Pruney fingers hint at new synthetic materials

It happens to all of us when we spend too much time in the shower, washing dishes, swimming or perhaps washing our hands (for those of us who are a little obsessive). Fingers get very wrinkled and pruney from water penetrating the surface of our skin.

Now mathematicians have found a more in depth explanation as to what happens when our skins become pruney and wrinkly from prolonged wetness.

Using computer models to represent keratin fibers in the skin, researchers at the Australian National University tested a model for how these fibers in the skin are arranged, and how they behave in the presence of water flooding the skin.

Their article detailing their methods and results was published last month in the Journal of the Royal Society.

Ordinarily, our skin is able to prevent excessive amounts of water from penetrating it by relying on a coating of an oily substance called sebum, which is secreted from the roots of hairs covering the skin.

As time passes while the skin is exposed to water, the sebum coating is washed off, allowing water to penetrate the skin at the epidermis, the outermost layer.

Skin at the fingers is the first to lose the sebum coating and become wet as it lacks hair and thus, direct secretion of sebum.

When water penetrates the epidermis, the cells that make up this layer of the skin swell along with the keratin fibers that expand greatly to accommodate the greater volume of swollen skin.

How these fibers were arranged had been uncertain, as particular arrangements might be able to allow the fibers to expand while others would cause the epidermis structure to collapse.

This question is what the mathematicians tackled, testing several different models that might explain how keratin fibers are layered.

Their simulations found that the model that best explains the keratin fibers casts them in a helical formation, which their results showed allowed for the fibers to expand up to seven times its volume while retaining its integrity.

Additional support for this model comes from x-ray crystallography studies of keratin fibers that are not swollen with water, with which the helical model matches up.

Another model based off of gyroids, infinitely connected triply periodic minimal surfaces, found that keratin fibers were not able to expand without crossing each other, and the structure of the skin would be compromised.

One of their major conclusions based off of their modeling is that skin cells are formed through a template process, and that this can be mimicked when manufacturing certain materials.

The knowledge of how some of our natural tissues assemble and arrange themselves can be applied towards engineering and producing products with similar qualities.