Materials and structural designs for electronic skin

Skin is an essential organ of human body for sensing external changes, such as pressure, temperature, and humidity. Thus, using electronic skin (e-skin) to simulate the functions and properties of real skin has become significantly important in the realm of soft electronics. The primary obstacle in the advancement of e-skin lies in achieving stretchability and flexibility while maintaining high performance. To overcome this obstacle, researchers have developed various materials and structures with distinct properties. This paper provides a comprehensive overview of the evolution of e-skin and technological advancements in materials, including CNT-based materials, graphene-based materials, polymer-based materials, and other novel materials. The paper also delves into novel structures such as wavy structures, island-bridge structures, fractal-inspired structures, and kirigami structures that promote the development of stretchable e-skin. In addition, this paper briefly summarizes the promising properties that further advance the performance of e-skin.