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Why liquids can appear to solidify during squeeze-out - Even when they don't
1Dept. of Materials Science and Engineering, Universität des Saarlandes, 66123 Saarbrücken, Germany.
Journal of Colloid and Interface Science
|December 17, 2019
Summary
Liquids squeezed between surfaces show layering and increased viscosity, often mistaken for solidification. This behavior is better explained by pressurized liquid structure, allowing load-bearing and suppressed flow under confinement.
Area of Science:
- Physics of confined liquids
- Materials science
- Rheology
Background:
- Liquids between surfaces can exhibit layering, load-bearing, and increased viscosity.
- This behavior is often termed confinement-induced solidification.
- Bulk liquids possess inherent structure, including density correlations beyond the nanoscale.
Purpose of the Study:
- To propose an alternative interpretation for liquid behavior under confinement.
- To explain phenomena like layering and load-bearing as a non-zero wavevector response.
- To investigate the role of liquid structure in confined environments.
Main Methods:
- Molecular-dynamics simulations were employed.
- A key commercial base-oil component (1-decene trimer) was studied.
- Simulations focused on liquid squeezed between a ridge and a substrate.
Main Results:
- Layering observed in confined oil mirrors bulk liquid density correlations.
- Confined liquids can sustain significant non-isotropic stresses (exceeding 100 MPa).
- Viscosity locally increases, suppressing liquid flow within the confined zone.
Conclusions:
- Confinement-induced phenomena in liquids are better explained by their inherent structure and pressurized state.
- The non-zero wavevector response allows liquids to sustain stress and resist flow.
- This provides a new framework for understanding liquid behavior in confined geometries.
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