Biomedical subjects

Sowmitri Tarimala

Publications and source records attributed to Sowmitri Tarimala.

4 recordsLinked to original sources

PubMed2006

Dynamics and collapse of two-dimensional colloidal lattices.

One interesting aspect of colloidal particles is the formation of colloidal crystals at the 2D and 3D levels. Here we report the dynamics and collapse of colloidal lattices at liquid-liquid interfaces using Pickering emulsions as an experimental template. The colloidal particles oscillate around their equilibrium positions. The short-time diffusion constant (<10 s) of single particles increases with increasing lattice spacing; the oil-phase viscosity has an effect on diffusion only at large interparticle distances. Strikingly, we observe that the equilibrium structure can be disturbed when increasing the output laser intensity in a confocal laser scanning microscope, which leads to the collapse of colloidal lattices in the presence of small laser powers.

Journal Article↗

PubMed2006

Dynamics of charged microparticles at oil-water interfaces.

Solid-stabilized emulsions have been used as a model system to investigate the dynamics of charged microparticles with diameters of 1.1 microm at oil-water interfaces. Using confocal microscopy, we investigated the influences of interfacial curvature, cluster size, and temperature on the diffusion of solid particles. Our work suggests that a highly curved emulsion interface slows the motion of solid particles. This qualitatively supports the theoretical work by Danov et al. (Danov, K. D.; Dimova, R.; Pouligny, B. Phys. Fluids 2000, 12, 2711); however, the interfacial curvature effect decreases with increasing oil-phase viscosity. The diffusion of multiparticle clusters at oil-water interfaces is a strong function of cluster size and oil-phase viscosity and can be quantitatively related to fractal dimension. Finally, we report the influence of temperature and quantify the diffusion activation energy and friction factor of the particles at the investigated oil-water interfaces.

Journal Article↗

PubMed2004

Mobility and in situ aggregation of charged microparticles at oil-water interfaces.

Particle mobility, aggregate structure, and the mechanism of aggregate growth at the two-dimensional level have been of long-standing interest. Here, we use solid-stabilized emulsions as a model system to investigate the mobility of charged microparticles at poly(dimethylsiloxane) (oil)-water interfaces using confocal laser scanning microscopy. Remarkably, the rate of diffusion of the charged colloidal-sized polystyrene particles at the oil-water interface is only moderately slower than that in the bulk water phase. The ambient diffusion constant of solid particles is significantly reduced from 1.1 x 10(-9) cm2/s to 2.1 x 10(-11) cm2/s when the viscosity of the oil phase increases from 5 cSt to 350 cSt. In addition, we successfully observe the in situ structural formation of solid particles at the oil-water interface.

Diffusion↗

PubMed2004

Structure of microparticles in solid-stabilized emulsions.

Emulsions of oil and water stabilized by adsorbed solid particles are known as solid-stabilized emulsions (often referred to as Pickering emulsions). Using confocal microscopy, we have studied the assembly of colloidal-sized polystyrene particles in poly(dimethylsiloxane)-in-water solid-stabilized emulsions. Monodisperse polystyrene particles, when included in the emulsions at low concentrations, were found to form small patches with local "hexagonal" order, separated by other particle-free domains. Polystyrene particles with different sizes (1 and 4 microm) and different wettability could simultaneously segregate to the emulsion interface; even mixtures of hydrophobic and hydrophilic solid particles were found to simultaneously segregate to the same interface.

Letter↗