Trying to lick a robotics challenge with inspiration from a cat's tongue
If time spent grooming is any indication, cats take a certain pride in their appearance. And it so happens there are a few lessons to be learned from this feline form of vanity, with the natural wonder-brush that is a cat's tongue providing scientists with inspiration to develop a flexible, gripping material that may find applications in fields ranging from wound cleaning to soft robotics.
The inspiration for the material came when Alexis Noel, a doctoral candidate in mechanical engineering at the Georgia Institute of Technology, watched as her cat's tongue became tangled in a thick, microfiber blanket. This piqued Noel's interest in the sharp spines that protrude from the tongue's surface, so she set out to explore their behavior in the lab.
Using macro and high-speed videography, Noel and her fellow researchers at Georgia Tech's Hu Biolocomotion Lab were able to gain a new, extremely close-up perspective on how these tongue spines behave during grooming. They describe them as Velcro-like hooks, which sweep through fur and catch on tangles to pull them undone. The team then sought to replicate this natural phenomenon by 3D-printing a cat-tongue-inspired material, at a scale of 400 percent.
The top row of this image shows a cat tongue at different phases of grooming. The second row show it straightened and then curled, while the bottom row shows the 3D-printed replica.
"Both the cat tongue and mimic are very good at cleaning and removing tangles in fur samples," she says. "We also discovered that the cat tongue is self-cleaning – it's easy to remove hair beneath the spines by simply brushing the tongue from tip to end."
The self-cleaning capacity Noel speaks of is a result of the spines' flexibility and how they lay flat against the surface when not in use, kind of like overlapping roof tiles. Picture a used hairbrush with a mat of tangled hair nesting on top, which would typically need to be yanked off by hand. The tongue spines gather hair in a similar fashion, except the angle of the spines and hooks allow it to simply be swept off, from front to back. This is the reason why cats end up swallowing (and coughing up) hairballs.
The researchers say these capabilities might lend themselves particularly well to soft robotics, an area where getting soft and flexible materials to latch onto things is a key focus. Beyond that, such a material could find its way into low-maintenance hairbrushes, and also provide a better way to clean wounds in medical settings.
From here, the team is looking to study how the spacing of the tongue spines influence frictional resistance, with a view to initially developing hairbrushes for human use. Beyond that, it plans to study the tongues of bigger cats like lions and tigers to understand how the spines scale across the family.
The research is being presented on November 20 to 22 at the Annual Meeting of the American Physical Society's Division of Fluid Dynamics.