Mechanical micro-patterning of multilayer soft materials

Abstract

Spontaneous deformation such as wrinkle, creasing and crack under the plane stress has been widely observed in the layered system of materials with large differences in Young's modules. These manipulations have recently been applied to various patterning processes because these system can be implemented simply and quickly. However, localized stress was rarely observed or studied in the experiment. In this study, we report on the localized stress generated by folding the layered system itself rather than the plane stresses and define the new dynamic mechanisms resulting from folding stress. As the layered system was folded, the total strain energy of the system increases and crease formation was formed on the surface to minimize the increased energy. And the localized deformation of the ordered stretch mark was formed at stiff film deposited on a soft layer by crease formation. In addition, the highly ordered stretch mark pattern can be controlled using various variables such as soft layer thickness, folding critical angle and pulling direction. With the simple and easy method, we demonstrated new mechanical patterning and application such as flexible microfluidics assisted by stretch mark pattern.