Thermal Conduction Suppresses Cracks in PDMS Wrinkling by Plasma Oxidation

We report a facile approach to suppress intrinsic crack formation during wrinkling of plasma-oxidized polydimethylsiloxane (PDMS) films, removing a major hindrance in the practical use of these ubiquitous, functional surface patterns. A combination of high heat transfer coefficient (HTC) of the film substrate and low PDMS thickness is shown to consistently yield crack-free wrinkling of glassy skin and PDMS bilayers. Employing optical and atomic force microscopy, light scattering, thermal measurements, and heat transport and stress calculations, we demonstrate that our findings hold for a range of glass, plastic, metal, and layered support materials and plasma processing conditions. Subsuming the PDMS contribution to thermal conduction, an overall HTC threshold of ∼800 W/(m² K), for typical plasma exposures, for crack-free wrinkling is obtained. While suppressing cracks, this simple approach retains the functionality of the glassy skin of plasma-oxidized PDMS.