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.

Progress of Proximity Sensors for Potential Applications in Electronic Skins

Recently,electronic skins and fl exible wearable devices have been developed for widespread applications in medical monitoring,artifi cial intelligence,human–machine interaction,and artifi cial prosthetics.Flexible proximity sensors can accurately perceive external objects without contact,introducing a new way to achieve an ultrasensitive perception of objects.This article reviews the progress of fl exible capacitive proximity sensors,fl exible triboelectric proximity sensors,and fl exible gate-enhanced proximity sensors,focusing on their applications in the electronic skin fi eld.Herein,their working mechanism,materials,preparation methods,and research progress are discussed in detail.Finally,we summarize the future challenges in developing fl exible proximity sensors.

Flexible wearable sensors:An emerging platform for monitoring of bacterial infection in skin wounds

Persistent inflammatory responses often occur when bacteria and other microorganisms frequently invade and colonize open wounds and eventually result in the formation of chronic wounds.Therefore,achieving real-time detection of invasive bacteria accurately and promptly is essential for efficient wound management and accelerat-ing the healing process.Recently,flexible wearable sensors have garnered significant attention,especially those designed for monitoring real-time biophysical or biochemical signals in wound sites in a minimally invasive manner.They provide more precise and continuous monitoring data,making them as emerging tools for clinical diagnostics.In this review,we first discuss the species and community distribution of different types of bacteria in chronic wounds.Next,we introduce currently developed techniques for detecting bacteria at wound sites.Fol-lowing that,we discuss the recent progress and unresolved issues of various flexible wearable sensors in detecting bacteria at wound sites.We believe that this review can provide meaningful guidance for the development of flexible wearable sensors for bacteria detection.

Recent advances of wearable and flexible piezoresistivity pressure sensor devices and its future prospects

The human skin inspired soft electronic devices have attracted broadly research attention in the past decades as the promising potential applications in health monitoring and diagnosis,robotics,and prosthetics.The soft wearable piezoresistivity pressure sensor is one of the most attractive candidates for the development of advanced electronic skin for its simple mechanism,compact structure,low cost and power energy consumption and ease of signal acquisition and transforms advantages.In this review,we will explore the recent progress and achievements in the field of piezoresistivity pressure sensor,focusing on the fundamentals of the piezoresistivity pressure sensor and the materials related to the devices,including active materials,substrate materials,and electrode materials.Subsequently,the challenges and outlook are discussed.We list several current challenges perspectives on the development of pressure sensors.Several critical topics for the optimization of the sensitivity and working range of sensing devices toward practical applications are discussed.Finally,perspectives on the slip and force vectors sensors,the developing technologies for multi-function and high-resolution sensor systems and signals process technologies are examined to highlight the near future development tendency in piezoresistivity pressure sensor research field.

Recent progress of flexible and wearable strain sensors for human-motion monitoring

With the rapid development of human artificial intelligence and the inevitably expanding markets, the past two decades have witnessed an urgent demand for the flexible and wearable devices, especially the flexible strain sensors. Flexible strain sensors, incorporated the merits of stretchability, high sensitivity and skin-mountable,are emerging as an extremely charming domain in virtue of their promising applications in artificial intelligent realms, human-machine systems and health-care devices. In this review, we concentrate on the transduction mechanisms, building blocks of flexible physical sensors, subsequently property optimization in terms of device structures and sensing materials in the direction of practical applications. Perspectives on the existing challenges are also highlighted in the end.

Wearable devices and IoT applications for symptom detection, infection tracking, and diffusion containment of the COVID-19 pandemic: a survey

