Flexible and wearable BaTiO_(3)/polyacrylonitrile-based piezoelectric sensor for human posture monitoring

Tactile sensors are essential components of wearable electronic devices,but there are still various problems in terms of energy supply,flexibility and skin adaptability.In this paper,we report a self-powered flexible tactile sensor(FTS)mainly composed of a BaTiO_(3)/polyacrylonitrile/Ecoflex(BTO/PAN/Ecoflex)composite film,which can be used for dynamically monitoring human plantar pressure,posture and other physiological and motion parameters.Combining the synergistic piezoelectric properties of PAN and BTO,the output voltage/current of the BTO/PAN/Ecoflex composite film is 4.5/5.8 times that of the BTO/Ecoflex composite film,with maximum instantaneous power that can reach up to 3.375μW.Under the action of external pressure stress,the FTS can reach a normalized voltage sensitivity and voltage linearity of 0.54 V/N and 0.98,respectively.Furthermore,a human-machine interaction test system is built,which can display the stress changes of human body monitoring parts in real time according to voltage changes and different color assignments.The developed human-machine interaction test system provides a new idea for the diagnosis of flatfoot and other medical diseases.Hence,this work proposes new FTSs that use a BTO/PAN/Ecoflex composite film with high sensitivity and great output performance,thus exhibiting immense potential application prospects in medical research,personalized recognition and human-machine interaction.

Smart Gas Sensors:Recent Developments and Future Prospective

Gas sensor is an indispensable part of modern society withwide applications in environmental monitoring,healthcare,food industry,public safety,etc.With the development of sensor technology,wireless communication,smart monitoring terminal,cloud storage/computing technology,and artificial intelligence,smart gas sensors represent the future of gassensing due to their merits of real-time multifunctional monitoring,earlywarning function,and intelligent and automated feature.Various electronicand optoelectronic gas sensors have been developed for high-performancesmart gas analysis.With the development of smart terminals and the maturityof integrated technology,flexible and wearable gas sensors play an increasingrole in gas analysis.This review highlights recent advances of smart gassensors in diverse applications.The structural components and fundamentalprinciples of electronic and optoelectronic gas sensors are described,andflexible and wearable gas sensor devices are highlighted.Moreover,sensorarray with artificial intelligence algorithms and smart gas sensors in“Internet of Things”paradigm are introduced.Finally,the challengesand perspectives of smart gas sensors are discussed regarding the future need of gas sensors for smart city and healthy living.

Recent progress in graphene-based wearable piezoresistive sensors:From 1D to 3D device geometries

Electronic skin and flexible wearable devices have attracted tremendous attention in the fields of human-machine interaction,energy storage,and intelligent robots.As a prevailing flexible pressure sensor with high performance,the piezoresistive sensor is believed to be one of the fundamental components of intelligent tactile skin.Furthermore,graphene can be used as a building block for highly flexible and wearable piezoresistive sensors owing to its light weight,high electrical conductivity,and excellent mechanical.This review provides a comprehensive summary of recent advances in graphene-based piezoresistive sensors,which we systematically classify as various configurations including one-dimensional fiber,two-dimensional thin film,and threedimensional foam geometries,followed by examples of practical applications for health monitoring,human motion sensing,multifunctional sensing,and system integration.We also present the sensing mechanisms and evaluation parameters of piezoresistive sensors.This review delivers broad insights on existing graphene-based piezoresistive sensors and challenges for the future generation of high-performance,multifunctional sensors in various applications.

Flexible aqueous Ca-ion full battery with super-flat discharge voltage plateau

Recently,multivalent metal-ion batteries have attracted considerable interests on the merits of their natural abundance and multielectron redox property.However,the development of Ca-ion battery is still in their preliminary stage because of the lack of suitable electrode material.The Ca-storage performance of the existing materials is still unsatisfactory with low capacity,poor cyclic stability,as well as sloping discharge profiles,which cannot provide stable energy output.In this work,transition metal oxide Sn-doped In2O3(ITO)has been explored as the aqueous Ca-ion battery anode,which could deliver a high discharge capacity of 71.2 mAh·g^(-1) with an ultra-flat discharge voltage plateau.The Ca storage mechanism was revealed to be reversible conversion reaction based on ex-situ X-ray diffraction(XRD),X-ray photoelectron spectroscopy(XPS),and transmission electron microscopy(TEM)characterizations.A flexible aqueous Ca-ion battery was subsequently assembled with zinc hexacyanoferrate(ZnHCF)cathode and ITO anode sandwiched by hydrogel electrolyte,which could deliver a high specific capacity of 75.3 mAh·g^(-1) at 0.4 A·g^(-1) with a flat output voltage plateau at around 0.8 V.The bendable and flexible Ca-ion battery with decent voltage output will pave the way for the energy storage devices towards practical applications in flexible and wearable electronics.