Invited paper: Fabrication of complexly patterned wavy structures using self-organized anisotropic wrinkling

In this work, we review a novel means of self-organized anisotropic wrinkling, which enables the patterning of wavy microstructures that are rarely achievable with conventional patterning approaches. The surface wrinkling phenomenon usually occurs in a system of stacked layers in the course of relieving the accumulated stress therein. For example, the polymer/metal bilayer system supported on a rigid substrate can generate random wrinkles on the surface due to the compressive stress resulting from thermal annealing. However, these random and isotropic wrinkles can be self-organized and ordered by an external confinement effect being guided in periodic microstructures of a patterned mold material. By exploiting the competitive wave interactions between the intrinsic wrinkling wavelength and periodic spacing of the externally imposed mold, complex wavy structures can be created with designed shape of the wrinkles. In addition, manipulating the contact condition of the external mold can allow controllability over the phase of patterned wrinkles. Therefore, the proposed technique is anticipated to be useful in a broad range of applications in micro-optics, microfluidic devices, and flexible electronics.