Berlin 2012 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 21: Poster: Wetting, Micro and nanofluidics

CPP 21.21: Poster

Mittwoch, 28. März 2012, 11:00–13:00, Poster A

Influence of solute–dependent wettability on the stability of films of mixtures and suspensions — •Desislava V. Todorova and Uwe Thiele — Department of Mathematical Sciences, Loughborough University, Loughborough, Leicestershire, LE11 3TU, UK

We discuss the behaviour of thin films of non-volatile liquid mixtures, colloidal suspensions and polymer solutions on a solid substrate. First, we reformulate the coupled long-wave time evolution equations for the film height and mean solute concentration for a ’passive’ solute in gradient dynamics. This form can then be extended to incorporate additional effects [1]. In particular, we focus on a concentration-dependent wettability. It is determined employing homogenisation techniques to obtain effective optical characteristics [2]. Combining this with classical theory of effective molecular interactions between the film surface and the substrate, we arrive at a Derjaguin (or disjoining) pressure that depends on film height and concentration.

We use the derived model to study the linear stability of flat homogeneous films. In particular, we investigate how the stability thresholds are influenced by the incorporation of the additional degree of freedom related to the concentration field. As an outlook we also analyse nonlinear thickness and concentration profiles for steady droplets.

[1] U. Thiele, Eur. Phys. J. Special Topics 197, 213-220 (2011).

[2] G. A. Niklasson, C. G. Granqvist, O. Hunderi, Appl. Optics 20, 26-30 (1981); D. Todorova et al., J. Optoelectron. Adv. Mater. 11, 1296-1299 (2009).

We acknowledge support by the EU (PITN-GA-2008-214919).