presented to grow and pattern polymer nanocone arrays with distinct superwettability on polydimethylsiloxane microfluidics, which facilitate highly efficient sweat transportation and collection. The nanoarray is synthesized by manipulating monomer supersaturation during iCVD to induce controlled nucleation and preferential vertical growth of fluorinated polymer. Subsequent selective vapor deposition of a conformal hydrogel nanolayer results in superhydrophilic nanoarray floor and walls within the microchannel that provide a large capillary force and a superhydrophobic ceiling that drastically reduces flow friction, enabling rapid sweat transport along varied flow directions. A carbon/hydrogel/enzyme nanocomposite electrode is then fabricated by sequential deposition of highly porous carbon nanoparticles and hydrogel nanocoating to achieve sensitive and stable sweat detection. Further encapsulation of the assembled sweatsensing patch with superhydrophobic nanoarray imparts self-cleaning and water-proof capability. Finally, the sweat sensing patch demonstrates selective and sensitive glucose and lactate detection during the on-body test.

Transpiration-Inspired Fabric Dressing for Acceleration Healing of Wound Infected with Biofilm

In chronic wound management, efficacious handling of exudate and bacterial infections stands as a paramount challenge. Here a novel biomimetic fabric, inspired by the natural transpiration mechanisms in plants, is introduced. Uniquely, the fabric combines a commercial polyethylene terephthalate (PET) fabric with asymmetrically grown 1D rutile titanium dioxide (TiO2) micro/nanostructures, emulating critical plant features: hierarchically porous networks and hydrophilic water conduction channels. This structure endows the fabric with exceptional antigravity wicking-evaporation performance, evidenced by a 780% one-way transport capability and a 0.75 g h-1 water evaporation rate, which significantly surpasses that of conventional moisture-wicking textiles. Moreover, the incorporated 1D rutile TiO2 micro/nanostructures present solar-light induced antibacterial activity, crucial for disrupting and eradicating wound biofilms. The biomimetic transpiration fabric is employed to drain exudate and eradicate biofilms in Staphylococcus aureus (S. aureus)-infected wounds, demonstrating a much faster infection eradication capability compared to clinically common ciprofloxacin irrigation. These findings illuminate the path for developing high-performance, textile-based wound dressings, offering efficient clinical platforms to combat biofilms associated with chronic wounds.

Flexible iontronics with super stretchability, toughness and enhanced conductivity based on collaborative design of high-entropy topology and multivalent ion-dipole interactions

All-solid-state ionic conductive elastomers (ASSICEs) are emerging as a promising alternative to hydrogels and ionogels in flexible electronics. Nevertheless, the synthesis of ASSICEs with concomitant mechanical robustness, superior ionic conductivity, and cost-effective recyclability poses a formidable challenge, primarily attributed to the inherent contradiction between mechanical strength and ionic conductivity. Herein, we present a collaborative design of high-entropy topological network and multivalent ion-dipole interaction for ASSICEs, and successfully mitigate the contradiction between mechanical robustness and ionic conductivity. Benefiting from the synergistic effect of this design, the coordination, de-coordination, and intrachain transfer of Li+ are effectively boomed. The resultant ASSICEs display exceptional mechanical robustness (breaking strength: 7.45 MPa, fracture elongation: 2621%, toughness: 107.19 MJ m-3) and impressive ionic conductivity (1.15 × 10-2 S m-1 at 25 °C). Furthermore, these ASSICEs exhibit excellent environmental stability (fracture elongation exceeding 1400% at 50 °C or -60 °C) and recyclability. Significantly, the application of these ASSICEs in a strain sensor highlights their potential in various fields, including human-interface communication, aerospace vacuum measurement, and medical balloon monitoring.

