Berlin 2012 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 36: Wetting, Micro and nanofluidics I

CPP 36.7: Vortrag

Donnerstag, 29. März 2012, 17:00–17:15, C 264

Imaging of wetting dynamics of a molecularly thin fluid film in a soft graphene-mica slit pore — •Nikolai Severin, Philipp Lange, Igor M. Sokolov, and Jürgen P. Rabe — Department of Physics, Humboldt-Universität zu Berlin, Newtonstr. 15, 12489 Berlin, Germany

The behavior of water and other molecular liquids confined to the nanoscale is of fundamental importance, e.g., in biology, material science, nanofluidics and tribology. Direct microscopic imaging of wetting dynamics in sub-nanometer pores is however challenging. We demonstrate high resolution imaging of a molecularly thin water film wetting the interface between mica and graphene. Ambient humidity allows to control the wetting and dewetting of the film. We follow these processes in space and time using scanning force microscopy imaging of the graphene conforming to the film. At sufficiently high humidity a continuous molecularly thin water film wets the interface between the graphene and mica. At lower humidities the film dewets with fractal depressions exhibiting dimensions around 1.7 and depths comparable to the size of a water molecule. The soft graphene cover offers a previously unexplored semi-hydrophilic slit pore of self-adjustable size, which enables high resolution imaging of confined molecularly thin fluid films. Moreover, the self-adjusting slit pore geometry implies prospects to experiment with other liquids and liquid mixtures with molecules of variable sizes. The soft electrically conducting cover offers interesting opportunities for the fabrication of novel nano-fluidic devices including an electrically driven pump.