High-energy fiber-shaped calcium-ion batteries enable integrated wearable electronics for human body monitoring

Electronic textiles hold the merits of high conformability with the human body and natural surrounding,possessing large market demand and wide application foreground in smart wearable and portable devices.However,their further application is largely hindered by the shortage of flexible and stable power sources with multifunctional designability.Herein,a free-standing ZnHCF@CF electrode(ZnHCF grown on carbon nanotube fiber)with good mechanical deformability and high electrochemical performance for aqueous fiber-shaped calcium ion battery(FCIB)is reported.Benefiting from the unique Ca^(2+)/H^(+)co-insertion mechanism,the ZnHCF@CF cathode can exhibit great ion storage capability within a broadened voltage window.By pairing with a polyaniline(PANI)@CF anode,a ZnHCF@CF//PANI@CF FCIB is successfully fabricated,which exhibits a desirable volumetric energy density of 43.2mWh cm^(-3)and maintains superior electrochemical properties under different deformations.Moreover,the high-energy FCIB can be harmoniously integrated with a fiber-shaped strain sensor(FSS)to achieve real-time physiological monitoring on knees during long-running,exhibiting great promise for the practical application of electronic textiles.

Rational Design of Cellulosic Triboelectric Materials for Self‑Powered Wearable Electronics

With the rapid development of the Internet of Things and flexible electronic technologies,there is a growing demand for wireless,sustainable,multifunctional,and independently operating self-powered wearable devices.Nevertheless,structural flexibility,long operating time,and wearing comfort have become key requirements for the widespread adoption of wearable electronics.Triboelectric nanogenerators as a distributed energy harvesting technology have great potential for application development in wearable sensing.Compared with rigid electronics,cellulosic self-powered wearable electronics have significant advantages in terms of flexibility,breathability,and functionality.In this paper,the research progress of advanced cellulosic triboelectric materials for self-powered wearable electronics is reviewed.The interfacial characteristics of cellulose are introduced from the top-down,bottom-up,and interfacial characteristics of the composite material preparation process.Meanwhile,the modulation strategies of triboelectric properties of cellulosic triboelectric materials are presented.Furthermore,the design strategies of triboelectric materials such as surface functionalization,interfacial structure design,and vacuum-assisted self-assembly are systematically discussed.In particular,cellulosic self-powered wearable electronics in the fields of human energy harvesting,tactile sensing,health monitoring,human–machine interaction,and intelligent fire warning are outlined in detail.Finally,the current challenges and future development directions of cellulosic triboelectric materials for self-powered wearable electronics are discussed.

Analytical transient phase change heat transfer model of wearable electronics with a thermal protection substrate

As thermal protection substrates for wearable electronics,functional soft composites made of polymer materials embedded with phase change materials and metal layers demonstrate unique capabilities for the thermal protection of human skin.Here,we develop an analytical transient phase change heat transfer model to investigate the thermal performance of a wearable electronic device with a thermal protection substrate.The model is validated by experiments and the finite element analysis(FEA).The effects of the substrate structure size and heat source power input on the temperature management efficiency are investigated systematically and comprehensively.The results show that the objective of thermal management for wearable electronics is achieved by the following thermal protection mechanism.The metal thin film helps to dissipate heat along the in-plane direction by reconfiguring the direction of heat flow,while the phase change material assimilates excessive heat.These results will not only promote the fundamental understanding of the thermal properties of wearable electronics incorporating thermal protection substrates,but also facilitate the rational design of thermal protection substrates for wearable electronics.

