Mechanical and Civil Engineering Seminar

Bacteria, beneficial and pathogenic alike, commonly interact with host cells along mucosal epithelia, which are often lined by dense fields of motile cilia. A central challenge for the host tissues in bacteria-host associations is determining a means to effectively deflect toxic molecules and undesirable (motile and non-motile) particles away from the tissue surfaces, while selectively recruiting members of the normal microbiota. The strategies employed should be robust with respect to variability in the environmental conditions and should limit the chances of encounter with pathogens and toxins. Organisms have developed multiple mechanisms to achieve this task, including cilia-generated flows, the focus of this talk, that move fluid and suspended particles across the epithelial surface. This mechanism belongs to a class of mathematical problems where the "control" is applied at the boundary (ciliary motion) to generate desired, multi-objective outcomes in the whole fluid domain (e.g., transporting fluid, dispersing/concentrating chemical signals, exporting/recruiting particles) — hence the title "soft control". In this talk, I will present recent results on the fluid mechanics of ciliated surfaces with emphasis on their role in mixing and transport of passive particles. I will conclude by commenting on how these models could be used to connect the biological function of ciliated surfaces in association with environmental bacteria to the physics of mass transport and bacterial motility in cilia-generated flows.