A5064606204- Material Dynamics and Properties
- Pickering emulsions and particle stabilization
- Theoretical and Computational Physics
- Surfactants and Colloidal Systems
- Phase Equilibria and Thermodynamics
- Adsorption, diffusion, and thermodynamic properties of materials
- Rheology and Fluid Dynamics Studies
- Force Microscopy Techniques and Applications
- Advanced Thermodynamics and Statistical Mechanics
- Liquid Crystal Research Advancements
- Polysaccharides Composition and Applications
- Micro and Nano Robotics
- Surface Roughness and Optical Measurements
- Minerals Flotation and Separation Techniques
- Random lasers and scattering media
- Electromagnetic Scattering and Analysis
- Hydrogels: synthesis, properties, applications
- Electrostatics and Colloid Interactions
- Spaceflight effects on biology
- Advanced Theoretical and Applied Studies in Material Sciences and Geometry
- Biocrusts and Microbial Ecology
- Cellular Mechanics and Interactions
- Proteins in Food Systems
- Optical Imaging and Spectroscopy Techniques
- Microfluidic and Bio-sensing Technologies
Université de Montpellier
2016-2025
Laboratoire Charles Coulomb
2016-2025
Institut Universitaire de France
2018-2025
Chimie Moléculaire, Macromoléculaire, Matériaux
2018-2025
Centre National de la Recherche Scientifique
2015-2024
Sciences et Ingénierie de la Matière Molle
2015-2020
Institut Charles Gerhardt Montpellier
2010
École Nationale Supérieure de Chimie de Montpellier
2010
Institut des Biomolécules Max Mousseron
2010
Harvard University
2000-2007
Understanding glass formation is a challenge because the existence of true state, distinct from liquid and solid, remains elusive: Glasses are liquids that have become too viscous to flow. An old idea, as yet unproven experimentally, dynamics becomes sluggish transition approaches increasingly larger regions material move simultaneously allow We introduce new multipoint dynamical susceptibilities estimate quantitatively size these provide direct experimental evidence molecular colloidal...
We use multispeckle dynamic light scattering to measure the structure factor, f(q,tau), of gels formed by aggregation colloids. Although gel is an elastic solid, f(q,tau) nearly completely decays on long time scales, with unusual form, f(q, tau) approximately exp{-(tau/tau(f))(mu)}, mu 1.5 and tau(f) proportional variant q(-1). A model for restructuring aging correctly accounts this behavior. Aging leads a dramatic increase in tau(f); however, all data can be scaled single master curve,...
We use dynamic light scattering and computer simulations to study equilibrium dynamics heterogeneity in concentrated suspensions of colloidal hard spheres. Our covers an unprecedented density range spans seven decades structural relaxation time, tau(alpha0, including measurements above phi(c), the location glass transition deduced from fitting our data mode-coupling theory. Instead falling out equilibrium, system remains ergodic phi(c) enters a new dynamical regime where tau(alpha) increases...
We use x-ray photon correlation spectroscopy to investigate the structural relaxation process in a metallic glass on atomic length scale. report evidence for dynamical crossover between supercooled liquid phase and metastable glassy state, suggesting different origins of across transition. Furthermore, using cooling rates, we observe complex hierarchy dynamic processes characterized by distinct aging regimes. Strong analogies with dynamics soft materials, such as gels concentrated colloidal...
We use conventional and multispeckle dynamic light scattering to investigate the dynamics of a wide variety jammed soft materials, including colloidal gels, concentrated emulsions, surfactant phases. For all systems, structure factor f(q,t) exhibits two-step decay. The initial decay is due thermally activated diffusive motion scatterers, as indicated by q−2 dependence characteristic relaxation time, where q vector. However, constrained scatterers in are arrested terminates plateau....
Measuring, characterizing and modelling the slow dynamics of glassy soft matter is a great challenge, with an impact that ranges from industrial applications to fundamental issues in modern statistical physics, such as glass transition description out-of-equilibrium systems. Although our understanding these phenomena still far complete, recent simulations novel theoretical approaches experimental methods have shed new light on materials. In this paper, we review work last few years, emphasis...
We use a charge coupled device (CCD) camera and multi-tau software correlator to measure dynamic light scattering (DLS) at many angles simultaneously, from 0.07° 5.1°. Real-time autocorrelation functions are calculated by averaging both over time CCD pixels, each corresponding different coherence area. In order cover the wide spectrum of decay times associated with large range accessible angles, we adopt multitau scheme, where channel spacing is quasilogarithmic rather than linear. A...
Attractive colloidal particles can exhibit a fluid to solid phase transition if the magnitude of attractive interaction is sufficiently large, volume fraction high, and applied stress small. The nature this similar for many different colloid systems, forms interaction. jamming captures common features these translations, by unifying behavior as function particle fraction, energy interparticle attractions, stress. This paper describes applicability state diagram, highlights those regions...
