Host: The Japan Society of Mechanical Engineers
Name : Mechanical Engineering Congress,Japan
Date : September 11, 2016 - September 14, 2016
In nature, there are a lot of functional anisotropic surface structures, such as drag reduction surface of shark skin. And these structures are formed by self-organization processes. For preparations of biomimetic anisotropic self-organized structures, wrinkle structures are suitable. Wrinkle structures are formed at the hard surface thin layer fixed on soft substrates when in-plane stress is applied. One of the characteristic properties of wrinkled surfaces is their shape-tunability in response to changes in the applied strain. However, the adhesion between the elastic hard thin layer and the soft substrate often cannot withstand the internal stress associated with the formation of wrinkles, leading to partial delamination known as buckling delamination. In this report, we show a fabrication of durable micro wrinkle structures by using self-organized honeycomb-patterned porous polymer films as embedded hard layers. We prepared honeycomb-patterned porous polymer films with polystyrene by breath figure method. After UV-O3 treatment, honeycomb-patterned films were fixed upside down to glass substrate with poly(styrene-co-allyl alcohol) as adhesive. After peeling off the bottom layer of the films by an adhesive tape, the fixed top layer on the glass substrate was turned upside down in ethanol, and put on a glass substrate. Poly(dimethylsiloxane) (PDMS) precursor mixed with the catalyst was poured into the top layer, and cross-linked by heat treatment (80 oC, 3h). And then, the porous network structure embedded in the PDMS substrate was obtained. By applying in-plane strain, successfully micro wrinkle structures were formed repeatedly. However, wrinkle periods were depended on periodicity of honeycomb-patterned films. To control the wrinkle period, aluminum was sputtered on the only top of honeycomb-patterned films before dividing into top and bottom layers. After that, same embedding processes were carried out. As a result, wrinkle structures were also formed, and wrinkle periods can be controlled by thickness of aluminum layers.
