Effective interactions of colloids on nematic films

• Published in: The European physical journal. E, Soft matter and biological physics Vol. 28; no. 2; pp. 99 - 111
• Main Authors: Oettel, M., Domınguez, A., Tasinkevych, M., Dietrich, S.
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer-Verlag 01-02-2009; EDP Sciences
• Subjects: Biological and Medical Physics; Biophysics; Chemistry; Colloidal state and disperse state; Complex Fluids and Microfluidics; Complex Systems; Exact sciences and technology; General and physical chemistry; Nanotechnology; Physical and chemical studies. Granulometry. Electrokinetic phenomena; Physics; Physics and Astronomy; Polymer Sciences; Regular Article; Soft and Granular Matter; Surfaces and Interfaces; Thin Films; 61.30.-v Liquid crystals; 68.03.Cd Surface tension and related phenomena; 82.70.Dd Colloids; Attraction; Patterning; Separation; Film; Force; Droplet; Liquid crystals; Colloid; Thickness; Substrate; Nematic state; Interface; Colloid particle
• ISSN: 1292-8941; 1292-895X
• DOI: 10.1140/epje/i2008-10360-1

The elastic and capillary interactions between a pair of colloidal particles trapped on top of a nematic film are studied theoretically for large separations
d
. The elastic interaction is repulsive and of quadrupolar type, varying as d
-5
. For macroscopically thick films, the capillary interaction is likewise repulsive and proportional to d
-5
as a consequence of mechanical isolation of the system comprised of the colloids and the interface. A finite film thickness introduces a nonvanishing force on the system (exerted by the substrate supporting the film) leading to logarithmically varying capillary attractions. However, their strength turns out to be too small to be of importance for the recently observed pattern formation of colloidal droplets on nematic films.