Non-Contact Friction

The van der Waals force, a weak force at work between two neutral but polar atoms or molecules (that is, the objects can possess a polarity), can be amplified in some settings. Thus atoms or molecules adsorbed onto a solid surface can act like a miniature dipole antenna which in turn attracts a similar adsorbed atom on another surface. In this way the non-contact van der Waals force between the surfaces---in effect, the friction between the surfaces---can be greatly amplified.

Reported by: Volokitin and Persson, Physical Review Letters, 5 September 2003

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