Hybrid Smart Fiber with Spontaneous Self‐Charging Mechanism for Sustainable Wearable Electronics

Smart wearable electronics that are fabricated on light‐weight fabrics or flexible substrates are considered to be of next‐generation and portable electronic device systems. Ideal wearable and portable applications not only require the device to be integrated into various fiber form factors, but also desire self‐powered system in such a way that the devices can be continuously supplied with power as well as simultaneously save the acquired energy for their portability and sustainability. Nevertheless, most of all self‐powered wearable electronics requiring both the generation of the electricity and storing of the harvested energy, which have been developed so far, have employed externally connected individual energy generation and storage fiber devices using external circuits. In this work, for the first time, a hybrid smart fiber that exhibits a spontaneous energy generation and storage process within a single fiber device that does not need any external electric circuit/connection is introduced. This is achieved through the employment of asymmetry coaxial structure in an electrolyte system of the supercapacitor that creates potential difference upon the creation of the triboelectric charges. This development in the self‐charging technology provides great opportunities to establish a new device platform in fiber/textile‐based electronics.     

Body Heat Powered Wirelessly Wearable System for Real-time Physiological and Biochemical Monitoring

Through harvesting energy from the environment or human body, self-power wearable electronics have an opportunity to break through the limitations of battery supply and achieving long-term continuous operation. Here, a wireless wearable monitoring system driven entirely by body heat is implemented. Based on the principle of maximizing heat utilization, while optimizing internal resistance and heat dissipation, the stretchable TEG improves the power density of previous similar devices from only a few microwatts per square centimeter to tens and makes it possible to continuously drive wireless wearable electronic systems. Furthermore, ceaseless self-power energy gives wearable electronics unparalleled continuous working ability, which can realize the tracking and monitoring of biochemical and physiological indicators at different time scale. A practical system demonstrates the ability to real-time monitor heart rate, sweat ingredient and body motion at a high sampling rate. This study marks an important advance of self-powered wearable electronics for wirelessly real-time healthy monitoring.     

A new wearable input device: SCURRY

A new wearable input device named SCURRY, developed by the Samsung Advanced Institute of Technology, is introduced in this paper. Based on inertial sensors, this device allows a human operator to select a specified character, an event, or an operation as the input he/she wants spatially through both hand motion and finger clicking. It is a glovelike device, which can be worn on the human hand, composed of a base module, including one controller and two angular-velocity sensors (gyroscopes) on the back of the hand, and four ring-type modules (rings), including two-axis acceleration sensors (accelerometers) on four fingers. The base and the ring modules are integrated modules containing sensors, a transceiver or receiver for communication, and a microcontroller, which makes the device compact and light. The two gyroscopes embedded in the base module have a role in detecting the direction (up, down, right, and left) of the hand motion, and the accelerometers have a role in detecting finger motion generated by finger clicking. An algorithm for the exact finger-click recognition composed of three parts (feature extraction, valid-click discrimination, and crosstalk avoidance) is proposed to improve the recognition performance of finger clicking on SCURRY. The experimental results and discussions are presented. SCURRY can be used as a wearable mouse spatially, by allowing any three fingers to be operated as the left, middle, and right mouse buttons, and in a similar manner, as a wearable keyboard, as it allows a human operator to point and select any character, event, or operation by his hand motion and finger clicking.     

Wireless,Flexible, Ionic,Perspiration-Rate Sensor System with Long-Time and High Sweat Volume Functions Toward Early-Stage,Real-Time Detection of Dehydration

