Why cat tongues make great hairbrushes

One day, you might detangle your hair with newfangled brushes based on one of nature’s long-ago inventions: cat tongues.

Combs and brushes have been around for thousands of years, says Alexis Noel, a mechanical engineer at Georgia Institute of Technology in Atlanta.

But the basic design has barely changed since the Stone Age. Even the fanciest brushes, she says, are nothing more than rigid spines projecting from a handle.

And that’s not how the tongue of many animals – including cows, deer and opossums – works, Noel said this week at a meeting of the American Physical Society’s Division of Fluid Dynamics in Portland, Oregon. 

Instead, their tongues are covered with claw-like spines called papillae.

Normally, these lie flat, but when the cat licks its fur, they catch on obstructions with a force that increases dramatically as the spines are pulled upright. That’s why cat tongues feel so raspy when one licks you. 

A cat-fancier herself, Noel wondered if the properties of cat tongues might be used to make the first major improvements in combs and hairbrushes for thousands of years.

Using a 3-D printer, she made a block of plastic that replicated a cat tongue, albeit with longer and stiffer spines.

And when she used it on fur samples, she says, it was far better than conventional brushes at removing tangles. “We call it a heat-seeking missile for snags,” she says.

It was also far easier to clean than a conventional hairbrush. “One [backwards] swipe with your finger and all of the fur is gone,” she says.

The next step, she says, is determining the right length of spines for brushing human hair and figuring out how the cat’s saliva makes its tongue even more effective at removing snags and fleas. 

Perhaps a commercially produced liquid (or simple tap water) might someday be put on cat-tongue-style hairbrushes, she says, making them even more effective. In fact, she adds, it might even be possible to use such brushes to help remove lice from human hair.

Megan Leftwich, a mechanical engineer from George Washington University in St. Louis, Missouri, who was not involved in the study, notes that Noel’s efforts are a great example of using nature’s solutions to solve human problems. 

“We can’t lick our hair [like cats], but we can have a better way to groom our hair based on how animals have done it.”