Effect of polymer orientation on pattern replication in a micro-hot embossing process: experiments and numerical simulation

The hot embossing process has been identified as a promising technique for fabricating micro-and nanostructures for polymer-based biological and chemical MEMS (micro electro mechanical systems). However, there has not been any investigation of the effect of polymer chain orientation in the base polymer substrate on replication during the micro-embossing process. Such effects could prove important because polymer chain orientation may develop in the polymer substrates during their production. In this investigation, it was observed that the degree and ease of microchannel replication are significantly influenced by the molecular chain orientation in injection-molded polymer substrates. Microchannels aligned along the flow direction of the polymer replicate easily compared to microchannels aligned across the flow direction of the polymer. The replication fidelity during hot embossing was investigated using a white-light confocal microscope. The anisotropy of injection-molded polymer plays a dominant role in the replication fidelity of microchannels, and the ability to model the anisotropic behavior of the material will enable understanding and prediction of the hot embossing process. Therefore, a material model that reflects the directionality was utilized to simulate the experimental embossing results obtained both along and across the flow direction of the polymer. By comparing experimental results with simulations, we observed that the model is reasonably realistic.