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 superlyophobic 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 degrees and receding angle of 163 degrees were achieved on a surface patterned with micropillars, each of which was textured with additional roughness. Pitch distance between pillars was 175 mu m. 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 similar to 3-mu L Galinstan droplet in the 3-D super-lyophobic channel was 3.11 +/- 0.23 mN.