聚丙烯压电驻极体薄膜声电传感器的性能

压电驻极体（也称为铁电驻极体）是以空间电荷驻极体为基体的一类新型压电功能材料,这种材料不仅具有与压电陶瓷相近的压电活性,同时拥有柔韧、低介电常数和低声阻抗等特点。本研究制备了基于聚丙烯（PP）压电驻极体薄膜的声电传感器,并采用电压放大电路和电荷放大电路对其在声频下的灵敏度进行了测量。结果表明,PP压电驻极体声电传感器在1 kHz下的电压灵敏度约为0.8 mV/Pa,并在300 Hz~10 kHz的声频范围内有良好的线性输出特性。     

Human Pulse Diagnosis for Medical Assessments Using a Wearable Piezoelectret Sensing System

Real‐time and continuous monitoring of physiological signals is essential for mobile health, which is becoming a popular tool for efficient and convenient medical services. Here, an active pulse sensing system that can detect the weak vibration patterns of the human radial artery is constructed with a sandwich‐structure piezoelectret that has high equivalent piezoelectricity. The high precision and stability of the system result in possible medical assessment applications, including the capability to identify common heart problems (such as arrhythmia); the feasibility to conduct pulse palpation measurements similar to well‐trained doctors in Traditional Chinese Medicine; and the possibility to measure and read blood pressure.     

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.     

Stretchable Electrode Based on Laterally Combed Carbon Nanotubes for Wearable Energy Harvesting and Storage Devices

Carbon nanotubes (CNTs) are a promising material for use as a flexible electrode in wearable energy devices due to their electrical conductivity, soft mechanical properties, electrochemical activity, and large surface area. However, their electrical resistance is higher than that of metals, and deformations such as stretching can lead to deterioration of electrical performances. To address these issues, here a novel stretchable electrode based on laterally combed CNT networks is presented. The increased percolation between combed CNTs provides a high electrical conductivity even under mechanical deformations. Additional nickel electroplating and serpentine electrode designs increase conductivity and deformability further. The resulting stretchable electrode exhibits an excellent sheet resistance, which is comparable to conventional metal film electrodes. The resistance change is minimal even when stretched by ≈100%. Such high conductivity and deformability in addition to intrinsic electrochemically active property of CNTs enable high performance stretchable energy harvesting (wireless charging coil and triboelectric generator) and storage (lithium ion battery and supercapacitor) devices. Monolithic integration of these devices forms a wearable energy supply system, successfully demonstrating its potential as a novel soft power supply module for wearable electronics.     

Flexible Hybrid Electronics: Direct Interfacing of Soft and Hard Electronics for Wearable Health Monitoring

The interfacing of soft and hard electronics is a key challenge for flexible hybrid electronics. Currently, a multisubstrate approach is employed, where soft and hard devices are fabricated or assembled on separate substrates, and bonded or interfaced using connectors; this hinders the flexibility of the device and is prone to interconnect issues. Here, a single substrate interfacing approach is reported, where soft devices, i.e., sensors, are directly printed on Kapton polyimide substrates that are widely used for fabricating flexible printed circuit boards (FPCBs). Utilizing a process flow compatible with the FPCB assembly process, a wearable sensor patch is fabricated composed of inkjet‐printed gold electrocardiography (ECG) electrodes and a stencil‐printed nickel oxide thermistor. The ECG electrodes provide 1 mVp–p ECG signal at 4.7 cm electrode spacing and the thermistor is highly sensitive at normal body temperatures, and demonstrates temperature coefficient, α ≈ –5.84% K^–1 and material constant, β ≈ 4330 K. This sensor platform can be extended to a more sophisticated multisensor platform where sensors fabricated using solution processable functional inks can be interfaced to hard electronics for health and performance monitoring, as well as internet of things applications.     

