As people age, they may find their wrinkled skin neither pleasing nor useful. But biological systems take advantage of such patterns. For example, wrinkles on the inner surface of the human intestine and on the surface of the brain have evolved to improve digestion and intelligence, respectively. To make wrinkle patterns, inhomogeneous stress fields in the intestine, brain, and other biological tissues induce mechanical instabilities that buckle and deform the tissues as they grow in volume. Although theoretical studies sometimes assume that tissues start with stress-free configurations, that’s not the case for many living ones.
Yangkun Du and Michel Destrade of the National University of Ireland Galway and their colleagues have now quantified the effects of initial stress fields on soft materials. They grew a pattern on a two-dimensional hydrogel. By then forming it into a tube and shrink-fitting it inside a ring of rubber, the researchers created a compressive...
