  When in a pristine state, gallium and its alloys have the largest interfacial
tensions of any liquid at room temperature. Nonetheless, applying as little as
0.8 V of electric potential across eutectic gallium indium (EGaIn) placed
within aqueous NaOH (or other electrolyte) solution will cause the metal to
behave as if its interfacial tension is near zero. The mechanism behind this
phenomenon has remained poorly understood because NaOH dissolves the oxide
species, making it difficult to directly measure the concentration, thickness,
or chemical composition of the film that forms at the interface. In addition,
the oxide layers formed are atomically-thin. Here, we present a suite of
techniques which allow us to simultaneously measure both electrical and
interfacial properties as a function of applied electric potential, allowing
for new insights into the mechanisms which cause the dramatic decrease in
interfacial tension. A key discovery from this work is that the interfacial
tension displays hysteresis while lowering the applied potential. We combine
these observations with electrochemical impedance spectroscopy to evaluate how
these changes in interfacial tension arise from chemical, electrical, and
mechanical changes on the interface, and close with ideas for how to build a
free energy model to predict these changes from first principles.