A Flexible Skin Bionic Thermally Comfortable Wearable for Machine Learning-Facilitated Ultrasensitive Sensing

Tremendous popularity is observed for multifunctional flexible electronics with appealing applications in intelligent electronic skins, human-machine interfaces, and healthcare sensing. However, the reported sensing electronics, mostly can hardly provide ultrasensitive sensing sensitivity, wider sensing range, and robust cycling stability simultaneously, and are limited of efficient heat conduction out from the contacted skin interface after wearing flexible electronics on human skin to satisfy thermal comfort of human skin. Inspired from the ultrasensitive tactile perception microstructure (epidermis/spinosum/signal transmission) of human skin, a flexible comfortably wearable ultrasensitive electronics is hereby prepared from thermal conductive boron nitride nanosheets-incorporated polyurethane elastomer matrix with MXene nanosheets-coated surface microdomes as epidermis/spinosum layers assembled with interdigitated electrode as sensing signal transmission layer. It demonstrates appealing sensing performance with ultrasensitive sensitivity (≈288.95 kPa-1), up to 300 kPa sensing range, and up to 20 000 sensing cycles from obvious contact area variation between microdome microstructures and the contact electrode under external compression. Furthermore, the bioinspired electronics present advanced thermal management by timely efficient thermal dissipation out from the contacted skin surface to meet human skin thermal comfort with the incorporated thermal conductive boron nitride nanosheets. Thus, it is vitally promising in wearable artificial electronic skins, intelligent human-interactive sensing, and personal health management.

Electronic Skin for Health Monitoring Systems: Properties, Functions, and Applications

Electronic skin (e-skin), a skin-like wearable electronic device, holds great promise in the fields of telemedicine and personalized healthcare because of its good flexibility, biocompatibility, skin conformability, and sensing performance. E-skin can monitor various health indicators of the human body in real time and over the long term, including physical indicators (exercise, respiration, blood pressure, etc.) and chemical indicators (saliva, sweat, urine, etc.). In recent years, the development of various materials, analysis, and manufacturing technologies has promoted significant development of e-skin, laying the foundation for the application of next-generation wearable medical technologies and devices. Herein, the properties required for e-skin health monitoring devices to achieve long-term and precise monitoring and summarize several detectable indicators in the health monitoring field are discussed. Subsequently, the applications of integrated e-skin health monitoring systems are reviewed. Finally, current challenges and future development directions in this field are discussed. This review is expected to generate great interest and inspiration for the development and improvement of e-skin and health monitoring systems.

Fluid Unidirectional Transport Induced by Structure and Ambient Elements across Porous Materials: From Principles to Applications

Spontaneous or nonspontaneous unidirectional fluid transport across multidimension can occur under specific structural designs and ambient elements for porous materials. While existing reviews have extensively summarized unidirectional fluid transport on surfaces, there is an absence of literature summarizing fluid's unidirectional transport across porous materials. This review introduces wetting phenomena observed on natural biological surfaces or porous structures. Subsequently, it offers an overview of diverse principles and potential applications in this field, emphasizing various physical and chemical structural designs (surface energy, capillary size, topographic curvature) and ambient elements (underwater, under oil, pressure, and solar energy). Applications encompass moisture-wicking fabric, sensors, skincare, fog collection, oil-water separation, electrochemistry, liquid-based gating, and solar evaporators. Additionally, significant principles and formulas from various studies are compelled to offer readers valuable references. Simultaneously, potential advantages and challenges are critically assessed in these applications and the perspectives are presented.

Robust Gradient Hydrogel-Loaded Nanofiber Fleshy Artificial Skin Via A Coupled Microfluidic Electrospinning-Reactive Coating Strategy

Skin regeneration attracts tremendous interest due to the important role of skin for human protection and beauty. Thus, methods allowing artificial skin to be carried out in a controllable fashion are potentially important for wound healing, which involves an intersection of materials, medicine, biology, and other disciplines. Herein, aiming at a new general methodology for fleshy materials, a new hydrogel-loaded hydrophobic-hydrophilic nanofiber fleshy artificial skin is designed and fabricated. The gradient hydrogel-loaded nanofiber artificial skin integrates both advantages of nanofiber and hydrogel, exhibiting fleshy feature (comparability to real skin in terms of appearance, texture, and function), excellent air permeability, compatibility, and good mechanical and antibacterial property. Interestingly, the efficient transport channels are formed throughout the hydrogel-loaded nanofiber structure, which is beneficial for water absorption and transfer. These advantages enable the establishment of a moist and favorable microenvironment; thus, greatly accelerating wound healing process. This work couples microfluidic electrospinning with reactive coating technique, which is in favor of material design and fabrication with controllable and uniform structures. The hydrogel-loaded nanofiber fleshy artificial skin shows comparability to real skin in terms of beauty, texture, and function, which would definitely provide new opportunities for the further optimization and upgrading of artificial skin.