Flexible sensors that can be attached to the body to collect vital data wirelessly enable real-time, early-stage diagnosis for human health management. Wearable sweat sensors have received considerable attention for real-time physiological monitoring. Unlike conventional methods that require blood-drawing in a clinic, sweat analyses may enable noninvasive tracking of health conditions for early-stage diagnosis. Even though a variety of studies to monitor metabolites and other substances have been conducted, automatic, continuous, long-term, simultaneous monitoring of perspiration rate and electrolytes, which are important parameters in dehydration, has yet to be achieved because of challenges related to sensor design. Here a wireless, wearable, integrated, microfluidic sensor system that can continuously measure these parameters in real-time for prolonged periods are presented. The proposed sensors are systematically characterized, and machine learning is used to predict device tilt angle to calibrate sensor output signals. Using the sensor design to form a water droplet in a fluidic channel, high-volume perspiration rate is continuously monitored for more than 7000 s (total sweat volume >170 µL). By testing 10 subjects, physiological responses to ingestion of a sports drink are confirmed by measuring perspiration rhythm changes extracted from real-time, continuous sweat impedance and rate.     

A low power wireless node for contact and contactless heart monitoring

Ubiquitous vital signs sensing and processing are promising alternatives to conventional clinical and ambulatory healthcare. Novel sensors, low power solutions for processing and wireless connectivity are creating new opportunities for wearable devices which allow continuous and long term monitoring, while maintaining freedom of movement for the users. This paper presents a low-power embedded platform with novel high sensitivity electric potential dry surface sensors that can be used in either contact or non-contact mode to measure biomedical signals. The proposed low power system is optimized to compute the heart rate and respiratory rate close to the sensors. This approach reduces the amount of data that needs to be transmitted to a host device. It allows also the platform to be autonomous and wearable or even be used in cars for applications such as driver drowsiness detection. Experimental measurements show the acquisition and the processing of data from sensors and the low power consumption achieved with the node in different modes of operation.     

Wearable Biosupercapacitor: Harvesting and Storing Energy from Sweat

This work demonstrates the first example of sweat-based wearable and stretchable biosupercapacitors (BSCs), capable of generating high-power pulses from human activity. The all-printed, dual-functional, conformal BSC platform can harvest and store energy from sweat lactate. By integrating energy harvesting and storage functionalities on the same footprint of a single epidermal device, the new wearable energy system can deliver high-power pulses and be rapidly self-charged by bioenergy conversion of sweat lactate generated from human activity while simplifying the design and fabrication. The mechanical robustness and conformability of the device are realized through island-bridge patterns and strain-enduring inks. The enhanced capacitance of the BSC is realized by the synergistic effect of carbon nanotube ink with electrodeposited polypyrrole on the anode and of porous cauliflower-like platinum on the cathode. In the presence of lactate, the BSC shows high power in pulsed output and stable cycling performance. Furthermore, the wearable device can store energy and deliver high-power pulses long after the perspiration stopped. The self-charging hybrid wearable device obtained high power of 1.7 mW cm⁻² in vitro, and 343 µW cm⁻² on the body during exercise, suggesting considerable potential as a power source for the next generation of wearable electronics.     

Leather-Based Multi-Stimuli Responsive Chromisms

Leather is made from the skin of animals and possesses special micro- and nanostructures. Due to the high breathability, durability, strength, elasticity, and softness, leather is widely used in daily life, and is an ideal substrate for future multi-functional wearable smart devices. Herein, two leather-based multi-stimuli responsive chromic devices denoted as UV/thermo/electro chromic device and UV sensor are developed. The UV/thermo/electro chromic device demonstrates instantaneous and reversible chromic responses to applied UV radiation, heat, and electrical voltage with different color changing styles. The pattern design with the assistance of 3D printed molds and the broad selection of dyes/pigments endow the device with high design flexibility and wide applicability. The leather-based UV sensor exhibits a change in color gradient when exposed to UV radiation with different intensities. For more versatile color options, inactive pigments/dyes can be mixed with stimuli-responsive ones in this system. Coating the leather surface with a polyacrylic finishing agent is also conducted, which is a practical and effective method to protect the pigments and/or dyes in the leather, and improves the usability/durability of the devices. This study opens a new avenue to design and develop wearable devices and individual customization/anti-counterfeiting of leather products.     

