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Mouillage à l'échelle nanométrique : effet des forces à longue portée et des hétérogénéités du substrat

Abstract : Wetting phenomena on the nanoscale remain poorly understood in spite of their growing theoretical and practical interest. In this context, the present work aimed at studying partial wetting of nanometer-sized alkane droplets on "model" surfaces build by self-assembly of organic monolayers. For this purpose a novel technique, based on "noncontact" Atomic Force Microscopy (AFM), has been developed to image, with minimal artefacts, drops of adjustable size directly condensed on solid surfaces. We have thus shown that contact angle of alkanes, wetting a weakly heterogeneous, silanized substrate, noticeably decreases from its macroscopic value for droplets sizes in the submicron range. The line tension, arising in this case from purely dispersive long-range interactions between the liquid and the substrate, is theoretically too weak to be responsible for the observed effect. Therefore we have supposed that contact angle is affected by mesoscopic chemical heterogeneities of the substrate whenever the droplets size becomes suciently small. This scenario has been supported by numerical simulations based on a simplified model of the spatial distribution of surface defects. Similar experiments, performed on different substrates (monolayers made of alcanethiols self-assembled on gold and of alkyl chains covalently bound onto a silicon surface), have also shown that wetting on small scales is strongly affected by minimal physical and chemical surface heterogeneities. Finally, to provide further examples of the potential of the above mentioned AFM technique, we have studied the wettability of nano-structured surfaces and the local wetting properties of hair.
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https://tel.archives-ouvertes.fr/tel-00003648
Contributor : Antonio Checco <>
Submitted on : Sunday, October 26, 2003 - 7:02:18 PM
Last modification on : Friday, March 5, 2021 - 3:00:47 PM
Long-term archiving on: : Wednesday, September 12, 2012 - 11:15:28 AM

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  • HAL Id : tel-00003648, version 1

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Antonio Checco. Mouillage à l'échelle nanométrique : effet des forces à longue portée et des hétérogénéités du substrat. Analyse de données, Statistiques et Probabilités [physics.data-an]. Université Pierre et Marie Curie - Paris VI, 2003. Français. ⟨tel-00003648⟩

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