60 research outputs found
The influence of droplet size on line tension
Within the effective interfacial Hamiltonian approach we evaluate the excess
line free energy associated with cylinder-shaped droplets sessile on a
stripe-like chemical inhomogeneity of a planar substrate. In the case of
short-range intermolecular forces the droplet morphology and the corresponding
expression for the line tension - which includes the inhomogeneity finite width
effects - are derived and discussed as functions of temperature and increasing
width. The width-dependent contributions to the line tension change their
structure at the stripe wetting temperature T_W1: for T<T_W1 they decay
exponentially while for T>T_W1 the decay is algebraic. In addition, a geometric
construction of the corresponding contact angle is carried out and its
implications are discussed
Phase Transitions in Multicomponent String Model
We propose a one-dimensional model of a string decorated with adhesion
molecules (stickers) to mimic multicomponent membranes in restricted
geometries. The string is bounded by two parallel walls and it interacts with
one of them by short range attractive forces while the stickers are attracted
by the other wall. The exact solution of the model in the case of infinite wall
separation predicts both continuous and discontinuous transitions between
phases characterised by low and high concentration of stickers on the string.
Our model exhibits also coexistence of these two phases, similarly to models of
multicomponent membranes.Comment: letter, 8 pages, 3 figure
Interfacial fluctuations near the critical filling transition
We propose a method to describe the short-distance behavior of an interface
fluctuating in the presence of the wedge-shaped substrate near the critical
filling transition. Two different length scales determined by the average
height of the interface at the wedge center can be identified. On one length
scale the one-dimensional approximation of Parry et al. \cite{Parry} which
allows to find the interfacial critical exponents is extracted from the full
description. On the other scale the short-distance fluctuations are analyzed by
the mean-field theory.Comment: 13 pages, 3 figure
Interfacial morphology and correlations in adsorption at a chemically structured substrate - exact results in d=2
Adsorption at a 1-dimensional planar substrate equipped with a localized
chemical inhomogeneity is studied within the framework of a continuum
interfacial model from the point of view of interfacial morphology and
correlation function properties. Exact expressions for the one-point and
two-point probability distribution functions and
, being the
interface position above a fixed point of the substrate, are derived
for temperature corresponding to the inhomogeneity's wetting transition. It is
demonstrated that in the limit of macroscopic inhomogeneity's size the net
effect of the remaining homogeneous parts of the substrate on the interfacial
morphology above the inhomogeneity is exactly equivalent to appropriate pinning
of the interface at its boundaries. The structure of the average interfacial
morphology and correlation function in this limit are discussed and compared to
earlier results obtained for systems with homogeneous substrate
Liquid drop in a cone - line tension effects
The shape of a liquid drop placed in a cone is analyzed macroscopically.
Depending on the values of the cone opening angle, the Young angle and the line
tension four different interfacial configurations may be realized. The phase
diagram in these variables is constructed and discussed; it contains both the
first- and the second-order transition lines. In particular, the tricritical
point is found and the value of the critical exponent characterizing the
behaviour of the system along the line of the first-order transitions in the
neighbourhood of this point is determined.Comment: 11 pages, 4 figure
Contact line stability of ridges and drops
Within the framework of a semi-microscopic interface displacement model we
analyze the linear stability of sessile ridges and drops of a non-volatile
liquid on a homogeneous, partially wet substrate, for both signs and arbitrary
amplitudes of the three-phase contact line tension. Focusing on perturbations
which correspond to deformations of the three-phase contact line, we find that
drops are generally stable while ridges are subject only to the long-wavelength
Rayleigh-Plateau instability leading to a breakup into droplets, in contrast to
the predictions of capillary models which take line tension into account. We
argue that the short-wavelength instabilities predicted within the framework of
the latter macroscopic capillary theory occur outside its range of validity and
thus are spurious.Comment: 6 pages, 1 figur
Universality for 2D Wedge Wetting
We study 2D wedge wetting using a continuum interfacial Hamiltonian model
which is solved by transfer-matrix methods. For arbitrary binding potentials,
we are able to exactly calculate the wedge free-energy and interface height
distribution function and, thus, can completely classify all types of critical
behaviour. We show that critical filling is characterized by strongly universal
fluctuation dominated critical exponents, whilst complete filling is determined
by the geometry rather than fluctuation effects. Related phenomena for
interface depinning from defect lines in the bulk are also considered.Comment: 4 pages, 1 figur
Wetting films on chemically heterogeneous substrates
Based on a microscopic density functional theory we investigate the
morphology of thin liquidlike wetting films adsorbed on substrates endowed with
well-defined chemical heterogeneities. As paradigmatic cases we focus on a
single chemical step and on a single stripe. In view of applications in
microfluidics the accuracy of guiding liquids by chemical microchannels is
discussed. Finally we give a general prescription of how to investigate
theoretically the wetting properties of substrates with arbitrary chemical
structures.Comment: 56 pages, RevTeX, 20 Figure
Critical adsorption near edges
Symmetry breaking surface fields give rise to nontrivial and long-ranged
order parameter profiles for critical systems such as fluids, alloys or magnets
confined to wedges. We discuss the properties of the corresponding universal
scaling functions of the order parameter profile and the two-point correlation
function and determine the critical exponents eta_parallel and
eta_perpendicular for the so-called normal transition.Comment: 22 pages, 5 figures, accepted for publication in PR
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