Determining partitioning and transport coefficients for hydrophobic chemicals in polydimethylsiloxane (PDMS)-based devices

Organ-on-chip devices are an emerging technology with many possible novel applications. These devices are commonly made using polydimethylsiloxane (PDMS), a ubiquitous, versatile, and inexpensive polymer. However, partitioning of hydrophobic compounds in PDMS limits the current ability of organ-on-chip devices to control dosage of chemical solutions accurately and precisely. Here, we measure and model chemical-PDMS interactions, accounting for chemical partitioning across the PDMS interface mediated by free energy differential and internal diffusion in bulk PDMS. The model is validated via optical measurements of fluorescent dyes binding to and diffusing within PDMS. Interaction experiments then extract relevant chemical-PDMS interaction parameters, including diffusion and partition constants. This is demonstrated for nine chemicals, selected for current use in organ-on-chip studies.