Wetting behavior of gallium-based room temperature liquid metal (LM) on nanosecond-laser-structured metal surfaces

Gallium-based room-temperature liquid metal (LM) is a promising emerging functional material in e-skin, soft robots and thermal management systems for its fluidity, conductivity and nontoxicity. However, the intricate wettability of the LM with various surfaces impedes its further development. Knowledge on the gallium-based LM wetting properties especially with structured metal surfaces is relatively insufficient. Herein, wetting behavior of eutectic gallium-indium (EGaIn) on various micro-structured metal surfaces processed by nano-second laser ablation method is systematically studied. Increasing surface roughness, synergized with a high oxygen content, significantly strengthens the LM resistance. Micro-patterns composed of small, discontinuous facets exhibit better EGaIn repellence. Relative humidity (RH) is substantiated to influence the LM wetting behavior as well. Metal surfaces with excellent superlyophobicity (the contact angle> 160°, the adhesion force< 10 μN) are obtained. The LM repellence stability and anti-corrosion properties of the optimized treated metal surfaces are proved via the droplet impacting experiment and the corrosion test. These findings improve the understanding of gallium-based LM wetting behavior on structured metal surfaces, and the obtained LM-repellent metal surfaces will reduce undesired adhesion, blockage or LM corrosion during device preparation and long-term applications, which will facilitate its potential use.