Stretchy Solar Cells Make Self-Powering 'Skin'

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What if robotic skin could detect and alert people of illness, drunkenness or toxic chemicals, and on top of that would be super flexible and sense the lightest of light touches? Stanford chemical engineer Zhenan Bao is working on just such a thing.

Her stretchy solar cells are pleated like an accordion and are able to expand up to 30 percent extra in two directions. The device's electrode is made from a unique liquid metal called eutectic gallium-indium, which conforms to a surface as it lengthens and relaxes. "Eutectic" refers to a mix of elements or compound that remains liquid at lower temperature than either of its components does alone. The gallium-indium compound is unique from other liquid metals, which tend to spontaneously “ball up” on the microscale (think mercury on the kitchen floor after the thermometer breaks); eutectic gallium-indium remains spread out, even as the surface it rests on buckles.

Solar power makes sense for the artificial skin, since it is simpler and lighter than batteries or wiring. And stretchability, not just flexibility, is necessary so that the solar cells don't crack as they move with different surfaces, which could include Bao's dream of super skin, but also cars, buildings, lenses – the list goes on. Like the world's tiniest computer I recently blogged about, the solar cells could theoretically be put to use with anything people want to make “smart.” Er, I suppose that is anything smart, but not for use in the dark.

Photo: L.A. Cicero