*Author for CorrespondenceL. K. NarangammanaE-mail: [email protected] 

Low-cost fabrication methods are now essential for expanding access to microfluidic technologies in biological and laboratory applications. In this work, we present a fused deposition modeling (FDM) based approach for the rapid fabrication of monolithic microfluidic droplet generators incorporating several T-junction and specific flow-focusing geometries, including a novel vertical channel configuration. All devices were fabricated without post-processing or bonding, demonstrating a simple and cost-effective workflow using commercially available desktop 3D printers. The fabrication quality and dimensional fidelity of the printed devices were systematically evaluated by comparing channel orientation and printer resolution. Vertical channel architecture exhibited improved channel continuity and reduced blockage compared to conventional horizontal designs. Droplet generation experiments using water-in-oil emulsions revealed stable and reproducible droplet formation across a range of flow conditions. Flow-focusing devices with vertical channels produced smaller droplets with reduced size variability and shorter formation times relative to horizontal configurations. Higher printer resolution further enhanced droplet uniformity and controllability. Finally, the capability of the developed devices for biological applications was demonstrated through the encapsulation of bacterial cells within discrete droplets. The results highlight the potential of low-cost FDM-printed microfluidic devices as accessible platforms for droplet-based biological experiments, particularly in resource-limited research environments.

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