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Electronic Materials

Peeling produces stretchable liquid-metal circuit

Technique breaks gallium alloy’s insulating oxide layer

by Kerri Jansen
June 17, 2018 | A version of this story appeared in Volume 96, Issue 25

A photo of a liquid-metal circuit being stretched.
Credit: Tang et al./iScience
This rubber circuit board with embedded liquid metals remains conductive even when stretched up to five times its length.

A new print-and-peel method for making stretchable electronics is based on liquid metals (iScience 2018, DOI: 10.1016/j.isci.2018.05.013). Gallium-based alloys are highly conductive and liquid at low temperatures, so they can serve as conductors in soft electronics that must bend and flex. Researchers can print custom circuit patterns using liquid-metal inks created by dispersing droplets of the alloy in a solvent. But droplets of gallium alloys quickly form a thin oxide skin, inhibiting conductivity in the printed pattern. To overcome that issue, a team led by Xingyu Jiang of China’s National Center for Nanoscience & Technology screen-printed a eutectic gallium-indium alloy onto a plastic substrate, then cast a flexible rubber layer on top of the liquid-metal pattern. After the rubber cured around the pattern, they peeled the rubber off. The oxide layer surrounding each droplet tends to stick to the substrate as the pattern is pulled away, so the oxide skin breaks and the droplets merge to form a conductive path embedded in the rubber layer. The liquid-metal circuit remained conductive even when stretched to five times its length.


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