Materials and Design Strategies of Stretchable Electrodes for Electronic Skin and its Applications

The human skin is an essential organ of the human body for sensing various changes in the external environment, including pressure, temperature, and humidity, as well as for interacting with the outside world. Therefore, in the field of soft electronics, the development of the electronic skin (e-skin) that mimics the functions and properties of the human skin is an important research topic. The potential applications of the e-skin technology include wearable electronics, soft robotics, human-machine interfaces (HMIs), and prosthetic devices. Toward such research goals, various technologies are required. Among these, the stretchable electrode technology is a key component for achieving soft, stretchable e-skin and its applications. Therefore, various materials and design strategies for stretchable electrodes have been developed by many research groups. The successful development of stretchable electrodes has resulted in the rapid progress of high-performance stretchable device components such as stretchable sensors and actuators. Moreover, the integration of these device components with stretchable interconnects has yielded an integrated e-skin system, through which interactive human-machine interfacing can be achieved. This paper presents an overview of state-of-the-art technological advances in materials and design strategies for the development of stretchable electrodes. In addition, e-skin systems and their HMI applications based on such stretchable electrodes are briefly reviewed.