Structure of capillary suspensions and their versatile applications in the creation of smart materials

Abstract

In this article, we review recent research in the field of capillary suspensions and highlight a variety of applications in the field of smart materials. Capillary suspensions are liquid-liquid-solid ternary systems where one liquid is only present in a few percent and induces a strong, capillary-induced particle network. These suspensions have a large potential for exploitation, particularly in the production of porous materials since the paste itself and the properties of the final material can be adapted. We also discuss the rheological properties of the suspension and network structure to highlight the various ways these systems can be tuned.

Yield Stress Enhancement of a Ternary Colloidal Suspension via the Addition of Minute Amounts of Sodium Alginate to the Interparticle Capillary Bridges

“…We note that the average pore diameter was relatively small given the particle geometry (basal diameter of ∼4 μm and plate thickness of ∼1 μm), and the porosity was ∼50% despite the particle volume percent of 25%, which indicate that significant shrinkage or structural collapse occurred during the sintering process. 2,46 Thus, the measured porosities reflect not only the presence of open pores as a result of interparticle bridging but also that of closed pores caused by local structural disruption. Despite the possible occurrence of structural disruption, it was determined that both the average pore diameter and porosity increased systematically as the SA content in the precursor increased.…”

“…The capillary-force-driven gelation of the suspension is, in principle, possible for both states, and that was demonstrated for a number of {B, S, P} combinations. 2 To date, various factors that affect the rheological properties of capillary suspensions have been investigated, 15−17 including the chemical identities of the B, S, and P phases, θ SB values for the given {B, S, P} combinations, volume fractions of all phases, and mixing conditions. Another factor that could affect the rheology of suspensions is the presence of additives, such as surfactants 16 or polymers, and this has been relatively less studied for capillary suspensions.…”

“…Capillary suspensions are three-phase colloidal systems comprising solid particles (P) and two immiscible liquids. − One of the two liquid phases is the bulk continuous medium (B) where the particles are primarily dispersed, and the other, often termed the secondary phase (S), consists of a small amount of bridging phase that interconnects the particles via strong capillary forces, which are known to be dominant over other surface forces, such as van der Waals, electrostatic, or steric forces . The addition of a small amount of secondary phase, typically a few vol % or less than 1 vol %, to a suspension of particles dispersed in a bulk phase could lead to the formation of a sample-spanning particle network via capillary forces even at much lower particle loadings than those of typical pastes.…”

Connecting particle clustering and rheology in attractive particle networks

“…23 This type of suspensions offers a wide domain of possible applications for the creation of smart materials. [24][25][26][27] Recent investigations on capillary suspensions have shown a broad range of options to tune the mechanical and rheological properties through changes in their composition, 28 which are directly related to changes in their microstructure. 22,29,30 Capillary suspensions show, in general, a gel-like behaviour with the storage modulus G 0 larger than the loss modulus G 00 and frequency independent behaviour inside of the linear viscoelastic region.…”

Connecting particle clustering and rheology in attractive particle networks

“…This type of suspensions offers a wide domain of possible applications for the creation of smart materials. [19,11,3,34] Recent investigations on capillary suspensions have shown a broad range of options to tune the mechanical and rheological properties through changes in their composition, [26] which are directly related to changes in their microstructure. [5,14,44] Capillary suspensions show, in general, a gel-like behaviour with the storage modulus G larger than the loss modulus G and frequency independent behaviour inside of the linear viscoelastic region.…”