The behavior of colloidal gels under pressure-driven flow in square microchannels is quantified by microscopic particle image velocimetry (muPIV) and compared to predictions of available rheological models. The gels consist of hydrophobically modified silica microspheres (phi = 0.15-0.33) suspended in a refractive index-matched fluid along with fluorescent tracers to aid visualization. Measured...

A vital part of microfluidic designs is to impose control over fluid streamlines by microscale structures. In this paper, we describe a method to control streamline steering through different microfluidic entangled networks. These networks were constructed by stacking two distinguishable layers of microchannels face-to-face. We have developed four fundamental nodes, called R, L, N and Z that we...

When a small amount (less than 1%) of a second immiscible liquid is added to the continuous phase of a suspension, the rheological properties of the admixture are dramatically altered and it can change from a fluid-like to a gel-like state. The rheological properties can be modified through changes in the particle size, temperature induced changes to the interfacial tension, and through the add...

We investigate theoretically the collective dynamics of soft active particles living in a viscous fluid. We focus on a minimal model for active but nonmotile particles consisting of N>1 elastic dimers deformed by active stresses and interacting hydrodynamically. We first derive a set of effective equations of motion for the positions of the particles. We then exploit these equations in two expe...

Primary electroviscous effect for a dilute suspension of porous spheres with fixed volumetric charge density is investigated theoretically. In the absence of flow, the electrical potential and solution charge density are assumed to satisfy the linearized Poisson-Boltzmann equation. With incorporation of the electrical body force, the Brinkman equation and the Stokes equation are used to govern ...

Magnetorheo]ogical (MR) fluids are colloidal suspensions of pammagnetic particles in a non-magnetic fluid. These fluids, along with their electrical analogues, electrorheologica] (ER) fluids, have been proposed as controllable fluids, for use in electromechanical devices such as dampers, clutches and brakes. [1] When exposed to an external magnetic field, the particles acquire dipole moments ag...

Analytic and numerical microscopic integral equation theory for polymer–particle suspensions is employed to investigate the dependence of fluid–fluid phase separation on size asymmetry, solvent quality, and higher order polymer–polymer interactions. For athermal good solvents, our prior novel prediction of enhanced miscibility with increasing ~decreasing! polymer ~particle! size is found not to...

The dynamic drying process is studied in spatially heterogeneous film-forming latex suspensions across a wide range of dispersion concentrations using optical imaging techniques. Systematic changes in latex suspension concentration are found to affect lateral drying heterogeneity and surface topology. A nonmonotonic decay in contact angle is observed at the edges of drying droplets by continuou...

In this paper, we investigate the ability to drive fluid streaming via a surface acoustic wave (SAW) into a porous bioscaffold structure, and to exploit this effect to deliver fluorescent particles/yeast cells into the scaffold as a potential rapid and efficient method for cell seeding in tissue engineering. The results demonstrate that the seeding process takes approximately 10 seconds, much s...

Using a model colloid-polymer suspension, we show that confinement induces solidification in attractive colloidal suspensions via a fundamentally different route from that active in hard sphere colloidal suspensions. For a range of polymer concentrations, the suspensions undergo a phase transition from a colloidal fluid of clusters to a colloidal gel as confinement increases while polymer and p...