Conductive fluids are one of the key components of emerging technologies in reconfigurable electronics, such as tunable radio frequency antennas and electronic switches. Gallium liquid metal alloys (GaLMAs) are nontoxic alternatives to mercury promising a wide range of applications in flexible, conformal, and stretchable electronics. However, their reconfigurability in microfluidic systems is hindered by the instantaneous formation of a surface oxide layer at ambient environment. This solid oxide film sticks to most surfaces leaving unwanted metallic residues that can cause undesired electronic properties. Additionally, GaLMAs readily alloy with common electrode materials (Au, Ag, Cu) deterring their reversible contact. In this report, residue-free reversible flow of a binary alloy of gallium (eutectic gallium indium) is presented via tailoring the liquid metal surface by thin films of alkyl phosphonic acids. The organic film protects the surface oxide of GaLMA, enabling the liquid metal to flow through microchannels without sticking to the channel material. Furthermore, modification of the GaLMA/copper interface by alkyl phosphonic acids prevent alloy formation enabling reversible contact between the liquid metal and the copper electrode. Characterization of these interfaces by spectroscopy and microscopy provided insight into the mechanistic details of the interfacial interactions in these systems.

Tailoring the surface of gallium liquid metal alloys with phosphonic acids to enable their application in reconfigurable electronics

252nd National Meeting (2016)

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