Scientists create ‘flexible’ artificial muscles from gold-plated onion skin cells

While scientists have previously demonstrated lab-grown variety of human-muscles that can ‘naturally’ respond to stimuli, they have been less successful in the realm of artificial muscles that mimic their organic counterpart. One of the challenges in this field pertained to how the artificial muscles were constrained in their naturalized motions – be it contracting, expanding or flexing. However, this time around, a team of researchers at the National Taiwan University have potentially concocted a breakthrough, and it entailed the use of gold-plated epidermal cells of onions.

For the process, the scientists started out by salvaging a single layer of epidermal cells from a freshly peeled onion. The water content from the vegetable was then removed by freeze-drying the onion, which led to its microstructure becoming both rigid and brittle. This stiffening state was then fixed by eliminating the hemicellulose in the skin – a protein responsible for the rigidity of the cells (in absence of water). The resultant skin substrate thus had its biological elasticity restored.

The researchers proceeded by coating this layer with gold electrodes on both sides – with a thinner coat of 24-nanometers on the top, and thicker coat of 50-nanometers on the lower surface. This allowed the onion layer to conduct electricity, while at the same time making it ‘supple’ for motional attributes like contracting and flexing. Finally, electricity was applied – with 0 to 50 volts causing the cells to extend and be flattened from their curved structure. And, on applying higher voltages of 50 to 1,000 volts, the onion ‘muscle’ began to contract and then bend in an upward manner. In fact, the scientists were able to use two such onion arrangements as tweezers that were successfully able to grip a small cotton ball.

So, what is the advantage of an onion epidermal cell over other live muscle solutions? According to one of the researchers, Wen-Pin Shih –

Culturing cells to form a piece of muscle tissue for generating pulling strength is still very challenging. People have tried to use live muscle before. But then how to keep the muscle cells alive becomes a problem. We use vegetable cells because the cell walls provide muscle strength whether the cells are alive or not.

Lastly, in terms of practicality, suffice it to say – the technology is still in nascent stage, with a long way to go. One of the predicaments of the experiment obviously relates to the high voltages required by the onion-based muscle contrivance to function in a proper manner, with power requirements far surpassing the capacity of tiny batteries that can be planted inside robotic mechanisms. Moreover till now, the gold plating is not enough to shield the cell walls from moisture invasions – a problem that can be potentially solved by ultra-thin fluoride coatings.

The study was published this week in Applied Physics Letters.


Via: Phys / Lower Image Credit: Shih Lab, National Taiwan University

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