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Cyclically sheared colloidal gels: structural change and delayed failure time
Himangsu Bhaumik1, James E Hallett2, Tanniemola B Liverpool3
1Yusuf Hamied Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge CB2 1EW, UK.
Soft Matter
|October 31, 2025
Summary
Cyclically shearing colloidal gels alters their structure and mechanical properties. Depending on shear conditions, gels can become more compliant (thixotropy) or stiffer (strain hardening), impacting their stability.
Area of Science:
- Colloidal science
- Soft matter physics
- Materials science
Background:
- Colloidal gels are complex fluids with applications in food, cosmetics, and pharmaceuticals.
- Understanding their response to mechanical stress is crucial for processing and stability.
Purpose of the Study:
- To investigate the structural and mechanical changes in colloidal gels under cyclic shear.
- To explore the relationship between shear history and gel behavior, including thixotropy and strain hardening.
Main Methods:
- Experimental studies on colloid-polymer mixture gels.
- Computer simulations using a model gel-former.
- Analysis of structural parameters (topological cluster classification, bond-order parameters, pore size distribution).
- Mechanical response analysis (stress, dissipation rate, creeping flow).
Main Results:
- Cyclic shear induces structural evolution and pore size increase in gels.
- A crossover from elastic to plastic behavior is observed with increasing strain amplitude.
- Gels exhibit both thixotropy (increased compliance) and strain hardening (reduced compliance) depending on parameters.
- Pre-sheared gels show increased stability under constant shear stress.
- Anisotropic structural features are imprinted by cyclic shear, influencing response orientation.
Conclusions:
- Cyclic shear significantly modifies colloidal gel microstructure and rheology.
- The observed thixotropy and strain hardening are key responses to shear history.
- Anisotropy introduced by cyclic shear plays a critical role in gel stability and flow behavior.
