Microfluidic devices are used to apply mechanical stimuli, such as compressive force and flow shear force, to cells for mechanobiology studies. Previously, we developed a microfluidic cell compressor in which cells embedded in hydrogel scaffolds were compressed by polydimethylsiloxane (PDMS) balloons, which were expanded pneumatically, in proportion to the balloon diameter. The device consisted of two PDMS layers. The bottom layer contained channels connected to circular wells and was fabricated using SU-8 photoresist molds. The top layer was a thin PDMS membrane separately prepared by spin coating PDMS on a plastic film. The two layers were bonded together using plasma bonding to form PDMS balloons and pneumatic channels. Therefore, fabrication of the device involved multiple steps of photolithography and soft lithography.

In this study, we have improved the fabrication method of the microfluidic cell compressor by printing a master mold using a commercial microfluidic 3D printer for more efficient and cost-effective fabrication with higher design flexibility. The new method is more efficient because it does not require separate preparation of PDMS layers, the mold fabrication can be completed quicker, and a photomask is not necessary. We found that proper printing, UV light exposure, cleaning, baking, and temperature control of the mold affected the ability of the 3D printed mold to cure PDMS.

Also, multiple maintenance requirements of the 3D printer were found for curing PDMS on the printed mold. For example, the resin within the 3D printer must be free of debris, the resin in the printer must be stirred before printing to ensure homogeneity, and the light filtering elements of the printer must be clean. With proper methodology and maintenance, the printer can be used to fabricate the microfluidic cell compressor and similar high-quality microfluidic devices capable of performing laboratory experiments efficiently. Further developing a methodology of creating 3D printed microfluidic device molds would expand access to microfluidics.

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