Rapid fabrication of polymethylmethacrylate micromold masters using a hot intrusion process

摘要

A method for rapid fabrication of mold masters for soft-molding of polydimethylsiloxane (PDMS) microfluidic devices is successfully developed and tested. The method involves laser micromachining and a hot-intrusion process, and produces mold masters from polymethylmethacrylate (PMMA) substrates. A metallic mask with microchannel line features of various widths (25 to 200 μm) is initially created by laser micromachining a 75-μm-thick brass sheet. Under the hot-intrusion process, a 2-mm-thick solid PMMA substrate is then heated and molded under pressure to force the softened material through the shaped micro-features in the mask. The height of the extruded microrelief is determined by the pressure, temperature, and time profile of the hot-intrusion process. A mathematical model that characterizes the rapid fabrication process and enables the operator to select appropriate process parameters is described. The derived empirical model is based on experimental observations where extruded microrelief heights were varied from 5 to 75 μm with aspect ratios from 0.1 to 0.46, and radii of the extruded profile from 12 to 270 μm. The proposed model is developed to describe the relationship between key process parameters and the extruded heights of the microreliefs. Furthermore, the model provides the operator with simple guidelines for selecting the process parameters. An example of PDMS microfluidic devices replicated by the rapid micromold fabrication methodology is presented to illustrate the quality of the resultant features Of microchannels.