Analysis and Transformations of Room-Temperature Liquid Metal Interfaces - A Closer Look through Interfacial Tension.

Room-temperature gallium-based liquid metals (e. g. Galinstan) are emerging materials for a wide range of applications spanning from soft robotics to a medium for running chemical reactions. However, Galinstan suffers from rapid oxide formation at the surface, limiting its application. Similarly, this surface oxidation renders it difficult to determine the surface free energy of Galinstan. Herein, the interfacial properties of Galinstan in contact with argon, acid, base, water, and organic solvents were investigated, yielding kinetic information regarding the removal by acids and bases, knowledge about oxo-hydroxide/hydroxide species at the Galinstan/water interface, and an estimated value of the dispersive contribution of the surface free energy. The dispersive contribution of the surface free energy of Galinstan was calculated to be (239.7±9.1) mN/m, around 40 % of the total surface free energy. By employing the dispersive surface tension of Galinstan, the interfacial tension between a liquid and Galinstan can be easily obtained, facilitating the design and application of liquid metal-based devices.