Researchers at the University of California, Santa Barbara plan to break that silence with genetically engineered proteins that can make silicon dioxide or titanium dioxide structures like those used in the computer chips and solar cells that we hold dear.

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Inorganic or mineral-based UVA filters titanium dioxide and zinc oxide, which don't break down as easily in sunlight and generally are not allergenic, are better options, according to Lawrence Gibson, professor of dermatology at the Mayo clinic in Minnesota.

WSJ: European Sunscreen Roadblock on U.S. Beaches

They built a thin layer, or "nanostructure, " using minute particles of titanium dioxide, a substance that reacts with sunlight to break down dirt and other organic material and can be coated on cotton to keep the fabric clean.

CNN: Washing no longer dirty work