Squirming through shear-thinning fluids

Abstract

Many microorganisms find themselves immersed in fluids displaying non-Newtonian rheological properties such as viscoelasticity and shear-thinning viscosity. The effects of viscoelasticity on swimming at low Reynolds numbers have already received considerable attention, but much less is known about swimming in shear-thinning fluids. A general understanding of the fundamental question of how shear-thinning rheology influences swimming still remains elusive. To probe this question further, we study a spherical squirmer in a shear-thinning fluid using a combination of asymptotic analysis and numerical simulations. Shear-thinning rheology is found to affect a squirming swimmer in nontrivial and surprising ways; we predict and show instances of both faster and slower swimming depending on the surface actuation of the squirmer. We also illustrate that while a drag and thrust decomposition can provide insights into swimming in Newtonian fluids, extending this intuition to problems in complex media can prove problematic.

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• Force moments of an active particle in a complex fluid
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• Higher-order force moments of active particles
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• Non-Newtonian effects on the slip and mobility of a self-propelling active particle
• Steering a thermally activated micromotor with a nearby isothermal wall
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• Self-diffusiophoretic propulsion of a spheroidal particle in a shear-thinning fluid
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• Self-sustained patchy turbulence in shear-thinning active fluids
• Vortex pattern stabilization in thin films resulting from shear thickening of active suspensions
• Micro-swimmer collective dynamics in Brinkman flows
• Pressure drop reduction due to coupling between shear-thinning fluid flow and a weakly deformable channel wall: A reciprocal theorem approach
• Micro-swimmer locomotion and hydrodynamics in Brinkman Flows
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