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Nanogeometry Matters: Unexpected Decrease of Capillary Adhesion Forces with Increasing Relative Humidity
Author(s) -
Köber Mariana,
Sahagún Enrique,
GarcíaMochales Pedro,
Briones Fernando,
Luna Monica,
Sáenz Juan José
Publication year - 2010
Publication title -
small
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.785
H-Index - 236
eISSN - 1613-6829
pISSN - 1613-6810
DOI - 10.1002/smll.201001297
Subject(s) - capillary action , relative humidity , materials science , asperity (geotechnical engineering) , meniscus , capillary condensation , adhesion , nanometre , humidity , critical relative humidity , mechanics , composite material , nanotechnology , chemical physics , thermodynamics , optics , chemistry , physics , adsorption , incidence (geometry) , organic chemistry
Abstract The sticking effect between hydrophilic surfaces occurring at increasing relative humidity (RH) is an everyday phenomenon with uncountable implications. Here experimental evidence is presented for a counterintuitive monotonous decrease of the capillary adhesion forces between hydrophilic surfaces with increasing RH for the whole humidity range. It is shown that this unexpected result is related to the actual shape of the asperity at the nanometer scale: a model based on macroscopic thermodynamics predicts this decrease in the adhesion force for a sharp object ending in an almost flat nanometer‐sized apex, in full agreement with experiments. This anomalous decrease is due to the fact that a significant growth of the liquid meniscus formed at the contact region with increasing humidity is hindered for this geometry. These results are relevant in the analysis of the dynamical behavior of nanomenisci. They could also have an outstanding value in technological applications, since the undesirable sticking effect between surfaces occurring at increasing RH could be avoided by controlling the shape of the surface asperities at the nanometric scale.