Thick SU-8 and PDMS Three-Dimensional Enclosed Channels for Free-Standing Polymer Microfluidic Systems

This paper presents the design, simulation, and fabrication of polymer 3D enclosed free-standing microchannels. These microchannels are designed to be combined with polymer interconnects for the eventual realization of modularly connected polymer microfluidic systems. Microchannels with a width of 200 mum, depth of 200 mum, and a channel length of 8400 mum were simulated using ANSYS CFD Flotran. Preliminary simulations with an input velocity of 0.02 m/s yielded an expected pressure drop along the microchannel of 52 Pa. PDMS and SU-8 microchannels were fabricated ranging in thicknesses from 200 mum to 300 mum, and a sacrificial process using thick photoresist (SC 1827) and structural SU-8 (SU-8 100) was developed for releasing the SU-8 enclosure layer. In addition, 200 mum to 300 mum thick SU-8 molds were employed for PDMS (Sylgard 184) processing. After bonding, the fabrication resulted in freestanding microchips in SU-8 or PDMS with enclosed microchannels that are compatible with microfluidic polymer interconnect.