I like a story about science research that starts with a question even if it does lead to another nanosunscreen posting this year (from a news item on Science Daily),

“What makes the ivy in [the] backyard cling to the fence so tightly?”

Associate professor of bioengineering at the University of Tennessee, Knoxville, Mingjun Zhang, asked himself that question one day while watching his son play in their back yard. Zhang’s answer may lead to the development of a new type of nanosunscreen, one that uses plant-based nanoparticles rather than metal-based ones.

Zhang speculated the greenery’s hidden power lay within a yellowish material secreted by the ivy for surface climbing. He placed this material onto a silicon wafer and examined it under an atomic force microscope and was surprised by what they found — lots of nanoparticles, tiny particles 1,000 times thinner than the diameter of a human hair. The properties of these tiny bits create the ability for the vine leaves to hold almost 2 million more times than its weight. It also has the ability to soak up and disperse light which is integral to sunscreens. [emphasis mine]

Michael Berger at Nanowerk has written an article (Harmless natural nanoparticles show potential to replace metal-based nanoparticles in sunscreen) discussing Dr. Zhang’s work in more depth,

Quite impressively, the team’s study indicates that ivy nanoparticles can improve the extinction of ultraviolet light at least four times better than its metal counterparts.

Zhang points out that sunscreens made with ivy nanoparticles may not need to be reapplied after swimming. “That’s because the plant’s nanoparticles are a bit more adhesive so sunscreens made with them may not wash off as easily as traditional sunscreens,” he says. “And while sunscreens made with metal-based nanoparticles give the skin a white tinge, sunscreens made with ivy nanoparticles are virtually invisible when applied to the skin.”

This certainly looks promising but they don’t seem to be anywhere near to producing sunscreens containing ivy nanoparticles.