TAIPEI, Taiwan, May 5 (UPI) -- En route to designing a new and improved synthetic muscle, researchers at National Taiwan University realized the cells of an onion might work just as well.
The goal was to build a more versatile artificial muscle -- one that can both expand and contract, allowing it to bend in different directions in reaction to the orientation of the electric current being applied. The structure of an onion cell turned out to be an ideal vehicle toward these ends.
"The initial goal was to develop an engineered microstructure in artificial muscles for increasing the actuation deformation [the amount the muscle can bend or stretch when triggered]," lead researcher Wen-Pin Shih said in a press release. "One day, we found that the onion's cell structure and its dimensions were similar to what we had been making."
So the scientists changed course, and constructed an artificial muscle using an onion. But it's not as simple as it sounds.
First, the researchers treated the cells with acid to neutralize hemicellulose, a fibrous protein that enhances the rigidity of cell walls. Next, researchers coated onion layers with gold, allowing the onion cells to conduct electricity. Bursts of voltage caused the gold-coated onion cells to bend and stretch like a muscle in action.
"We intentionally made the top and bottom electrodes a different thickness so that the cell stiffness becomes asymmetric from top to bottom," explained Shih.
The asymmetric coating cause the faux muscle to respond to different voltage levels -- a small shock caused the onion cells to flex downward, while a more intense shock caused the muscle to flex upward.
Shih and his colleagues tested their onion muscles by installing them onto a pair of tweezers. Using a choreographed series of electric shocks, researchers were able to manipulate the tweezers and pick up a cotton ball.
Researchers plan on conducting further experiments in order to scale up their technology -- increasing lifting power while reducing the amount of voltage needed to flex the artificial muscle.
The study was published in the latest issue of the journal Applied Physics Letters.