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Université de Fribourg

Linear and nonlinear rheology of dense emulsions across the glass and the jamming regimes

Scheffold, Frank ; Cardinaux, Frédéric ; Mason, Thomas G.

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...

Université de Fribourg

Elasticity and glassy dynamics of dense emulsions

Cardinaux, Frédéric ; Mason, Thomas G. ; Scheffold, Frank

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...

Université de Fribourg

Direct laser writing of three-dimensional network structures as templates for disordered photonic materials

Haberko, Jakub ; Muller, Nicolas ; Scheffold, Frank

In: Physical Review A, 2014, vol. 88, no. 4, p. 043822

In the present article we substantially expand on our recent study about the fabrication of mesoscale polymeric templates of disordered photonic network materials [Haberko and Scheffold, Opt. Expr. 21, 1057 (2013)]. We present a detailed analysis and discussion of important technical aspects related to the fabrication and characterization of these fascinating materials. Compared to our initial...

Université de Fribourg

Silicon hyperuniform disordered photonic materials with a pronounced gap in the shortwave infrared

Muller, Nicolas ; Haberko, Jakub ; Marichy, Catherine ; Scheffold, Frank

In: Advanced Optical Materials, 2014, vol. 2, no. 2, p. 115-119

The mesoscale fabrication of silicon hyperuniform disordered materials with a broad and pronounced photonic gap in the shortwave infrared is reported. Due to their unique structure and their high refractive index, these fascinating materials are predicted to possess a complete photonic bandgap in the absence of any long-range order.

Université de Fribourg

Effect of a marginal inclination on pattern formation in a binary liquid mixture under thermal stress

Croccolo, Fabrizio ; Scheffold, Frank ; Vailati, Alberto

In: Physical Review Letters, 2013, vol. 111, no. 1, p. 014502

Convective motions in a fluid layer are affected by its orientation with respect to the gravitational field. We investigate the long-term stability of a thermally stressed layer of a binary liquid mixture and show that pattern formation is strongly affected by marginal inclinations as small as a few milliradians. At small Rayleigh numbers, the mass transfer is dominated by the induced large scale...

Université de Fribourg

A general method to label metal oxide particles with fluorescent dyes using aryldiazonium salts

Dechézelles, Jean-François ; Griffete, Nébéwia ; Dietsch, Hervé ; Scheffold, Frank

In: Particle & Particle Systems Characterization, 2013, vol. 30, no. 7, p. 579-583

Different metal oxide particles are dye labeled by a novel and versatile approach based on aryldiazonium salt chemistry. For dye labeling the particles, the simplicity of aryldiazonium salts to be grafted onto metallic or metal oxide surface is advantageous. The salt is used as a linking agent for attaching the fluorescent molecules.

Université de Fribourg

Mass transport properties of the tetrahydronaphthalene/n-dodecane mixture measured by investigating non-equilibrium fluctuations

Croccolo, Fabrizio ; Scheffold, Frank ; Bataller, Henri

In: Comptes Rendus Mécanique, 2013, vol. 341, no. 4–5, p. 378–385

We present preliminary near-field light scattering (NFS) data concerning the analysis of the static power spectrum and of the relaxation time constant as a function of the wave vector for non-equilibrium fluctuations (NEFs). The goal of these measurements is to obtain information about the Soret and the mass diffusion coefficients of a binary mixture undergoing thermodiffusion. In particular, we...

Université de Fribourg

A light scattering study of non equilibrium fluctuations in liquid mixtures to measure the Soret and mass diffusion coefficient

Croccolo, Fabrizio ; Bataller, Henri ; Scheffold, Frank

In: Journal of Chemical Physics, 2012, vol. 137, no. 23, p. 234202

We use dynamic near field scattering to measure the dynamics of concentration non equilibrium fluctuations at the steady-state of Soret separation. The analysis reveals that above a threshold wave vector qc, the dynamics is governed by diffusion while at smaller wave vectors, gravity dominates. From the measurements, we extract both the mass diffusion and the Soret...

Université de Fribourg

Quasi-real-time analysis of dynamic near field scattering data using a graphics processing unit

Cerchiari, Giovanni ; Croccolo, Fabrizio ; Cardinaux, Frédéric ; Scheffold, Frank

In: Review of Scientific Instruments, 2012, vol. 83, no. 10, p. 106101

We present an implementation of the analysis of dynamic near field scattering (NFS) data using a graphics processing unit. We introduce an optimized data management scheme thereby limiting the number of operations required. Overall, we reduce the processing time from hours to minutes, for typical experimental conditions. Previously the limiting step in such experiments, the processing time is now...

Université de Fribourg

Rapid high resolution imaging of diffusive properties in turbid media

Scheffold, Frank ; Block, Ian D.

In: Optics Express, 2012, vol. 20, no. 1, p. 192-200

We propose a laser speckle based scheme that allows the analysis of local scattering properties of light diffusely reflected from turbid media. This turbid medium can be a soft material such as a colloidal or polymeric material but can also be biological tissue. The method provides a 2D map of the scattering properties of a complex, multiple scattering medium by recording a single image. We...