Micro injection molding of a micro-fluidic platform

Micro fabrication of polymers is becoming increasingly important and is considered a low-cost alternative to silicon- or glass-based MEMS technologies. However, very little work has been done to study the influence of polymer resin on the replication accuracy of the micro features in micro injection molding. In this study, micro injection molding was applied to a micro-featured fluidic platform used for DNA/RNA testing. LIGA-like processes were used to prepare a silicon-based SU-8 photoresist, followed by electroforming to make a Ni–Co-based stamp. The micro features in the stamp consisted of a micro-channel array 50 μm in pitch size. COC, PC, PMMA and PS were used as the injection molding materials. The effect of various polymer resins and molding conditions on the replication accuracy of the micro features was investigated. The width and depth of the micro-channels within the molded devices were measured and analyzed. For the micro-injection-molded devices, the accuracy of the width and depth of the micro-channels increased with increasing mold temperature, melt temperature, injection velocity and packing pressure within the regular processing window. The molded parts showed excellent replication accuracy for the COC polymer resin due to its low viscosity and low, isotropic shrinkage. The PS resin also achieved acceptable micro-channel replication accuracy under specific molding conditions.