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Dynamic surface force measurement. I. van der Waals collisions Phil Attarda)

Summary: Dynamic surface force measurement. I. van der Waals collisions
Phil Attarda)
Ian Wark Research Institute, University of South Australia, The Levels, SA 5095, Australia
Jamie C. Schulz and Mark W. Rutland
School of Chemistry F11, University of Sydney, NSW, 2006, Australia
Received 7 July 1998; accepted for publication 12 August 1998
Theoretical calculations and experimental measurements are used to show that hitherto neglected
inertial effects can be significant in computer-controlled surface force measurement devices such as
the atomic force microscope. The problem is analyzed in detail for the case of the van der Waals
attraction in air. It is demonstrated that equating the cantilever deflection to the surface force
systematically underestimates the magnitude of the surface force, increasingly so as the speed of
approach is increased. It is also shown that the surface separation becomes lost at high accelerations
due to a dynamic uncoupling of the cantilever deflection and angle. The effects of elastic
deformation of the bodies are taken into account, including the collision-induced elastic vibrations
in the solids. Experimental data are obtained for the van der Waals attraction and collision of glass
surfaces in air using the measurement and analysis of surface forces device. All of the effects found
in the theoretical calculations are identified in the experimental data. 1998 American Institute of
Physics. S0034-6748 98 03511-4
A new era in direct surface force measurement began


Source: Attard, Phil - School of Chemistry, University of Sydney


Collections: Chemistry