Thinning and thickening in active microrheology

Abstract

When pulling a probe particle in a many-particle system with fixed velocity, the probe's effective friction, defined as average pulling force over its velocity, ${\gamma }_{eff}:=⟨F_{ex}⟩/u$, first keeps constant (linear response), then decreases (thinning) and finally increases (thickening). We propose a three-time-scales picture (TTSP) to unify thinning and thickening behaviour. The points of the TTSP are that there are three distinct time scales of bath particles: diffusion, damping, and single probe-bath (P-B) collision; the dominating time scales, which are controlled by the pulling velocity, determine the behaviour of the probe's friction. We confirm the TTSP by Langevin dynamics simulation. Microscopically, we find that for computing the effective friction, Maxwellian distribution of bath particles' velocities works in low Reynolds number (Re) but fails in high Re. It can be understood based on the microscopic mechanism of thickening obtained in the $T=0$ limit. Based on the TTSP, we explain different thinning and thickening observations in some earlier literature.

References in corpus (5)

• Fluctuation-Dissipation: Response Theory in Statistical Physics
• A unified description of the rheology of hard-particle suspensions
• Active and Nonlinear Microrheology in Dense Colloidal Suspensions
• Probing linear and nonlinear microrheology of viscoelastic fluids
• Thinning or thickening? Multiple rheological regimes in dense suspensions of soft particles

Cited by in corpus (8)

• Nonlinear response and emerging nonequilibrium micro-structures for biased diffusion in confined crowding environments
• Time-Dependent Fluctuations and Superdiffusivity in the Driven Lattice Lorentz Gas
• Unified rheology of vibro-fluidized dry granular media: From slow dense flows to fast gas-like regimes
• Force renormalization for probes immersed in an active bath
• Dynamics and friction of a large colloidal particle in a bath of hard spheres: Langevin dynamics simulations and hydrodynamic description
• Time-dependent active microrheology in dilute colloidal suspensions
• Time-dependent perpendicular fluctuations in the driven lattice Lorentz gas
• Discontinuous Thinning in Active Microrheology of Soft Complex Matter