Controlling dimensions when injection molding microfluidic devices

The control of part dimensions for injection molded microfluidic channels were investigated using positive metal tooling with microscale features and three amorphous materials. Molded samples and the tooling were characterized using a stylus profilometer and scanning electron microscopy. Channel dimensions improved with higher mold and melt temperatures. The depths of the molded channels exhibited a linear dependence on melt viscosity which adjusted for melt and mold temperature effects. The width of channel bottoms increased with channel depth, but did not depend on melt viscosity or cooling time. The lands between channels were not formed until the channel depths were complete and then increased with longer times before solidification. Surprisingly, the channels widths were harder to control than the channel depth. Changing the flow direction did not change formation of the channel depths, but did reduce the widths. Backing materials for the tooling and vacuum venting had no effect on replication.