Silicone rubber as a base – nanoparticles ensure a firm grip on icy surfaces
The soles of the gecko’s feet have inspired researchers led by Vipin Richhariya from the University of Minho (https://www.uminho.pt/EN ) and Ashis Tripathy from the Vellore Institute of Technology (https://vit.ac.in/ ) to develop a new non-slip material for shoe soles. They coated it with nanoparticles of zirconium dioxide that attract water. They then rolled out the composite material into a thin film and etched a groove pattern into its surface, exposing the hydrophilic nanoparticles.
Capillary effect is crucial
When the film comes into contact with water molecules in the ice, it adheres to the slippery surface because the polymer mimics the capillary action of the non-slip soles of feet. The films contain between one and nine per cent zirconium dioxide. Using infrared spectroscopy and simulated friction tests, the researchers have determined that the most slip-resistant nanocomposites contain three to five per cent zirconium dioxide.
When this film is pressed onto ice, it removes the water film within just 1.5 milliseconds, creating a firm bond between the film and the dry ice. The tiny amounts of water evaporate as soon as the film loses contact with the surface. When transferred to shoe soles, this means that the foot detaches from the surface, so that the material absorbs water again with the next ‘step’. According to the WHO (https://www.who.int/), falls due to slipperiness are responsible for 38 million accidents worldwide every year.
