Microbes are constantly on the move in complex environments, from friendly microbes navigating plant roots and soils, to pathogenic microbes infecting tissues and surfaces. In these real-world environments, microbes often perform collective chemotaxis, moving as a group in response to structured chemical stimuli such as gradients in nutrients, attractants, and even toxins. Yet, laboratory studies typically observe microbial behavior in well-mixed, liquid media, which lacks the spatial structure and complexity of real environments. Further, approaches to study bacterial migration in structured environments often depend on complex and costly microfluidic systems or advanced additive manufacturing, limiting accessibility and widespread use. The overall objective of this research is to develop scalable and low-cost resin-based 3D printing approaches to create structured pathways for investigating bacterial collective migration. We use a consumer-grade LCD screen printer to create microscale paths from clear resins with complex geometries like bends and mazes. To evaluate washing protocols and biocompatible adhesives for attachment of printed devices to glass slides, we characterize the impact of resin and adhesive on GFP-expressing Escherichia coli (E. coli) growth using plate reader growth curve assays. Once the device is assembled, we fill device channels with microporous swimming gels (0.3 wt.% agar in 2 wt.% Lennox Broth [LB] media) and inoculate a dense suspension of E. coli on one end of the pathway. Using time-lapse fluorescence microscopy, we visualize E. coli collective migration in defined 5 cm-long pathways over 18 hours. Key features of this system include the ability to rapidly fabricate devices within a 2-hour period, as well as the ability to reuse devices multiple times for migration studies. In our ongoing work, we continue to refine device design, study bacterial chemotaxis in more complex geometries, and introduce fluid flow to our system. Overall, resin printing provides an accessible and modular route to study bacterial migration in spatially structured and complex environments, which helps bridge the gap between traditional cell culture conditions and real-world environments.