Until a safe and effective vaccine to fight the SARS-CoV-2 virus is developed and available for the global population, preventive measures, such as wearable tracking and monitoring systems supported by Internet of Things(IoT) infrastructures, are valuable tools for containing the pandemic. In this review paper we analyze innovative wearable systems for limiting the virus spread, early detection of the first symptoms of the coronavirus disease COVID-19 infection, and remote monitoring of the health conditions of infected patients during the quarantine. The attention is focused on systems allowing quick user screening through ready-to-use hardware and software components. Such sensor-based systems monitor the principal vital signs, detect symptoms related to COVID-19 early, and alert patients and medical staff. Novel wearable devices for complying with social distancing rules and limiting interpersonal contagion(such as smart masks) are investigated and analyzed. In addition, an overview of implantable devices for monitoring the effects of COVID-19 on the cardiovascular system is presented. Then we report an overview of tracing strategies and technologies for containing the COVID-19 pandemic based on IoT technologies, wearable devices, and cloud computing. In detail, we demonstrate the potential of radio frequency based signal technology, including Bluetooth Low Energy(BLE), Wi-Fi, and radio frequency identification(RFID), often combined with Apps and cloud technology. Finally, critical analysis and comparisons of the different discussed solutions are presented, highlighting their potential and providing new insights for developing innovative tools for facing future pandemics.

Recent Progress for Gallium-Based Liquid Metal in Smart Wearable Textiles

The development of smart textiles has presentend new requirements for integrated devices that can be compatible with both conductivity and deformation.At room temperature,liquid metal presents both metallic properties and flexible properties,as well as low toxicity and biocompatible,which makes it more and more popular on the research of liquid metal based electronic devices.This review summarizes the basic physical properties,and the key points to be fabricated into fibers and fabrics including oxides and wettability.Meantime,the application in the field of textiles is presented.Liquid metal based electrical conductive fibers and flexible sensors can be fabricated mainly by injection and printing,as well as direct-writing for smart fabrics.Liquid metal can be integrated as functional components for smart wearable devices in the future by assembling the as-prepared fibers and fabrics with textile technology,such as twisting,sewing,knitting,and embroidering.

可穿戴汗液传感器系统的研究进展

在新材料和新技术广泛应用的背景下,柔性可穿戴汗液监测设备成为当前国内外研究的热点。目前,基于柔性可穿戴设备的汗液检测一般需要3个环节:汗液的取样、目标分析物的选择性检测以及系统的集成与控制。本文主要从汗液原位检测的优势出发,总结了汗液的刺激和提取的方法,并对电化学类的汗液传感器的研究进展进行多角度的分析与评价。最后讨论了可穿戴的汗液传感器存在的不足,以及未来系统的发展方向。

面向人体运动检测的水凝胶基柔性应变传感器设计

在可穿戴电子设备迅猛发展的背景下,构建面向人体运动检测的可穿戴柔性应变传感器成为目前传感器研究的重点之一。基于聚丙烯酰胺(PAM)、纤维素纳米晶(CNCs)、单宁酸(TA)构建了一种导电水凝胶基柔性应变传感器。机械性能与电学性能测试结果表明,相较于其他柔性应变传感器,聚丙烯酰胺-纤维素纳米晶-单宁酸导电水凝胶基柔性应变传感器具有超长的拉伸范围(0%~2 900%)、较好的黏附性、快速的响应时间(280 ms)和良好的稳定性(超320次加载-卸载循环)。该传感器对人体关节弯曲的大应变与喉部活动的小应变等运动信号具备良好的检测功能,可用作人体运动检测的柔性可穿戴传感器。

纸基柔性传感器可穿戴设备在人体运动中的应用

纸基柔性材料是一种新型材料,其具有轻便性、高延展性能。柔性可穿戴设备由柔性材料制作而成,有轻便、舒适性高、应用范围较广等优点,有望弥补传统的可穿戴设备的不足,被广泛应用于各领域中。国内外有不少文献报道用纸基柔性材料制备的柔性可穿戴设备应用领域。相较于传统设备,它们不仅在用户体验舒适度方面取得巨大突破,还在功能上得到延伸创新以满足多种临床应用场景的需求。基于此,简单介绍纸基柔性可穿戴设备的工作原理及分类,并围绕人们的运动、居家康复、健康检测等几个方面阐述近年来柔性可穿戴设备在康复领域中的研究进展。

