The cost of manufacture of high tech on a very small scale remains an economic obstacle to building more efficient solar panels and storage batteries, but a researcher at UC Riverside thinks he may have a way to help build the kind of microscopic structures that can make photovoltaics and lithium ion batteries far more efficient than they are now -- and it involves stealing tricks from a snail that lives off the coast of California.
The snail in question is a gumboot chiton, a brown, softball-sized denizen of rocky seabed along the coast that eats algae off rocks. As David Kisailus, an assistant professor of chemical and environmental engineering at UC Riverside, writes in a paper published Wednesday, the marine gastropod puts its teeth through extremely hard use: the snail basically attaches itself to submerged stones and rasps away at the algae growing on the rock. The snails have thus had to evolve ways of keeping their teeth from being permanently ground down.
As it turns out, the gumboot chiton's teeth are made of magnetite, an incredibly hard oxide of iron. Gumboot chiton teeth, according to Kisailus, are the hardest biomaterial known. But even magnetite will wear down eventually when it's used to grind rock in seawater. The chiton has to grow its teeth back non-stop somehow, so that it doesn't starve to death.
Kisailus found that gumboot chiton teeth regrow their magnetite by secreting a softer iron oxide in a matrix of chitin, a common exoskeleton material, that makes up the snail's "radula" -- the organ that molluscs use the way we use our teeth and tongues. That iron oxide is converted to magnetite in place in the radula, eventually forming parallel fibers that lend chiton teeth their strength and durability.
"Incredibly, all of this occurs at room temperature and under environmentally benign conditions," Kisailus says. "This makes it appealing to utilize similar strategies to make nanomaterials in a cost-effective manner."
One of the barriers to maximum efficiency in both photovoltaic cells and storage batteries is that light and electrons interact with materials at a much smaller scale than we're readily able to handle during manufacturing. Even the tiniest irregularity in crystals can interfere with light being captured and turned into electrical power, or electrons being stored efficiently in a battery. Kisailus hopes that he and his colleagues will be able to borrow the gumboot chiton's tooth-growing technique to build very small crystals at room temperature, thus cutting costs of nanotech-style manufacture. In this video, he gives some background on his work:
You never know what you'll find when you look to the big world out there for ideas.
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