Axisymmetric Squirmers in Stokes Fluid with Nonuniform Viscosity

Abstract

The ciliary locomotion and feeding of an axisymmetric micro-swimmer in a complex fluid whose viscosity depends on nutrient concentration are investigated numerically. The micro-swimmer is modeled as having spheroidal geometry, and ciliary beating is modeled by a slip velocity; i.e. a squirmer is adapted. Looking at the coupling between swimming and feeding of spheroidal squirmers, it is found that swimming speed and feeding are most affected by a non-uniform viscosity environment when the ratio of advection-forces to diffusion-transport, characterized by the nondimensional Peclét number, is moderate ($\text{Pe}\approx 10$). These changes are correlated to significant increases in the pressure force on the surface of the squirmer. The swimming and feeding changes are found to be more significant in oblate spheroids than prolate spheroids. Most interestingly, nontrivial symmetric slip boundary conditions on the surface of the squirmer, which results in zero net motion in a constant viscosity fluid, can yield non-zero propulsion when paired with asymmetric nutrient boundary conditions. The fact that symmetric fluid boundary conditions can result in asymmetric propulsion has implications for the design of artificial micro-swimmers and other low-$\text{Re}$ squirmers in complex fluids.

References in corpus (22)

• Designing phoretic micro- and nano-swimmers
• Rheology of Active-Particle Suspensions
• Green Algae as Model Organisms for Biological Fluid Dynamics
• Effective viscosity of microswimmer suspensions
• Adaptive locomotion of artificial microswimmers
• Oscillatory Flows Induced by Microorganisms Swimming in Two-dimensions
• Efficiency optimization and symmetry-breaking in a model of ciliary locomotion
• Active colloids in complex fluids
• A new model for simulating colloidal dynamics
• Squirming through shear-thinning fluids
• Viscotaxis: microswimmer navigation in viscosity gradients
• Optimal feeding is optimal swimming for all Péclet numbers
• A steering mechanism for phototaxis in Chlamydomonas
• A boundary element regularised Stokeslet method applied to cilia and flagella-driven flow
• Active particles in viscosity gradients
• Geometric tuning of self-propulsion for Janus catalytic particles
• An active particle in a complex fluid
• Lévy Fluctuations and Tracer Diffusion in Dilute Suspensions of Algae and Bacteria
• The cost of swimming in generalized Newtonian fluids: Experiments with C. elegans
• Swimming efficiency in a shear-thinning fluid
• Autophoretic locomotion in weakly viscoelastic fluids at finite Péclet number
• A note on the reciprocal theorem for the swimming of simple bodies

Cited by in corpus (6)

• Dynamics of a helical swimmer crossing viscosity gradients
• Reorientation dynamics of microswimmers at fluid-fluid interfaces
• Squirmer locomotion in a yield stress fluid
• Dynamics of microswimmers near a liquid-liquid interface with viscosity difference
• Geometric phase methods with Stokes theorem for a general viscous swimmer
• Viscous tweezers: controlling particle orientation with viscosity