The origin of ultrasound-induced friction reduction in microscopic mechanical contacts

• Published in: IEEE transactions on ultrasonics, ferroelectrics, and frequency control ferroelectrics, and frequency control, 2002-03, Vol.49 (3), p.356-364
• Main Authors: Hesjedal, T., Behme, G.
• Format: Article
• Language: English
• Subjects: Acoustic propagation; Acoustic signal detection; Acoustic waves; Acoustics - instrumentation; Diodes; Equipment Design - methods; Exact sciences and technology; Friction; Friction reduction; Fundamental areas of phenomenology (including applications); Love waves; Lubrication; Mechanical contact (friction...); Microelectrodes; Microscopy; Microscopy, Atomic Force - instrumentation; Microscopy, Atomic Force - methods; Miniaturization - instrumentation; Miniaturization - methods; Nanotechnology - instrumentation; Nanotechnology - methods; Origins; Oscillations; Physics; Polarization; Radio Waves; Sawing machines; Saws; Sensitivity and Specificity; Silicon - chemistry; Solid mechanics; Structural and continuum mechanics; Surface acoustic waves; Transducers; Tribology and mechanical contacts; Ultrasonic imaging; Ultrasonics; Wave propagation
• ISSN: 0885-3010; 1525-8955
• DOI: 10.1109/58.990954

We present a study of the origin of ultrasound-induced friction reduction in microscopic mechanical contacts. The effect of friction reduction caused by Rayleigh-type surface acoustic waves (SAWs) is demonstrated for propagating and two-dimensional, standing wave fields using lateral force microscopy (LFM). It is shown that with increasing wave amplitude, friction is completely suppressed. To detect and distinguish between the effect of lateral and vertical surface oscillation components on the cantilever movement, we employed multimode scanning acoustic force microscopy (SAFM). We found that the friction reduction effect is only due to the vertical oscillation component. Because this effect does not appear for purely in-plane polarized Love waves, we concluded that the mechanical diode effect is most probably responsible for the SAW-induced lubrication. This explanation is also supported by vertical and longitudinal SAFM measurements, which show that, in areas where friction is completely suppressed, low frequency vertical cantilever oscillations can still be observed, whereas lateral or torsional oscillations are no longer excited.