Dresden 2011 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 7: Interfaces and Thin Films II
CPP 7.10: Vortrag
Montag, 14. März 2011, 16:30–16:45, ZEU 114
Microcantilever sensors for monitoring microdrop evaporation of pure liquids and binary mixtures — •Dmytro Golovko1, Chuanjun Liu1,2, and Elmar Bonaccurso1 — 1Center of Smart Interfaces, TU-Darmstadt, Germany — 2Max Planck Institute for Polymer Research, Mainz, Germany
We describe in detail a nonimaging technique [1] that allows the measurement of the mass, the radius, and the contact angle of evaporating sessile microdrops of pure liquids and binary mixtures. The microdrops were deposited onto hydrophobized silicon microcantilevers whose bending and resonance frequency were monitored during drop evaporation. We verify the laws of evaporation kinetics for microdrops with diameters from 80 down to 10 um.
The evaporation of mixtures of water/ethanol drops confirmed previous results with millimeter sized drops. N,N-dimethylformamide drops undergo a transformation from an initial spherical shape to a thin film. Flattening of the drop causes a slowdown of the evaporation kinetics at the end. Two concurring factors are at its origin: the rising disjoining pressure stabilizes the thin liquid film and the increasing radius of curvature of the drop reduces the vapor pressure [2].
[1] Bonaccurso E., Butt, H.-J., J. Phys. Chem. B 109, 253 (2005). [2] Liu C.J. & Bonaccurso E., Rev. Sci. Instrum. 81, 013702 (2010).