A Rational Design of Bio-Derived Disulfide CANs for Wearable Capacitive Pressure Sensor

Classic approaches to integrate flexible capacitive sensor performance are to on-demand microstructuring dielectric layers and to adjust dielectric material compositions via the introduction of insoluble carbon additives (to increase sensitivity) or dynamic interactions (to achieve self-healing). However, the sensor's enhanced performances often come with increased material complexity, discouraging its circular economy. Herein, a new intrinsic self-healable, closed-loop recyclable dielectric layer material, a fully nature-derived dynamic covalent poly(disulfide) decorated with rich H bonding and metal-catechol complexations is introduced. The polymer network possesses a mechanically ductile character with an Arrhenius-type temperature-dependent viscoelasticity. The assembled capacitive pressure sensor is able to achieve a sensitivity of up to 9.26 kPa-1, fast response/recovery time of 32/24 ms, and can deliver consistent signals of continuous consecutive cycles even after being self-healed or closed-loop recycled for real-time detection of human motions. This is expected to be of high interest for current capacitive sensing research to move toward a life-like, high performance, and circular economy direction.

Directional Moisture-Wicking Triboelectric Materials Enabled by Laplace Pressure Differences

Wearable sensors are experiencing vibrant growth in the fields of health monitoring systems and human motion detection, with comfort becoming a significant research direction for wearable sensing devices. However, the weak moisture-wicking capability of sensor materials leads to liquid retention, severely restricting the comfort of the wearable sensors. This study employs a pattern-guided alignment strategy to construct microhill arrays, endowing triboelectric materials with directional moisture-wicking capability. Within 2.25 s, triboelectric materials can quickly and directionally remove the droplets, driven by the Laplace pressure differences and the wettability gradient. The directional moisture-wicking triboelectric materials exhibit excellent pressure sensing performance, enabling rapid response/recovery (29.1/37.0 ms), thereby achieving real-time online monitoring of human respiration and movement states. This work addresses the long-standing challenge of insufficient moisture-wicking driving force in flexible electronic sensing materials, holding significant implications for enhancing the comfort and application potential of electronic skin and wearable electronic devices.

Biocompatible Electronic Skins for Cardiovascular Health Monitoring

Cardiovascular diseases represent a significant threat to the overall well-being of the global population. Continuous monitoring of vital signs related to cardiovascular health is essential for improving daily health management. Currently, there has been remarkable proliferation of technology focused on collecting data related to cardiovascular diseases through daily electronic skin monitoring. However, concerns have arisen regarding potential skin irritation and inflammation due to the necessity for prolonged wear of wearable devices. To ensure comfortable and uninterrupted cardiovascular health monitoring, the concept of biocompatible electronic skin has gained substantial attention. In this review, biocompatible electronic skins for cardiovascular health monitoring are comprehensively summarized and discussed. The recent achievements of biocompatible electronic skin in cardiovascular health monitoring are introduced. Their working principles, fabrication processes, and performances in sensing technologies, materials, and integration systems are highlighted, and comparisons are made with other electronic skins used for cardiovascular monitoring. In addition, the significance of integrating sensing systems and the updating wireless communication for the development of the smart medical field is explored. Finally, the opportunities and challenges for wearable electronic skin are also examined.

Janus Membrane-Based Wearable pH Sensor with Sweat Absorption, Gas Permeability, and Self-Adhesiveness

Wearable biomedical sensors have enabled noninvasive and continuous physiological monitoring for daily health management and early detection of chronic diseases. Among biomedical sensors, wearable pH sensors attracted significant interest, as pH influences most biological reactions. However, conformable pH sensors that have sweat absorption ability, are self-adhesive to the skin, and are gas permeable remain largely unexplored. In this study, we present a pioneering approach to this problem by developing a Janus membrane-based pH sensor with self-adhesiveness on the skin. The sensor is composed of a hydrophobic polyurethane-polydimethylsiloxane porous hundreds nanometer-thick substrate and a hydrophilic poly(vinyl alcohol)-poly(acrylic acid) porous nanofiber layer. This Janus membrane exhibits a thickness of around 10 μm, providing a conformable adhesion to the skin. The simultaneous realization of solution absorption, gas permeability, and self-adhesiveness makes it suitable for long-term continuous monitoring without compromising the comfort of the wearer. The pH sensor was tested successfully for continuous monitoring for 7.5 h, demonstrating its potential for stable analysis of skin health conditions. The Janus membrane-based pH sensor holds significant promise for comprehensive skin health monitoring and wearable biomedical applications.

