CiteULike: Author Bibette

From shear thickening to shear-induced jamming

Emanuel Bertrand — 2008-05-13T14:34:43-00:00

Physical Review E, Vol. 66, No. 6. (11 December 2002), 060401.

Measuring the Kinetics of Biomolecular Recognition with Magnetic Colloids

Cohen Tannoudji — 2008-05-07T23:01:32-00:00

Physical Review Letters, Vol. 100, No. 10. (2008)

We introduce a general methodology based on magnetic colloids to study the recognition kinetics of tethered biomolecules. Access to the full kinetics of the reaction is provided by an explicit measure of the time evolution of the reactant densities. Binding between a single ligand and its complementary receptor is here limited by the colloidal rotational diffusion. It occurs within a binding distance that can be extracted by a reaction-diffusion theory that properly accounts for the rotational Brownian dynamics. Our reaction geometry allows us to probe a large diversity of bioadhesive molecules and tethers, thus providing a quantitative guidance for designing more efficient reactive biomimetic surfaces, as required for diagnostic, therapeutic, and tissue engineering techniques.

Stability criteria for emulsions

J Bibette — 2008-04-28T16:23:12-00:00

Physical Review Letters, Vol. 69, No. 16. (19 October 1992), 2439.

Yielding and Flow of Monodisperse Emulsions

TG Mason — 2008-04-28T16:14:56-00:00

Journal of Colloid and Interface Science, Vol. 179, No. 2. (10 May 1996), pp. 439-448.

We have measured the yield transition of monodisperse emulsions as the volume fraction, [phi], and droplet radius,a, are varied. We study the crossover from the perturbative shear regime, which reflects the linear viscoelastic properties, to the steady shear regime, which reflects nonlinear, plastic flow. For small oscillatory strains of peak amplitude [gamma], the peak stress, [tau], is linearly proportional to [gamma]. As the strain is increased, the stress becomes nonlinear in [gamma] at the yield strain, [gamma]y. The [phi] dependence of [gamma]yis independent ofaand exhibits a minimum near the critical volume fraction, [phi]c[approximate] 0.635, associated with the random close packing of monodisperse spheres. We show that the yield stress, [tau]y, increases dramatically as the volume fraction increases above [phi]c; [tau]yalso scales with the Laplace pressure, [sigma]/a, where [sigma] is the interfacial tension. For comparison, we also determine the steady shear stress over a wide range of strain rates, [gamma]. Below [phi] [approximate] 0.70, the flow is homogeneous throughout the sample, while for higher [phi], the emulsion fractures resulting in highly inhomogeneous flow along the fracture plane. Above [phi] [approximate] 0.58, the steady shear stress exhibits a low strain rate plateau which corresponds with the yield stress measured with the oscillatory technique. Moreover, [tau]yexhibits a robust power law dependence on [gamma] with exponents decreasing with [phi], varying from to . Below [phi] [approximate] 0.58, associated with the colloidal glass transition, the plateau stress disappears entirely, suggesting that the equilibrium glassy dynamics are important in identifying the onset of the yield behavior.

Shear Rupturing of Droplets in Complex Fluids

TG Mason — 2008-04-27T00:19:24-00:00

Langmuir, Vol. 13, No. 17. (20 August 1997), pp. 4600-4613.

Abstract: We have experimentally studied the shear-induced rupturing of viscous droplets in viscoelastic complex fluids. Remarkably, a premixed emulsion of large, polydisperse droplets can be ruptured into monodisperse emulsions of uniform colloidal droplets. The monodispersity becomes most pronounced when the premixed emulsion is viscoelastic and has a shear-thinning viscosity. Since viscoelastic materials may fracture, we reduce the gap of our shear cell to ensure a spatially uniform strain rate for rupturing. We observe monodispersity whether the viscoelasticity arises from the suspending fluid (e.g., concentrated surfactant solution) or droplet deformation as in compressed emulsions. Our observations suggest that the monodispersity results from droplet rupturing alone and that the capillary instability is inhibited by the partial elasticity of the complex fluid. We use the monodispersity to study how the droplet size depends upon the shear rate and composition.

