Mechanically assembled polymer interconnects with dead volume analysis for microfluidic systems

The mechanical and fluidic properties of silicon and polymer peg-in-hole type interconnect structures are analyzed, tested, and compared in this paper. Microfluidic interconnects composed of interlocking cylindrical posts and holes are microfabricated of polydimethylsiloxane (PDMS) and SU-8 polymers and are mechanically tested together with existing silicon interconnects. PDMS cylindrical posts experimentally assemble with lower force (20-81mN) than comparable SU-8 cylindrical posts (44-227mN) for PDMS, SU-8, and silicon holes. In addition to interconnect fabrication and experimental demonstration of substrate-to-substrate attachment, fluidic properties of the interconnects are analyzed via ANSYS simulation to predict whether pressure drop is expected to result in disassembly. Pressures due to simulated fluid flow at 1mL/min are expected to be 383.6Pa at the interconnect interface. Worst-case interconnect dead volume is simulated using ANSYS and Matlab. We estimate the dead volume at maximum fluid flow rates (50µL/min and 1mL/min) to range from 5.8 to 33nL. The fluidic analysis predicts sudden expansions should have larger dead volumes with lower pressure drops, and sudden contractions should have lower dead volumes and higher pressure drops along the interconnect for the same change in channel width.