Regensburg 2010 – wissenschaftliches Programm

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SYNT: Symposium Nanotribology

SYNT 1: Symposium Nanotribology

SYNT 1.6: Hauptvortrag

Freitag, 26. März 2010, 12:45–13:15, H1

Influence of humidity on nano- and micromechanical contact adhesion — •Hans-Jürgen Butt — Planck Institute for Polymer Research, Mainz, Germany

The interaction between hydrophilic surfaces or particles in air is often dominated by capillary forces. In this case capillary forces are caused by liquid menisci forming in the gap between the surfaces by capillary condensation. Significant progress has been made during the last decade in understanding capillary forces. In particular the influence of surface roughness is now better understood. After giving an introduction into the subject recent results are presented. To analyse capillary forces we measured the adhesion forces between atomic force microscope (AFM) tips or particles attached to AFM cantilevers and different solid samples. Humidity was adjusted relatively fast to minimize tip wear during one experiment. It is demonstrated that the results can be interpreted with simple continuum theory of the meniscus force. The capillary force between two fine particles or between the AFM tip and a sample depends on the precise geometry of the contact region on the 1 nm length scale. We demonstrate that vice versa from a measurement of the adhesion force versus humidity one can calculate the shape of the AFM tip. Finally, a simple, approximate formalism is described to calculate capillary forces between solid surfaces analytically.