Permeable Bioelectronics toward Biointegrated Systems

Bioelectronics integrates electronics with biological organs, sustaining the natural functions of the organs. Organs dynamically interact with the external environment, managing internal equilibrium and responding to external stimuli. These interactions are crucial for maintaining homeostasis. Additionally, biological organs possess a soft and stretchable nature; encountering objects with differing properties can disrupt their function. Therefore, when electronic devices come into contact with biological objects, the permeability of these devices, enabling interactions and substance exchanges with the external environment, and the mechanical compliance are crucial for maintaining the inherent functionality of biological organs. This review discusses recent advancements in soft and permeable bioelectronics, emphasizing materials, structures, and a wide range of applications. The review also addresses current challenges and potential solutions, providing insights into the integration of electronics with biological organs.

Sweat permeable and ultrahigh strength 3D PVDF piezoelectric nanoyarn fabric strain sensor

Commercial wearable piezoelectric sensors possess excellent anti-interference stability due to their electronic packaging. However, this packaging renders them barely breathable and compromises human comfort. To address this issue, we develop a PVDF piezoelectric nanoyarns with an ultrahigh strength of 313.3 MPa, weaving them with different yarns to form three-dimensional piezoelectric fabric (3DPF) sensor using the advanced 3D textile technology. The tensile strength (46.0 MPa) of 3DPF exhibits the highest among the reported flexible piezoelectric sensors. The 3DPF features anti-gravity unidirectional liquid transport that allows sweat to move from the inner layer near to the skin to the outer layer in 4 s, resulting in a comfortable and dry environment for the user. It should be noted that sweating does not weaken the piezoelectric properties of 3DPF, but rather enhances. Additionally, the durability and comfortability of 3DPF are similar to those of the commercial cotton T-shirts. This work provides a strategy for developing comfortable flexible wearable electronic devices.

In Vitro Antibacterial and Anti-Inflammatory Properties of Imidazolium Poly(ionic liquids) Microspheres Loaded in GelMA-PEG Hydrogels

Repairing damaged tissue caused by bacterial infection poses a significant challenge. Traditional antibacterial hydrogels typically incorporate various components such as metal antimicrobials, inorganic antimicrobials, organic antimicrobials, and more. However, drawbacks such as the emergence of multi-drug resistance to antibiotics, the low antibacterial efficacy of natural agents, and the potential cytotoxicity associated with metal antibacterial nanoparticles in hydrogels hindered their broader clinical application. In this study, we successfully developed imidazolium poly(ionic liquids) (PILs) polymer microspheres (APMs) through emulsion polymerization. These APMs exhibited notable antibacterial effectiveness and demonstrated minimal cell toxicity. Subsequently, we integrated the APMs into a gelatin methacryloyl (GelMA)-polyethylene glycol (PEG) hydrogel. This composite hydrogel not only showcased strong antibacterial and anti-inflammatory properties but also facilitated the migration of human skin fibroblasts (HSF) and human umbilical vein endothelial cells (HUVECs) and promoted osteogenic differentiation in vitro.

