Deformation behavior in 3D molding: experimental and simulation studies

Abstract

Three-dimensional (3D) molding is a simple and effective technique using a modified hot embossing process to produce large area, hierarchical 3D micro/nanostructures in polymer substrates. However, the use of a thin intermediate polydimethylsiloxane (PDMS) stamp inevitably causes dimensional changes in the 3D molded channel, with respect to those in the brass mold protrusion and the intermediate PDMS stamp structures. Here we investigate the deformation behavior of the 3D molded poly(methyl methacrylate) (PMMA) substrate and the intermediate PDMS stamp in 3D molding through both experimentation and numerical simulation. Depending on the height, period and aspect ratio of the brass mold protrusions and the thickness of the intermediate PDMS stamp, strain contours of the intermediate PDMS stamp layer along the periphery of the 3D molded channels are varying, which leads to a nonuniform elongation of the imprinted structures in the 3D molded channel. Increasing the height and decreasing the period of brass mold protrusions leads to higher total strain of the intermediate PDMS stamp. It was found that for high aspect ratio brass mold protrusions the maximum strain of the intermediate layer occurs in the bottom center of the 3D channels. However, with decreasing aspect ratio of the brass mold protrusion the highest elongation occurs at the bottom corners of the channel causing less elongation of the intermediate PDMS stamp and imprinted structures on the bottom surface of the 3D channel. These experimental results are in good agreement with the results obtained from the numerical simulation performed with a simple 2D model.