可穿戴离子检测及电促渗系统研究

汗液作为一种非侵入性健康监测的资源,含有丰富的生理信息,可以进行实时无创监测。然而,人在久坐或者睡眠时无法获得足够的汗液进行采样分析,若要实现汗液成分的长期原位监测并不容易。基于以上两点问题,主要通过电化学传感器与可穿戴传感技术相结合,以非侵入的方式监测汗液中的Na+,并开发测试了一套集成的可穿戴平台,用于实时采集和分析汗液中Na+的浓度。本系统Na+在浓度为20 mmol/L~160 mmol/L的测试范围内,灵敏度达到61.6 mV/decade。除此之外,可以根据受试者自身出汗量情况来调节系统刺激出汗的相关参数,从而能够减小长期电促渗药物刺激对于受试者的影响。

柔性汗液传感器的研究及其应用进展

可穿戴传感器以独特的监测模式(实时、连续、非侵入性)在医疗、体育、健康监测等领域得到了迅速发展。汗液中含有多种生物标记物,如代谢物、电解质和各种激素等。汗液可以反映人体的劳累程度、疾病、压力水平、运动情况等,与可穿戴技术相结合,汗液传感器有望实现低成本、实时、原位的汗液监测。本文从柔性汗液传感器的基底材料种类入手,介绍了近年来汗液传感器常用的基底材料,并概述了柔性汗液传感器在监测方面的应用。最后,总结了目前存在的局限性及对未来发展的展望。

基于光电容积脉搏波描记法的柔性血压传感器标定方法研究

基于光电容积脉搏波描记法(Photo Plethysmo Graphy,PPG)的柔性传感器可进行心率(Heart Rate,HR)和血压(Blood Pressure,BP)检测,但是对其检测结果的标定报道甚少.据此,本文提出一种基于模拟血液循环的反射式PPG心率检测和血压标定系统.以蠕动泵来产生脉动流,通过调节其转速的大小来控制模拟血液输送的频率和压力,从而引起弹性乳胶管内模拟血液体积的变化,而改变反射光的信号周期与强度,贴近于人体脉搏测量过程的实际场景.该系统心率检测误差均值为0.27778,95%一致性界限为(-2.59562,3.15117),所测收缩压(Systolic Blood Pressure,SBP)和舒张压(Diastolic Blood Pressure,DBP)的拟合优度分别为0.97185和0.98111.经标定后的柔性PPG传感器对4名志愿者检测的SBP和DBP的平均偏差(Mean Deviation,MD)±标准差(Standard Deviation,SD)均值分别为(1.21±2.16)mmHg和(0.76±2.02)mmHg,均符合且远小于美国医疗仪器促进协会(Association for the Advancement of Medical Instrumentation,AAMI)所制定的衡量血压计精度的标准指标(5±8)mmHg.结果表明,该系统能够准确高效地标定柔性PPG传感器,为实现便携式可穿戴设备的精准血压检测提供标定基础.

ZnO/Ecoflex自驱动柔性压电传感器及其人体姿态监测微系统设计

压力传感器是可穿戴电子设备的重要组成部分,但在能量供应、灵活性和皮肤适应性方面仍存在各种问题。研制了一种主要由ZnO/Ecoflex复合薄膜构成的自驱动柔性压力传感器,并构建了人体姿态监测系统,可用于动态监测人体姿态信号和其他运动参数。在外部压力应力的作用下,所制备的传感器表现出优异的灵敏度(0.068 V/N)、良好的线性度(约0.98)、宽的测量范围(5~80 N)以及卓越的耐久性(超过10000次循环)。此外,基于制备的传感器设计了硬件电路,建立了人机交互测试系统,实现了对人体姿态信号的远程传输功能。因此,这项工作不仅开发了一种新型的无铅化自驱动压力传感器,还设计了人体姿态监测微系统,为信号处理和智能传感提供了新思路,在医学研究、个性化识别和人机交互方面具有重要的应用潜力。

