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Shear-driven aggregation of SU-8 microrods in suspension
Pramukta Kumar1, David Gold, Daniel L Blair
1Dept. of Physics and Institute for Soft Matter Synthesis and Metrology, Georgetown University, Washington, DC, USA. psk7@georgetown.edu.
Soft Matter
|July 1, 2014
Summary
Non-Brownian rod suspensions form aggregates under shear, dramatically increasing viscosity. Aggregate size and structure depend on shear rate and concentration, offering insights into microscopic properties.
Area of Science:
- Physics
- Materials Science
- Chemical Engineering
Background:
- Non-Brownian suspensions exhibit complex behaviors under shear.
- Shear-driven aggregation can significantly alter fluid properties like viscosity.
Purpose of the Study:
- To investigate the relationship between shear-driven aggregation and viscosity enhancement in rod suspensions.
- To quantitatively model aggregate formation and infer microscopic properties.
Main Methods:
- Combined rheometry and fluorescence microscopy to image aggregate formation.
- Quantitative analysis of aggregate size, structure, and early-stage growth.
- Modeling aggregation using collision-driven growth and constitutive relationships.
Main Results:
- Reversible, disordered aggregate formation observed, leading to viscosity enhancement at low shear rates.
- Aggregate size and structure are dependent on shear rate and concentration.
- Aggregate density increases with shear rate, as suggested by modeling.
Conclusions:
- Direct experimental evidence links aggregation to viscosity enhancement in rod suspensions.
- Microscopic geometric properties of dynamic systems can be inferred from rheology and imaging.
- The study provides a quantitative framework for understanding shear-induced phenomena in suspensions.
