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Harnessing the wetting and drying of hydrophobic nanopores - Cyril Picard

Laboratoire Interdisciplinaire de Physique, Grenoble


Hydrophobic nanoporous materials behave as anti-sponges when immersed within aqueous solutions. The liquid, that can be forced to enter the nanopores at high pressure, is spontaneously expelled out of the pores when the pressure is released. This forced wetting and spontaneous drying combination can be harnessed to characterize experimentally the physical behavior of liquids within strong hydrophobic confinement. Selecting the nanopore size, fluids can be studied up to the limit of validity of the continuum approach and beyond. In model hydrophobic nanopores of diameter larger than typically ten water molecules, it has been shown that macroscopic concepts still hold and that interfacial phenomena control both the forced wetting poreuse and spontaneous drying of the pores. With subnanometric pores, such as those of zeolites or Metal Organic Frameworks (MOF), a breakdown occurs. We have recently demonstrated from macroscopic measurements on electrolyte solutions that molecular sieving of hydrated ions leads to giant osmotic pressures that have to be overcome to be able to fill the pores. I will show from mechanical measurement done in dynamical regime at various temperature that the pure water case is nonetheless particularly intriguing.

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