In electrolyte solutions, the differential migration of ionic species induced by presence a thermal gradient leads to buildup steady-state electric field. Similarly what happens for Seebeck effect in solids, sample behaves therefore as thermocell. Here, we provide clear evidence thermoelectric fields liquids detecting and quantifying their strong effects on colloid thermophoresis. Specifically, contrasting addition NaCl or NaOH Soret micellar solutions sodium dodecyl sulfate, show that...

A large variety of engaging phenomena, ranging from crystallization in protein solutions to the formation colloidal gels and glasses via depletion forces, stems occurrence very short-ranged attractive forces. From depolarized light scattering measurements equilibrium sedimentation profiles, we obtain an accurate description equation state phase diagram colloids where forces are tuned by addition a surfactant. For weak depletion, fluid fully described Baxter's "sticky" hard sphere model...

Alginate is a natural biopolymer that forms, in the presence of divalent cations, ionic-bound gels typifying large class biological stabilized by non-covalent cross-links, and displaying consistent restructuring kinetics. We investigate kinetics formation aging alginate slow permeation curing CaCl2 agent means photon correlation imaging, novel optical technique allows obtaining microscopic dynamics sample, while retaining at same time spatial resolution imaging techniques. Specifically,...

Measuring the concentration profiles induced by gravity settling is known to be an efficient route obtain equation of state a colloidal suspension, inspect fine details phase diagram and provide clues on nature metastable phases. Here we show that careful analysis transient may add valuable information for what concerns hydrodynamics. In particular, numerical inversion kinetic profile yields full hydrodynamic factor K(Φ) up original unsettled dilute part 'dynamic' gravitation length also...

We use a combination of original light scattering techniques and particles with unique optical properties to investigate the behavior suspensions attractive colloids under gravitational stress, following over time concentration profile, velocity microscopic dynamics. During compression regime, sedimentation grows nearly linearly height, implying that gel settling may be fully described by (time-dependent) strain rate. find dynamics exhibit remarkable scaling when is normalized rate, showing...

Particle settling is a pervasive process in nature, and centrifugation versatile separation technique. Yet, the results of ultracentrifugation experiments often appear to contradict very law on which they are based: Archimedes' principle – arguably, oldest physical law. The purpose this paper delving into roots concept buoyancy by means combined experimental–theoretical study sedimentation profiles colloidal mixtures. Our analysis shows that standard only limiting approximation, valid for...

We describe and test a new approach to particle velocimetry, based on imaging cross correlating the scattering speckle pattern generated near-field plane by flowing tracers with size far below diffraction limit, which allows reconstructing velocity in microfluidic channels without perturbing flow. As matter of fact, adding is not even strictly required, provided that sample displays sufficiently refractive-index fluctuations. For instance, phase separation liquid mixtures presence shear...

Depletion interactions and the critical Casimir effect are usually regarded as distinct phenomena in colloidal suspensions. By experimentally investigating how Asakura-Oosawa picture, appropriate for a weakly correlated depletant, is modified when correlations develop within depletion agent, we conversely show that former merges continuously into latter, leading to distinctive scaling behavior solely dictated by depletant correlation length. A model based on density functional theory...

Sedimentation has played a key role in the development of colloid science. In fact, it is because celebrated experiments by Perrin, yielding concrete demonstration molecular reality and giving strong support to Einstein's theory Brownian motion, that colloids enter realm basic physics. Subsequent investigations have shown lot more can be learnt both from sedimentation equilibrium particle settling dynamics. These advances, together with new experimental approaches, will reviewed this paper....

Pectin is a natural biopolymer that forms, in the presence of divalent cations, ionic-bound gels typifying large class biological stabilized by non-covalent cross-links. We investigate and compare kinetics formation aging pectin obtained either through external gelation via perfusion free Ca2+ ions, or internal due to supply same ions from dissolution CaCO3 nanoparticles. The microscopic dynamics with photon correlation imaging, novel optical technique allows obtaining sample while retaining...

Dense suspensions of motile bacteria, possibly including the human gut microbiome, exhibit collective dynamics akin to those observed in classic, high Reynolds number turbulence with important implications for chemical and biological transport, yet this analogy has remained primarily qualitative. Here, we present experiments which a dense suspension Bacillus subtilis bacteria was flowed through microchannels velocity statistics flowing were quantified using recently developed velocimetry...

A large variety of engaging phenomena stems from the occurrence short-ranged attractive depletion forces. Yet, so far, most experimental studies have been interpreted on basis simple Asakura-Oosawa model, where agent can be regarded as ideal. Here, conversely, we focus a system strong electrostatic coupling is present in suspension. Specifically, measurements equilibrium sedimentation profiles, obtain an equation states for colloidal forces are tuned by addition surfactant. At fixed colloid...

