Onions are already known as tearjerkers, but the humble allium’s contribution to a recent robotics breakthrough may be reason for tears of joy. In the journal Applied Physics Letters, researchers at National Taiwan University announced their development of a new method for creating artificial muscle by applying layers of gold to the outer skin of an onion. “Like human muscles, [onion skin] can bend and contract simultaneously,” says Wen-Pin Shih, a mechanical engineer on the project. “That’s something previous models couldn’t do.” When refined, the gold-onion artificial muscle could have profound implications for the future of prosthetics.


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The onion’s application as artificial muscle tissue was not immediately apparent. Previously, the researchers had been experimenting with artificial polymers before realizing that the unique skin of an onion could provide a more affordable, natural alternative. Those who cook with onions will be familiar with the translucent, often slimy layer right below the onion’s outer skin. This layer is flexible and surprisingly responsive to electricity, which provided a solid foundation upon which muscle could be built.

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To prepare the onion, the researchers dried the skin, bathed it in dilute sulfuric acid to aid its elasticity, then finally covered it with two layers of gold and fitted it with an electrode. The gold-onion skin expands upward when low voltage is applied and contracts downward when high voltage is used. This principle has been applied to create a “tweezer,” featured below. Though the design is promising, the application is currently only capable of picking up objects that weigh two milligrams or less. There is still much that the researchers have yet to learn about their engineered onions. “We still don’t fully understand the structure of the cell walls and its associated properties,” Shih says. “We’re just reporting what we have so far to exchange ideas.”

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This novel approach to building artificial muscles is a reminder that nature’s design often yields the best answer to human problems. From plastic-eating fungus to shrubs that consume toxic heavy metals from the soil, the natural world provides many simple solutions to the complex problems that we have created. The next time you caramelize and crunch into an onion, thank your tasty friend for helping to build the next level of robotics.

+ Applied Physics Letters

Via The Verge

Images via Shutterstock,  Jar/Flickr and Applied Physics Letters