Researchers at National Taiwan University have devised a way of turning onion cells into tiny muscles that expand or contract at the flick of a switch.
It’s a bizarre use for a root vegetable, and wasn’t entirely planned. According to lead researcher Wen-Pin Shih, the initial aim was to develop a completely artificial structure that would contract when triggered.
“One day, we found that the onion’s cell structure and its dimensions were similar to what we had been making,” he says.
The cells were taken from the onion’s epidermis – the delicate skin just beneath the vegetable’s surface – and Shih and his team coated each side of this layer in gold, to act as electrodes.
As well as conducting the electricity needed to trigger a contraction, the gold is also central to the muscles’ ability to bend in different directions depending on the voltage applied.
“We intentionally made the top and bottom electrodes a different thickness so that the cell stiffness becomes asymmetric from top to bottom,” says Shih.
This asymmetry means that when a high voltage is applied, the cells contract and flex up towards the thinner top layer, while a low voltage has the opposite effect. It’s this behaviour that makes them different to previous artificial muscles.
There’s still a long way to go before these onion muscles can truly be considered useful, though. So far, the heaviest load they’ve been able to lift is a ball of cotton wool.