Microwave irradiation-based rapid curing of PDMS for microfluidic applications

Abstract

Microfluidic devices are routinely fabricated using replica moulding. The master relief structure is generally constructed on a silicon substrate and the stamps are made using polydimethylsiloxane (PDMS), cured via the slow process of hot-air convective heating. An alternative method that greatly reduces this cure time is presented here. It employs a low-cost, consumer-grade microwave oven and speeds up the curing process by permitting a much higher heat flux to be applied to the prepolymer. A specific pulsed irradiation protocol has been devised which achieves precisely controlled energy delivery for this purpose. This is necessary because silicon’s relatively much stronger microwave absorption causes uncontrollable temperature overshoots that could degrade PDMS if continuously irradiated. The protocol has been arrived at after due optimization of operational parameters, achieved via simulation of a finite element model. It has been implemented by modifying the control circuitry of the consumer grade oven. Cure times as low as two minutes have been demonstrated. Optical and mechanical characterization results show no adverse effect on the performance of PDMS cured using the proposed method. Thus, it can be used for the rapid fabrication of PDMS-based microfluidic devices and would be especially beneficial for research labs looking to speed up microfluidic device development iterations.