We re-examine the classical problem of irreversible colloid aggregation, showing that application Digital Fourier Imaging (DFI), a class optical correlation methods combine power light scattering and imaging, allows one to pick out novel useful evidence concerning restructuring processes taking place in strong colloidal gel. In particular, spatially-resolved displacement fields provided by DFI strongly suggest temporally-intermittent local rearrangements course gel ageing are characterized...

By exploiting photon correlation imaging and ghost particle velocimetry, two novel optical techniques particularly suited to the investigation of microscopic dynamics spatially heterogeneous samples, we investigate settling restructuring colloidal gels generated by short-ranged depletion interactions. Three distinct regions can be clearly set apart within liquid–liquid coexistence region phase diagram where gel formation is observed. When forces are barely sufficient drive system metastable...

By experimenting on model colloids where depletion forces can be carefully tuned and quantified, we show that attractive interactions consistently "promote" particle settling, so much the sedimentation velocity of a moderately concentrated dispersion even exceed its single-particle value. At larger volume fraction ϕ, however, hydrodynamic hindrance eventually takes over. Hence, v(ϕ) actually displays nonmonotonic trend may threaten stability settling front to thermal perturbations. Finally,...

Forward Osmosis is a promising strategy for desalination processes, however some aspects have to be better characterized make it competitive with other affirmed technologies. One of these the selection draw agent, i.e., polymeric solution that has fulfill different requirements guarantee both high membrane performances and good regeneration process. Previous studies identified thermoresponsive copolymer known as PAGB2000 potential agent. However, in open literature there no information on...

Depletion interactions in correlated fluids are investigated both theoretically and experimentally. A formally exact derivation of a general expression for depletion is presented then specialized to the case critical correlations depletant by employing long wavelength approximate analysis. scaling obtained region, suggesting close connection Casimir effect. As result we able compute full function effect terms known form equation state. These predictions experimentally tested colloidal...

We study the sedimentation of colloidal gels by using a combination light scattering, polarimetry and video imaging. The asymptotic concentration profiles $\varphi(z,t\rightarrow \infty)$ exhibit remarkable scaling properties: for prepared at different initial volume fractions particle interactions can be superimposed onto single master curve suitable reduced variables. show theoretically that this behavior stems from power law dependence compressive elastic modulus \textit{vs} $\varphi$,...

Relaxation of internal stresses through a cascade microscopic restructuring events is the hallmark many materials, ranging from amorphous solids like glasses and gels to geological structures subjected persistent external load. By means photon correlation imaging, recently developed technique that blends powers scattering we provide spatially temporally resolved survey aging processes spontaneously occur in physical originating an arrested phase separation. We show temporal dynamics...

Gravity or ultracentrifuge settling of colloidal particles and macromolecules usually involves several disperse species, either because natural industrial colloids display a large size polydispersity, additives are put in on purpose to allow for density-based fractionation the suspension. Such 'macromolecular crowding', however, may have surprising effects sedimentation, it strongly affects buoyant force felt by particle. Here we show that, as matter fact, standard Archimedes' principle is...

We propose a new method to produce fluorinated nanoparticles (NPs) based on ab initio reversible addition-fragmentation chain transfer (RAFT) emulsion polymerization without the use of toxic surfactants. NP size, surface charge, and chemistry can be controlled via adoption different macromolecular agents produced RAFT amphiphilic monomers. Thanks this versatility, interparticle interactions easily tuned by changing solvent composition temperature. In addition, refractive index density...

We investigate the rheo-mechanical properties of Mebiol Gel®, a thermosensitive gel-forming polymer extensively used as medium for cellular culture, using passive microrheology made either by standard dynamic light scattering or photon correlation imaging. In dilute limit, displays Newtonian behavior with an effective viscosity that decreases temperature, consistent peculiar aggregation mechanism characterized increase molecular weight simultaneous reduction aggregate size. By increasing...

The buoyancy concept is critically re-examined for applications to dispersions of nano-particles, such as colloids, proteins, or macromolecules. It shown that when the size buoyant particle not too different (say, at most a factor ten) from dispersed particles, new intriguing phenomena emerge, leading violation Archimedes' principle. resulting force depends only on volume and mass density dispersion, but also relative their geometry, interactions between fluid. Explicit expressions...

Self-assembling peptides (SAPs) have been increasingly studied as hydrogel-former gelators because they can create biocompatible environments. A common strategy to trigger gelation, is use a pH variation, but most methods result in change that too rapid, leading gels with hardly reproducible properties. Here, we the urea-urease reaction tune gel properties, by slow and uniform increase. We were able produce very homogeneous transparent at several SAP concentrations, ranging from c=1g/L...