一种用于癫痫发作状态检测的可穿戴脑电传感器

针对癫痫患者多场景下的健康监护问题,研发了一种无线可穿戴脑电传感器,可以在本地实时识别癫痫发作。该传感器首先使用ADS1299模数转换芯片采集脑电信号,在STM32F4微处理器中使用工频陷波器和带通滤波器对脑电信号进行实时滤波,然后周期性地提取不同频段的Hjorth特征得到特征向量,利用支持向量机(Support Vector Machine,SVM)分类器进行癫痫发作识别,最后通过低功耗蓝牙(BLE)将癫痫发作状态发送到外部设备,联动外部设备实现癫痫发作报警。为了能够实现实时识别癫痫发作,从STM32的架构和中断机制入手对数据传输和算法执行进行了优化。经CHB-MIT癫痫数据集测试,该传感器可以实时、有效地识别癫痫发作状态,平均识别准确率达97%。

针织一体成形电容传感器设计及其性能

针对柔性电容传感器的电极易暴露于外界环境和穿着舒适性差等问题,提出一种表面绝缘电极与介质层一体成形的针织电容传感器设计方法。进一步对传感器的力学性能、表面绝缘性能和传感性能进行探究,揭示了织物厚度与间隔丝直径对其性能的影响。研究发现,织物厚度越大,间隔丝直径越小的传感器综合性能越好,其中厚度为8.0 mm、间隔丝直径为0.15 mm的传感器表现最佳,其灵敏度为0.033 kPa^(-1),并且具有较低的迟滞性和快速响应时间,对不同性质输入信号(不同压缩距离和不同压缩频率)均具有良好的分辨响应能力,且具有2 000次循环内的重复稳定性,在手部动作识别及液体称重场景展现出较好的压力传感能力。该传感器降低了生产成本,且应用过程中信号稳定,在可穿戴、医疗监测及人机交互界面展现出巨大的应用潜力。

柔性相变复合材料及其应用研究进展

柔性相变复合材料因其兼具优异的相变储能特性、耐受外力形变的柔性及与控温器件复合的可加工性,在智能材料开发中受到研究者的广泛关注。文中详述了通过聚合物网络共混、多孔骨架吸附及相变分子结构设计等3种支撑结构策略制备柔性相变复合材料的研究现状;总结了其在电池热管理器件、可穿戴电子器件和柔性传感器等领域的应用;最后,对柔性相变复合材料的研究重点和未来发展方向进行了展望。

基于有机场效应晶体管的可穿戴柔性监测设备在生物医学领域的研究现状

介绍了基于有机场效应晶体管(organic field effect transistor,OFET)技术的柔性半导体器件的工作原理和发展概况,综述了基于OFET的生物力学监测设备、文身生物监测设备、细胞检测设备等可穿戴柔性监测设备的研究现状,分析了基于OFET的可穿戴柔性监测设备存在的不足,指出了微型化、个性化、多元化等是未来基于OFET的可穿戴柔性监测设备的发展方向。

新型柔性传感器在可穿戴设备中的应用研究

随着技术的进步,新型柔性传感器越来越多地应用于可穿戴设备。对新型柔性传感器在健康监测,运动追踪,环境监测以及交互体验方面的应用进行研究,并对其优点,面临的挑战以及未来的发展趋势进行分析。采用文献综述及案例分析等研究手段,对柔性传感器材料特性,工作原理,发展过程及其在可穿戴设备上的应用状况进行系统论述。发现柔性传感器对于提高设备性能和改善用户体验有显著优势。

Recent Progress on Smart Fiber and Textile Based Wearable Strain Sensors:Materials,Fabrications and Applications

With the rapid development of smart products,fexible and stretchable smart wearable electronic devices gradually play an important role,and they are considered as the pioneers of the new generation of fexible electronic devices.Among these intelligent devices,fexible and stretchable strain sensors have been widely studied for their good fexibility,high sensitivity,high repeatability and huge potential for application in personal healthcare and motion detection.Moreover,unlike traditional rigid bulky sensors,the high-performance fexible strain sensors are lightweight portable devices with excellent mechanical and electrical performance,which can meet personalized needs and become more popular.Herein,the research progress of fexible strain sensors in recent years are reviewed,which mainly introducing the sensing principles and key parameters of strain sensors,commonly used conductive materials and fexible substrates and common preparation methods,and fnally proposes the future application and prospects of strain sensors.