High‑Performance and Long‑Term Stability of MXene/PEDOT:PSS‑Decorated Cotton Yarn for Wearable Electronics Applications

High-performance wearable electronics are highly desirable for the development of body warming and human health monitoring devices.In the present study,high electrically conductive and photothermal cotton yarns(CYs)with long-term stability were prepared as wearable electronics.The process contains back-to-back decoration of the fiber surface by Ti_(3)C_(2)T_(x)(MXene)nanosheets,and the poly(3,4-ethylenedioxythiophene)polystyrene sulfonate(PEDOT:PSS)composite,to form a core–shell structure(MP@CY).The addition of a small amount of PEDOT:PSS plays a dual role of protecting the MXene from oxidation and increasing the electrical conductivity.The resulting yarn exhibits excellent electrical conductivity(21.8Ωcm^(−1)),rapid electrothermal response,and superb photothermal conversion capability,supporting its application as an optical/electrical dual-drive heater.A three-dimensional(3D)honeycomb-like textile wearable heater based on MP@CY as weft yarn demonstrates outstanding electrical thermal properties(0–2.5 V,30–196.8°C)and exceptional photothermal conversion(130 mW cm^(−2),64.2°C).Using an Internet of Things(IoT)microcontroller and Espressif(ESP)electronics chip,which are combined with wireless fidelity(Wi-Fi)and smartphone,real-time visualization and precise control of the temperature interface can be achieved.Furthermore,MP@CY-based knitted sensors,obtained by hand-knitting,are utilized for monitoring human movement and health,exhibiting high sensitivity and long-term cycling stability.

Bionic-leaf vein inspired breathable anti-impact wearable electronics with health monitoring,electromagnetic interference shielding and thermal management

Breathable and stretchable conductive materials are ideal for healthcare wearable electronic devices.However,the tradeoffbetween the sensitivity and detection range of electronic sensors and the challenge posed by simple-functional electronics limits their development.Here,inspired by the bionic-leaf vein conductive path,silver nanowires(AgNWs)-Ti_(3)C_(2)T_(x)(MXene)hybrid structure assembled on the nonwoven fabrics(NWF)is well sandwiched between porous polyborosiloxane elastomer(PBSE)to construct the multifunctional breathable wearable electronics with both high anti-impact performance and good sensing behavior.Benefiting from the high conductive AgNWs-MXene hybrid structure,the NWF/AgNWsMXene/PBSE nanocomposite exhibits high sensitivity(GF=1158.1),wide monitoring range(57%),controllable thermal management properties,and excellent electromagnetic interference shielding effect(SE_(T)=41.46 dB).Moreover,owing to the wonderful shear stiffening effect of PBSE,the NWF/AgNWsMXene/PBSE possesses a high energy absorption performance.Combining with deep learning,this breathable electronic device can be further applied to wireless sensing gloves and multifunctional medical belts,which will drive the development of electronic skin,human-machine interaction,and personalized healthcare monitoring applications.

Pressure Regulated Printing of Semiliquid Metal on Electrospinning Film Enables Breathable and Waterproof Wearable Electronics

Application of liquid metals and electrospun nanofibers offer a promising solution to insufficient resilience and human com-fort of wearable electronics.However,a sustainable manufacturing process is hindered by the low surface tension of liquid metal,and it's poor attachment to the surface of the fabric.This research reveals that tuning the pressure can control the adhesion of semiliquid metal(SLM)on substrates with varying roughness to achieve selective adhesion.Furthermore,a simple and rapid(30 s)fabrication method based on selective adhesion and low mobility of SLM is presented for preparing a multilayered monitoring device capable of measuring human body temperature and ECG signals for 24 h.This device exhibits excellent air permeability of 311.1 g·m^(-2)·h^(-1),water resistance(washing for 120 min).Our novel approach can inspire the development of methods for printing liquid metal circuits on roughness substrates and enable the practical use of waterproof and breathable wearable electronic devices in the future.

Biomechanical energy harvesting technologies for wearable electronics:Theories and devices

Wearable biomechanical energy harvesting devices have received a lot of attention recently,benefiting from the rapid advancement of theories and devices in the field of the micro electromechanical system(MEMS).They not only fulfil the requirements for powering wearable electronic devices but also provide an attractive prospect for powering self-powered flexible electronic devices when wearing.In this article,we provide a review of the theories and devices of biomechanical energy harvesting technology for wearable applications.Three different forms of biomechanical energy harvesting mechanisms,including the piezoelectric effect,electromagnetic effect,and electrostatic effect,are investigated in detail.The fundamental principle of converting other types of energy from the biomechanical environment into electrical energy,as well as the most commonly-used analytical theoretical models,are outlined for each process.Therefore,the features,properties,and applications of energy harvesting devices are summarized.In addition,the coupled multi-effect hybrid energy harvesting devices are listed,showing the various possibilities of biomechanical energy harvesting devices for serving as sources,sensors,and actuators.Finally,we present perspectives on the future trends of biomechanical energy harvesting devices for wearable electronics applications.

