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The European Physical Journal E

, Volume 33, Issue 3, pp 219–242 | Cite as

Free energy of colloidal particles at the surface of sessile drops

  • J. GuzowskiEmail author
  • M. Tasinkevych
  • S. Dietrich
Regular Article

Abstract.

The influence of finite system size on the free energy of a spherical particle floating at the surface of a sessile droplet is studied both analytically and numerically. In the special case that the contact angle at the substrate equals \( \pi\)/2 , a capillary analogue of the method of images is applied in order to calculate small deformations of the droplet shape if an external force is applied to the particle. The type of boundary conditions for the droplet shape at the substrate determines the sign of the capillary monopole associated with the image particle. Therefore, the free energy of the particle, which is proportional to the interaction energy of the original particle with its image, can be of either sign, too. The analytic solutions, given by the Green's function of the capillary equation, are constructed such that the condition of the forces acting on the droplet being balanced and of the volume constraint are fulfilled. Besides the known phenomena of attraction of a particle to a free contact line and repulsion from a pinned one, we observe a local free-energy minimum for the particle being located at the drop apex or at an intermediate angle, respectively. This peculiarity can be traced back to a non-monotonic behavior of the Green's function, which reflects the interplay between the deformations of the droplet shape and the volume constraint.

Keywords

Free Energy Contact Angle Colloidal Particle Contact Line Volume Constraint 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

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Copyright information

© EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg 2010

Authors and Affiliations

  1. 1.Institut für Theoretische und Angewandte PhysikMax-Planck-Institut für MetallforschungStuttgartGermany
  2. 2.Universität StuttgartStuttgartGermany

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