3D structuring of polymer parts using thermoforming processes

A new technique for the realization of complex three dimensional (3D) structures in polymer materials is presented. The described process can be applied for the fabrication of 3D structured foils as well as for 3D structured polymer parts using a replica molding process. In the first step, the foil is structured by Hot Embossing. This structured foil is then blown into a structured mold by pressure at high temperature, using a thermoforming process. The thermoforming process is realized in an especially designed tool, where different mold inserts can be applied. In the thermoforming process this tool, containing the mold insert and the structured foil is heated up and a pressure is applied which assures, that the foil covers the structured mold insert. Due to parameter optimization, high pattern fidelity can be achieved. As structures a porefield with a pore diameter of 500 nm and lines and spaces with a width of 1.6 mu m were used. Besides a Moth Eye structure with a period of 280 nm and a blazed grating with a period of 1 mu m and a blazed angle of 15 degrees were imprinted and blown into the structured mold. The results show, that this process can be used to fabricate 3D structured foils with good structure fidelity. Besides the structured foils, additional poly(dimethylsiloxane) (PDMS) replications can be made out of this foils. These PDMS replications are used as stamps in a replica molding process. A micro fluidic system containing hydrophobic and hydrophilic channels was created using this process. (C) 2010 Elsevier B.V. All rights reserved.