Topological separation of bacterial active matter

Bacteria inhabit complex environments where dynamic flows and geometries strongly influence fundamental processes such as colonization and nutrient uptake. Microfluidics have greatly advanced the study of bacterial motility under flow, yet how environmental structure and fluid motion jointly shape bacterial currents remains poorly understood. Here, we integrate microbiology experiments, nanofabrication, and mathematical modeling to investigate how physical boundaries and flow patterns govern bacterial swimming behavior. Building on these insights, we design a fluidic diode that directs bacterial currents, enabling the construction of bacterial microfluidic circuits that defy classical electronic laws. These active circuits allow spatiotemporal control of microbial populations in flow systems, exhibiting functions analogous to electronic components, such as amplification, regulation, sorting, and logic gating. By combining these topological modules, we assemble sophisticated active current controllers. Using this platform, we further explore ecological dynamics, including interspecies competition in flowing environments. Our findings highlight the pivotal role of hydrodynamics in controlling bacterial colonization in complex network. More broadly, these bacterial current circuits provide a powerful framework for controlling and studying microbial populations in structured hydrodynamic networks.