10.1　Overview of Electronic Skin

Skin is the largest organ in human body and a physical barrier between human body and the environment.Skin is also the most important organ for sensing，with very excellent properties，including self-healing ability，tactile sensing capability（e.g.，temperature，pain and pressure），and others.The skin involves a variety of specific sensory receptors，which can convert physical contact into electric signals.Then，the electric signals are transmitted to the central nervous system and ultimately processed by the brain's somatosensory cortex.

When the skin is damaged in a large area，it is difficult for the skin to self-heal，resulting in the loss of physical barrier，the destruction of the sensory receptors in the skin，and even the loss of tactile sense.At present，dermatoplasty is the main method for treating large areas of skin damage.However，there are still problems，such as limited skin sources and high difficulty in skin function reconstruction.In addition，due to the rapid development of robots and artificial intelligence，people expect to give robots more functions，such as skin sensing performance similar to humans.Robots with skin sensing capabilities have important applications in patient care，disease diagnosis and monitoring，and can achieve more complex interactive tasks.The above-mentioned demands have promoted the rapid development of electronic skin（e-skin）.

The so-called e-skin，also known as smart skin，refers to an artificial skin device that simulates the functions of the real human skin（Figure 10-1）.The e-skin devices can not only have the sensory function of the skin，but also can integrate more functions that the real skin doesn't have.For example，chemical or biological sensors can be integrated into the e-skin to detect gas and liquid substances in the environment and the human body，so as to monitor environmental changes or changes in the physiological state of the human body.E-skin is expected to be transplanted to the human body as a prosthesis to replace missing or diseased skin.In addition，e-skin has very broad application prospects in soft robots.It is expected to give robots more functions to complete interactive tasks through simulating the sensing function of skin.(https://www.daowen.com)

The development of e-skin devices has gone through a process from single functional devices to multifunctional integrated devices.According to different demands and application scenarios，people can design the structures and functions of the e-skin devices.This chapter will introduce the design principles，types and applications of e-skin devices.