Polymerized and Colloidal Ionic Liquids─Syntheses and Applications

The breadth and importance of polymerized ionic liquids (PILs) are steadily expanding, and this review updates advances and trends in syntheses, properties, and applications over the past five to six years. We begin with an historical overview of the genesis and growth of the PIL field as a subset of materials science. The genesis of ionic liquids (ILs) over nano to meso length-scales exhibiting 0D, 1D, 2D, and 3D topologies defines colloidal ionic liquids, CILs, which compose a subclass of PILs and provide a synthetic bridge between IL monomers (ILMs) and micro to macro-scale PIL materials. The second focus of this review addresses design and syntheses of ILMs and their polymerization reactions to yield PILs and PIL-based materials. A burgeoning diversity of ILMs reflects increasing use of nonimidazolium nuclei and an expanding use of step-growth chemistries in synthesizing PIL materials. Radical chain polymerization remains a primary method of making PILs and reflects an increasing use of controlled polymerization methods. Step-growth chemistries used in creating some CILs utilize extensive cross-linking. This cross-linking is enabled by incorporating reactive functionalities in CILs and PILs, and some of these CILs and PILs may be viewed as exotic cross-linking agents. The third part of this update focuses upon some advances in key properties, including molecular weight, thermal properties, rheology, ion transport, self-healing, and stimuli-responsiveness. Glass transitions, critical solution temperatures, and liquidity are key thermal properties that tie to PIL rheology and viscoelasticity. These properties in turn modulate mechanical properties and ion transport, which are foundational in increasing applications of PILs. Cross-linking in gelation and ionogels and reversible step-growth chemistries are essential for self-healing PILs. Stimuli-responsiveness distinguishes PILs from many other classes of polymers, and it emphasizes the importance of segmentally controlling and tuning solvation in CILs and PILs. The fourth part of this review addresses development of applications, and the diverse scope of such applications supports the increasing importance of PILs in materials science. Adhesion applications are supported by ionogel properties, especially cross-linking and solvation tunable interactions with adjacent phases. Antimicrobial and antifouling applications are consequences of the cationic nature of PILs. Similarly, emulsion and dispersion applications rely on tunable solvation of functional groups and on how such groups interact with continuous phases and substrates. Catalysis is another significant application, and this is an historical tie between ILs and PILs. This component also provides a connection to diverse and porous carbon phases templated by PILs that are catalysts or serve as supports for catalysts. Devices, including sensors and actuators, also rely on solvation tuning and stimuli-responsiveness that include photo and electrochemical stimuli. We conclude our view of applications with 3D printing. The largest components of these applications are energy related and include developments for supercapacitors, batteries, fuel cells, and solar cells. We conclude with our vision of how PIL development will evolve over the next decade.

Fully Screen-Printed and Gentle-to-Skin Wet ECG Electrodes with Compact Wireless Readout for Cardiac Diagnosis and Remote Monitoring

Recent advances in electrocardiogram (ECG) diagnosis and monitoring have triggered a demand for smart and wearable ECG electrodes and readout systems. Here, we report the development of a fully screen-printed gentle-to-skin wet ECG electrode integrated with a scaled-down printed circuit board (PCB) packaged inside a 3D-printed antenna-on-package (AoP). All three components of the wet ECG electrode (i.e., silver nanowire-based conductive part, electrode gel, and adhesive gel) are screen-printed on a flexible plastic substrate and only require 265 times less metal for the conductive part and 176 times less ECG electrode gel than the standard commercial wet ECG electrodes. In addition, our electrically small AoP achieved a maximum read range of 142 m and offers a 4 times larger wireless communication range than the typical commercial chip antenna. The adult volunteers' study results indicated that our system recorded ECG data that correlated well with data from a commercial ECG system and electrodes. Furthermore, in the context of a 12-lead ECG diagnostic system, the fully printed wet ECG electrodes demonstrated a performance similar to that of commercially available wet ECG electrodes while being gentle on the skin. This was confirmed through a blind review method by two cardiology consultants and one family medicine consultant, validating the consistency of the diagnostic information obtained from both electrodes. In conclusion, these findings highlight the potential of fully screen-printed wet ECG electrodes for both monitoring and diagnostic purposes. These electrodes could serve as potential candidates for clinical practice, and the screen-printing method has the capability to facilitate industrial mass production.

Ionic liquids as the effective technology for enhancing transdermal drug delivery: Design principles, roles, mechanisms, and future challenges

Ionic liquids (ILs) have been proven to be an effective technology for enhancing drug transdermal absorption. However, due to the unique structural components of ILs, the design of efficient ILs and elucidation of action mechanisms remain to be explored. In this review, basic design principles of ideal ILs for transdermal drug delivery system (TDDS) are discussed considering melting point, skin permeability, and toxicity, which depend on the molar ratios, types, functional groups of ions and inter-ionic interactions. Secondly, the contributions of ILs to the development of TDDS through different roles are described: as novel skin penetration enhancers for enhancing transdermal absorption of drugs; as novel solvents for improving the solubility of drugs in carriers; as novel active pharmaceutical ingredients (API-ILs) for regulating skin permeability, solubility, release, and pharmacokinetic behaviors of drugs; and as novel polymers for the development of smart medical materials. Moreover, diverse action mechanisms, mainly including the interactions among ILs, drugs, polymers, and skin components, are summarized. Finally, future challenges related to ILs are discussed, including underlying quantitative structure-activity relationships, complex interaction forces between anions, drugs, polymers and skin microenvironment, long-term stability, and in vivo safety issues. In summary, this article will promote the development of TDDS based on ILs.

