friction

the-physics-of-frilly-swiss-cheese-“flowers”

The physics of frilly Swiss cheese “flowers”

For their experiments, the authors of the PRL paper selected samples of Monk’s head cheese wheels from the Fromagerie de Bellelay brand that had been aged between three and six months. They cut each cheese wheel in half and mounted each half on a Girolle, motorizing the base to ensure a constant speed of rotation and making sure the blade was in a fixed position. Their measurements of how the cheese deformed during scraping enabled them to build a model based on metal dynamics on a two-dimensional surface that had “cheese-like properties.”

The results showed that there was a variable friction between the core and the edge of the cheese wheel, because the core stayed fresher during the ripening process. Because the harder outer edge had lower friction with the blade, the edges of the cheese shavings were uneven in thickness—hence the resemblance to frilly rosettes.

This essentially amounts to a new shaping mechanism with the possibility of being able to one day program complex shaping from “a simple scraping process,” per the authors. “Our analysis provides the tools for a better control of flower chip morphogenesis through plasticity in the shaping of other delicacies, but also in metal cutting,” they concluded. Granted, “flower-shaped chips have never been reported in metal cutting. But even in such uniform materials, the fact that friction properties control the metric change is particularly interesting for material shaping.”

Physical Review Letters, 2025. DOI: 10.1103/PhysRevLett.134.208201  (About DOIs).

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Gecko feet inspire anti-slip shoe soles

Just add zirconia nanoparticles…

diagram of wet ice's quasi slippery layer and design of anti-slip shoe soles inspired by gecko and toad foot pads

Credit: V. Richhariya et al., 2025

It’s the “hydrophilic capillary-enhanced adhesion”of gecko feet that most interested the authors of this latest paper. Per the World Health Organization, 684,000 people die and another 38 million are injured every year in slips and falls, with correspondingly higher health care costs. Most antislip products (crampons, chains, studs, cleats), tread designs, or materials (fiberglass, carbon fiber, rubber) are generally only effective for specific purposes or short periods of time. And they often don’t perform as well on wet ice, which has a nanoscale quasi-liquid layer (QLL) that makes it even more slippery.

So Vipin Richhariya of the University of Minho in Portugal and co-authors turned to gecko toe pads (as well as those of toads) for a better solution. To get similar properties in their silicone rubber polymers, they added zirconia nanoparticles, which attract water molecules. The polymers were rolled into a thin film and hardened, and then a laser etched groove patterns onto the surface—essentially creating micro cavities that exposed the zirconia nanoparticles, thus enhancing the material’s hydrophilic effects.

Infrared spectroscopy and simulated friction tests revealed that the composites containing 3 percent and 5 percent zirconia nanoparticles were the most slip-resistant. “This optimized composite has the potential to change the dynamics of slip-and-fall accidents, providing a nature-inspired solution to prevent one of the most common causes of accidents worldwide,” the authors concluded. The material could also be used for electronic skin, artificial skin, or wound healing.

DOI: ACS Applied Materials & Interfaces, 2025. 10.1021/acsami.4c14496  (About DOIs).

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