Breathable Wearable Electronics by 3D Liquid Diode

Wearable electronics,poised to revolutionize real-time health monitoring,encounter significant challenges due to sweat accumulation,including skin irritation,peeling,short circuits,and corrosion.A groundbreaking study published in Nature presents a sustainable solution:three-dimensional(3D)liquid diodes that effectively pump sweat away,thereby maintaining the wearables’breathability and stable sensing of biometrics or environments without getting messed up by perspiration.This advancement has immense potential for the development of comfortable and skin-friendly intelligent wearable technologies that seamlessly incorporate sophisticated electronics even in sweaty conditions.

Transparent, stretchable, and rapid-response humidity sensor for body-attachable wearable electronics

Stretchable and conformal humidity sensors that can be attached to the human body for continuously monitoring the humidity of the environment around the human body or the moisture level of the human skin can play an important role in electronic skin and personal healthcare applications. However, most stretchable humidity sensors are based on the geometric engineering of non-stretchable components and only a few detailed studies are available on stretchable humidity sensors under applied mechanical deformations. In this paper, we propose a transparent, stretchable humidity sensor with a simple fabrication process, having intrinsically stretchable components that provide high stretchability, sensitivity, and stability along with fast response and relaxation time. Composed of reduced graphene oxide-polyurethane composites and an elastomeric conductive electrode, this device exhibits impressive response and relaxation time as fast as 3.5 and 7 s, respectively. The responsivity and the response and relaxation time of the device in the presence of humidity remain almost unchanged under stretching up to a strain of 60% and after 10,000 stretching cycles at a 40% strain. Further, these stretchable humidity sensors can be easily and conformally attached to a finger for monitoring the humidity levels of the environment around the human body, wet objects, or human skin.

Progress in wearable electronics/photonics—Moving toward the era of artificial intelligence and internet of things

The past few years have witnessed the significant impacts of wearable electronics/photonics on various aspects of our daily life,for example,healthcare monitoring and treatment,ambient monitoring,soft robotics,prosthetics,flexible display,communication,human-machine interactions,and so on.According to the development in recent years,the next-generation wearable electronics and photonics are advancing rapidly toward the era of artificial intelligence(AI)and internet of things(IoT),to achieve a higher level of comfort,convenience,connection,and intelligence.Herein,this review provides an opportune overview of the recent progress in wearable electronics,photonics,and systems,in terms of emerging materials,transducing mechanisms,structural configurations,applications,and their further integration with other technologies.First,development of general wearable electronics and photonics is summarized for the applications of physical sensing,chemical sensing,humanmachine interaction,display,communication,and so on.Then self-sustainable wearable electronics/photonics and systems are discussed based on system integration with energy harvesting and storage technologies.Next,technology fusion of wearable systems and AI is reviewed,showing the emergence and rapid development of intelligent/smart systems.In the last section of this review,perspectives about the future development trends of the next-generation wearable electronics/photonics are provided,that is,toward multifunctional,self-sustainable,and intelligent wearable systems in the AI/IoT era.

Liquid metal-integrated ultra-elastic conductive microfibers from microfluidics for wearable electronics

Liquid metal(LM) has shown potential values in different areas. Attempts to implement LM are tending to develop new functions and make it versatile to improve its performance for practical applications.Here, we present an unprecedented LM-integrated ultra-elastic microfiber with distinctive features for wearable electronics. The microfiber with a polyurethane shell and an LM core was continuously generated by using a sequenced microfluidic spinning and injection method. Due to the precise fluid manipulation of microfluidics, the resultant microfiber could be tailored with tunable morphologies and responsive conductivities. We have demonstrated that the microfiber could act as dynamic force sensor and motion indicator when it was embedded into elastic films. In addition, the values of the LMintegrated ultra-elastic microfiber on energy conversions such as electro-magnetic or electro-thermal conversions have also been realized. These features indicate that LM-integrated microfiber will open up new frontiers in LM-integrated materials and the wearable electronics field.