Porous Poly(ionic Liquid) Membrane with Metal Nanoparticle Gradient: A Smart Actuator for Visualizing Chemical Reactions

Poly(ionic liquid) (PIL)-based porous membranes are extensively investigated as soft polymer actuators. While PILs have shown significant advancements in membrane fabrication and stabilization of metal nanoparticles (MNPs), research on integrating MNPs into porous membranes to achieve actuation behavior under multiple stimuli is limited. Herein, this work presents a new paradigm for designing a porous PIL-polyacrylic acid (PAA) membrane with a distinct MNP gradient via a top-bottom diffusion approach involving a metal salt precursor solution and NaBH4 as a reducing agent. The strong binding sites provided by PILs, combined with the gradient distribution of -COO- groups across the membrane cross-section, play a significant role in controlling the MNPs' gradient distribution. Interestingly, the MNPs within the membrane display excellent catalytic activity in exothermic reactions such as H2O2 decomposition, dissipating uneven heat that quickly permeates the membrane network. This induces asymmetrical swelling of polymer chains, resulting in rapid membrane bending. Furthermore, such MNP-loaded membrane could serve as a portable test paper for visually monitoring H2O2. This advancement paves the way for the development of intricate smart actuation materials and expands their practical applications in various real-life scenarios.

A three-dimensional liquid diode for soft, integrated permeable electronics

Wearable electronics with great breathability enable a comfortable wearing experience and facilitate continuous biosignal monitoring over extended periods1-3. However, current research on permeable electronics is predominantly at the stage of electrode and substrate development, which is far behind practical applications with comprehensive integration with diverse electronic components (for example, circuitry, electronics, encapsulation)4-8. Achieving permeability and multifunctionality in a singular, integrated wearable electronic system remains a formidable challenge. Here we present a general strategy for integrated moisture-permeable wearable electronics based on three-dimensional liquid diode (3D LD) configurations. By constructing spatially heterogeneous wettability, the 3D LD unidirectionally self-pumps the sweat from the skin to the outlet at a maximum flow rate of 11.6 ml cm-2 min-1, 4,000 times greater than the physiological sweat rate during exercise, presenting exceptional skin-friendliness, user comfort and stable signal-reading behaviour even under sweating conditions. A detachable design incorporating a replaceable vapour/sweat-discharging substrate enables the reuse of soft circuitry/electronics, increasing its sustainability and cost-effectiveness. We demonstrated this fundamental technology in both advanced skin-integrated electronics and textile-integrated electronics, highlighting its potential for scalable, user-friendly wearable devices.

Wettability Gradient-Induced Diode: MXene-Engineered Membrane for Passive-Evaporative Cooling

Thermoregulatory textiles, leveraging high-emissivity structural materials, have arisen as a promising candidate for personal cooling management; however, their advancement has been hindered by the underperformed water moisture transportation capacity, which impacts on their thermophysiological comfort. Herein, we designed a wettability-gradient-induced-diode (WGID) membrane achieving by MXene-engineered electrospun technology, which could facilitate heat dissipation and moisture-wicking transportation. As a result, the obtained WGID membrane could obtain a cooling temperature of 1.5 °C in the "dry" state, and 7.1 °C in the "wet" state, which was ascribed to its high emissivity of 96.40% in the MIR range, superior thermal conductivity of 0.3349 W m-1 K-1 (based on radiation- and conduction-controlled mechanisms), and unidirectional moisture transportation property. The proposed design offers an approach for meticulously engineering electrospun membranes with enhanced heat dissipation and moisture transportation, thereby paving the way for developing more efficient and comfortable thermoregulatory textiles in a high-humidity microenvironment.

