Traditionally Nonwetting Surface Made to Wet Mercury

We present a surface-engineering approach that turns all liquids highly wetting, including ultra-high surface tension fluids such as mercury. Previously, highly wetting behavior was only possible for intrinsically wetting liquid/material combinations. Here, we show that roughness made of reentrant structures allows for a metastable hemiwicking state even for nonwetting liquids as predicted by our surface energy model. We experimentally demonstrated this concept with microfabricated reentrant channels. Notably, we show an apparent contact angle as low as 35° for mercury on structured silicon surfaces with fluorinated coatings, on which the intrinsic contact angle of mercury is 143°, turning a highly nonwetting liquid/material combination highly wetting through surface engineering. Our work enables highly wetting behavior for previously inaccessible material/liquid combinations and thus expands the design space for various thermofluidic applications.

Related Article: PNAS 2022

Media Coverage: MIT News – Spotlight