Nested self-similar wrinkling patterns in skins

摘要

Stiff thin films on soft substrates are both ancient and commonplace in nature;for instance,animal skin comprises a stiff epidermis attached to a soft dermis.Although more recent and rare,artificial skins are increasingly used in a broad range of applications,including flexible electronics,tunable diffraction gratings,force spectroscopy in cells,modern metrology methods,and other devices.Here we show that model elastomeric artificial skins wrinkle in a hierarchical pattern consisting of self-similar buckles extending over five orders of magnitude in length scale,ranging from a few nanometres to a few millimetres.We provide a mechanism for the formation of this hierarchical wrinkling pattern,and quantify our experimental findings with both computations and a simple scaling theory.This allows us to harness the substrates for applications.In particular,we show how to use the multigeneration-wrinkled substrate for separating particles based on their size,while simultaneously forming linear chains of monodisperse particles.