The humble raisin doesn't usually inspire much thought (beyond pondering the ethics of their occasional chocolate chip impersonation), but scientists at MIT have spent a lot of time modeling just how raisins wrinkle. And their findings may change how we understand the way fingerprints form.
A recent paper published in Nature Materials details a theory that seeks to explain how wrinkles form on curved surfaces, along with an accompanying prediction equation. The more curved a surface is, note the researchers, the more like it is to have a regular, often hexagonal, pattern. On thinner surfaces, however, curvature plays less of a role and the expected regimented pattern is increasingly broken up and more random.
So what does this all have to do with fingerprints? These kinds of patterns aren't just limited to raisins, they've been spotted in all different kinds of creasing patterns, including those on our fingertips. One of the papers authors, Jörn Dunkel, explained it in a statement like so:
If you look at skin, there's a harder layer of tissue, and underneath is a softer layer, and you see these wrinkling patterns that make fingerprints. Could you, in principle, predict these patterns? It's a complicated system, but there seems to be something generic going on, because you see very similar patterns over a huge range of scales.
The full paper is over at Nature Materials.