While it may sound silly, it turns out onion tweezers may turn out to be the next endeavor in the study of biomedical engineering. And while this root vegetable is known to pack a pungent smell, it turns out that its epidermal cells pack quite a punch too-enough to even inspire artificial muscle formation. Okay, so this one needs a bit more explaining.
In a new study published this week in the journal Applied Physics Letters, researchers with National Taiwan University devised an artificial muscle system entirely composed of onion cells that can not only react to certain voltages, but also expand and contract to have functional abilities as well. Looking into the unique tightly-packed lattice just below the surface layer of an onion, lead researcher of the study Wen-Pin Shih found that the epidermal cells of this root vegetable were the perfect candidate to create an artificial muscle capable of expansion or contraction while also bending at the same time-a feat that has eluded researchers to date.
"The initial goal was to develop an engineered microstructure in artificial muscles for increasing the actuation deformation" Shih says. "One day, we found that the onion's cell structure and its dimensions were similar to what we had been making."
But in order to function as a muscle, capable of reacting to electrical impulses, the epidermal cells of the onion had to be modified with a few shinier changes. First researchers removed hemicellulose proteins from within the cell walls around the plant cell to diminish the rigidity of the system. Then they coated both sides of the onion cells with pure gold-one side thicker than the other.
"We intentionally made the top and the bottom electrodes a different thickness so that the cell stiffness becomes asymmetric from top to bottom" Shih says. "We found that the single-layer lattice structure can generate unique actuation modes that engineered artificial muscle has never achieved before."
The asymmetry of the gold contacts allow researchers to have control over the muscle's responses, giving the onion cells not only the ability to expand and contract, but also the ability to flex depending on the voltage applied. Then, to really flex their new muscles to demonstrate their functionality, the researchers combined two of the muscle systems made from single layer lattices of onion cells to make a pair of tweezers. Now their next goal is to lift the power of the muscles while also reducing the voltage driving the action, to create a functional artificial muscle capable of accomplishing many daily tasks.