Recent progress of fiber-shaped batteries towards wearable application

Rapid development of portable or wearable devices, which is inspired by requirements of instant messaging,health monitoring and handling official business, urgently demands more tiny, flexible and light power sources. Fibershaped batteries explored in recent years become a prospective candidate to satisfy these demands. With 1D architecture,the fiber-shaped batteries could be adapted to various deformations and integrated into soft textile and other devices.Numerous researches have been reported and achieved huge promotion. To give an overview of fiber-shaped batteries,we summarized the development of fiber-shaped batteries in this review, and discussed the structure and materials in fiber-shaped batteries. The flexibility of batteries with the potential application of the batteries was also exhibited and showed the future perspective. Finally, challenges in this field were discussed, hoping to reveal research direction towards further development of fiber-shaped batteries.

Recent Progress of Graphene Fiber/Fabric Supercapacitors:From Building Block Architecture,Fiber Assembly,and Fabric Construction to Wearable Applications

High-performance fiber-shaped power sources are anticipated to considerably contribute to the continuous development of smart wearable devices.As one-/two-dimensional(1D/2D)frameworks constructed from graphene sheets,graphene fibers and fabrics inherit the merits of graphene,including its lightweight nature,high electrical conductivity,and exceptional mechanical strength.The as-fabricated graphene fiber/fabric flexible supercapacitor(FSC)is,therefore,regarded as a promis-ing candidate for next-generation wearable energy storage devices owing to its high energy/power density,adequate safety,satisfactory flexibility,and extended cycle life.The gap between practical applications and experimental demonstrations of FSC is drastically reduced as a result of technological advancements.To this end,herein,recent advancements of FSCs in fiber element regulation,fiber/fabric construction,and practical applications are methodically reviewed and a forecast of their growth is presented.

Swift Assembly of Adaptive Thermocell Arrays for Device‑Level Healable and Energy‑Autonomous Motion Sensors

The evolution of wearable technology has prompted the need for adaptive,self-healable,and energy-autonomous energy devices.This study innovatively addresses this challenge by introducing an MXene-boosted hydrogel electrolyte,which expedites the assembly process of flexible thermocell(TEC)arrays and thus circumvents the complicated fabrication of typical wearable electronics.Our findings underscore the hydrogel electrolyte’s superior thermoelectrochemical performance under substantial deformations and repeated self-healing cycles.The resulting hydrogel-based TEC yields a maximum power output of 1032.1 nW under theΔT of 20 K when being stretched to 500%for 1000 cycles,corresponding to 80%of its initial state;meanwhile,it sustains 1179.1 nW under theΔT of 20 K even after 60 cuthealing cycles,approximately 92%of its initial state.The as-assembled TEC array exhibits device-level self-healing capability and high adaptability to human body.It is readily applied for touch-based encrypted communication where distinct voltage signals can be converted into alphabet letters;it is also employed as a self-powered sensor to in-situ monitor a variety of body motions for complex human actions.The swift assembly approach,combined with the versatile functionality of the TEC device,paves the way for future advancements in wearable electronics targeting at fitness monitoring and human–machine interfaces.

Regulating Thermogalvanic Effect and Mechanical Robustness via Redox Ions for Flexible Quasi‑Solid‑State Thermocells

The design of power supply systems for wearable applications requires both flexibility and durability.Thermoelectrochemical cells(TECs)with large Seebeck coefficient can efficiently convert lowgrade heat into electricity,thus having attracted considerable attention in recent years.Utilizing hydrogel electrolyte essentially addresses the electrolyte leakage and complicated packaging issues existing in conventional liquid-based TECs,which well satisfies the need for flexibility.Whereas,the concern of mechanical robustness to ensure stable energy output remains yet to be addressed.Herein,a flexible quasisolid-state TEC is proposed based on the rational design of a hydrogel electrolyte,of which the thermogalvanic effect and mechanical robustness are simultaneously regulated via the multivalent ions of a redox couple.The introduced redox ions not only endow the hydrogel with excellent heat-to-electricity conversion capability,but also act as ionic crosslinks to afford a dual-crosslinked structure,resulting in reversible bonds for effective energy dissipation.The optimized TEC exhibits a high Seebeck coefficient of 1.43 mV K−1 and a significantly improved fracture toughness of 3555 J m^(−2),thereby can maintain a stable thermoelectrochemical performance against various harsh mechanical stimuli.This study reveals the high potential of the quasi-solid-state TEC as a flexible and durable energy supply system for wearable applications.

