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Université de Fribourg

Relationship between rheology and structure of interpenetrating, deforming and compressing microgels

Conley, Gaurasundar M. ; Zhang, Chi ; Aebischer, Philippe ; Harden, James L. ; Scheffold, Frank

In: Nature Communications, 2019, vol. 10, no. 1, p. 2436

Thermosensitive microgels are widely studied hybrid systems combining properties of polymers and colloidal particles in a unique way. Due to their complex morphology, their interactions and packing, and consequentially the viscoelasticity of suspensions made from microgels, are still not fully understood, in particular under dense packing conditions. Here we study the frequency-dependent...

Public access from Nov 1, 2019
Consortium of Swiss Academic Libraries

Static versus dynamic analysis of the influence of gravity on concentration non-equilibrium fluctuations

Croccolo, Fabrizio ; Bataller, Henri ; Scheffold, Frank

In: The European Physical Journal E, 2014, vol. 37, no. 11, p. 1-5

Université de Fribourg

When black and white make green: the surprising interplay of structure and pigments

Sai, Tianqi ; Wilts, Bodo D. ; Sicher, Alba ; Steiner, Ullrich ; Scheffold, Frank ; Dufresne, Eric R.

In: CHIMIA International Journal for Chemistry, 2019, vol. 73, no. 1, p. 47–50

The natural world is teeming with color, which originates either from the wavelength- dependent absorp- tion of light by pigments or from scattering from nanoscale structures, or both. While the latter ' structural color ' has been a topic of intense study in recent years, the most vibrant colors in nature involve contributions from both structure and pigment. The study of structure–pigment...

Université de Fribourg

Structure and sedimentation kinetics of dense suspensions of fibroblast cells

Zenuni, Arbnor ; Zhang, Chi ; Haeni, Laetitia ; Rothen-Rutishauser, Barbara ; Scheffold, Frank

In: CHIMIA International Journal for Chemistry, 2019, vol. 73, no. 1, p. 43–46

We investigate the structure and the dynamics of dense suspensions of NIH 3T3 fibroblast cells. Using two-photon microscopy we obtain three dimensional (3D) images from which the size and the packing structure of the dense cell suspensions can be extracted. In addition, we analyse the global time-dependent behaviour of the suspensions by time-lapse measurements of cell sedimentation. Since...

Université de Fribourg

Observation of strongly heterogeneous dynamics at the depinning transition in a colloidal glass

Şenbil, Nesrin ; Gruber, Markus ; Zhang, Chi ; Fuchs, Matthias ; Scheffold, Frank

In: Physical Review Letters, 2019, vol. 122, no. 10, p. 108002

We study experimentally the origin of heterogeneous dynamics in strongly driven glass-forming systems. Thereto, we apply a well-defined force with a laser line trap on individual colloidal polystyrene probe particles seeded in an emulsion glass composed of droplets of the same size. Fluid and glass states can be probed. We monitor the trajectories of the probe and measure displacements and...

Université de Fribourg

Diffusing wave microrheology of highly scattering concentrated monodisperse emulsions

Kim, Ha Seong ; Şenbil, Nesrin ; Zhang, Chi ; Scheffold, Frank ; Mason, Thomas G.

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 low-frequency plateau elastic shear moduli G′p of concentrated, monodisperse, disordered oil-in- water emulsions as droplets jam. In such experiments, the...

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...