Archimedean spiral wrinkles on a film-substrate system induced by torsion

Spiral surface patterns endow materials with unique properties and functions. Surface wrinkling in a system consisting of a thin film on a compliant substrate subjected to surface torsion is explored. We find that each spiral wrinkle has the shape of an Archimedean spiral curve. A scaling law is derived to characterize the correlation between the wavenumber and the properties of the system. Both experiments and numerical simulations are performed to validate the scaling relation. Our results foresee the feasibility of fabricating spiral patterns by wrinkling-based techniques and have potential applications in the measurement of local mechanical properties of inhomogeneous soft materials. (C) 2014 AIP Publishing LLC.