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Université de Fribourg

Tunable 2D binary colloidal alloys for soft nanotemplating

Fernández-Rodríguez, Miguel Ángel ; Elnathan, Roey ; Ditcovski, Ran ; Grillo, Fabio ; Conley, Gaurasundar Marc ; Timpu, Flavia ; Rauh, Astrid ; Geisel, Karen ; Ellenbogen, Tal ; Grange, Rachel ; Scheffold, Frank ; Karg, Matthias ; Richtering, Walter ; Voelcker, Nicolas H. ; Isa, Lucio

In: Nanoscale, 2018, vol. 10, no. 47, p. 22189–22195

The realization of non-close-packed nanoscale patterns with multiple feature sizes and length scales via colloidal self-assembly is a highly challenging task. We demonstrate here the creation of a variety of tunable particle arrays by harnessing the sequential self-assembly and deposition of two differently sized microgel particles at the fluid–fluid interface. The two-step process is...

Université de Fribourg

Nonequilibrium solid-solid phase transition in a lattice of liquid jets

Croccolo, Fabrizio ; Castellini, Stefano ; Scheffold, Frank ; Vailati, Alberto

In: Physical Review E, 2018, vol. 98, no. 6, p. 063104

Solid-solid phase transitions are commonly encountered at the atomic scale in alloys and in superatomic mesoscopic systems of colloidal particles. Here we investigate a solid-solid phase transition occurring at the macroscopic scale between lattices of liquid jets with different symmetries generated by convection in a horizontal layer of a binary liquid mixture. In the absence of a shear...

Université de Fribourg

Brownian dynamics of colloidal microspheres with tunable elastic properties from soft to hard

Yoon, Jiwon ; Cardinaux, Frédéric ; Lapointe, Clayton ; Zhang, Chi ; Mason, Thomas G. ; Ahn, Kyung Hyun ; Scheffold, Frank

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 α-eicosene wax into an aqueous surfactant solution of sodium dodecyl sulfate (SDS). When this waxy oil-in-water 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...

Université de Fribourg

Jamming and overpacking fuzzy microgels: Deformation, interpenetration, and compression

Conley, Gaurasundar M. ; Aebischer, Philippe ; Nöjd, Sofi ; Schurtenberger, Peter ; Scheffold, Frank

In: Science Advances, 2017, vol. 3, no. 10, p. e1700969

Tuning the solubility of fuzzy polymer microgels by external triggers, such as temperature or pH, provides a unique mechanism for controlling the porosity and size of colloidal particles on the nanoscale. As a consequence, these smart microgel particles are being considered for applications ranging from viscosity modifiers and sensing to drug delivery and as models for the glass and the...

Université de Fribourg

The liquid-glass-jamming transition in disordered ionic nanoemulsions

Braibanti, Marco ; Kim, Ha Seong ; ªenbil, Nesrin ; Pagenkopp, Matthew J. ; Mason, Thomas G. ; Scheffold, Frank

In: Scientific Reports, 2017, vol. 7, no. 1, p. 13879

In quenched disordered out-of-equilibrium many-body colloidal systems, there are important distinctions between the glass transition, which is related to the onset of nonergodicity and loss of low-frequency 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...

Université de Fribourg

Improved diffusing wave spectroscopy based on the automatized determination of the optical transport and absorption mean free path

Zhang, Chi ; Reufer, Mathias ; Gaudino, Danila ; Scheffold, Frank

In: Korea-Australia Rheology Journal, 2017, vol. 29, no. 4, p. 241–247

Diffusing wave spectroscopy (DWS) can be employed as an optical rheology tool with numerous applications for studying the structure, dynamics and linear viscoelastic properties of complex fluids, foams, glasses and gels. To carry out DWS measurements, one first needs to quantify the static optical properties of the sample under investigation, i.e. the transport mean free path l* and the...

Université de Fribourg

Band gap formation and Anderson localization in disordered photonic materials with structural correlations

Froufe-Pérez, Luis S. ; Engel, Michael ; Sáenz, Juan José ; Scheffold, Frank

In: Proceedings of the National Academy of Sciences, 2017, vol. 114, no. 36, p. 9570–9574

Disordered dielectric materials with structural correlations show unconventional optical behavior: They can be transparent to long-wavelength radiation, while at the same time have isotropic band gaps in another frequency range. This phenomenon raises fundamental questions concerning photon transport through disordered media. While optical transparency in these materials is robust against...

Université de Fribourg

Photonic hyperuniform networks obtained by silicon double inversion of polymer templates

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

In: Optica, 2017, vol. 4, no. 3, p. 361–366

Hyperuniform disordered networks belong to a peculiar class of structured materials predicted to display isotropic complete photonic bandgaps for a refractive index contrast larger than 3. The practical realization of such photonic designer materials is challenging, however, as it requires control over a multi-step fabrication process on optical length scales. Here we report the direct-laser...

Université de Fribourg

Fluctuations of the electromagnetic local density of states as a probe for structural phase switching

Sousa, N. de ; Sáenz, Juan José ; Scheffold, Frank ; García-Martín, A. ; Froufe-Pérez, Luis S.

In: Physical Review A, 2016, vol. 94, no. 4, p. 043832

We study the statistics of the fluorescence decay rates for single quantum emitters embedded in a scattering medium undergoing a phase transition. Under certain circumstances, the structural properties of the scattering medium explore a regime in which the system dynamically switches between two different phases. While in that regime the light-scattering properties of both phases are hardly...

Université de Fribourg

Dynamical and structural signatures of the glass transition in emulsions

Zhang, Chi ; Gnan, Nicoletta ; Mason, Thomas G ; Zaccarelli, Emanuela ; Scheffold, Frank

In: Journal of Statistical Mechanics: Theory and Experiment, 2016, vol. 2016, no. 9, p. 094003

We investigate structural and dynamical properties of moderately polydisperse emulsions across an extended range of droplet volume fractions phgr, encompassing fluid and glassy states up to jamming. Combining experiments and simulations, we show that when phgr approaches the glass transition volume fraction ${{\phi}_{g}}$ , dynamical heterogeneities and amorphous order arise within the...