The cusp topography of a crumpled paper appears markedly different from a smooth wrinkled skin. Nevertheless, a work that was published recently in Phys.Rev.Lett. suggests that both morphologies may simply reflect different coexistence forms between a few common “elastic building blocks”. These elementary shapes can be classified into two types: “diffuse-stress” (e.g. smooth wrinkles) and “focused-stress” (e.g. sharp folds). They have been known so far to appear, separately, under certain conditions. However, when an elastic sheet was simulated under rather general confinement, that mimic the behavior of simple curtain shape, the emerging pattern decomposed spontaneously into separate regions, each of them dominated by an elementary shape of another type. This finding may hint on a fascinating direction – rather than solving a complicated set of equations, one may construct many shapes by joining together building blocks of various types, as if they were Lego bricks. It remains to be seen whether such formalism does indeed capture the variety of patterns on thin sheets.
The paper, by Robert D. Schroll, Eleni Katifori and Benny Davidovitch, was published in Phys.Rev.Lett. 106, 074301 (2011).
It was the subject of Physics Focus and was featured on the journal cover.
A commentary “Discretizing Wrinkling”(by Eran Sharon) was published in the Journal Club for Condensed Matter Physics.