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

• Published in: Journal of microelectromechanical systems Vol. 21; no. 2; pp. 443 - 450
• Main Authors: Tingyi Liu, Sen, P., Chang-Jin Kim
• Format: Journal Article
• Language: English
• Published: New York, NY IEEE 01.04.2012; Institute of Electrical and Electronics Engineers
• Subjects: Applied fluid mechanics; Condensed matter: structure, mechanical and thermal properties; Electrowetting-on-dielectric (EWOD); Exact sciences and technology; Fluid dynamics; Fluid surfaces and fluid-fluid interfaces; Fluidics; Fundamental areas of phenomenology (including applications); Galinstan; Galinstan contact angle; Galinstan oxidation; Galinstan surface tension; Glass; Instruments, apparatus, components and techniques common to several branches of physics and astronomy; liquid-metal; Mechanical instruments, equipment and techniques; Metals; Micromechanical devices and systems; Oxidation; Physics; Rough surfaces; Solid-fluid interfaces; Surface energy (surface tension, interface tension, angle of contact, etc.); Surface roughness; Surface tension; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Wetting; liquid-metal; Glass; Liquid metals; Contact angle; Experimental study; Wettability; Galinstan surface tension; Galinstan contact angle; Drops; Humidity; Electrowetting-on-dielectric (EWOD); Droplets; Oxidation; Surface tension; Mechanical contacts; Galinstan; Mercury; Microelectromechanical device; Microfluidics; Fluidics; Galinstan oxidation
• ISSN: 1057-7157; 1941-0158
• DOI: 10.1109/JMEMS.2011.2174421

We have obtained interfacial properties of Galinstan, a nontoxic liquid-metal alloy, to help replace mercury in miniature 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 investigated: 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 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.