Enhancement of the thermo-mechanical properties of PDMS molds for the hot embossing of PMMA microfluidic devices

Abstract

We present a cost-efficient and rapid prototyping technique for polymethylmethacrylate (PMMA) microfluidic devices using a polydimethylsiloxane (PDMS)-based hot embossing process. Compared to conventional hot embossing methods, this technique uses PDMS molds with enhanced thermo-mechanical properties. To improve the replication performance, increases in both PDMS stiffness and hardness were achieved through several processing and curing means. First, the amount of curing agent was increased from 1/10 to 1/5 with respect to the amount of prepolymer. Second, the cured PDMS was thermally aged either over three days at 85 °C or for 30 min at 250 °C. Those combined steps led to increases in stiffness and hardness of up to 150% and 32%, respectively, as compared to standard PDMS molds. Using these enhanced molds, structures with features of the order of 100 µm in PMMA are successfully embossed using a standard laboratory press at 150 °C. The PDMS molds and process produce identical structures through multiple embossing cycles (≥10) without any mold damage or deterioration. A Y-shaped microfluidic mixer was fabricated with this technique. The successful demonstration of this enhanced PDMS-based hot embossing technique introduces a new approach for the rapid prototyping of polymer-based microfluidic devices at low-cost.