Researchers create artificial muscle using onion cells

We've seen different varieties of artificial muscles — which will be used in things like robotics — in the past, though none of them have thus far offered something equal to real muscle. That could be changing soon thanks to onions, particularly the thin skin-like substance that lies beneath the husk and over the meat of the onion. Using that layer, a little bit of gold, and an electrical current, researchers were able to create an artificial muscle that both contracts and bends, solving a problem that has long-plagued researchers.

Making an artificial muscle both able to contract and bend at the same time has been a necessary step in creating artificial muscles for use in medical situations and robotics, among others. Researchers at the National Taiwan University in Taipei came up with a solution, developing a microstructure they thought would work and then finding that an onion's skin has an almost-identical structure.

The researchers removed a layer of epidermal cells from a fresh onion, then washed it and freeze-dried it so that it wouldn't have any water but would still have intact cell walls. An acid wash was then used to strip away hemicellulose, making the freeze-dried onion skin elastic again (whereas it was previously brittle and hard from being freeze-dried).

With all that out of the way, the layer of skin was then coated with gold, with one side having a 24 nanometers-thick coating, and the other having a 50 nanometers-thick coating. These different thicknesses cause the cells to stretch and bend in way that are described as "lifelike". When charged with a lower voltage (up to 50 volts), the cells could expand and flatten, while voltages above that would cause them to both contract and bend.

Tweaking the voltages causes different movements; using two of these structures, the researchers turned the gold-plated onion skin into a pair of tweezers and used it to grab a cotton ball.

SOURCE: Smithsonian