Comparison of Friction Measurements Using the Atomic Force Microscope and the Surface Forces Apparatus: The Issue of Scale

Published

May 1, 2001

Author(s)

P M. McGuiggan, J Zhang, Stephen M. Hsu

Abstract

Results are presented of lateral force measurements using the atomic force microscope (AFM) and the Surface Forces Apparatus (SFA). Two different probes are used in the AFM measurements: sharp silicon nitride tip (radius R {nearly equal to} 20 nm) and a glass ball (R {nearly equal to} 15 microυ) . The lateral force is measured between the (silicon nitride or glass) probe and a mica surface which had been coated by a thin lubricant film. In the SFA, a thin lubricant film separates two molecularly smooth mica surfaces (R{nearly equal to} lcm) which are slid relative to each other. Perfluoropolyether (PFPE) and polydimethylsiloxane (PDMS) were used as the lubricant films. With a large probe, the PFPE film shows much lower friction than PDMS. However, as the size of the probe decreases, the friction decreases until no clear distinction between the tribological properties of the films can be made. Hence, there is a correlation between the measured coefficient of friction and the size of the meassurement probe, at least for small dimensions.

Citation

Tribology Letters

Volume

10

Issue

No. 4

Pub Type

Journals

Keywords

atomic force microscopy, friction, friction of thin films, surface forces apparatus, tribology, uncertainties

Citation

McGuiggan, P. , Zhang, J. and Hsu, S. (2001), Comparison of Friction Measurements Using the Atomic Force Microscope and the Surface Forces Apparatus: The Issue of Scale, Tribology Letters (Accessed March 13, 2025)