Anyone who’s ever been licked by a cat knows that their tongue feels like sandpaper. This is because a cat’s tongue is covered in about 300 tiny hooks called papillae. Until recently, it was thought that the roughness of their tongue helped with grooming by catching and combing the fur. However, a study by David Hu and his PhD student Alexis Noel, at Georgia Tech, has shown that the papillae are far more complex than simple hooks.
The hooks are actually hollow cones that point backwards towards the throat. The hollowness combined with the curved shape allows the papillae to wick up a small amount of saliva (4.1 microliters). This saliva can then be deposited right at the base of the hair when grooming, rather than just skimming over the surface. Each papilla only picks up the tiniest amount of saliva. However, over the course of a day about 48ml, or a fifth of a cup, is transferred to the cat’s coat.
This sounds like a tiny difference, but it is very important. It means that cats can clean their dense coats right the way down to the skin. The papillae can also flex and rotate which helps them tease out matts in the undercoat. It also has a cooling effect of up to 30ºF between the skin surface and the outermost hairs. As cats can only sweat from the pads of their feet, this is a vital mechanism for regulating their body temperature. Dogs pant of course, but for cats, panting is a sign of distress.
An unusual point they found was that the papillae did not increase in size with the size of the cat. Most things in nature scale up (feet, teeth etc) but in the case of tongues, larger cats such as tigers simply have more papillae, upto 1200.
So far, so interesting. The scientists then 3D printed a brush which was essentially an enlarged cat tongue, complete with papillae. Its name is the TIGR brush (Tongue Inspired GRooming). When tested, the TIGR brush was more effective than standard brushes at removing matts from fibres. It was also much easier to clean. The hair came away when swiped with a finger, rather than having to be picked out from the teeth.
Other possible uses could involve using the design to be able to deposit fluids for cleaning hairy or fuzzy materials. It could even be used to apply creams to animals without having to shave their fur first. Even applying styling products through human hair could become easier!
The TIGR brush is still in development, patent pending, but watch this space!