Wearable Biosensors for Body Computing

The challenges of growing and aging populations combined with limited clinical resources have created huge demand for wearable and portable healthcare devices. Research advances in wearable biosensors have made it easier to achieve reliable noninvasive monitoring of health and body status. In this review, recent progress in the development of body computing systems for personalized healthcare is presented, with key considerations and case studies. Critical form factors for wearable sensors, their materials, structures, power sources, modes of data communication, and the types of information they can extract from the body are summarized. Statistically meaningful data analysis considerations, including using cohort and longitudinal correlation studies, are reviewed to understand how raw sensor signals can provide actionable information on the state of the body. This informs discussions on how collected sensor data can be used for personalized and even preventative care, such as by guiding closed-loop medical interventions. Finally, outstanding challenges for making wearable sensor systems reliable, practical, and ubiquitous are considered in order to disrupt traditional medical paradigms with personalized and precision care.     

Transparent and Stretchable Interactive Human Machine Interface Based on Patterned Graphene Heterostructures

An interactive human‐machine interface (iHMI) enables humans to control hardware and collect feedback information. In particular, wearable iHMI systems have attracted tremendous attention owing to their potential for use in personal mobile electronics and the Internet of Things. Although significant progress has been made in the development of iHMI systems, those based on rigid electronics have constraints in terms of wearability, comfortability, signal‐to‐noise ratio (SNR), and aesthetics. Herein the fabrication of a transparent and stretchable iHMI system composed of wearable mechanical sensors and stimulators is reported. The ultrathin and lightweight design of the system allows superior wearability and high SNR. The use of conductive/piezoelectric graphene heterostructures, which consist of poly(l ‐lactic acid), single‐walled carbon nanotubes, and silver nanowires, results in high transparency, excellent performance, and low power consumption as well as mechanical deformability. The control of a robot arm for various motions and the feedback stimulation upon successful executions of commands are demonstrated using the wearable iHMI system.     

Wearable Organic Electrochemical Transistor Array for Skin-Surface Electrocardiogram Mapping Above a Human Heart

Electrocardiogram (ECG) mapping can provide vital information in sports training and cardiac disease diagnosis. However, most electronic devices for monitoring ECG signals need to use multiple long wires, which limit their wearability and conformability in practical applications, while wearable ECG mapping based on integrated sensor arrays has been rarely reported. Herein, ultra-flexible organic electrochemical transistor (OECT) arrays used for wearable ECG mapping on the skin surface above a human heart are presented. QRS complexes of ECG signals at different recording distances and directions relative to the heart are obtained. Furthermore, the ECG signals are successfully analyzed by the devices before and after exercise, indicating potential applications in some sports training and fitness scenarios. The OECT arrays that can conveniently monitor spacial ECG signals in the heart region may find niche applications in wearable electronics and healthcare products in the future.     

Flexible and Highly Sensitive Strain Sensors Fabricated by Pencil Drawn for Wearable Monitor

Functional electrical devices have promising potentials in structural health monitoring system, human‐friendly wearable interactive system, smart robotics, and even future multifunctional intelligent room. Here, a low‐cost fabrication strategy to efficiently construct highly sensitive graphite‐based strain sensors by pencil‐trace drawn on flexible printing papers is reported. The strain sensors can be operated at only two batteries voltage of 3 V, and can be applied to variously monitoring microstructural changes and human motions with fast response/relaxation times of 110 ms, a high gauge factor (GF) of 536.6, and high stability >10 000 bending–unbending cycles. Through investigation of service behaviors of the sensors, it is found that the microcracks occur on the surface of the pencil‐trace and have a major influence on the functions of the strain sensors. These performances of the strain sensor attain and even surpass the properties of recent strain sensing devices with subtle design of materials and device architectures. The pen‐on‐paper (PoP) approach may further develop portable, environmentally friendly, and economical lab‐on‐paper applications and offer a valuable method to fabricate other multifunctional devices.     

