Hydrophilic modification of SLA 3D printed droplet generators by photochemical grafting

Few droplet generators manufactured using desktop stereolithography 3D printers have been reported in the literature. Moreover, 3D printed microfluidic chips are typically hydrophobic, limiting their application to water in oil droplets. Herein, we present designs for concentric and planar 3D printed microfluidic devices suitable for making polymeric microparticles using an off-the-shelf commercial stereolithography printer and resin. The devices consist of a microscope slide, binder clips, and printed components. Channels were modified by an ultraviolet grafting of methacrylic acid to the surface of chips, yielding a hydrophilic coating without modification to the bulk polymer. The water contact angle decreased from 97.0 degrees to 25.4 degrees after grafting. The presence of the coating was confirmed by microscopy and spectroscopy techniques. Polystyrene microparticles in the <100 mu m size range were generated with varying molecular weights using the described microfluidic chips. Our work provides a facile method to construct droplet generators from commercial stereolithography printers and resins, and a rapid surface modification technique that has been under-utilized in 3D printed microfluidics. A wide range of microfluidic devices for other applications can be engineered using the methods described.

Automated summary

This study introduces designs for concentric and planar 3D printed microfluidic devices made with commercial stereolithography printers and resins, suitable for producing polymeric microparticles. Surface modification through UV grafting of methacrylic acid on the chips enabled the creation of a hydrophilic coating, allowing for new applications in water in oil droplets. This work also demonstrates the generation of polystyrene microparticles using the modified microfluidic chips, highlighting the versatility and potential of these devices for various applications.