In the animal kingdom, few are as sticky as geckos. Their ability to scamper up walls and across ceilings is delightful to watch. But it’s not just their grip on dry surfaces that’s remarkable. Geckos can also cling to wet, slippery surfaces with ease. Now, researchers have taken inspiration from these tiny lizards to create a new polymer that could one day keep humans from slipping on ice.
The secret lies in the gecko’s toe pads. Each pad is covered in rows of microscopic hair-like structures called setae. These structures are separated by narrow grooves that draw in liquid water through capillary action, creating suction. This suction allows geckos to maintain their grip even on surfaces slick with water.
Anti-Slip Shoes Inspired By Geckos
An international team of scientists has replicated this phenomenon in a human-made material. By combining silicone rubber with nanoparticles of a water-attracting ceramic called zirconia, they’ve developed a polymer that sticks to ice. The material, described in a recent paper published in ACS Applied Materials & Interfaces, could pave the way for anti-slip shoe soles that prevent injuries caused by falls on icy surfaces.
Ice is slippery because of a thin layer of liquid water that forms on its surface, even in freezing temperatures. This layer exists because water molecules at the surface aren’t held in place by molecules above them, unlike those within the solid ice. When we walk on ice, the pressure and friction from our feet can further melt the surface, making it even more treacherous.
Traditional anti-slip materials, such as natural rubber, repel water. But on ice, this approach can backfire. The pressure from a shoe sole can melt the ice, creating a slippery layer that defeats the purpose of the anti-slip design.
Instead of repelling water, the newly developed polymer attracts it. The researchers started with silicone rubber and added zirconia nanoparticles, which are hydrophilic, or “water-loving”. They then rolled the material into a thin sheet and laser-etched a grooved pattern onto its surface. When pressed against wet ice, the nanoparticles drew water into the grooves, creating suction that pulled the material down onto the ice in just 1.5 milliseconds.
After testing various formulations, the team found that the polymer was most effective when it contained 3% to 5% zirconia nanoparticles by weight. “The material mimics the capillary action of gecko footpads,” said Dr. Vipin Richhariya, one of the study’s lead authors. “It’s a completely new way to think about anti-slip technology.”
A Global Problem with a Nature-Inspired Solution
Slips and falls are a major public health concern. According to the World Health Organization, they account for more than 38 million injuries and 684,000 deaths annually. Nearly half of these incidents occur on ice. The new polymer could help address this problem, as well as other issues caused by unwanted fluids. Applications include medical devices like electronic skin and artificial skin, where polymers interact with fluid layers.
The research team, which included scientists from Portugal’s University of Minho, India’s Vellore Institute of Technology, and Australia’s University of Adelaide, is optimistic about the material’s potential. However, there’s no word yet on when it might reach commercial production.
For now, the study stands as a testament to the power of biomimicry, drawing inspiration from nature to solve human problems. Sometimes, the best solutions are already out there, waiting to be discovered in the natural world.
