Study on two-stage hot embossing microreplication: silicon to polymer to polymer

Hot embossing microfabrication has been used for the replication of a mold onto a polymer substrate for the past decade, with the molds usually made using techniques like wet etching, CNC machining, and laser writing. Fabricating a male mold using a laser and CNC machining consumes a lot of resources in mold design, mold fabrication time, and smooth surface finish of the mold. In this work, a novel approach called two-stage embossing that is a slight modification of the existing process is proposed. This process still requires a primary mold (of the same shape as the final desired part) that is used to emboss on a polymer of higher glass transition temperature than the substrate to be used for the second stage embossing. Finally this polymer secondary mold is used for the final replication on the desired substrate. Preliminary experimental results focusing on mold quality with respect to the number of embossing cycles of the secondary mold, the embossing quality of the final substrate as compared to the primary silicon mold, and the life of the secondary mold are presented. The experimental results confirm the viability of the process as a candidate process for hot embossing microreplication applications.