Polymer embossing tools for rapid prototyping of plastic microfluidic devices

In this paper, we describe a simple and rapid method of fabricating hot embossing tools using polydimethylsiloxane (PDMS), which are then used to rapidly fabricate microchannels in polymethylmethacrylate (PMMA). A negative photoepoxy SU-8 or thick positive photoresist AZ4620 on silicon was used for molding during PDMS casting. Fabrication time of these PDMS tools was considerably less than those using conventional techniques and remains the same regardless of the aspect ratio of features. The described approach was used to emboss microchannels in PMMA of aspect ratios up to 2, with depths from 5 to 250 μm and widths over 40 μm. The technique was also applied to fabricating orthogonal 3D microchannels using multiple lithography steps. The use of a soft tool material increased cycle time and limited the tool lifetime to approximately 20 cycles. Our successful demonstration of PDMS embossing tools presents an alternative approach for rapidly prototyping microfluidic biochips when fast processing and low cost are important and the number of samples is relatively low.