We use a custom shear cell coupled to an optical microscope investigate at the particle level yielding transition in concentrated emulsions subjected oscillatory deformation. By performing experiments lasting thousands of cycles on samples several volume fractions and for variety applied strain amplitudes, we obtain comprehensive, microscopic picture transition. find that irreversible motion sharply increases beyond volume-fraction dependent critical strain, which is found be close agreement...
We introduce a new scheme for investigating temporally heterogeneous dynamics, which is termed time-resolved correlation (TRC). TRC applied to data obtained by diffusing wave spectroscopy probing the slow dynamics of strongly aggregated colloidal gel. Other examples data, collected different jammed materials in single and multiple scattering, are provided demonstrate wide range applicability this method. In all cases we find evidence that results from series discrete steps rather than...
We use linear rheology and multispeckle dynamic light scattering (MDLS) to investigate the aging of a gel composed multilamellar vesicles. Light data indicate rearrangement through an unusual ultraslow ballistic motion. A dramatic slowdown dynamics with sample age t(w) is observed for both MDLS, characteristic relaxation time scaling as t(mu)w. find same exponent mu = 0.78 techniques, suggesting that they probe similar physical processes, applied or internal stresses respectively. simple...
Time resolved correlation (TRC) is a recently introduced light scattering technique that allows one to detect and quantify dynamic heterogeneities. The based on the analysis of temporal evolution speckle pattern generated by scattered sample, which quantified cI(t, tau), degree between images recorded at time t + tau. Heterogeneous dynamics results in significant fluctuations cI(t,tau) with t. We describe how optimize TRC measurements avoid possible artifacts. statistical properties cI are...
We use time-resolved dynamic light scattering to investigate the slow dynamics of a colloidal gel. The final decay average intensity autocorrelation function is well described by g2(q,τ) − 1 ∼ exp [ (τ/τf)p], with τf q−1 and p decreasing from 1.5 increasing q. show that not due continuous ballistic process, as proposed in previous works, but rather rare, intermittent rearrangements. quantify dynamical fluctuations resulting intermittency means variance χ(τ,q) instantaneous function,...
We introduce a new dynamic light scattering method, termed photon correlation imaging, which enables us to resolve the dynamics of soft matter in space and time. demonstrate imaging by investigating slow quasi-two-dimensional coarsening foam made highly packed, deformable bubbles rigid gel network formed dilute, attractive colloidal particles. find both systems be determined intermittent rearrangement events. For foam, rearrangements extend over few bubbles, but small dynamical is observed...
We explore the glassy dynamics of soft colloids using microgels and charged particles interacting by steric screened Coulomb interactions, respectively. In supercooled regime, structural relaxation time $\tau_\alpha$ both systems grows steeply with volume fraction, reminiscent behavior colloidal hard spheres. Computer simulations confirm that growth on approaching glass transition is independent particle softness. By contrast, softness becomes relevant at very large packing fractions when...
Significance The sudden, catastrophic failure of materials under a constant mechanical load is widespread, occurring from geological scales, as in earthquakes, to biological and soft-matter systems, protein, polymer, colloidal gels. Failure often preceded by long induction time, with little if any macroscopic signs weakening, making it unpredictable. Here, we investigate the model gel load, measuring simultaneously its response microscopic dynamics. We show that undergoes burst plastic...
Power law rheology is of widespread occurrence in complex materials that are characterized by the presence a very broad range microstructural length and time scales. Although phenomenological models able to reproduce observed rheological features exist, general well-established connection with microscopic origin this mechanical behavior still missing. As model system, work focuses on fractal colloidal gel. We thoroughly characterize linear power sample its age dependence. show at all ages...
Optical tracer-microrheology has been applied to study the rheological properties of a concentrated surfactant solution. Under chosen conditions these surfactants self-assemble form giant polymer-like micelles, resulting in strongly viscoelastic liquid. A novel approach analysis local dynamic tracer particles is presented, based on combination single- and multi-speckle diffusing wave spectroscopy (DWS). With this technique we could significantly extend accessible frequency range key as given...
We study phase separation in a deeply quenched colloid-polymer mixture microgravity on the International Space Station using small-angle light scattering and direct imaging. observe clear crossover from early-stage spinodal decomposition to late-stage, interfacial-tension-driven coarsening. Data acquired over 5 orders of magnitude time show more than 3 increase domain size, following nearly same evolution as that binary liquid mixtures. The late-stage growth approaches expected linear rate...
We use time-resolved x-ray photon correlation spectroscopy to investigate the slow dynamics of colloidal gels made moderately attractive carbon black particles. show that is temporally heterogeneous and quantify its fluctuations by measuring variance chi instantaneous intensity function. The amplitude dynamical has a nonmonotonic dependence on scattering vector q, in stark contrast with recent experiments strongly [Duri Cipelletti, Europhys. Lett. 76, 972 (2006)]. propose simple scaling...