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Université de Fribourg

Colloidal gelation, a means to study elasto-capillarity effects in foam

Mikhailovskaya, Alesya ; Trappe, Véronique ; Salonen, Anniina

In: Soft Matter, 2020, vol. 16, no. 9, p. 2249–2255

We explore the evolution of the mechanical properties of a coarsening foam containing colloidal particles that undergo a sol–gel transition in the continuous phase. This enables us to investigate the impact of elasto-capillarity on foam mechanics over a wide range of elasto-capillary numbers. Right after initiating aggregation the foam mechanics is predominantly determined by the elasticity...

Université de Fribourg

Accounting for effective interactions among charged microgels

Aguirre-Manzo, L. A. ; Ledesma-Motolinía, Mónica ; Rojas-Ochoa, Luis Fernando ; Trappe, Véronique ; Callejas-Fernández, J. ; Haro-Pérez, Catalina ; González-Mozuelos, P.

In: Physical Review E, 2019, vol. 100, no. 3, p. 032602

We introduce a theoretical approach to describe structural correlations among charged permeable spheres at finite particle concentrations. This theory explicitly accounts for correlations among microions and between microions and macroions and allows for the proposal of an effective interaction among macroions that successfully captures structural correlations observed in poly- N -isopropyl...

Université de Fribourg

Glass transition of soft colloids

Philippe, Adrian-Marie ; Truzzolillo, Domenico ; Galvan-Myoshi, Julian ; Dieudonné-George, Philippe ; Trappe, Véronique ; Berthier, Ludovic ; Cipelletti, Luca

In: Physical Review E, 2018, vol. 97, no. 4, p. 040601

We explore the glassy dynamics of soft colloids using microgels and charged particles interacting by steric and screened Coulomb interactions, respectively. In the supercooled regime, the structural relaxation time τα of both systems grows steeply with volume fraction, reminiscent of the behavior of colloidal hard spheres. Computer simulations confirm that the growth of τα on approaching...

Université de Fribourg

Differential dynamic microscopy microrheology of soft materials: A tracking-free determination of the frequency-dependent loss and storage moduli

Edera, Paolo ; Bergamini, Davide ; Trappe, Véronique ; Giavazzi, Fabio ; Cerbino, Roberto

In: Physical Review Materials, 2017, vol. 1, no. 7, p. 073804

Particle-tracking microrheology (PT-μr) exploits the thermal motion of embedded particles to probe the local mechanical properties of soft materials. Despite its appealing conceptual simplicity, PT-μr requires calibration procedures and operating assumptions that constitute a practical barrier to its wider application. Here we demonstrate differential dynamic microscopy microrheology...

Université de Fribourg

Interplay of coarsening, aging, and stress hardening impacting the creep behavior of a colloidal gel

Calzolari, D. C. E. ; Bischofberger, Irmgard ; Nazzani, Francesco ; Trappe, Véronique

In: Journal of Rheology, 2017, vol. 61, no. 4, p. 817–831

We explore the dynamical and mechanical characteristics of an evolving gel in diffusing wave spectroscopy (DWS) and rheometry, aiming to assess how the gel evolution impacts the creep response of the system. Our gel is formed by inducing the aggregation of thermosensitive colloids by a variation in temperature. We find experimental evidence that the long time evolution of this gel is due to...

Université de Fribourg

Impact of volume transition on the net charge of poly-$N$-isopropyl acrylamide microgels

Braibanti, Marco ; Haro-Pérez, Catalina ; Quesada-Pérez, M. ; Rojas-Ochoa, Luis Fernando ; Trappe, Véronique

In: Physical Review E, 2016, vol. 94, no. 3, p. 032601

We explore the electrostatic properties of poly-N-isopropyl acrylamide microgels in dilute, quasi-de-ionized dispersions and show that the apparent net charge of these thermosensitive microgels is an increasing function of their size, the size being conveniently varied by temperature. Our experimental results obtained in a combination of light scattering, conductivity, and mobility...

Université de Fribourg

Viscoelasticity of nematic liquid crystals at a glance

Giavazzi, Fabio ; Crotti, Stefano ; Speciale, Antonio ; Serra, Francesca ; Zanchetta, Giuliano ; Trappe, Véronique ; Buscaglia, Marco ; Bellini, Tommaso ; Cerbino, Roberto

In: Soft Matter, 2014, vol. 10, no. 22, p. 3938–3949

Polarised microscopy is shown to be a powerful alternative to light scattering for the determination of the viscoelasticity of aligned nematic liquid crystals. We perform experiments in a wide range of temperatures by using an adapted version of the recently introduced differential dynamic microscopy technique, which enables us to extract scattering information directly from the microscope...

Université de Fribourg

Hydrophobic hydration of poly-N-isopropyl acrylamide: a matter of the mean energetic state of water

Bischofberger, Irmgard ; Calzolari, D. C. E. ; Rios, Paolo De Los ; Jelezarov, I. ; Trappe, Véronique

In: Scientific Reports, 2014, vol. 4, p. -

The enthalpically favoured hydration of hydrophobic entities, termed hydrophobic hydration, impacts the phase behaviour of numerous amphiphiles in water. Here, we show experimental evidence that hydrophobic hydration is strongly determined by the mean energetics of the aqueous medium. We investigate the aggregation and collapse of an amphiphilic polymer, poly-N-isopropyl acrylamide (PNiPAM), in...

Université de Fribourg

Unexpected Decoupling of Stretching and Bending Modes in Protein Gels

Gibaud, Thomas ; Zaccone, Alessio ; Gado, Emanuela Del ; Trappe, Véronique ; Schurtenberger, Peter

In: Physical Review Letters, 2013, vol. 110, no. 5, p. 058303

We show that gels formed by arrested spinodal decomposition of protein solutions exhibit elastic properties in two distinct frequency domains, both elastic moduli exhibiting a remarkably strong dependence on volume fraction. Considering the large difference between the protein size and the characteristic length of the network we model the gels as porous media and show that the high and low...

Université de Fribourg

Ultra-long range correlations of the dynamics of jammed soft matter

Maccarrone, S. ; Brambilla, G. ; Pravaz, O. ; Duri, Agnès ; Ciccotti, M. ; Fromental, J.-M. ; Pashkovski, E. ; Lips, A. ; Sessoms, David ; Trappe, Véronique ; Cipelletti, Luca

In: Soft Matter, 2010, vol. 6, no. 21, p. 5514-5522

We use photon correlation imaging, a recently introduced space-resolved dynamic light scattering method, to investigate the spatial correlation of the dynamics of a variety of jammed and glassy soft materials. Strikingly, we find that in deeply jammed soft materials spatial correlations of the dynamics are quite generally ultra-long ranged, extending up to the system size, orders of magnitude...