Fabrication of hierarchical wrinkled morphologies through sequential UVO treatments

Abstract

The fabrication, in a controlled manner, of well-defined micrometer size topographical features on polymer surfaces is a great challenge due to the large variety of potential applications of these materials ranging from adhesion, optics to responsive interfaces. A challenging issue concerns the fabrication of interfaces having surface moieties with sizes at different length scales. Herein we describe the fabrication of hierarchical wrinkled surfaces involving two sequential ultraviolet-ozone (UVO) treatments. This methodology allowed us to tailor the shape of PDMS surfaces and create a large variety of different patterns expected to have a broad range of applications requiring surface features with variable sizes. More interestingly, the employment of UVO treatments to produce surfaces with up to three distinct levels of order since they enable the rigidification of the interface by formation of a SiOx layer or the degradation of the PDMS surface when longer treatments. The surfaces prepared by using this approach presented patterns three different scales: the structure provided by the mask employed, the wrinkled surface inside of the directly exposed areas (related to the hole size of the mask) and the wrinkled surface protected during the first treatment by the mask (which is related to the mesh dimensions of the mask employed).