Semi‐Liquid‐Metal‐(Ni‐EGaIn)‐Based Ultraconformable Electronic Tattoo

Abstract Because of its seamless skin interface, electronic skin has attracted increasing attention in the field of biomedical sensors and medical devices. Most electronic skins are based on organic or inorganic electronic materials. However, the low flexibility of inorganic materials and the limited conductivity of organic materials restricts their widespread use. A new approach is reported to fabricate electronic tattoos from Ni‐EGaIn, which has high conductivity (1.61 × 10 6 S m −1 ) and human‐skin compliance. This time‐effective and low‐cost method is mainly based on the adhesion selectivity of semi‐liquid metal (Ni‐EGaIn) on skin and polymethacrylate glue. Light‐emitting diode arrays, temperature sensors, heaters, and surface electrodes are successfully printed onto skin, and their function in monitoring, diagnosis, and medical treatment is demonstrated. Moreover, a human–machine interface is fabricated using this technique to fully bridge the gap between a human and an electronic circuit. This novel strategy not only provides an ultraconformable interface for use in biomedicine but also represents a path towards personal customization of electronic devices.