Effect of weak attractive interactions on flow behavior of highly concentrated crystalline suspensions

Abstract

SynopsisWeak attractive interactions lead to a substantial broadening of the fluid-crystalline coexistence region of crystalline, colloidal hard-sphere dispersions. Here, we demonstrate that a weak depletion attraction introduced by nonadsorbing polymer added to the continuous phase results in a strong decrease of the low shear viscosity even at particle concentrations up to U ¼ 0.65 analogous to the re-entry phenomenon in highly concentrated glassy systems. This promotes flow in macroscopic channels but the scenario changes in confined, microfluidic geometries. Pure crystalline suspensions exhibit flow induced melting in the region of highest shear rates close to the wall, and this promotes flow through microchannels (<100 lm). In contrast, weak attractive interactions fortify preferential crystallization at the channel walls finally resulting in channel clogging and cessation of flow. This wall crystallization phenomenon particularly impairs viscosity determination from classical parallel plate rotational rheometry if the gap width is set too low. These findings may find application in the important biotechnological field of protein preparation and crystallization.

Microstructure, local dynamics, and flow behavior of colloidal suspensions with weak attractive interactions

“…A substantial reduction in viscosity was observed for ϕ polymer = 3 g/l whereas η drastically increased at ϕ polymer = 10 g/l compared to the pure suspension. Similar results with a pronounced minimum in low shear viscosity as a function of polymer concentration were found for other particle loadings and were also reported previously for a similar colloidal suspension, but at different ϕ, ϕ polymer , and M w 43 .…”

Effect of Nanoparticles on the Bulk Shear Viscosity of a Lung Surfactant Fluid

“…Recent studies have found that for dense suspensions stabilized by short range repulsion (as it is the case for Curosurf® vesicles), the addition of weak attractive interaction leads to a decrease in viscosity. [59][60][61][62] In these reports, the colloids are beads and microgels and the attraction is due to depleting non-adsorbing polymers. 59,61,62 It was found that a minute amount of depleting agents leads to the formation of large cohesive aggregates and thereby to a decrease of the effective volume fraction.…”

“…[59][60][61][62] In these reports, the colloids are beads and microgels and the attraction is due to depleting non-adsorbing polymers. 59,61,62 It was found that a minute amount of depleting agents leads to the formation of large cohesive aggregates and thereby to a decrease of the effective volume fraction. As a result, the suspension bulk viscosity decreases, in proportions similar to those of Fig.…”

The dark side of microrheology: Non-optical techniques

“…A number of recent studies have used the above mentioned adaptations and gap error corrections of parallel-plate setups with micrometer gap separations with a focus on studying fluids a high shear rates [23,24,46,60,75], and on confinement effects [23,24,46,89,95]. In addition, these setups have been used to study small sample volumes [60], and to mimic usage or processing environment conditions [23,46,89].…”