Mass fabrication of PDMS microfluidic devices by injection molding and applications in sensitive 3D spheroid and explant culture

This study investigates the use of industrial-grade polydimethylsiloxane (PDMS) for mass production of microfluidic chips through Liquid Silicone Rubber Injection Molding (LSR-IM) technologies. Injection molding of PDMS is ubiquitous in the automotive and aerospace industries. Yet, it is not currently applied to large-scale production of microfluidic devices. Here, we manufactured PDMS microfluidics devices using industrial IM systems and measured the values of several physicochemical properties of PDMS important in microfluidics. For the two grades of injection-moldable PDMS studied, properties were found close to those of the standard Sylgard 184 PDMS, except Young's modulus, which varied from 66% to 250% of the Sylgard 184 value and the absorption of small molecules, which was lower or equal to that within Sylgard 184. Yet, the main benefits of LSR-IM production lie in its systematic process, resulting in an increase in reproducibility of both PDMS surface and bulk properties by decreasing the variance within and between production batches of several variables: Young's modulus (30-fold), oxygen permeation (10-fold), mean fluorescence intensity of Nile Red (5-fold). Emphasis on biocompatibility of LSR-IM was evaluated by culturing complex and sensitive 3D biology models (tumor spheroids and explants) in injection-molded PDMS devices. We observed no significant differences in cell proliferation relative to samples cultured on conventional Sylgard 184 PDMS devices. Overall, these findings open a direct path from benchtop prototyping to industrialization of PDMS-based microfluidic devices for applications in healthcare.