In: Proceedings of the National Academy of Sciences, 2019, vol. 116, no. 16, p. 7766–7771
Motivated by improvements in diffusing wave spectroscopy (DWS) for nonergodic, highly optically scattering soft matter and by cursory treatment of collective scattering effects in prior DWS microrheology experiments, we investigate the lowfrequency plateau elastic shear moduli G′p of concentrated, monodisperse, disordered oilin water emulsions as droplets jam. In such experiments, the...

In: Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2018, vol. 546, p. 360–365
We study the Brownian thermal motion of a colloidal model system made by emulsifying hot liquid αeicosene wax into an aqueous surfactant solution of sodium dodecyl sulfate (SDS). When this waxy oilinwater emulsion is cooled below α eicosene's melting point of Tc ≃ 25 °C, the microscale emulsion droplets solidify, effectively yielding a dispersed particulate system. So, the...

In: Scientific Reports, 2017, vol. 7, no. 1, p. 13879
In quenched disordered outofequilibrium manybody colloidal systems, there are important distinctions between the glass transition, which is related to the onset of nonergodicity and loss of lowfrequency relaxations caused by crowding, and the jamming transition, which is related to the dramatic increase in elasticity of the system caused by the deformation of constituent objects. For...

In: Rheologica Acta, 2016, vol. 55, no. 8, p. 683–697
We develop a free energy model that describes two key thermodynamic properties, the osmotic pressure Π and the linear elastic shear modulus G′p (i.e. plateau storage modulus), of concentrated monodisperse emulsions which have isotropic, disordered, droplet structures, and are stabilized using ionic surfactants. This model effectively incorporates the concept of random close packing or...

In: Physical Review E, 2015, vol. 91, no. 3, p. 032302
We model the packing structure of a marginally jammed bulk ensemble of polydisperse spheres. To this end we expand on the granocentric model [Clusel et al., Nature (London) 460, 611 (2009)], explicitly taking into account rattlers. This leads to a relationship between the characteristic parameters of the packing, such as the mean number of neighbors and the fraction of rattlers, and the radial...

In: Soft Matter, 2014, vol. 10, no. 28, p. 5040–5044
Oilinwater emulsions composed of colloidalscale droplets are often stabilized using ionic surfactants that provide a repulsive interaction between neighboring droplet interfaces, thereby inhibiting coalescence. If the droplet volume fraction is raised rapidly by applying an osmotic pressure, the droplets remain disordered, undergo an ergodic–nonergodic transition, and jam. If the applied...

In: Soft Matter, 2014, vol. 10, no. 36, p. 7109–7116
We develop a simple predictive model of the osmotic pressure Π and linear shear elastic modulus G′p of uniform disordered emulsions that includes energetic contributions from entropy and interfacial deformation. This model yields a smooth crossover between an entropically dominated G′p ∼...

In: Journal of Physics: Condensed Matter, 2013, vol. 25, no. 50, p. 502101
We discuss the linear and nonlinear rheology of concentrated microscale emulsions, amorphous disordered solids composed of repulsive and deformable soft colloidal spheres. Based on recent results from simulation and theory, we derive quantitative predictions for the dependences of the elastic shear modulus and the yield stress on the droplet volume fraction. The remarkable agreement with...

In: AIP Conference Proceedings, 2013, vol. 1518, p. 222–226
We present a rheology and light scattering study of the dynamical properties of dense emulsions at volume fractions ranging from viscous liquid to deeply jammed states. From temporally and spatially revolved dynamic light scattering we obtain detailed information about the internal dynamics. Our measurements thus allow a direct study of heterogeneous nature of the relaxation processes involved in...

In: Soft Matter, 2013, vol. 9, no. 32, p. 7843–7854
We present a study of the elastic alignment, accompanying director field distortions, and elastic pair interactions of starshaped colloids suspended in aligned nematic liquid crystals. We design and fabricate lithographic colloids, “Nstars”, containing N rodlike protrusions (i.e. “rays” or “arms”) each having a constant angle between adjacent rays. Nstar geometries contain concave...
