A strong and flexible electronic vessel for real-time monitoring of temperature, motions and flow

A Multifunctional Flexible Tactile Sensor Based on Resistive Effect for Simultaneous Sensing of Pressure and Temperature

Flexible tactile sensors with multifunctional sensing functions have attracted much attention due to their wide applications in artificial limbs, intelligent robots, human-machine interfaces, and health monitoring devices. Here, a multifunctional flexible tactile sensor based on resistive effect for simultaneous sensing of pressure and temperature is reported. The sensor features a simple design with patterned metal film on a soft substrate with cavities and protrusions. The decoupling of pressure and temperature sensing is achieved by the reasonable arrangement of metal layers in the patterned metal film. Systematically experimental and numerical studies are carried out to reveal the multifunctional sensing mechanism and show that the proposed sensor exhibits good linearity, fast response, high stability, good mechanical flexibility, and good microfabrication compatibility. Demonstrations of the multifunctional flexible tactile sensor to monitor touch, breathing, pulse and objects grabbing/releasing in various application scenarios involving coupled temperature/pressure stimuli illustrate its excellent capability of measuring pressure and temperature simultaneously. These results offer an effective tool for multifunctional sensing of pressure and temperature and create engineering opportunities for applications of wearable health monitoring and human-machine interfaces.

Recent Advances in Multiresponsive Flexible Sensors towards E-skin: A Delicate Design for Versatile Sensing

Multiresponsive flexile sensors with strain, temperature, humidity, and other sensing abilities serving as real electronic skin (e-skin) have manifested great application potential in flexible electronics, artificial intelligence (AI), and Internet of Things (IoT). Although numerous flexible sensors with sole sensing function have already been reported since the concept of e-skin, that mimics the sensing features of human skin, was proposed about a decade ago, the ones with more sensing capacities as new emergences are urgently demanded. However, highly integrated and highly sensitive flexible sensors with multiresponsive functions are becoming a big thrust for the detection of human body motions, physiological signals (e.g., skin temperature, blood pressure, electrocardiograms (ECG), electromyograms (EMG), sweat, etc.) and environmental stimuli (e.g., light, magnetic field, volatile organic compounds (VOCs)), which are vital to real-time and all-round human health monitoring and management. Herein, this review summarizes the design, manufacturing, and application of multiresponsive flexible sensors and presents the future challenges of fabricating these sensors for the next-generation e-skin and wearable electronics.

Wearable Thermoelectric Materials and Devices for Self-Powered Electronic Systems

The emergence of artificial intelligence and the Internet of Things has led to a growing demand for wearable and maintenance-free power sources. The continual push toward lower operating voltages and power consumption in modern integrated circuits has made the development of devices powered by body heat finally feasible. In this context, thermoelectric (TE) materials have emerged as promising candidates for the effective conversion of body heat into electricity to power wearable devices without being limited by environmental conditions. Driven by rapid advances in processing technology and the performance of TE materials over the past two decades, wearable thermoelectric generators (WTEGs) have gradually become more flexible and stretchable so that they can be used on complex and dynamic surfaces. In this review, the functional materials, processing techniques, and strategies for the device design of different types of WTEGs are comprehensively covered. Wearable self-powered systems based on WTEGs are summarized, including multi-function TE modules, hybrid energy harvesting, and all-in-one energy devices. Challenges in organic TE materials, interfacial engineering, and assessments of device performance are discussed, and suggestions for future developments in the area are provided. This review will promote the rapid implementation of wearable TE materials and devices in self-powered electronic systems.

A piezoelectric poly(vinylidene fluoride) tube featuring highly-sensitive and isotropic piezoelectric output for compression

Piezoelectric polymers have aroused tremendous attention in self-powered flexible wearable electronics. However, conventional plate-like piezoelectric devices demonstrated insufficient output power and monotonous piezoelectric energy harvesting performance only in one direction, failing to accommodate the complex multi-dimensional stress field. In this study, a poly(vinylidene fluoride) tube featuring all-directional piezoelectric energy harvesting performance with excellent rebound resilience was prepared via a fast industrial extrusion. Benefitting from the isotropic hollow tubular structure, the piezoelectric tube experienced large deformation at a small external load and thus exhibited a strong load-amplifying function to generate the optimized output power at multi-stresses from any direction, with sensitive piezoelectric performance, quick response and mechanical robustness. Finally, the practical potential as a robust energy harvester was evaluated by harvesting small energy from irregular human motions. This study provides a facile structure designing strategy for the preparation of functional piezoelectric devices for multi-directional mechanical energy harvesting applications.

A Multiparameter Pressure-Temperature-Humidity Sensor Based on Mixed Ionic-Electronic Cellulose Aerogels

Pressure (P), temperature (T), and humidity (H) are physical key parameters of great relevance for various applications such as in distributed diagnostics, robotics, electronic skins, functional clothing, and many other Internet-of-Things (IoT) solutions. Previous studies on monitoring and recording these three parameters have focused on the integration of three individual single-parameter sensors into an electronic circuit, also comprising dedicated sense amplifiers, signal processing, and communication interfaces. To limit complexity in, e.g., multifunctional IoT systems, and thus reducing the manufacturing costs of such sensing/communication outposts, it is desirable to achieve one single-sensor device that simultaneously or consecutively measures P-T-H without cross-talks in the sensing functionality. Herein, a novel organic mixed ion-electron conducting aerogel is reported, which can sense P-T-H with minimal cross-talk between the measured parameters. The exclusive read-out of the three individual parameters is performed electronically in one single device configuration and is enabled by the use of a novel strategy that combines electronic and ionic Seebeck effect along with mixed ion-electron conduction in an elastic aerogel. The findings promise for multipurpose IoT technology with reduced complexity and production costs, features that are highly anticipated in distributed diagnostics, monitoring, safety, and security applications.

Stretchable and Wearable Triboelectric Nanogenerator Based on Kinesio Tape for Self-Powered Human Motion Sensing

Recently, wearable, self-powered, active human motion sensors have attracted a great deal of attention for biomechanics, physiology, kinesiology, and entertainment. Although some progress has been achieved, new types of stretchable and wearable devices are urgently required to promote the practical application. In this article, targeted at self-powered active human motion sensing, a stretchable, flexible, and wearable triboelectric nanogenerator based on kinesio tapes (KT-TENG) haven been designed and investigated systematically. The device can effectively work during stretching or bending. Both the short-circuit transferred charge and open-circuit voltage exhibit an excellent linear relationship with the stretched displacements and bending angles, enabling its application as a wearable self-powered sensor for real-time human motion monitoring, like knee joint bending and human gestures. Moreover, the KT-TENG shows good stability and durability for long-term operation. Compared with the previous works, the KT-TENG without a macro-scale air gap inside, or stretchable triboelectric layers, possesses various advantages, such as simple fabrication, compact structure, superior flexibility and stability, excellent conformable contact with skin, and wide-range selection of triboelectric materials. This work provides a new prospect for a wearable, self-powered, active human motion sensor and has numerous potential applications in the fields of healthcare monitoring, human-machine interfacing, and prosthesis developing.