High‑Performance Stretchable Supercapacitors Based on Centrifugal Electrospinning‑Directed Hetero‑structured Graphene–Polyaniline Hierarchical Fabric

Stretchable supercapacitors(S-SCs)are of considerable interest as prospective energy-storage devices for wearable electronics and smart products.However,achieving high energy density and stable output under large deformations remains an urgent challenge.Here,we develop a high-performance S-SC based on a robust heterostructured graphene–polyaniline(G-PANI)anchored hierarchical fabric(G-PANI@pcPU).By precisely manipulating centrifugal electrospinning and PANI-induced two-step self-assembly process,the G-PANI@pcPU features an inter-linkage porous backbone,which open ions migration/intercalation pathways,high mechanical flexibility(elongation:400%),and large production area(>90 cm^(2)).The resultant G-PANI@pcPU presents ultra-large specific areal capacitance(Careal)of 5093.7 mF cm^(-2)(about 35 mg cm^(-2)mass loading of G-PANI)and redox reversibility in 1 M H_(2)SO_(4) electrolyte.Additionally,the G-PANI@pcPU fabric-based solid-state S-SCs show a high energy density of 69.2μWh cm^(-2)and capacitance of 3113.7 mF cm^(-2).More importantly,the superior stretchable stability(84.1%capacitance retentions after 5000 cycles)and foldable performance(86.7%capacitance retentions after 5000 cycles)of S-SCs are impressively achieved.Finally,the S-SCs realize potential applications of steady powering light-emitting diode(LED)lights at 100%strain,smart watch at bending deformation,toy car,and lamp.This work can offer an overwhelming foundation for designing advanced flexible electrodes toward new energy and smart wearable applications.

Ultrasensitive,stretchable,and transparent humidity sensor based on ionconductive double-network hydrogel thin films

Ion-conductive hydrogels with intrinsic biocompatibility,stretchability,and stimuli-responsive capability have attracted considerable attention because of their extensive application potential in wearable sensing devices.The miniaturization and integration of hydrogel-based devices are currently expected to achieve breakthroughs in device performance and promote their practical application.However,currently,hydrogel film is rarely reported because it can be easily wrinkled,torn,and dehydrated,which severely hinders its development in microelectronics.Herein,thin,stretchable,and transparent ion-conductive double-network hydrogel films with controllable thickness are integrated with stretchable elastomer substrates,which show good environmental stability and ultrahigh sensitivity to humidity(78,785.5%/% relative humidity(RH)).Benefiting from the ultrahigh surface-area-to-volume ratio,abundant active sites,and short diffusion distance,the hydrogel film humidity sensor exhibits2×10^(5)times increased response to 98% RH,as well as 5.9 and7.6 times accelerated response and recovery speeds compared with the bulk counterpart,indicating its remarkable thicknessdependent humidity-sensing properties.The humidity-sensing mechanism reveals that the adsorption of water improves the ion migration and dielectric constant,as well as establishes the electrical double layer.Furthermore,the noncontact human-machine interaction and real-time respiratory frequency detection are enabled by the sensors.This work provides an innovative strategy to achieve further breakthroughs in device performance and promote the development of hydrogel-based miniaturized and integrated electronics.

Borophene gas sensor

High-performance gas sensing devices have been extensively studied in industrial production,clinical medicine and environmental monitoring.Among the materials used to fabricate gas sensors,two-dimensional(2D)materials are viewed as favorable candidate sensing materials because of their high surface-to-volume ratios,abundant surface activity,defect sites.However,gas sensors based on the previously reported 2D materials have some disadvantages such as poor air-stability and slow dynamic response.Recently,borophene,as a unique 2D material,has been theoretically predicted to have excellent gas sensing characteristic,especially for nitrogen dioxide(NO_(2)).However,the gas sensing property of borophene has not been still reported experimentally.Here,we report that a chemiresistive sensor device based on borophene shows high sensitivity,fast response,high selectivity,good flexibility and long-time stability.It is found that the sensor has a low experimental detection limit of around 200 ppb,a large detection range from 200 ppb to 100 ppm,and fast response time of 30 s and recovery time of 200 s at room temperature,which are remarkably superior to those of reported 2D materials.The underlying NO_(2) sensing mechanism of borophene is revealed by first-principles calculations.In line with theoretical predication,it has also been confirmed experimentally that the borophene-based sensor has a unique selectivity to NO_(2) compared with other common gases.Furthermore,the sensor also displays superior flexibility and stability under different bending angles.This study shows excellent electronic and sensing characteristic of borophene,which indicates that it has great potential application value in high-performance sensing and detection in the future.