Geometry-Dictated Wrinkle Patterns in Vapor-Deposited Thin Films on Liquid Substrates*

Surface patterns and wrinkles in thin films are of fundamental and technological interest for their use in tuning morphological, mechanical, optical, and surface properties. Here, we use initiated chemical vapor deposition (iCVD) to generate polymer films with controlled wrinkle patterns and geometries. The iCVD technique is a solvent-free method to produce functional polymer coatings by free-radical polymerization of surface adsorbed monomers. Previously, iCVD has been used to produce parallel and herringbone wrinkles by deposition onto pre-strained elastomers and random wrinkles by deposition onto compliant amorphous substrates. We examine wrinkle formation in thin films on liquid substrates. The resulting wrinkle patterns are dictated by the topography and boundaries of the liquid surface pinned in micropost arrays with various post sizes, spacings, and shapes. Properties of the wrinkled films also depend on the iCVD deposition conditions. This presentation will demonstrate control of the wrinkle patterns and elucidate the mechanism of wrinkle formation in thin films grown on liquid surfaces.