Plasma-Treated PDMS as Intrinsically Non-Wetting Surface for Gallium-Alloy Liquid Metal Microfluidics

We report the CF4/O2 plasma treatment of polydimethylsiloxane (PMDS) surface as a new method to create an intrinsically non-wetting surface for gallium-based liquid metal microfluidics. It was found that CF4/O2 plasma on PDMS for > 120s creates nanoscale roughness which exhibits a non-wetting property against liquid metals. Static contact angles and contact angle hysteresis (CAH) of the plasma-treated PDMS surfaces using gallium-based liquid metal droplets were found to be > 144° and < 16.8°, respectively. Rolling test with 15° inclined surfaces were used to confirm non-wetting property of the surface.