Ultrastretchable E-Skin Based on Conductive Hydrogel Microfibers for Wearable Sensors

Conductive microfibers play a significant role in the flexibility, stretchability, and conductivity of electronic skin (e-skin). Currently, the fabrication of conductive microfibers suffers from either time-consuming and complex operations or is limited in complex fabrication environments. Thus, it presents a one-step method to prepare conductive hydrogel microfibers based on microfluidics for the construction of ultrastretchable e-skin. The microfibers are achieved with conductive MXene cores and hydrogel shells, which are solidified with the covalent cross-linking between sodium alginate and calcium chloride, and mechanically enhanced by the complexation reaction of poly(vinyl alcohol) and sodium hydroxide. The microfiber conductivities are tailorable by adjusting the flow rate and concentration of core and shell fluids, which is essential to more practical applications in complex scenarios. More importantly, patterned e-skin based on conductive hydrogel microfibers can be constructed by combining microfluidics with 3D printing technology. Because of the great advantages in mechanical and electrical performance of the microfibers, the achieved e-skin shows impressive stretching and sensitivity, which also demonstrate attractive application values in motion monitoring and gesture recognition. These characteristics indicate that the ultrastretchable e-skin based on conductive hydrogel microfibers has great potential for applications in health monitoring, wearable devices, and smart medicine.

Porous Conductive Textiles for Wearable Electronics

Over the years, researchers have made significant strides in the development of novel flexible/stretchable and conductive materials, enabling the creation of cutting-edge electronic devices for wearable applications. Among these, porous conductive textiles (PCTs) have emerged as an ideal material platform for wearable electronics, owing to their light weight, flexibility, permeability, and wearing comfort. This Review aims to present a comprehensive overview of the progress and state of the art of utilizing PCTs for the design and fabrication of a wide variety of wearable electronic devices and their integrated wearable systems. To begin with, we elucidate how PCTs revolutionize the form factors of wearable electronics. We then discuss the preparation strategies of PCTs, in terms of the raw materials, fabrication processes, and key properties. Afterward, we provide detailed illustrations of how PCTs are used as basic building blocks to design and fabricate a wide variety of intrinsically flexible or stretchable devices, including sensors, actuators, therapeutic devices, energy-harvesting and storage devices, and displays. We further describe the techniques and strategies for wearable electronic systems either by hybridizing conventional off-the-shelf rigid electronic components with PCTs or by integrating multiple fibrous devices made of PCTs. Subsequently, we highlight some important wearable application scenarios in healthcare, sports and training, converging technologies, and professional specialists. At the end of the Review, we discuss the challenges and perspectives on future research directions and give overall conclusions. As the demand for more personalized and interconnected devices continues to grow, PCT-based wearables hold immense potential to redefine the landscape of wearable technology and reshape the way we live, work, and play.

An Environment-Tolerant Ion-Conducting Double-Network Composite Hydrogel for High-Performance Flexible Electronic Devices

High-performance ion-conducting hydrogels (ICHs) are vital for developing flexible electronic devices. However, the robustness and ion-conducting behavior of ICHs deteriorate at extreme temperatures, hampering their use in soft electronics. To resolve these issues, a method involving freeze-thawing and ionizing radiation technology is reported herein for synthesizing a novel double-network (DN) ICH based on a poly(ionic liquid)/MXene/poly(vinyl alcohol) (PMP DN ICH) system. The well-designed ICH exhibits outstanding ionic conductivity (63.89 mS cm-1 at 25 °C), excellent temperature resistance (- 60-80 °C), prolonged stability (30 d at ambient temperature), high oxidation resistance, remarkable antibacterial activity, decent mechanical performance, and adhesion. Additionally, the ICH performs effectively in a flexible wireless strain sensor, thermal sensor, all-solid-state supercapacitor, and single-electrode triboelectric nanogenerator, thereby highlighting its viability in constructing soft electronic devices. The highly integrated gel structure endows these flexible electronic devices with stable, reliable signal output performance. In particular, the all-solid-state supercapacitor containing the PMP DN ICH electrolyte exhibits a high areal specific capacitance of 253.38 mF cm-2 (current density, 1 mA cm-2) and excellent environmental adaptability. This study paves the way for the design and fabrication of high-performance multifunctional/flexible ICHs for wearable sensing, energy-storage, and energy-harvesting applications.