Math Model Explains Pruney Fingers

Experts at the Australian National University (ANU) have recently compiled a new mathematical model, that goes a long way towards explaining the physics behind the pruney fingers we get if we stay in the water for prolonged periods of time.

Evolutionary biologists say that this is an evolutionary adaptation we developed, which allows us to get a better grip on objects if we remain submerged for a long time. This skin condition is only temporary.

But wrinkly skin has a geometry of its own, mathematicians say. Understanding it could lead to the development of materials that are able to stretch in a variety of ways without losing their strength.

Even after it absorbs large amounts of water, our skin can still fulfill its protective function flawlessly, which is what makes it so interesting to materials scientists and biologists alike.

“The paper explains a mechanism that can explain the structural stability of keratin in skin and its ability to absorb very large quantities of water. This is a major breakthrough, says Gerd Schröder-Turk.

The expert, based at the University of Erlangen-Nürnberg in Germany, was not a part of the new study.

“Your skin wrinkles, yet it maintains its structure. It doesn’t just fall apart and dissolve into the water,” explains ANU mathematician Myfanwy Evans, the lead author of the research.

The protein keratin is widely believed to be responsible for this ability the skin has. It can form intricate network of fibrous proteins, and it can be found in the outer layer of skin, hair and nails.

Scientists learned some time ago that the keratin network was very important, but what they didn't know was how these fibers were arranged to make this possible, Wired reports.

Working together with ANU colleague Stephen Hyde, Evans developed a model of these network by accident, while investigating interesting topological shapes from a mathematical point of view.

In the March 8 issue of the Journal of the Royal Society Interface, the team published a full explanation of their stringy skin model. “It explains a lot of mechanical features that hadn’t really been able to be explained before,” Evans says.

The expert was studying Gyroids, beautiful mathematical shapes that can be seen all over the natural world, from the wings of butterflies to the lipid membranes around cells. “It’s an interesting fusion of maths and experimental science. These are popping up everywhere,” she says.

“This [model] could be a really good target for bio-inspired materials. It’s not a matter of testing it in the lab, it’s a matter of understanding its geometry in order to understand its physical properties, Evans argues.

“We hope this paper will put that idea out there, and maybe lead to some new interesting materials,” the expert concludes.