Unravel the transport and rotation properties of a squirmer in viscoelastic fluids

Microorganisms such as bacteria and algae naturally inhabit complex environments. Understanding their ubiquitous behavior in, e.g., biofilms, is fundamental for medical and industrial applications. We study the rotational motion and transport peculiarities of a single swimmer in a viscoelastic fluid via Lattice Boltzmann (LB) simulations. Here, the generic squirmer model is employed and fluid viscoelasticity is achieved by added flexible polymer chains. For systems with low viscosity, due to no-slip boundary condition, heterogenous collisions between squirmer and polymers yield additional torques, which enhance squirmer’s rotational motion by more than an order of magnitude. However, asymmetric collisions barely have evident contributions to the rotational enhancement in the high viscosity regime, where the viscous force damps the transport of polymers so that the momentum and angular momentum exchanges between squirmer and polymers are suppressed. Our results can facilitate the understanding of the behavior of the microorganisms in the complex systems and guide the design of microfluidic devices by harnessing these properties.