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A precision hot embossing mold fabricated by high-resolution powder blasting with polydimethylsiloxane and SU-8 masking technology

In this paper, we applied a three-dimensional micromold by using micropowder and micropattern masking technology. High-resolution powder blasting with polydimethylsiloxane (PDMS) and SU-8 masking is developed for the fabrication of a precision microfluidic mold for hot embossing fabrication. The PDMS is a suitable masking material for powder blasting due to its high erosion resistance. First, a 100 µm SU-8 negative pattern was developed on a stainless steel substrate by standard photolithography. A PDMS solution was then applied to the substrate, mainly filling recessed regions. Excess of PDMS was then physically removed by a blade. The PDMS/SU-8 structure was then cured. Next, silicon carbine (SiC) powder with an average diameter of 50 µm was blasted on a PDMS/SU-8 coated stainless sheet at a constant pressure between 4 and 6 bar and a PDMS mask was removed by ultrasonic cleaning in isopropanol. The three-dimensional structure was examined by an optical microscope, optical white light interferometer and scanning electron microscope. The PDMS pattern is found to be 50 µm wide, and the maximum etched depth at this thickness is around 150 µm at a blasting pressure of 6.2 bar; thus, an aspect ratio of 3 is easily obtained. In principle, the low-cost micromachining hot embossing mold developed can be improved to yield submicrometer- and nanometer-scale resolution.