Transport and Chemotaxis of Swimming Cells in Porous Media Flows

The goal of this project is to determine the physical mechanisms that govern transport and chemotaxis of swimming cells in porous media. Many kinds of cells are capable of generating their own propulsion in liquids. In their natural habitats and in engineered systems, swimming cells have to navigate through complex microstructures in response to various chemical signals from food sources and other organisms. The investigators will use a combination of theory, numerical simulation, and experiments to examine the relative importance of fluid flows, boundary structures and chemical stimuli on the locomotion of individual cells and collections of cells. The results will be applicable to ecological processes and diverse technologies, including bioreactors, bioremediation, and preservation of clean water. Local high-school students will be recruited to participate in the project.

Swimming cells and synthetic self-propelled particles comprise an emerging class of active suspensions, whose transport properties can differ significantly from those of passive scalars and particulate flows. The effects of suspension microstructure and flow on cell transport in porous media will be investigated for dilute and dense suspensions of various cells that span canonical swimming styles and body shapes. Microfluidic devices will be designed to create well-controlled environments that simulate natural flow conditions and chemical gradients in a porous medium. High-speed video microscopy of microbial suspensions will provide a statistical characterization of large cell ensembles as well as a mechanistic cell-scale view of the flagellar and hydrodynamic interactions mediating large-scale behaviors. The effects of porous media structure on the transport coefficients of chemotaxing cells in chemical gradients will also be examined. Continuum and particle-based models will be implemented numerically and results will be systematically validated against experiments to establish a quantitative, predictive framework for active cell transport in porous media flows.