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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 38: Micro and Nanofluidics II

CPP 38.2: Vortrag

Donnerstag, 25. März 2010, 09:45–10:00, H39

Stability of Nanobubbles — •Ralf Kaminke and Klaus Mecke — Institut für Theoretische Physik I, Staudtstr. 7, D - 91058 Erlangen

Gas nanobubbles on substrates were expected to be unstable due to a large Laplace pressure. But AFM images combined with infrared spectroscopy confirmed that they exist and that they are relatively stable [Zhan et al., Phys. Rev. Lett. 98, 136101 (2007)]. As they are not observable in bulk liquids, the substrate must play an important role and therefore density functional theory is the appropriate approach. The bubbles are modelled by spherical caps of nanometer thickness on a flat substrate, so that pressure and density inside the cap is determined by the substrate potential. The gas density is influenced by the substrate strength, the contact angle and the liquid density outside the cap. For a given radius of the spherical cap it is possible to find a contact angle, which minimizes the grand canonical potential and gives a metastable or stable solution depending on the size of the cap. This explains the existence of nanobubbles by substrate potentials.