The active transport of microswimmers through complex fluids is of great importance for biological and potential technolgical applications. Here we use the well-known squirmer microswimmer model to show the importance of the local fluid microstructure and non-continuum effects which determine the swimming speed of squirmers in different polymeric and filamentous fluids. Surprisingly, we find that different squirmer types (contractile/extensile) move at considerably different speed in filamentous fluids which cannot be explained by existing continuum models, but by considering the local fluid and polymer properties around the squirmers. Furthermore, neglecting hydrodynamic flow fields by using a simple Active Brownian Particle (ABP) model strongly decreases the speed compared to squirmers [1]. Our approach allows us to disentangle hydrodynamic from steric hindrance effects, which enables to bridge the gap between commonly used continuum hydrodynamic models and ABP models.
[1] A. Zöttl, Dynamics of squirmers in explicitly modeled polymer solutions, EPL 143, 17003, (2023).