Influence of humidity on the nanoadhesion between a hydrophobic and a hydrophilic surface

• Published in: Chemical physics letters 2011-02, Vol.503 (1-3), p.66-70
• Main Authors: Ptak, A., Gojzewski, H., Kappl, M., Butt, H.-J.
• Format: Article
• Language: English
• ISSN: 0009-2614; 1873-4448
• DOI: 10.1016/j.cplett.2010.12.088

[Display omitted] ► Strong dependence of the adhesion force on the loading rate due to the uncooperative behavior of van der Waals interactions (bonds). ► The JKR model of mechanical-adhesive contact and the DHS model of thermally activated unbinding applied to extract kinetic and interaction potential parameters for a single adhesive bond. ► Increase of the van der Waals interaction strength per molecule versus humidity due to gradual adsorption of water into tip surface hollows. The adhesion force between a silicon nitride tip and a 1-dodecanethiol monolayer have been measured at different loading rates and different humidity. A way to extract the kinetic and interaction potential parameters for a single molecule interaction is demonstrated. The effect of the increase of van der Waals interaction strength per molecule with increasing humidity is explained by assuming a gradual adsorption of water into the tip surface hollows. The study should help in better understanding of the humidity effect on molecular level and in avoiding the underestimation of adhesion forces in micro- and nano-engineering in ambient conditions.