可穿戴设备发展现状及趋势

目前可穿戴设备尚没有标准的分类,文章从设备的物理形态、应用类型和通信方式对可穿戴设备进行划分,为可穿戴设备研究提供分类依据。并通过对驱动可穿戴设备的芯片、智能操作系统、电池和人机交互技术现状和发展分析,为可穿戴设备的发展提供预测依据。     

Textile Resistance Switching Memory for Fabric Electronics

A new type of wearable electronic device, called a textile memory, is reported. This is created by combining the unique properties of Al‐coated threads with a native layer of Al₂O₃ as a resistance switching layer, and carbon fiber as the counter‐electrode, which induces a fluent redox reaction at the interface under a small electrical bias (typically 2–3 V). These two materials can be embroidered into an existing cloth or woven into a novel cloth. The electrical resistance of the contacts is repeatedly switched by the bias polarity, as observed in the recently highlighted resistance switching memory. The devices with different structure from the solid metal‐insulator‐metal devices show reliable resistance switching behaviors in textile form by single stitch and in array as well that would render this new type of material system applicable to a broad range of emerging wearable devices. Such behavior cannot be achieved in other material choices, revealing the uniqueness of this material system.     

An Adaptive and Wearable Thermal Camouflage Device

Thermal cloaking and camouflage have attracted increasing attention with the progress of infrared surveillance technologies. Previous studies have been mainly focused on emissivity manipulation or using sophisticated thermal metamaterials. However, emissivity control is only applicable for objects that are warmer than the environment and lower emissivity is usually accompanied with high reflectance of the surrounding thermal signals if they have nonuniform temperature. Metamaterial‐based thermal camouflage holds great promise but their applications on human subjects are yet to be realized. Direct temperature control represents a more desirable strategy to realize dynamically adjustable camouflage within a wide ambient temperature range, but a wearable, portable, and adjustable thermo‐regulation system that is suitable for human subjects has not been developed. This work demonstrates a wearable and adaptive infrared camouflage device responding to the background temperature change based on the thermoelectric cooling and heating effect. The flexible thermoelectric device can realize the infrared camouflage effect to effectively shield the metabolic heat from skin within a wide range of background temperature: 7 °C below and 15 °C above the ambient temperature, showing promise for a broad range of potential applications, such as security, counter‐surveillance, and adaptive heat shielding and thermal control.     

3D Printed High‐Loading Lithium‐Sulfur Battery Toward Wearable Energy Storage

Wearable electronic devices are the new darling of consumer electronics, and energy storage devices are an important part of them. Here, a wearable lithium‐sulfur (Li‐S) bracelet battery using three‐dimensional (3D) printing technology (additive manufacturing) is designed and manufactured for the first time. The bracelet battery can be easily worn to power the wearable device. The “additive” manufacturing characteristic of 3D printing provides excellent controllability of the electrode thickness with much simplified process in a cost‐effective manner. Due to the conductive 3D skeleton providing interpenetrating transmission paths and channels for electrons and ions, the 3D Li‐S battery can provide 505.4 mAh g^?1 specific capacity after 500 cycles with an active material loading as high as 10.2 mg cm^?1. The practicality is illustrated by wearing the bracelet battery on the wrist and illuminating the red light‐emitting diode. Therefore, the bracelet battery manufactured by 3D printing technology can address the needs of the wearable power supply.     

Light‐Powered Healing of a Wearable Electrical Conductor

Mechanical failure along a conductive pathway can cause unexpected shutdown of an electronic devices, ultimately limiting the device lifetime. To address this problem, various systems to realize healable electrical conductors have been proposed; however, rapid, noninvasive, and on‐demand healing, factors that are all synergistically required, especially for wearable device applications, still remains challenging. Here, a light‐powered healable electrical conductor (conceptualized as photofluidic diffusional system) is proposed for simple‐, fast‐, and easy‐to‐implement wearable devices (e.g., the electronic skin, sensitive to mechanical motion). Contrary to other implementations such as capsules, heat, water, and mechanical forces, green light even with low intensity has potential to provide fast (less than 3 min) and repetitive recovery of a damaged electrical conductor without any direct invasion. Also, the multiple, irregular cracks resulting from vigorous motions of wearable devices can be simultaneously recovered regardless of the light incident angles and crack propagation directions, thus, making light‐powered healing more accessible to wearable devices beyond existing system options. To develop and demonstrate the key concepts of this system, combined studies on materials, integrations, and light‐powering strategy for recovering a damaged wearable electrical conductor are systematically carried out in the present work.     

