Furry and fresh

Fur is important for keeping animals warm and dry, but that hairy covering also keeps them clean, scientists have found. New insights about animal hair as a cleaning device could help engineers design self-cleaning systems.

David Hu of Georgia Tech and Guillermo Amador of the Max Planck Institute studied dozens of animals—from flies and honeybees to squirrels and otters—to learn how they cleaned themselves. An animal’s hair actually increases the total surface area on which dirt particles can land. This larger surface area traps the dirt particles, suspending them above the animal’s body and facilitating their removal.

“We found that on average, hair increases an animal’s apparent surface area by a factor of a hundred,” wrote Hu and Amador at The Conversation, a research commentary website. “Thus, a cat has a surface area of a pingpong table. … A chinchilla has the surface area of an SUV. And a sea otter has the surface area of a hockey rink.”

Although it seems counterintuitive that body hair would facilitate cleaning, Hu and Amador pointed out several examples of what they call “renewable cleaning strategies—those that don’t require energy from the animal, but come for free.” Eyelashes sweep up tiny particles as we move or blink, microscopic pincushions on cicada wings pop bacteria like water balloons, and rain rolls off the fur of a hairy animal, taking dirt particles along with it.

Engineers could apply these self-cleaning principles to technology such as solar panels, which they could design like insect eyes, with thin filaments that suspend dust above the panel but still let light in, according to Hu and Amador. “Cleaning the panel would amount simply to swiping it with another brush.” Tabletops of the future could come with nanoscale hairs that “kill bacteria on contact.”

“We typically envision future robots covered in smooth shiny surfaces, like a chrome-buffed automobile,” they wrote. “But in nature, smooth surfaces are hardly the norm.”

The future, according to Hu and Amador, “may be looking rather hairy.”

Decoders at court

Crime scene DNA can be a powerful tool for building a prosecution’s case. But crime scenes are often complex and DNA from multiple people may commingle, making otherwise valuable evidence inconclusive. To untangle such mixed-up DNA, some crime labs rely on a computer program called TrueAllele.

Now that program has come under fire from defense attorneys who want to examine the source code to ensure the software isn’t erroneously linking their clients to crimes they didn’t commit, according to The Wall Street Journal.

Mark Perlin, the computer scientist who developed the software and licenses it to law enforcement, says authorities have used TrueAllele in more than 500 cases since 2009. He calls the source code a trade secret. But defense lawyers, citing the Sixth Amendment’s guarantee of a defendant’s right to question witnesses, say they can’t question Perlin and his program if they don’t know how it works.

Perlin counters that his software’s 170,000 lines of source code would provide less insight into the program than validation studies and peer-reviewed journal articles. He told the Journal, “TrueAllele’s basic math and methods are described in scientific papers and patents going back 20 years.” —M.C.