Solvent Compatibility of Poly(dimethylsiloxane)-Based Microfluidic Devices

TLDR

The paper examines PDMS compatibility with organic solvents, a key factor for its use in microfluidic devices such as microreactors for organic chemistry. The study aims to assess PDMS compatibility with organic solvents. The authors evaluated PDMS compatibility by measuring swelling, solute partitioning, and oligomer dissolution, correlating swelling with the solubility parameter δ and identifying solvents that cause minimal or maximal swelling. Swelling was the most influential compatibility factor, with minimal swelling in water, nitromethane, DMSO, ethylene glycol, perfluorotributylamine, perfluorodecalin, acetonitrile, and propylene carbonate, whereas highly swelling solvents could extract contaminants and modify surface properties, and a Diels–Alder reaction was successfully performed in a PDMS microchannel.

Abstract

This paper describes the compatibility of poly(dimethylsiloxane) (PDMS) with organic solvents; this compatibility is important in considering the potential of PDMS-based microfluidic devices in a number of applications, including that of microreactors for organic reactions. We considered three aspects of compatibility: the swelling of PDMS in a solvent, the partitioning of solutes between a solvent and PDMS, and the dissolution of PDMS oligomers in a solvent. Of these three parameters that determine the compatibility of PDMS with a solvent, the swelling of PDMS had the greatest influence. Experimental measurements of swelling were correlated with the solubility parameter, δ (cal1/2 cm-3/2), which is based on the cohesive energy densities, c (cal/cm3), of the materials. Solvents that swelled PDMS the least included water, nitromethane, dimethyl sulfoxide, ethylene glycol, perfluorotributylamine, perfluorodecalin, acetonitrile, and propylene carbonate; solvents that swelled PDMS the most were diisopropylamine, triethylamine, pentane, and xylenes. Highly swelling solvents were useful for extracting contaminants from bulk PDMS and for changing the surface properties of PDMS. The feasibility of performing organic reactions in PDMS was demonstrated by performing a Diels−Alder reaction in a microchannel.