Session: 06-02 Micro/Nanofluidic Sytems, Techniques and Devices

Paper Number: 87613

87613 - Fabrication of a Microfluidic Cell Compressor Using a 3D-Printed Mold 

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 it 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. A connection port was then bonded to the device to allow for easy and reversible connection to an air pump. 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 (CADworks3D) 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.

Through several iterations of troubleshooting, we have established the following protocol. (1) The mold printed using the 3D printer is allowed to drip dry overnight. (2) The mold is washed in 99% isopropyl alcohol (IPA) for 60 minutes using a shaker while the mold is removed from the IPA bath every 10 minutes and dried using compressed air. (3) The mold is baked in a UV oven for 40 minutes to finalize the solidification of the mold material. (4) The mold is baked at 130°C to complete any unfinished chemical reactions within the mold material. (5) PDMS is poured onto the mold, and a glass slide is secured to the mold to control the final device thickness. (6) Cured PDMS is removed from the mold and then bonded onto a glass plate.  Through this process, high quality and reusable cell compression devices can be fabricated for laboratory use.

As the above methodology was developed, multiple maintenance requirements of the 3D printer were found that if not completed, will prohibit PDMS from being cured on the mold. For example, the resin within the 3D printer must be free of debris and must be filtered if debris is introduced to the resin, the resin in the printer must be mixed 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 similarly 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.

Presenting Author: Carson Emeigh University of Nebraska-Lincoln