Room temperature eutectic liquid metals have seen significant growth in application usage recently due to their ability to deform under high strains while maintaining high thermal and electronic conductivity.  In particular, eutectic gallium-indium-tin, galinstan, is of interest due to its very low melting point (-19<sup>o</sup>C), which makes it useful in a large variety of operational conditions.   While many studies have looked at using galinstan as an electronic and thermal conductor, little has been done to characterize the interfacial properties of thin oxide shell that surrounds the liquid metal and gives it many of its mechanical properties.  In this work, galinstan was studied using interfacial tensiometry and interfacial rheology in acidic aqueous environments in order to obtain a deeper understanding of the interaction of the molecules on the interface as well as an ability to manipulate that interface for future applications.  Surprisingly, by manipulating the concentration of hydrochloric acid in the galinstan aqueous environment, IFT can be reduced by up to 70%.  Contrary to what has been hypothesized in previous literature, interfacial rheology does not show a weakening of the interface in terms of modulus or yield stress for the galinstan oxide interface until 1M HCl, at which condition the oxide skin has been chemically removed.  Based on the results of these experiments, aqueous dispersions of galinstan were improved through the addition of tin oxide.  Interestingly, aqueous dispersions of eutectic gallium-indium (EGaIn) were similarly improved even though the liquid metal is not composed of tin.  The ability to manipulate and improve galinstan interfacial interactions based on, but not tied to, acidic aqueous environments presents an exciting way to use liquid metals in non-aqueous applications.

Understanding the galinstan oxide interface through interfacial tension and interfacial rheology for use in stretchable applications

255th National Meeting (2018)

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