Contact-line fluctuations and dynamic wetting

Autor: J. C. Fernández-Toledano, T. D. Blake, J. De Coninck
Rok vydání: 2019
Předmět:
Zdroj: Journal of Colloid and Interface Science. 540:322-329
ISSN: 0021-9797
DOI: 10.1016/j.jcis.2019.01.041
Popis: Hypothesis The thermal fluctuations of the three-phase contact line formed between a liquid and a solid at equilibrium can be used to determine key parameters that control dynamic wetting. Methods We use large-scale molecular dynamics simulations and Lennard-Jones potentials to model a liquid bridge between two molecularly smooth solid surfaces and study the positional fluctuations of the contact lines so formed as a function of the solid–liquid interaction. Findings We show that the fluctuations have a Gaussian distribution and may be modelled as an overdamped one-dimensional Langevin oscillator. Our analysis allows us to extract the coefficients of friction per unit length of the contact lines ζ , which arise from the collective interaction of the contact-line’s constituent liquid atoms with each other and the solid surface. We then compare these coefficients with those obtained by measuring the dynamic contact angle as a function of contact-line speed in independent simulations and applying the molecular-kinetic theory of dynamic wetting. We find excellent agreement between the two, with the same dependence on solid–liquid interaction and, therefore, the equilibrium contact angle θ 0 . As well as providing further evidence for the underlying validity of the molecular-kinetic model, our results suggest that it should be possible to predict the dynamics of wetting and, in particular, the velocity-dependence of the local, microscopic dynamic contact angle, by experimentally measuring the fluctuations of the contact line of a capillary system at equilibrium. This would circumvent the need to measure the microscopic dynamic contact angle directly.
Databáze: OpenAIRE
Externí odkaz: