Solvent-induced Surface Wrinkling In A Tri-layer System

In recent years, much attention has been paid to preparation of ordered surfacewrinkles in a rigid crust that is resting on the polydimethylsiloxane (PDMS)elastomeric substrate. Especially, ethanol-responsive wrinkles of the SiOx/PDMSbilayer have attracted intense interest. Here the SiOx crust is formed when PDMS isexposed to UVO. However, fabrication of the tri-layer system based on the smartSiOx/PDMS and study of its wrinkling have not been carried out yet.In this thesis we report the controllable wrinkling on the polymer/SiOx/PDMStri-layer by means of the ethanol-responsive SiOx interlayer. The trilayer system isfabricated by spin coating of polymer film on the UVO-exposed PDMS substrate.After treated by ethanol vapor, a variety of isotropic wrinkled patterns have beeninduced in the polymer/SiOx/PDMS system. Here we systematically investigate theinfluence of the experimental conditions on the resulting patterns. They include theUVO exposure duration, the applied polymer structure (e.g., PVP and PS) and filmthickness from different concentrations. Compared with the SiOx/PDMS system, thetri-layer can retain the ethanol-induced wrinkles even after the full evaporation ofethanol. The underlying physics as well as the different patterns from PVP and PS hasbeen discussed.In the latter part, the polymer film composed of different weight ratios of PS andPVP has been coated on the SiOx/PDMS to fabricate the (PS+PVP)/SiOx/PDMS.Consequently, hierarchical patterns have been induced via the combination ofethanol–indcued wrinkling and phase-separation between PS and PVP.