PDMS treated with dichloromethane: swollen weight without underestimation due to the solvent volatility and thermal aging to reduce swelling and morphology damage

Poly(dimethylsiloxane) (PDMS) is widely used in integrated microfluidics and biomedical platforms due to its many advantageous properties. However, the use of common organic solvents in synthesis and diagnostic protocols performed in PDMS-based devices has prompted the search for treatments of PDMS able to avoid the undesirable consequences of the PDMS swelling. Due to the solvent volatility, systematic underestimation of the weight-gain can result from standard measurements of swollen weight in open environment and affected by time-delay comparable to the solvent evaporation rate. In this study, we consider dichloromethane (DCM) as an example-solvent that swells PDMS and consider: i) an experimental procedure properly designed for measuring the swollen weight of PDMS with control on the weight loss due to the solvent volatility, and ii) post-curing thermal aging of PDMS for effectively improving its chemical resistance against swelling and removing its morphology degradation upon chemical treatment. Based on X-ray spectroscopy (XPS) analysis and microscope imaging we explore the surface chemistry and morphological degradation of PDMS treated by DCM and show the temporal evolution of the swelling ratio of PDMS thermally aged up to 150°C for 24 hours.