A Super-Lyophobic 3-D PDMS Channel as a Novel Microfluidic Platform to Manipulate Oxidized Galinstan

We report a 3-D super-lyophobic polydimethylsiloxane (PDMS) microfluidic channel patterned with an array of multi-scale surface texture as a novel microfluidic platform to mobilize naturally oxidized Galinstan. Galinstan is a liquid metal that has multiple advantages over mercury such as non-toxicity, higher thermal conductivity, and lower electrical resistivity. However, Galinstan gets easily oxidized in an air environment and it becomes a viscoelastic liquid that wets almost any solid surface. We studied the feasibility of developing super-lyophobic surfaces against Galinstan, using various flat and textured surfaces including PDMS micropillar and microridge arrays by measuring static and dynamic contact angles. The highest advancing angle of 175 ^° and receding angle of 163 ^° were achieved on a surface patterned with micropillars, each of which was textured with additional roughness. Pitch distance between pillars was 175 μm. An extremely simple PDMS-PDMS bonding technique was used to fabricate a 3-D super-lyophobic channel structure as a microfluidic platform for oxidized Galinstan droplets. The driving force to actuate a ~ 3-μL Galinstan droplet in the 3-D super-lyophobic channel was 3.11±0.23 mN.