Effect of an excess of surfactant on thermophoresis, mass diffusion and viscosity in an oily surfactant-stabilized ferrofluid.

The effect of an excess of surfactant on the thermophoresis of a sterically stabilized ferrofluid is investigated experimentally by forced Rayleigh scattering (FRS). The experiments are performed with a stable magnetic fluid sample to which controlled amounts of surfactant are added. A decrease in the thermally induced transport of magnetic nanoparticles is observed while increasing the temperature T.

Optothermal grid activation of microflow with magnetic nanoparticle thermophoresis for microfluidics.

We report focused light-induced activation of intense magnetic microconvection mediated by suspended magnetic nanoparticles in microscale two-dimensional optothermal grids. Fully anisotropic control of microflow and mass transport fluxes is achieved by engaging the magnetic field along one or the other preferred directions. The effect is based on the recently described thermal diffusion-magnetomechanical coupling in synthetic magnetic nanofluids.

Self-assembly and rheology of dipolar colloids in simple shear studied using multi-particle collision dynamics.

Magnetic nanoparticles in a colloidal solution self-assemble in various aligned structures, which has a profound influence on the flow behavior. However, the precise role of the microstructure in the development of the rheological response has not been reliably quantified. We investigate the self-assembly of dipolar colloids in simple shear using hybrid molecular dynamics and multi-particle collision dynamics simulations with explicit coarse-grained hydrodynamics, conduct simulated rheometric studies and apply micromechanical models to produce master curves, showing evidence of the universality of the structural behavior governed by the competition between the bonding (dipolar) and erosive (thermal and/or hydrodynamic) stresses.

Numerical investigation of thermo-magneto-solutal flow of ferrocolloid through ordered and disordered permeable membranes.

We explore the mechanism of ferroparticle transfer in porous structures in the conditions of simultaneous action of the thermal gradient and the magnetic field. We show that when a ferrocolloid saturated porous matrix is placed in a homogeneous magnetic field the grains of the porous frame notably distort the uniformity of the internal field by creating sharp gradients in the vicinity of the interface. On the other hand, the application of the temperature gradient creates an imbalance of the ferroparticle concentration in the bulk of the porous structure due to colloidal thermophoresis.

Diffusive and thermodiffusive transfer of magnetic nanoparticles in porous media.

Experimental results on mass transfer within a thin porous layer saturated with ferrofluid are outlined in this paper. From the analysis of particle concentration distribution across the layer it is shown that both the mass diffusion and the Soret coefficients of nanoparticles are remarkably less than those measured in free fluid. The particle transport coefficient changes due to an external uniform magnetic field qualitatively well agree with the predictions of existing theoretical research.