Microswimming in viscoelastic fluids

The locomotion of microorganisms and spermatozoa in complex viscoelastic fluids is critical importance many biological processes such as fertilization, infection, biofilm formation. Depending on their propulsion mechanisms, microswimmers display various responses to a fluid environment: increasing or decreasing swimming speed efficiency, modifying kinematics gaits, experiencing different hydrodynamic interactions with surroundings. In this article, we review the fundamental physics synthetic fluids. Starting from continuum framework, describe main theoretical approaches developed model microswimming fluids, which typically rely asymptotically-small dimensionless parameters. We then summarize recent progress mobility single cells propelled by cilia, waving flagella rotating helical unbounded next briefly discuss impact other physical factors, including micro-scale heterogeneity role Brownian fluctuations microswimmers, effect polymer entanglement influence shear-thinning viscosity. particular, for solution long chains whose sizes are comparable radius flagella, models cannot be used instead Dynamics polymers can predict dynamics. Finally, viscoelasticity dynamics presence surfaces external flows its collective cellular behavior.