Combining Hydrophilic And Hydrophobic Materials In 3d Printing For Fabricating Microfluidic Devices With Spatial Wettability

The fabrication of microfluidic flow cells via projection micro-stereolithography (P mu SL) has excited researchers in recent years. However, due to the inherent process properties of most commercial P mu SL, microfluidic devices are fabricated in a monolithic fashion with uniform material properties across a flow cell. Yet, the large surface-to-volume ratio in microfluidics demands to tailor microchannel surface properties-particularly in planar microchannel arrangements-with spatial control and micron-scale resolution to form a desired flow profile, e.g., emulsion droplets. The fabrication of planar microfluidic devices by P mu SLbased 3D printing with spatial control over surface properties is presented. For that, homemade photopolymer formulations being either hydrophilic or hydrophobic is designed. Adding acrylic acid to a resin containing poly(ethylene glycol) diacrylate lowers the contact angle down to 0 degrees against water creating a superhydrophilic surface. By utilizing 1H,1H,2H,2H-perfluorodecyl acrylate, a photopolymer formulation allowing for 3D-printing a hydrophobic microchannel surface with a contact angle >120 degrees against water is obtained. Combining these two materials, it is 3D-print microfluidic flow cells with spatially defined wettability for emulsion formation. Finally, the resin vat of the commercial P mu SL printer during the printing process for fabricating multimaterial geometries is switched, exemplarily applied for realizing a hydrophobic-hydrophilic-hydrophobic device for forming O/W/O double emulsions.