Multifunctional and Wearable Patches Based on Flexible Piezoelectric Acoustics for Integrated Sensing,Localization, and Underwater Communication

Flexible and wearable sensors are highly desired for health monitoring, agriculture, sport, and indoor positioning systems applications. However, the currently developed wireless wearable sensors, which are communicated through radio signals, can only provide limited positioning accuracy and are often ineffective in underwater conditions. In this paper, a wireless platform based on flexible piezoelectric acoustics is developed with multiple functions of sensing, communication, and positioning. Under a high frequency (≈13 MHz) stimulation, Lamb waves are generated for respiratory monitoring. Whereas under low-frequency stimulation (≈20 kHz), this device is agitated as a vibrating membrane, which can be implemented for communication and positioning applications. Indoor communication is demonstrated within 2.8 m at 200 bps or 4.2 m at 25 bps. In combination with the sensing function, real-time respiratory monitoring and wireless communication are achieved simultaneously. The distance measurement is achieved based on the phase differences of transmitted and received acoustic signals within a range of 100 cm, with a maximum error of 3 cm. This study offers new insights into the communication and positioning applications using flexible acoustic wave devices, which are promising for wireless and wearable sensor networks.     

Dynamic Photomask‐Assisted Direct Ink Writing Multimaterial for Multilevel Triboelectric Nanogenerator

Triboelectric nanogenerator (TENG) devices are extensively studied as a mechanical energy harvester and self‐powered sensor for wearable electronics and physiological monitoring. However, the conventional TENG fabrication involving assembling steps and using the single property of matrix material suffers from simple devices shape and a single level of mechanical response for sensing and energy harvesting. Here, the printed multimaterial matrix for multilevel mechanical‐responsive TENG with on‐demand reconfiguration of shape is reported. A multimaterial 3D printing approach by using dynamic photomask‐assisted direct ink writing printing together with a two‐stage curing hybrid ink is first developed. Multimaterial structures with location‐specific properties, such as tensile modulus, failure stress, and glass transition temperature for controlled deformation, crack propagation path, and sequential shape memory, are directly printed. The printed multimaterial structure with sequential deformation behavior is used to fabricate a multilevel‐TENG (mTENG) device for multiple level mechanical energy harvesters and sensors. It is demonstrated that the mTENG can be embedded in shoe insoles to achieve both comfortable wearing and motion state monitoring. This work provides a new approach to combine multimaterial 3D printing with TENG devices for functional wearable electronics as energy harvester and sensors.     

Reflective terahertz tunable polarization controller

This paper proposes an optical device which can continuously change the polarization state of terahertz (THz) waves. The device consists of metal gate, anti-reflection coatings, liquid crystal and mirror. By changing the refractive index of liquid crystal in the interface between the metal gate and the mirror, the phase difference between two beams with orthogonal polarization is varied and a continuous phase shift is achieved. The phase shift of the device is calculated by using the finite difference time domain (FDTD) method, and the transmittance and reflectance are calculated by using the rigorous coupled wave analysis (RCWA) method. The results reveal that the structure can realize continuously tunable phase shift for THz wave at 1 THz.     

