Soft Electronics for the Skin: From Health Monitors to Human–Machine Interfaces

Conventional bulky and rigid electronics prevent compliant interfacing with soft human skin for health monitoring and human–machine interaction, due to the incompatible mechanical characteristics. To overcome the limitations, soft skin-mountable electronics with superior mechanical softness, flexibility, and stretchability provide an effective platform for intimate interaction with humans. In addition, soft electronics offer comfortability when worn on the soft, curvilinear, and dynamic human skin. Herein, recent advances in soft electronics as health monitors and human–machine interfaces (HMIs) are briefly discussed. Strategies to achieve softness in soft electronics including structural designs, material innovations, and approaches to optimize the interface between human skin and soft electronics are briefly reviewed. Characteristics and performances of soft electronic devices for health monitoring, including temperature sensors, pressure sensors for pulse monitoring, pulse oximeters, electrophysiological sensors, and sweat sensors, exemplify their wide range of utility. Furthermore, the soft electronic devices for prosthetic limb, household object, mobile machine, and virtual object control are presented to highlight the current and potential implementations of soft electronics for a broad range of HMI applications. Finally, the current limitations and future opportunities of soft skin-mountable electronics are also discussed.