Skin, the largest organ in the human body, is sensitive to external stimuli.In recent years, an increasing number of skin-inspired electronics, including wearable electronics, implantable electronics, and electronic skin, have been developed because of their broad applications in healthcare and robotics.Physical sensors are one of the key building blocks of skin-inspired electronics. Typical physical sensors include mechanical sensors, temperature sensors, humidity sensors, electrophysiological sensors, and so on. In this review, we systematically review the latest advances of skin-inspired mechanical sensors, temperature sensors, and humidity sensors. The working mechanisms, key materials, device structures, and performance of various physical sensors are summarized and discussed in detail. Their applications in health monitoring, human disease diagnosis and treatment, and intelligent robots are reviewed. In addition, several novel properties of skin-inspired physical sensors such as versatility, self-healability, and implantability are introduced. Finally, the existing challenges and future perspectives of physical sensors for practical applications are discussed and proposed. K E Y W O R D Selectronics skin, flexible electronics, humidity sensors, mechanical sensors, temperature sensors, wearable sensors

Numerous studies have shown flexible electronics play important roles in health management. The way of power supply is always an essential factor of devices and self-powered ones are very attractive because of the fabrication easiness, usage comfort and aesthetics of the system. In this work, based on the metal-air redox reaction, which is usually used in designing metal-air batteries, we design a self-powered chemoelectric humidity sensor where a silk fibroin (SF) and LiBr gel matrix containing parallel aligned graphene oxide (GO) flakes serve as the electrolyte. The abundant hydrophilic groups in GO/SF and the hygroscopicity of LiBr lead to tight dependence of the output current on the humidity, enabling the sensor high sensitivity (0.09 μA/s/1%), fast response (1.05 s) and quick recovery (0.80 s). As proofs of concept, we design an all-in-one respiratory monitoring-diagnosing-treatment system and a non-contact human-machine interface, demonstrating the applications of the chemoelectric humidity sensor in health management.

Conformable robotic systems are attractive for applications in which they can be used to actuate structures with large surface areas, to provide forces through wearable garments, or to realize autonomous robotic systems. We present a new family of soft actuators that we refer to as Fluidic Fabric Muscle Sheets (FFMS). They are composite fabric structures that integrate fluidic transmissions based on arrays of elastic tubes. These sheet-like actuators can strain, squeeze, bend, and conform to hard or soft objects of arbitrary shapes or sizes, including the human body. We show how to design and fabricate FFMS actuators via facile apparel engineering methods, including computerized sewing techniques. Together, these determine the distributions of stresses and strains that can be generated by the FFMS. We present a simple mathematical model that proves effective for predicting their performance. FFMS can operate at frequencies of 5 Hertz or more, achieve engineering strains exceeding 100%, and exert forces greater than 115 times their own weight. They can be safely used in intimate contact with the human body even when delivering stresses exceeding 10 6 Pascals. We demonstrate their versatility for actuating a variety of bodies or structures, and in configurations that perform multi-axis actuation, including bending and shape change. As we also show, FFMS can be used to exert forces on body tissues for wearable and biomedical applications. We demonstrate several potential use cases, including a miniature steerable robot, a glove for grasp assistance, garments for applying compression to the extremities, and devices for actuating small body regions or tissues via localized skin stretch.forces upon, or generate shape changes in complex or compliant structures. 1-3 Wearable soft robotic devices interfaced with the human body may prove valuable for rehabilitation, movement assistance, or virtual reality. [4][5][6] Soft actuators are also of interest for controlling motion in distributed or deformable structures. They can be used for tasks such as grasping, terrestrial locomotion, surgery, or underwater operation. 7-9 Such applications span systems of greatly varying length scales, ranging from millimeter-scale biomedical robots to large, deployable structures. 10,11 Biological systems provide a rich source of information to guide the design of soft robots. 12 The motile capabilities of animals are enabled by composite systems of muscle, connective, and other tissues. The forces and motions they can produce depend on the properties of individual muscle fibers, the arrangement of fibers, and the muscle morphology and attachments. Muscle morphologies vary widely. There are fusiform shapes like the human biceps brachii, that produce large-amplitude motion. There are also fan shapes, such as the pectoralis major, that yield larger forces, sphincter morphologies that contract, and layered muscle sheets, like the transverse abdominis (Fig. 1A), that compress or transfer forces around the torso. 13 The great variety of biologica...

No abstract