Recent developments in self-powered smart chemical sensors for wearable electronics

The next generation of electronics technology is purely going to be based on wearable sensing systems. Wearable electronic sensors that can operate in a continuous and sustainable manner without the need of an external power sources, are essential for portable and mobile electronic applications. In this review article, the recent progress and advantages of wearable self-powered smart chemical sensors systems for wearable electronics are presented. An overview of various modes of energy conversion and storage technologies for self-powered devices is provided. Self-powered chemical sensors (SPCS) systems with integrated energy units are then discussed, separated as solar cell-based SPCS, triboelectric nano-generators based SPCS, piezoelectric nano-generators based SPCS, energy storage device based SPCS, and thermal energy-based SPCS. Finally, the outlook on future prospects of wearable chemical sensors in self-powered sensing systems is addressed.

Ultraflexible,highly efficient electromagnetic interference shielding,and self-healable triboelectric nanogenerator based on Ti_(3)C_(2)T_(x) MXene for self-powered wearable electronics

Integrating smart functions into one flexible electronic is vastly valuable in improving their working performances and broadening applications.Here,this work reports a ultraflexible,highly efficient electromagnetic interference(EMI)shielding,and self-healable triboelectric nanogenerator(TENG)that is assembled by modified Ti_(3)C_(2)T_(x) MXene(m-MXene)-based nanocomposite elastomers.Benefitting from the excellent electronegativity of m-MXene,the single-electrode mode-based TENG can generate high open-circuit voltage(V_(oc))oscillating between-65 and 245 V,high short-circuit current(I_(sc))of 29 μA,and an instantaneously maximum peak power density of 1150 mW m^(-2) that can power twenty light-emitting diodes(LEDs).Moreover,the resultant TENG possesses outstanding EMI shielding performance with the maximum shielding effectiveness of 48.1 dB in the X-band.The enhanced shielding capability is dominated by the electromagnetic absorption owning to high conduction loss in m-MXene network,multiple reflections between m-MXene sheets,and polarization effect on the surface of m-MXene sheets.Additionally,a self-powered wearable sensor is fabricated based on the as-prepared TENG.The sensor shows an intrinsic healing ability with healing efficiency of 98.2% and can accurately detect the human large-scale motions and delicate physical signal.This work provides an enhanced way to fabricate the wearable electronics integrated with smart functions,and the reported MXene-based TENG may have a broad prospect in the fields of aerospace,artificial intelligence,and healthcare systems.

Graphene-based flexible and wearable electronics

Graphene with an exceptional combination of electronic, optical and outstanding mechanical features has been proved to lead a completely different kind of 2-D electronics. The most exciting feature of graphene is its ultra-thin thickness, that can be conformally contacted to any kind of rough surface without losing much of its transparency and conductivity. Graphene has been explored demonstrating various prototype flexible electronic applications, however, its potentiality has been proven wherever transparent conductive electrodes（TCEs） are needed in a flexible, stretchable format. Graphene-based TCEs in flexible electronic applications showed greatly superior performance over their conventionally available competitor indium tin oxide（ITO）. Moreover, enormous applications have been emerging, especially in wearable devices that can be potentially used in our daily life as well as in biomedical areas. However, the production of high-quality, defect-free large area graphene is still a challenge and the main hurdle in the commercialization of flexible and wearable products. The objective of the present review paper is to summarize the progress made so far in graphene-based flexible and wearable applications. The current developments including challenges and future perspectives arc also highlighted.

