Growth of Patterned Micropores in Poly-Dimethylsiloxane (PDMS) Using the Thermocapillary Effect

Poly-dimethylsiloxane (PDMS) is a well-known soft polymer with applications in a wide variety of research fields. PDMS is a particularly attractive material for miniaturized bioanalytical systems because of its biocompatibility, gas permeability, chemical inertness and the ability to reproduce miniature features such as microchannels in PDMS. This paper describes a technique to obtain through-membrane pores in thin PDMS membranes. This is based on thermocapillary effect in a MEMS-based microheater device made on a glass substrate. Uncured PDMS is poured on a microheater device that has been coated with a hydrophilic substrate such as poly-ethylene oxide (PEO). Upon heating, PEO evaporates and form gas bubbles in PDMS. The gas bubbles are attracted towards the hot region of the microheater device. The bubbles eventually self-assemble along the hottest isotherm, which in this case is the microheater line. In this manner, self-assembled pores in the desired pattern are obtained. Experiments conducted at different temperatures and PDMS thicknesses throw light on the physical phenomena behind this process and demonstrate the trade-off between PDMS curing rate and bubble escape rate. Results presented in this work are expected to aid in the design of novel PDMS-based membranes for filtration, separation and concentration.