Model aggregated 2D suspensions in shear and compression: From a fluid layer to an auxetic interface?
Alexandra Alicke1, Laura Stricker1, Jan Vermant1
1Department of Materials, ETH Zurich, Vladimir-Prelog-Weg 5, Zurich 8093, Switzerland.
Journal of Colloid and Interface Science
|August 19, 2023
Summary
Particle-laden interfaces exhibit distinct mechanical responses under compression and shear. Their compressive moduli depend on void fraction, while shear moduli correlate with aggregate fractal dimension, revealing complex microstructural changes.
Area of Science:
- Materials Science
- Soft Matter Physics
- Colloid Science
Background:
- Particle-laden interfaces are vital for multiphase system stability.
- Understanding their mechanical properties under deformation is limited.
- Microstructural changes accompanying mechanical response require further investigation.
Purpose of the Study:
- Investigate interfacial rheological moduli in aggregated 2D particle suspensions.
- Correlate rheological moduli with microstructural evolution under shear and compression.
- Explore the auxetic behavior of these heterogeneous networks.
Main Methods:
- Conducted interfacial rheological experiments in simple shear flow (double wall-ring geometry) and isotropic compression (radial trough).
- Varied surface coverage and maintained clean kinematic conditions.
- Monitored microstructural evolution during deformation.
Main Results:
- Compressive moduli increase non-monotonically with decreasing void fraction due to aggregate densification and void closure.
- Shear moduli increase monotonically with increasing fractal dimension of the aggregate backbone.
- Observed 2D auxetic behavior at intermediate coverages, suggesting resilience to deformation.
Conclusions:
- Interfacial rheology is strongly linked to microstructural changes in particle networks.
- Distinct deformation mechanisms govern compressive and shear moduli.
- The auxetic nature of these interfaces has implications for particle-coated droplet and bubble stability.
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