Preface to the Special Issue on Flexible and Wearable Electronics： from Materials to Applications

Electronic systems that can cover large areas on flexible/stretchable substrateshave received increasing attention in the past several years because they enable new classes of applications that lie outside those easily addressed with wafer-based microelectronics.Some attractive examples include flexible displays,flexible solar cells,electronic textiles,sensory skins,detectors,active antennas,etc.The field expends very fast and great developments have been obtained

Wearable multilead ECG sensing systems using on-skin stretchable and breathable dry adhesives

Electrocardiogram(ECG)monitoring is used to diagnose cardiovascular diseases,for which wearable electronics have attracted much attention due to their lightweight,comfort,and long-term use.This study developed a wearablemultilead ECG sensing system with on-skin stretchable and conductive silver(Ag)-coated fiber/silicone(AgCF-S)dry adhesives.Tangential and normal adhesion to pigskin(0.43 and 0.20 N/cm2,respectively)was optimized by the active control of fiber density and mixing ratio,resulting in close contact in the electrode–skin interface.The breathableAgCF-S dry electrodewas nonallergenic after continuous fit for 24 h and can be reused/cleaned(>100 times)without loss of adhesion.The AgCF encapsulated inside silicone elastomers was overlapped to construct a dynamic network under repeated stretching(10%strain)and bending(90°)deformations,enabling small intrinsic impedance(0.3,0.1 Hz)and contact impedance variation(0.7 k)in high-frequency vibration(70 Hz).All hard/soft modules of the multilead ECG system were integrated into lightweight clothing and equipped with wireless transmission for signal visualization.By synchronous acquisition of I–III,aVR,aVL,aVF,and V4 lead data,the multilead ECG sensing system was suitable for various scenarios,such as exercise,rest,and sleep,with extremely high signal-to-noise ratios.

Review of Recent Advances in Non-invasive, Flexible,Wearable Sweat Monitoring Sensors

Wearable health-monitoring devices are novel and integral developments based on smart-textiles.Conventional wearable technology consists of micro-controllers and a variety of electronic devices embedded on the skin,or incorporated into the apparels,where they act as signal receptors,analytical devices and transmitters of the signals generated from the human body.Invasive methods are currently more commonly practiced where biofluids are obtained by penetrating the body by incision or injection,while in non-invasive methods no such penetrations take place.A critical review of current non-invasive wearable technology,including colorimetric,enzymatic,pH based,electrochemical and conductivity sensors,is presented in this paper along with the challenges and limitations they pose.Additionally,novel techniques of analysis have been explored concluding that a textile-based medium offers higher compatibility for integration of such sensors in comparison to other existing substrates.

A Comprehensive Review of Wearable Applications and Material Construction

Wearable electronic systems are able to monitor and measure multiple biophysical, biochemical signals to help researchers develop further understandings of human health and correlation between human performance and diseases. Driven by increasing demand for need in sports training, health monitoring and disease diagnose, bio-integrated systems are developing at a significant speed based on recent advances in material science, structure design and chemical techniques. A wide range of wearable systems are created and feature unique measuring targets, methods and soft, transparent, stretchable characters. This review summarizes the recent advances in wearable electronic technologies that also include material science, chemical science and electronic engineering. The introduction to basic wearable fundamentals covers subsequent consideration for materials, system integration and promising platforms. Detailed classification towards their functions of physical, chemical detection is also mentioned. Strategies to achieve stretchability and promising material, AgNW, are fully discussed. This paper concludes with consideration of main challenging obstacles in this emerging filed and promises in materials that possess excellent potentials for predicted progress.

Wearable activity trackers and health awareness: Nursing implications

Purpose:Wearable devices are commonly used to measure physical activity.However,it remains unclear the effect of wearing these devices on health awareness.Our aim was to provide evidence related to wearing physical activity trackers and health awareness.Methods:A quantitative comparison study design was used comparing participants who wore physical activity tracking devices(n=108)and those who did not(n=112).A paper-based Physical Health Knowledge survey designed for the purpose of this research was used for data collection in 2018.Results:A difference between participants who wore physical activity tracking devices and those that did not was identified in relation to activity levels and physical health awareness.Wearable devices are suggested as an opportunity for nurses to engage people in physical activity with the potential to improve their health awareness.Conclusions:Nurses are well placed in the healthcare landscape to work with patients who own an activity tracker device concerning increasing activity self-monitoring.This information the patient has from the device can also form the basis of health discussions between nurses and the people in their care.