Berlin 2018 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 33: Poster Session III

CPP 33.28: Poster

Tuesday, March 13, 2018, 14:00–16:00, Poster C

Beyond the standard line tension: Size-dependent contact angles of water nanodroplets — •Matej Kanduc — Soft Matter and Functional Materials, Helmholtz-Zentrum Berlin für Materialien und Energie, Hahn-Meitner-Platz 1, D-14109 Berlin, Germany

The dependence of the contact angle on the size of a nanoscopic droplet residing on a flat substrate is traditionally ascribed solely to line tension. Other contributions, stemming from the droplet geometry dependence of the surface tension and line tension, are typically ignored. We performed molecular dynamics simulations of water droplets of cylindrical morphology on surfaces of a wide range of polarities. In the cylindrical geometry, where the line tension is not operative directly, we found significant contact angle dependence on the droplet size [1]. The effect is most pronounced on hydrophilic surfaces, with the contact angle increase of up to 10° with a decreasing droplet size. On hydrophobic surfaces, the trend is reversed and considerably weaker. Our analysis suggests that these effects can be attributed to the Tolman correction due to the curved water-vapor interface and to a generalized line tension that possesses a contact angle dependence. The latter is operative also in the cylindrical geometry and yields a comparable contribution to the contact angle as the line tension itself in case of spherical droplets.

[1] M. Kanduc, J. Chem. Phys. 147, 174701 (2017)