Nonlinear Mechanics of Colloidal Gels: Creep, Fatigue, and Shear-Induced Yielding

Abstract

• Colloids-Refers to entities, such as particles or polymers, smaller than a few microns in size and sensitive to thermal agitation. Colloids therefore display Brownian motion when dispersed at low volume fraction in a solvent. They encompass a broad range of entities from proteins and clay particles to synthetic polymeric particles and come in all sorts of geometrical shapes, such as spheres, platelets and rods. Colloids are also subject to a wide variety of interactions, which gives rise to rich state diagrams including fluid and crystalline equilibrium phases as well as out-of-equilibrium states such as gels and glasses. • Colloidal gels-Refers to soft solids, whose structure is composed of attractive colloids that form a spacespanning network. Colloidal gels are in an out-of-equilibrium state and display mainly solid-like properties at rest and under mild deformations, i.e. their elastic modulus is much larger than their viscous modulus in the linear regime. Upon increasing external mechanical constraints, their viscoelastic response becomes nonlinear and generally involves a yield point above which colloidal gels show liquid-like properties (see "Yielding" below). • Creep-Refers to the motion induced by imposing a constant load to a material, whose response is quantified by the resulting deformation or strain. • Fatigue-Refers to the phenomena induced by imposing an oscillatory load of constant amplitude to a material, whose response is quantified via the temporal evolution of its viscoelastic properties. • Yielding-Refers to a solid-to-liquid transition induced by imposing some deformation or stress to a material. The yield stress and yield strain are respectively the critical stress and strain above which a complex material starts to flow or loses its integrity. The yielding transition often involves a complex spatio-temporal scenario, which is still the topic of intense research effort.

Release of Tretinoin Solubilized in Microemulsion from Carbopol and Xanthan Gel: In Vitro versus Ex Vivo Permeation Study

“…Depending on the type of polymer and its interconnecting structures, respectively, different gel structures are formed that can react to mechanical stress differently. Generally, two types of gels are distinguished: (a) reversible, the structure of which is restored after the mechanical action has subsided; and (b) irreversible, which has an irreversibly broken structure due to the mechanical stress [ 30 ].…”

Growth and stability of bubbles in a yield stress fluid

“…Recent rheological studies (Perge et al. 2014; Gibaud, Divoux & Manneville 2020) revealed similar behaviour for gels when subjected to cyclic deformation or stress. Perge et al.…”

Light-Controlled Aggregation and Gelation of Viologen-Based Coordination Polymers

“…The associated ⟨Δ r 2 ⟩ shows a diffusion process at short time scales and then a plateau at long time scales, Figure b. This behavior is typical of viscoelastic solids, , Figure d. At high frequencies f , just like the viscoelastic fluid, G ″ > G ′, the sample dissipate energy due to the thermal vibrations of the network against the background solvent, but at intermediate and small frequencies f , G ′ dominates G ″ and G ′ plateaus to G ′ ≃ 0.3 Pa: the sample cannot rearrange on long time scales and is as such an elastic solid.…”