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Shearing active gels close to the isotropic-nematic transition
M E Cates1, S M Fielding, D Marenduzzo
1SUPA, School of Physics, University of Edinburgh, Edinburgh EH9 3JZ, United Kingdom.
Physical Review Letters
|September 4, 2008
Summary
This study numerically investigates active gel rheology near the isotropic-nematic transition. We found flow behavior depends on size, boundaries, and constitutive curves, revealing distinct viscosity behaviors for contractile and extensile systems.
Area of Science:
- Soft matter physics
- Rheology
- Active matter physics
Background:
- Active gels exhibit complex rheological properties influenced by internal stresses and phase transitions.
- The isotropic-nematic transition in active matter systems is a critical phenomenon affecting material flow.
- Understanding these transitions is crucial for applications involving biological tissues and synthetic active materials.
Purpose of the Study:
- To numerically investigate the rheological properties of active gel slabs near the isotropic-nematic transition.
- To analyze the influence of sample size, boundary conditions, and bulk constitutive curves on flow behavior.
- To characterize the activity-induced discontinuity in the nematic phase and its precursors in the isotropic phase.
Main Methods:
- Numerical simulations of active gel rheology.
- Analysis of flow behavior dependence on system parameters.
- Characterization of constitutive curves and phase transitions.
Main Results:
- Flow behavior is highly sensitive to sample size and boundary conditions.
- An activity-induced discontinuity appears in the constitutive curve upon entering the nematic phase.
- Contractile systems show a viscosity divergence in the metastable isotropic phase.
- Extensile systems exhibit shear-banded flow with zero apparent viscosity in the isotropic phase.
Conclusions:
- The rheology of active gels near the isotropic-nematic transition is complex and system-dependent.
- Distinct flow behaviors (viscosity divergence vs. shear banding) arise from precursors to the nematic phase in contractile and extensile systems.
- These findings provide insights into the fundamental physics of active matter and have implications for material design.
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