Polymer mechanically interlocking structures as interconnects for microfluidic systems

This paper describes peg-in-hole type mechanical interconnects made of SU-8 photopolymer, polydimethylsiloxane (PDMS) and silicon for joining microfluidic components of disparate materials to create complex microinstruments. Interconnects assemble as compliant interlocking cylinders that deform when assembled with holes that are smaller by several to several tens of microns, thus providing mechanical attachment as well as fluid interconnects between substrates. Example structures have nominal outer radii of 100–200 µm, inner radii of 50–100 µm and lengths of 200–400 µm. ANSYS mechanical simulations are employed to analyze the optimal interconnect sizing for a mechanical attachment, as well as predict disassembly forces ranging from zero to 232 mN. The interconnects are fabricated and experimentally tested with a controlled-force linear actuator to yield disassembly forces ranging from 20 to 130 mN. Pressurization tests demonstrate that SU-8 interconnects hold water pressure to 200 kPa without leaking and PDMS interconnects hold air pressure to 21 kPa and water pressure to roughly 6.9 kPa.