title: Direct flow visualization of colloidal gels in microfluidic channels.
abstract: 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 velocity flow profiles show a transition from plug flow to more fluid-like behavior with increasing volumetric flow rate (Q) at all phi. This transition is not captured by theoretical predictions of the flow profile based on the Herschel-Bulkley model. Rather, a model that accounts for gel breakup into a suspension of clusters at elevated shear rates by assuming a finite viscosity at infinite shear is needed to accurately predict the flow behavior of colloidal gels at large Q.
authors.affiliation: Frederick Seitz Materials Research Laboratory, Materials Science and Engineering Department, University of Illinois, Urbana, Illinois 61801, USA.
authors.forename: Mark T
authors.initials: MT
authors.lastname: Roberts
authors.forename: Ali
authors.initials: A
authors.lastname: Mohraz
authors.forename: Kenneth T
authors.initials: KT
authors.lastname: Christensen
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Lewis