Mimicking Human and Biological Skins for Multifunctional Skin Electronics

Electronic skin (e‐skin) technology is an exciting frontier to drive the next generation of wearable electronics owing to its high level of wearability, enabling high accuracy to harvest information of users and their surroundings. Recently, biomimicry of human and biological skins has become a great inspiration for realizing novel wearable electronic systems with exceptional multifunctionality as well as advanced sensory functions. This review covers and highlights bioinspired e‐skins mimicking perceptive features of human and biological skins. In particular, five main components in tactile sensation processes of human skin are individually discussed with recent advances of e‐skins that mimic the unique sensing mechanisms of human skin. In addition, diverse functionalities in user‐interactive, skin‐attachable, and ultrasensitive e‐skins are introduced with the inspiration from unique architectures and functionalities, such as visual expression of stimuli, reversible adhesion, easy deformability, and camouflage, in biological skins of natural creatures. Furthermore, emerging wearable sensor systems using bioinspired e‐skins for body motion tracking, healthcare monitoring, and prosthesis are described. Finally, several challenges that should be considered for the realization of next‐generation skin electronics are discussed with recent outcomes for addressing these challenges.     

Wearable Stretchable Dry and Self-Adhesive Strain Sensors with Conformal Contact to Skin for High-Quality Motion Monitoring

Wearable stretchable strain sensors can have important applications in many areas. However, the high noise is a big hurdle for their application to monitor body movement. The noise is mainly due to the motion artifacts related to the poor contact between the sensors and skin. Here, wearable stretchable dry and self-adhesive strain sensors that can always form conformal contact to skin even during body movement are demonstrated. They are prepared via solution coating and consist of two layers, a dry adhesive layer made of biocompatible elastomeric waterborne polyurethane and a sensing layer made of a non-adhesive composite of reduced graphene oxide and carbon nanotubes. The adhesive layer makes the sensors conformal to skin, while the sensing layer exhibits a resistance sensitive to strain. The sensors are used to accurately monitor both small- and large-scale body movements, including various joint movements and muscle movements. They can always generate high-quality signals even on curvilinear skin surface and during irregular skin deformation. The sensitivity is remarkably higher while the noise is saliently lower than the non-adhesive strain sensors. They can also be used to monitor the movements along two perpendicular directions, which cannot be achieved by the non-adhesive strain sensors.     

基于能量采集异构蜂窝网络的功率分配算法研究

针对能量采集异构蜂窝网络,由于能量到达和信道状态的随机性导致离线功率分配算法只能取得理论最优,本文提出了一种在线功率分配算法.算法在每个时隙开始时,基站控制器通过能量判别选出满足开启条件的小蜂窝基站,然后采用基于拉格朗日乘子的两层迭代算法对所选择的小蜂窝基站分配发射功率,能够实际最大化系统在每个时隙的能效.仿真表明在满足基站开启条件的情况下,所提算法可以为密集异构网络提供更高的能量效率.该算法适用于信道状态和能量状态不可预测的网络.     

Emerging Wearable Sensors for Plant Health Monitoring

Emerging plant diseases, caused by pathogens, pests, and climate change, are critical threats to not only the natural ecosystem but also human life. To mitigate crop loss due to various biotic and abiotic stresses, new sensor technologies to monitor plant health, predict, and track plant diseases in real time are desired. Wearable electronics have recently been developed for human health monitoring. However, the application of wearable electronics to agriculture and plant science is in its infancy. Wearable technologies mean that the sensors will be directly placed on the surfaces of plant organs such as leaves and stems. The sensors are designed to detect the status of plant health by profiling various trait biomarkers and microenvironmental parameters, transducing bio-signals to electric readout for data analytics. In this perspective, the recent progress in wearable plant sensors is summarized and they are categorized by the functionality, namely plant growth sensors, physiology, and microclimate sensors, chemical sensors, and multifunctional sensors. The design and mechanism of each type of wearable sensors are discussed and their applications to address the current challenges of precision agriculture are highlighted. Finally, challenges and perspectives for the future development of wearable plant sensors are presented.     