Elasticity of Compressed Emulsions

TG Mason — 2008-04-26T23:57:13-00:00

Physical Review Letters, Vol. 75, No. 10. (1995), 2051.

Irreversible Shear-Activated Aggregation in Non-Brownian Suspensions

J Guery — 2008-04-23T18:01:46-00:00

Physical Review Letters, Vol. 96, No. 19. (2006)

We have studied the effect of shear on the stability of suspensions made of non-Brownian solid particles. We demonstrate the existence of an irreversible transition where the solid particles aggregate at remarkably low volume fractions (0.1). This shear-induced aggregation is dramatic and exhibits a very sudden change in the viscosity, which increases sharply after a shear-dependent induction time. We show that this induction time is related exponentially to the shear rate, reflecting the importance of the hydrodynamic forces in reducing the repulsive energy barrier that prevents the particles from aggregating.

Microscopic artificial swimmers

Rémi Dreyfus — 2005-10-05T22:35:21-00:00

Nature, Vol. 437, No. 7060., pp. 862-865.

Osmotic pressure and viscoelastic shear moduli of concentrated emulsions

TG Mason — 2007-09-29T02:16:47-00:00

Physical Review E, Vol. 56, No. 3. (1997), 3150.

We present an experimental study of the frequency ω dependence and volume fraction φ dependence of the complex shear modulus G * (ω;φ) of monodisperse emulsions which have been concentrated by an osmotic pressure Π. At a given φ; the elastic storage modulus G ′ (ω)=Re[ G * (ω)] exhibits a low-frequency plateau G p ′ ; dominating the dissipative loss modulus G ′′ (ω)=Im[ G * (ω)] which exhibits a minimum. Above a critical packing fraction φ c ; we find that both Π(φ) and G p ′ (φ) increase quasilinearly; scaling as (φ-φ c ) μ ; where φ c ≈φ c rcp ; the volume fraction of a random close packing of spheres; and μ is an exponent close to unity. To explain this result; we develop a model of disordered droplets which interact through an effective repulsive anharmonic potential; based on results obtained for a compressed droplet. A simulation based on this model yields a calculated static shear modulus G and osmotic pressure Π that are in excellent agreement with the experimental values of G p ′ and Π.

Rotational diffusion in a chain of particles

Holger Stark — 2007-06-30T22:43:10-00:00

Journal of Physics: Condensed Matter, Vol. 17, No. 45. (2005), pp. S3631-S3637.

We study the coupled rotational diffusion in a two-particle chain on the basis of a Smoluchowski equation and calculate time correlation functions that are measurable in an experiment. This approach might be used to explore hydrodynamic interactions in the limit where lubrication theory is valid.

Preparation of Doublet, Triangular, and Tetrahedral Colloidal Clusters by Controlled Emulsification

D Zerrouki — 2007-06-14T03:52:26-00:00

Langmuir, Vol. 22, No. 1. (3 January 2006), pp. 57-62.

Abstract: We describe a six-step method for making colloidal clusters of 2, 3, or 4 silica particles with a radius of 1.2 m. This method, originally described by Manoharan et al. (Manoharan, V. N.; Elsesser, M. T.; Pine, D. J. Science 2003, 301, 483), is based on the encapsulation of silica spheres in emulsion droplets. The originality of our work lies in the preparation of monodisperse emulsions, which allows us to obtain some high yields of small aggregates over a wide range of conditions. Using optical microscopy and disk centrifugation, we show that the relative fractions of 2, 3, and 4 particle aggregates are controlled by the emulsification conditions, particularly the concentration of silica in the dispersed phase. Our best yields are obtained using low to moderate shear rates, a highly viscous continuous phase, and intermediate amounts of silica. The sedimentation of the colloidal solution into a gradient of concentration leads to aqueous suspensions of identical clusters. Since the overall process can easily be scaled up, large quantities of identical clusters may be prepared, which should allow the thermodynamic properties of these new colloidal objects to be measured for the first time. These nonspherical particles could serve as building blocks for more complex assemblies, such as colloidal crystals which could find applications as photonic materials.