Structure of Colloidal Gels during Microchannel Flow

We investigate the flow behavior of colloidal gels in microchannels using confocal microscopy. We study two model systems: one in which silica microspheres are flocculated via polyelectrolyte additions, and the other composed of hydrophobically modified silica microspheres. Both of these attractive colloid suspensions exhibit shear-thinning behavior with a finite yield stress. Under shear flow, the bulk flow profiles change from plug-like at low pressures to fluid-like at high pressures. We vary the applied pressure, the microchannel geometry, and the colloid volume fraction, and systematically study the structure of each model system during flow.