| Gas assisted injection molding (GAIM) was investigated as a method to improve replication during injection molding of microscale features on the surface of macroscale parts. Three representative materials (polypropylene, polymethylmethacrylate, and a thermoplastic polyurethane elastomer) exhibited enhanced feature depths with high aspect ratio tooling, but no improvements with low aspect ratio positive tooling. The gas assisted micro injection molding also eliminated the severe sink marks in the parts molded from the semi-crystalline polymer. An examination of GAIM processing parameters using polymethylmethacrylate showed that high melt and mold temperatures were necessary to achieve complete replication with low aspect ratio positive tooling. Replication also improved slightly with increasing shot size and gas pressure, but the process required a very short gas delay time. Overall, gas assist micro injection molding shows promise in improving the replication of microscale features in injection molded polymeric microfluidic devices and other applications. |
