Cool Shapeshifting Metal

Researchers at NC State have developed a new method to control the interfacial energy of a liquid metal via electrochemical deposition (or removal) of an oxide layer on its surface using ~1 volt.

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Liquid metals have very large surface tension and therefore typically adopt a spherical shape. Surfactants, like soap, can lower the interfacial tension between two dissimilar liquids (for example, water and oil), but have negligible impact on the large interfacial tensions of liquid metal. Unlike conventional surfactants, the approach here can tune the interfacial tension of a metal significantly (from ~7x that of water to near zero), rapidly, and reversibly using only modest voltages. These properties can be harnessed to induce new electrohydrodynamic phenomena for manipulating liquid metal alloys based on gallium, which may enable shape-reconfigurable metallic components in electronic, electromagnetic, and microfluidic devices without the use of toxic mercury. The results also suggest that oxides—which are ubiquitous on most metals and semiconductors—may be harnessed to lower interfacial energy between dissimilar materials.

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