Low-Reynolds-number swimming in viscous two-phase fluids.

The fluid media surrounding many microorganisms are often mixtures of multiple materials with very different physical properties. The composition and rheology of the mixture may strongly affect the related locomotive behaviors. We study the classical Taylor's swimming sheet problem within a two-fluid model, which consists of two intermixed viscous fluids with different viscosities, with both numerical experiments and analysis. Our results indicate that both the swimming speed and efficiency may be decreased substantially relative to those for a single-phase fluid.