Wall slip across the jamming transition of soft thermoresponsive particles

Abstract

Flows of suspensions are often affected by wall slip, that is the fluid velocity v f in the vicinity of a boundary differs from the wall velocity vw due to the presence of a lubrication layer. While the slip velocity vs = |v f − vw| robustly scales linearly with the stress σ at the wall in dilute suspensions, there is no consensus regarding denser suspensions that are sheared in the bulk, for which slip velocities have been reported to scale as a vs ∝ σ p with exponents p inconsistently ranging between 0 and 2. Here we focus on a suspension of soft thermoresponsive particles and show that vs actually scales as a power law of the viscous stress σ − σc, where σc denotes the yield stress of the bulk material. By tuning the temperature across the jamming transition, we further demonstrate that this scaling holds true over a large range of packing fractions φ on both sides of the jamming point and that the exponent p increases continuously with φ, from p = 1 in the case of dilute suspensions to p = 2 for jammed assemblies. These results allow us to successfully revisit inconsistent data from the literature and paves the way for a continuous description of wall slip above and below jamming.

Normal stress measurement in foams and emulsions in the presence of slip

“…Divoux et al [47] plotted slip velocity data versus the difference τ -τ y for a thermoresponsive microgel suspension and an emulsion, where τ is the shear stress and τ y is the yield stress, and they found power-law behavior with slopes between 1 and 2. Our data are plotted in this manner in Fig.…”

Particle–wall tribology of slippery hydrogel particle suspensions

“…29 Slip in concentrated soft particle suspensions, such as colloidal pastes or emulsions, has attracted a lot of attention in the recent years. [33][34][35][36][37][38][39][40][41][42] These materials have a close-packed amorphous structure and flow past one another appreciably only when a large enough stress is applied, greater than the so-called yield stress. For steady shear flows, Meeker et al proposed a model where the particle deformation is coupled to the flow through the pressure field so that the flat contacts existing between the particles and the bounding surfaces are deformed asymmetrically.…”

Physical aging and structural recovery in a colloidal glass subjected to volume-fraction jump conditions

“…Finally, we comment on the possibility of wall slip in our creep experiments, which is a recognized problem in the measurement of flow in colloidal dispersions [48][49][50]. Here, we remark that there the results are consistent with slip being very small for several reasons.…”