Article
Squeeze-out dynamics of nanoconfined water: A detailed nanomechanical study
Physical review E: Statistical, nonlinear, and soft matter physics
(2015)
Abstract
In this study, we present a detailed analysis of the squeeze-out dynamics of nanoconfined water confined between two hydrophilic surfaces measured by small-amplitude dynamic atomic force microscopy. Explicitly considering the instantaneous tip-surface separation during squeeze-out, we confirm the existence of an adsorbed molecular water layer on mica and at least two hydration layers. We also confirm the previous observation of a sharp transition in the viscoelastic response of the nanoconfined water as the compression rate is increased beyond a critical value (previously determined to be about 0.8 nm/s). We find that below the critical value, the tip passes smoothly through the molecular layers of the film, while above the critical speed, the tip encounters "pinning" at separations where the film is able to temporarily order. Preordering of the film is accompanied by increased force fluctuations, which lead to increased damping preceding a peak in the film stiffness once ordering is completed. We analyze the data using both Kelvin-Voigt and Maxwell viscoelastic models. This provides a complementary picture of the viscoelastic response of the confined water film.
Disciplines
Publication Date
2015
DOI
https://doi.org/10.1103/PhysRevE.92.042403
Citation Information
Peter M. Hoffmann and Shah H. Khan. "Squeeze-out dynamics of nanoconfined water: A detailed nanomechanical study" Physical review E: Statistical, nonlinear, and soft matter physics (2015) Available at: http://works.bepress.com/peter_m_hoffmann/14/