Forces due to dynamic structure in thin liquid films (original) (raw)
Related papers
Dynamic Properties of Molecularly Thin Liquid Films
Science, 1988
An experimental technique is described for simultaneously measuring the static and dynamic interactions of very thin liquid films between two surfaces as they are moved normally or laterally relative to each other. Film thickness can be measured and controlled to 1 angstrom. Initial results are presented of the transition in the physical properties of liquid films only one molecular layer thick to thicker films whose properties are practically indistinguishable from the bulk. In particular, the results show that two molecularly smooth surfaces, when close together in simple liquids, slide (shear) past each other while separated by a discrete number of molecular layers, and that the frictional force is "quantized" with the number of layers.
Advances in Colloid and Interface Science, 2013
In this paper we review simulation and experimental studies of thermal capillary wave fluctuations as an ideal means for probing the underlying disjoining pressure and surface tensions, and more generally, fine details of the Interfacial Hamiltonian Model. We discuss recent simulation results that reveal a film-height-dependent surface tension not accounted for in the classical Interfacial Hamiltonian Model. We show how this observation may be explained bottom-up from sound principles of statistical thermodynamics and discuss some of its implications.
Experimental Confirmation of the Universal Law for the Vibrational Density of States of Liquids
2022
An analytical model describing the vibrational phonon density of states (VDOS) of liquids has long been elusive, mainly due to the difficulty in dealing with the imaginary modes dominant in the low-energy region, as described by the instantaneous normal mode (INM) approach. Nevertheless, Zaccone and Baggioli have recently developed such a model based on overdamped Langevin liquid dynamics. The model was proposed to be the universal law for the vibrational density of states of liquids. Distinct from the Debye law, g({\omega}) ~ {\omega}2, for solids, the universal law for liquids reveals a linear relationship, g({\omega}) ~ {\omega}, in the low-energy region. The universal law has been successfully verified with computer simulated VDOS for Lennard-Jones liquids. We further confirm this universal law with experimental VDOS measured by inelastic neutron scattering on real liquid systems including water, liquid metal, and polymer liquids. We have applied this model and extracted the eff...
Disjoining pressure in thin liquid films on charged structured surfaces
Submitted for the DFD10 Meeting of The American Physical Society Disjoining pressure in thin liquid films on charged structured surfaces CHRISTIAAN KETELAAR, VLADIMIR AJAEV, Southern Methodist University-We consider thin liquid films on various structured surfaces and compute the electrostatic component of disjoining pressure in the film. The regions of solid phase in contact with the liquid are assumed to be at a constant electrical potential. Presence of ions in the liquid implies that the electrical field there is described by the Poisson-Boltzmann equation. Situations are considered when liquid fills the spaces between the elements of the structure (e.g. grooves) and when pockets of air remain trapped there. The formulas for disjoining pressure are incorporated into a numerical method for calculation of deformations of air-liquid interfaces. Applications of our mathematical model to recent experiments on evaporation of thin liquid droplets on structured surfaces are discussed.
Theory of slope-dependent disjoining pressure with application to Lennard–Jones liquid films
Journal of Colloid and Interface Science, 2007
A liquid film of thickness h < 100 nm is subject to additional intermolecular forces, which are collectively called disjoining pressure Π. Since Π dominates at small film thicknesses, it determines the stability and wettability of thin films. Current theory derived for uniform films gives Π = Π(h). This solution has been applied recently to non-uniform films and becomes unbounded near a contact line as h → 0. Consequently, many different effects have been considered to eliminate or circumvent this singularity. We present a mean-field theory of Π that depends on the slope h x as well as the height h of the film. When this theory is implemented for Lennard-Jones liquid films, the new Π = Π(h, h x ) is bounded near a contact line as h → 0. Thus, the singularity in Π(h) is artificial because it results from extending a theory beyond its range of validity. We also show that the new Π can capture all three regimes of drop behavior (complete wetting, partial wetting, and pseudo-partial wetting) without altering the signs of the long and short-range interactions. We find that a drop with a precursor film is linearly stable.
Unexpected effect of internal degrees of freedom on transverse phonons in supercooled liquids
Europhysics Letters (EPL), 2006
We show experimentally that in a supercooled liquid composed of molecules with internal degrees of freedom the internal modes contribute to the frequency dependent shear viscosity and damping of transverse phonons, which results in an additional broadening of the transverse Brillouin lines. Earlier, only the effect of internal modes on the frequency dependent bulk viscosity and damping of longitudinal phonons was observed and explained theoretically in the limit of weak coupling of internal degrees of freedom to translational motion. A new theory is needed to describe this new effect. We also demonstrate, that the contributions of structural relaxation and internal processes to the width of the Brillouin lines can be separated by measurements under high pressure.