Life and death of colloidal bonds control the rate-dependent rheology of gels

Abstract

Colloidal gels exhibit rich rheological responses under flowing conditions. A clear understanding of the coupling between the kinetics of the formation/rupture of colloidal bonds and the rheological response of attractive gels is lacking. In particular, for gels under different flow regimes, the correlation between the complex rheological response, the bond kinetics, microscopic forces, and an overall micromechanistic view is missing in previous works. Here, we report the bond dynamics in short-range attractive particles, microscopically measured stresses on individual particles and the spatiotemporal evolution of the colloidal structures in different flow regimes. The interplay between interparticle attraction and hydrodynamic stresses is found to be the key to unraveling the physical underpinnings of colloidal gel rheology. Attractive stresses, mostly originating from older bonds dominate the response at low Mason number (the ratio of shearing to attractive forces) while hydrodynamic stresses tend to control the rheology at higher Mason numbers, mostly arising from short-lived bonds. Finally, we present visual mapping of particle bond numbers, their life times and their borne stresses under different flow regimes.

Designing Stress-Adaptive Dense Suspensions Using Dynamic Covalent Chemistry

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A simple method to reprogram the binding specificity of DNA-coated colloids that crystallize

“…We think that our method will help quickly produce a wide variety of different DNA-coated colloids from a single feed-stock and optimize their designs so applications and experiments requiring many different DNA-coated colloids come within reach. Our method may also help expand the use of DNA-coated particles beyond crystallization and self-assembly to sub-fields of colloid science such as gelation and rheology [44,45,46].…”

The behavior of capillary suspensions at diverse length scales: From single capillary bridges to bulk

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