Rheology of Soft Materials

Abstract

Research on soft materials, including colloidal suspensions, glasses, pastes, emulsions, foams, polymer networks, liquid crystals, granular materials, and cells, has captured the interest of scientists and engineers in fields ranging from physics and chemical engineering to materials science and cell biology. Recent advances in rheological methods to probe mechanical responses of these complex media have been instrumental for producing new understanding of soft matter and for generating novel technological applications. This review surveys these technical developments and current work in the field, with partial aim to illustrate open questions for future research.

Graphene oxide dispersions: tuning rheology to enable fabrication

“…In our system, jamming resulted in the development of a finite yield stress 12 at concentrations approximately three orders of magnitude lower than the theoretical value for spherical colloidal suspensions ( ℎ ≈ 2.2×10 -4 vs. ≈ 0.5). 10 Jamming at such low concentrations is due to the extremely large aspect ratio of ultra large wrinkled GO sheets used in this study (Fig. S1).…”

“…9 Probing and quantifying this dynamic behaviour will be instrumental in generating novel applications, such as coatings, fillers and molecular electronics by advancing our fundamental knowledge of soft materials. 10 Despite the importance for fundamental, practical, and industrial applications, the rheological behaviour of GO monolayer dispersions and its origin remains an unexplored area. This, in turn, hinders the development of fabrication protocols for two dimensional soft materials, including GO dispersions.…”

“…Over all time-scales, in the low concentration region (<0.25 mg ml -1 ), the dispersions exhibited a liquid-like response with G'' being slightly higher than G' suggesting a viscoelastic liquid like behaviour similar to colloidal suspensions near their crystallization point at volume fractions ~ 0.5. 10 The dominance of G'' along with a large G'…”

“…The rheological behaviour of GO dispersions at concentrations as high as 2.5 mg ml -1 resembles that of soft glassy materials (SGMs), liquid crystals, and/or weak gels. 10,20 This rheological behaviour suggests that the processing of GO dispersions is possible with established fabrication techniques usually reserved for processing weak gel-like materials (such as the wet-spinning approach). 1,[21][22][23][24] However, in contrast to cross-linked biopolymers 10 and biological gels 13 no strain stiffening is observed (Fig.…”

Asymmetry between pushing and pulling for crawling cells

“…Membrane and cortex elasticity can be modeled in a prototypical setting as a mean field elastic feedback provided by elastic springs linking different parts of the cell [23,24]. Visco-elastic properties of cytoskeleton strongly depend on the characteristic time of the problem [49][50][51] and the corresponding corrections to the active gel model in the bulk of the cell are usually incorporated either in the framework of a short time (Maxwell) elastic model [28,30,[52][53][54] or a long time (Kelvin-Voigt) elastic model [31,55,56].…”