Characterization of Nontoxic Liquid-Metal Alloy Galinstan for Applications in Microdevices

Abstract—We have obtained interfacial properties of Galinstan, a nontoxic liquid-metal alloy, to help replace mercury in minia-ture devices. To prevent formation of an oxide skin that severely hinders the fluidic behavior of small Galinstan droplets and leads to inaccurate property data, we performed our experiments in a nitrogen-filled glove box. It was found that only if never exposed to oxygen levels above 1 part per million (ppm) would Galinstan droplets behave like a liquid. Two key properties were then investi-gated: contact angles and surface tension. Advancing and receding contact angles of Galinstan were measured from sessile droplets on various materials: for example, 146.8 ◦ and 121.5◦, respectively, on glass. Surface tension was measured by the pendant-drop method to be 534.6 ± 10.7 mN/m. All the measurements were done in nitrogen at 28 ◦C with oxygen and moisture levels below 0.5 ppm. To help design droplet-based microfluidic devices, we tested the response of Galinstan to electrowetting-on-dielectric actuation. [2011-0124