Preparation of a nonwetting and conductive interface by gallium liquid metal micro-droplet coating

As a liquid conductive material, gallium-based liquid metal (LM) is suitable for various applications from soft electronics and robotics to medical treatment and energy equipment. Although LM has high surface tension, it is easy to adhere to most substrate surfaces due to its easy oxidation in the air and the existence of gallium oxide layer on the surface. The applications of gallium-based liquid metal are limited by the wetting nature. In response to the issue, we propose a simple and low-cost ultrasonic method to prepare LM micro-droplet coating (LMDC), thereby converting various surfaces into nonwetting surfaces and further preventing the adhesion of LM. The LM does not leave any residue when moving, bouncing, and rolling on the coating surface. Moreover, the coating has certain conductivity, which can realize stable conductive connection between LM and metal substrate. This surface solves the problem of wettability and conductivity of LM. In order to prove the practicability of LMDC, we prepared floating switch to monitor the movement of human hands and temperature warning for drug storage. The results showed the LMDC interface had the non-wettability and conductivity of LM, which will broaden gallium-based liquid metal applications.