Berlin 2008 – wissenschaftliches Programm

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 26: Micro and Nano Fluidics I: Liquids at structured materials

CPP 26.1: Hauptvortrag

Mittwoch, 27. Februar 2008, 14:00–14:30, C 264

The Capillary Rise of Liquids in Nanopores — •Patrick Huber — Faculty of Physics, Saarland University, D-66041 Saarbruecken

Liquid flow driven by capillary forces is one of the most intriguing transport mechanisms in nature and technology. It is governed by a fascinating interplay of interfacial, inertia, viscous drag as well as gravity forces which liquids encounter upon invasion into geometries with often complex topologies, such as capillary networks of trees or interconnected pores and fractures in soils and ice. Whereas a detailed understanding of this phenomenon has been achieved on macroscopic scales, it is poorly explored on the meso- and nanoscale, where predictions regarding its mechanisms are hampered due to a possible break-down of continuum hydrodynamics, conflicting reports with respect to the conservation of the fluidity and capillarity of liquids upon spatial confinement. Here we present optical and gravimetrical measurements on the capillary rise of liquids as a function of their complexity (water, chain-like hydrocarbons and rod-like liquid crystals) in networks of silica capillaries with 2.5 nm and 5 nm radii (monolithic mesoporous Vycor). We find classical Lucas-Washburn square-root-of-time invasion dynamics over the entire capillary rise time investigated (up to several hours). We demonstrate that conserved macroscopic capillary rise hydrodynamics are intimately related to the capillary condensation/evaporation hysteresis characteristic of the thermodynamic state of spatially nanoconfined liquids.

This work has been supported within the DFG priority program 1164, Nano- & Microfluidics (Hu850/2).