Interactions of motile bacteria at complex fluid interfaces with topological defects

Liquid crystals (LCs) are complex fluids that exhibit properties of both solids and liquids, mimicking conditions similar to natural bacterial environments. Being highly reconfigurable, LCs provide a robust platform to establish relevant interfaces and investigate the behavior of bacteria. Although research on bacteria at simple interfaces is available, their behavior at complex fluid interfaces remains less explored. In our studies, we bridge this gap by investigating the interactions of motile bacteria at complex environments through engineered interfaces of the thermotropic LC, 8CB (4'cyano-4'octylbiphenyl), at smectic, nematic, and isotropic phases. We previously confirmed the existence of a correlation between the interfacial properties and the dynamics of bacteria that included parameters like residence time at the interface, average speed and the trajectories of the bacteria. Now, we aim to investigate the interfacial effects of topological defects such as focal conic domains (FCDs) on these properties, in addition to the preferred swimming trajectories of the bacteria. A better understanding of these interfacial effects on the fundamental behaviors of bacteria will allow us to help develop strategies to potentially guide bacterial movement and can be utilized to develop micromachines and micro-robots.