基于ZigBee的穿戴式医疗监护系统节点的设计与实现

为了满足当今社会对穿戴式医疗监护的需求,设计并制作出了一种基于ZigBee技术的穿戴式医疗监护系统节点。该节点硬件部分采用了CC2530单片机和多种传感器,软件部分使用TI公司的Z-Stack协议栈,最终以相对低的成本实现了低生理、心理负荷下对人体体温、脉搏、生理姿态的获取。     

An Autofluorescent Hydrogel with Water-Dependent Emission for Dehydration-Visualizable Smart Wearable Electronics

Wearable flexible electronics that are derived from hydrogels inevitably undergo dehydration, and the sensing performance is highly affected because the stretchability and conductivity weaken. Monitoring the water retention rate of hydrogels as they operate without dismantling the assembled sensing device is vital for evaluating sensing performances and intervening in a timely manner to address the problem. However, relevant research is still lacking. Herein, an autofluorescent hydrogel is engineered based on clusterization-triggered emission (CTE) for wearable strain-sensing electronics that can undergo self-visualizing dehydration. The fluorescence intensity of the CTE-type autofluorescent hydrogel depends on the aggregation level of molecule clusters that are dangled on the gel networks, which is dominated by the water retention rate of the hydrogel. Thus, the dehydration process can be reflected by the fluorescent images taken in a scenario of long-term strain-sensing. This strategy helps the operator evaluate the water retention rate of the hydrogel without removing it from the assembled electronics and then quickly address the problem. In addition, this strategy is also applicable for dehydration-tolerant systems, demonstrating the versatility of the autofluorescent hydrogel. Overall, the CTE-type autofluorescent hydrogel will promote the development of high-performance and smart wearable electronics.     

Development and evaluation of an ambulatory stress monitor based on wearable sensors

Chronic stress is endemic to modern society. However, as it is unfeasible for physicians to continuously monitor stress levels, its diagnosis is nontrivial. Wireless body sensor networks offer opportunities to ubiquitously detect and monitor mental stress levels, enabling improved diagnosis, and early treatment. This article describes the development of a wearable sensor platform to monitor a number of physiological correlates of mental stress. We discuss tradeoffs in both system design and sensor selection to balance information content and wearability. Using experimental signals collected from the wearable sensor, we describe a selected number of physiological features that show good correlation with mental stress. In particular, we propose a new spectral feature that estimates the balance of the autonomic nervous system by combining information from the power spectral density of respiration and heart rate variability. We validate the effectiveness of our approach on a binary discrimination problem when subjects are placed under two psychophysiological conditions: mental stress and relaxation. When used in a logistic regression model, our feature set is able to discriminate between these two mental states with a success rate of 81% across subjects.     

一种可穿戴人体运动轨迹测评装置的液晶显示设计

基于TMS320F28335设计了一种人体运动识别与测评装置。利用运动传感器MPU6050获取人体运动姿态数据,并与标准数据相比较,能够实时提醒使用者动作的规范程度。独特的可编程教练模式,能够现场采集和处理标准数据,适用于体育训练和患者康复。该装置使用串口LCD作为显示模块,能够显示所测人体运动的加速度、角度和人体运动轨迹的测评与分析结果。给出了系统液晶显示电路的硬件设计和软件流程图。实验结果表明,所设计的显示电路模块接口简单,使用方便,体积适中,能够满足可穿戴人体运动轨迹测评的显示要求。     

Wear-free indoor fall detection based on RFID and deep residual networks

Since falls of the elderly can easily cause serious health problems in daily life, fall detection has received the attention of researchers. Traditionally, wearable sensors have been used to detect whether a person has fallen. However, wearable sensors may bring inconvenience to users' activities and affect user experience. In this paper, a fall detection approach based on RFID is proposed. In the proposed approach, non-contact passive tags are used to construct an array of tags. Fall detection will be performed without the user wearing the device. The RSSI and phase data are collected when the reader queries the tags. Furthermore, an action segmentation algorithm is designed to quickly extract human action information based on the short-term variance change of the phase signal. Subsequently, a deep residual network is built to classify fall movements and daily movements. Experiments show that the system can handle differences among users and locations and has an excellent performance in terms of recognition accuracy and efficiency, with an average accuracy rate of 96.77%.