Scientists from National Taiwan University has created a short strip of artificial muscle cells using the gold-plated epidermal cells of an onion. Prior to the study, various researchers attempted to create artificial cells from polymers that could expand or contract. However, the selected polymers could not bend at the same time, as would be required for an artificial muscle.

This time, researchers have created a chain of artificial muscle cells that bend and contract in response to an external stimulus, just like a normal human muscle. During the research, the scientists separated a thin layer of epidermal cell from the outer layer of the peeled onion using tweezers. The scientists then freeze-dried the cells for 24 hours before coating them with gold after the acid treatment to loosen the frozen stiffened cells.

Upon passing the electric current through the loosened cells, the researchers observed that the cells were able to expand and contract, depending on the magnitude of the voltage passed. In addition, the entire length of the cell could bend as the cells expanded or contracted.

When a current between 0 and 50 volts was passed through the epidermal muscle derived from the onion, the top part of the cells elongated, thus making the muscle bend downward. Between 50 and 1,000 volts, the cells became concave and the muscle bent upward. The researchers decided to use biomaterial for the experiment this time because polymers proved to be an expensive option that yielded little success.

"When we were in elementary school, we studied plant cell structure by observing onion cells under the microscope. So when we recently searched for plant cells to replace our engineered artificial muscles, we thought about onion cells again," lead researcher Wen-Pin Shih said, as the Los Angeles Times reported.

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