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Confocal Imaging of Confined Quiescent and Flowing Colloid-polymer Mixtures
Published on: May 20, 2014
Direct flow visualization of colloidal gels in microfluidic channels.
Mark T Roberts1, Ali Mohraz, Kenneth T Christensen
1Frederick Seitz Materials Research Laboratory, Materials Science and Engineering Department, University of Illinois, Urbana, Illinois 61801, USA.
Langmuir : the ACS Journal of Surfaces and Colloids
|July 17, 2007
Summary
Colloidal gels exhibit fluid-like flow at high rates, deviating from standard models. A new model accounting for gel breakup is needed for accurate predictions of colloidal gel behavior.
Area of Science:
- Materials Science
- Fluid Dynamics
- Colloid Science
Background:
- Colloidal gels are complex fluids with unique flow properties.
- Understanding their behavior under flow is crucial for various applications.
- Existing rheological models often fail to capture non-Newtonian behaviors.
Purpose of the Study:
- To quantify the flow behavior of colloidal gels in microchannels.
- To compare experimental results with predictions from rheological models.
- To identify limitations of current models and propose improvements.
Main Methods:
- Microscopic particle image velocimetry (muPIV) was used to measure velocity profiles.
- Experiments were conducted on hydrophobically modified silica microsphere gels.
- Flow behavior was analyzed across varying volumetric flow rates (Q) and particle concentrations (phi).
Main Results:
- Flow profiles transitioned from plug-like to more fluid-like with increasing flow rate (Q).
- This transition was observed across all particle concentrations (phi).
- The Herschel-Bulkley model failed to predict the observed flow behavior at high Q.
Conclusions:
- Standard rheological models are insufficient for describing colloidal gel flow at high shear rates.
- A modified model incorporating gel breakup and finite infinite-shear viscosity is required.
- Accurate prediction of colloidal gel dynamics necessitates accounting for shear-induced structural changes.