Degradable and Fully Recyclable Dynamic Thermoset Elastomer for 3D-Printed Wearable Electronics

Wearable electronics have become an important part of daily lives. However, its rapid development results in the problem of electronic waste (e-waste). Consequently, recyclable materials suitable for wearable electronics are highly sought after. In this study, a conductive recyclable composite (PFBC) is designed based on a dynamic covalently cross-linked elastomer and hierarchical hybrid nanofillers. The PFBC shows excellent wide-ranging properties including processability, elasticity, conductivity, and stability, which are superior to previous materials used for recyclable electronics, and exhibits outstanding mechanical properties and environmental tolerance including high temperature, high humidity, brine, and ethanol owing to its covalent cross-linking. Reversible dissociation of Diels–Alder networks allows for convenient processing and recycling. After three recycles, the toughness of the PFBC remained at 10.1 MJ m⁻³, which is conspicuous among the reported recyclable electronic materials. Three types of PFBC-based wearable electronics including a triboelectric nanogenerator, a capacitive pressure sensor, and a flexible keyboard, are successfully 3D printed with excellent performance. The PFBC possessed both recyclability and degradability, the combination of which provides a new way to reduce e-waste. This is the first work to recycle electronics using direct 3D printing and presents promising new design principles and materials for wearable electronics.     

On‐Body Bioelectronics: Wearable Biofuel Cells for Bioenergy Harvesting and Self‐Powered Biosensing

The growing power demands of wearable electronic devices have stimulated the development of on‐body energy‐harvesting strategies. This article reviews the recent progress on rapidly emerging wearable biofuel cells (BFCs), along with related challenges and prospects. Advanced on‐body BFCs in various wearable platforms, e.g., textiles, patches, temporary tattoo, or contact lenses, enable attractive advantages for bioenergy harnessing and self‐powered biosensing. These noninvasive BFCs open up unique opportunities for utilizing bioenergy or monitoring biomarkers present in biofluids, e.g., sweat, saliva, interstitial fluid, and tears, toward new biomedical, fitness, or defense applications. However, the realization of effective wearable BFC requires high‐quality enzyme‐electronic interface with efficient enzymatic and electrochemical processes and mechanical flexibility. Understanding the kinetics and mechanisms involved in the electron transfer process, as well as enzyme immobilization techniques, is essential for efficient and stable bioenergy harvesting under diverse mechanical strains and changing operational conditions expected in different biofluids and in a variety of outdoor activities. These key challenges of wearable BFCs are discussed along with potential solutions and future prospects. Understanding these obstacles and opportunities is crucial for transforming traditional bench‐top BFCs to effective and successful wearable BFCs.     

Energy Harvesting From Human and Machine Motion for Wireless Electronic Devices

Energy harvesting generators are attractive as inexhaustible replacements for batteries in low-power wireless electronic devices and have received increasing research interest in recent years. Ambient motion is one of the main sources of energy for harvesting, and a wide range of motion-powered energy harvesters have been proposed or demonstrated, particularly at the microscale. This paper reviews the principles and state-of-art in motion-driven miniature energy harvesters and discusses trends, suitable applications, and possible future developments.      

High‐Performance Polypyrrole/Graphene/SnCl2 Modified Polyester Textile Electrodes and Yarn Electrodes for Wearable Energy Storage

Flexible supercapacitors have potential for wearable energy storage due to their high energy/power densities and long operating lifetimes. High electrochemical performance with robust mechanical properties is highly desired for flexible supercapacitor electrodes. Usually, the mechanical properties are improved by choosing high flexible textile substrates but at the much expense of electrochemical performance due to the nonideal contact between conductive materials and textile substrates. Herein, the authors present an efficient, scalable, and general strategy for the simultaneous fabrication of high‐performance textile electrodes and yarn electrodes. It is interesting to find that the conformal reduced graphene oxide (RGO) layer is uniformly and successively painted on the surface of SnCl₂ modified polyester fibers (M‐PEF) via a repeated “dyeing and drying” strategy. The large‐area textile electrodes and ultralong yarn electrodes are fabricated by using RGO/M‐PEF as substrate with subsequent deposition of polypyrrole. This work provides new opportunities for developing high flexible textile electrodes and yarn electrodes with further increased electrochemical performance and scalable production.