While scientists have made extraordinarily strong artificial muscles, they hadn’t been to pull a subtler challenge: muscles that can contract and expand while also bending, just like human muscles. That’s until onion skin came along.
That’s right, muscles made of onion skin, freeze-dried and plated in gold. Researchers have been tinkering with all sorts of polymers for new artificial muscles, and a group of Taiwanese scientists realized onion skin actually had the microstructure for the properties they wanted. The onion skin in question is the epidermis, which is not the papery stuff you peel off but is the translucent layer (pictured below) you may remember studying under a microscope in intro to biology.
Once the skin was peeled off, the team treated it with acid to rid it of the molecule that gives the cells rigidity. It was then freeze-dried and coated in gold to make it conduct electricity. Here was the result, as described by Smithsonian:
Lower voltages of 0 to 50 volts caused the cells to elongate and flatten out from their original curved structure, while higher voltages of 50 to 1000 volts caused the veggie muscle to contract and bend upwards. By controlling these voltages to vary muscle movements, two of the onion arrangements were used as tweezers to grip a small cotton ball.
Those voltages are still too high to be practical in a robot, though the device could certainly improve. In any case, the study is a yet another reminder that novel solutions can come from the most unexpected and humble places.
Images: Chen et al / AIP
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