Vibration-induced nanoscale friction modulation on piezoelectric materials

Abstract

Mechanical vibration, as an alternative of application of solid/liquid lubricants, has been an effective means to modulate friction at the macroscale. Recently, atomic force microscopy (AFM) experiments and model simulations also suggest a similar vibration-induced friction reduction effect for nanoscale contact interfaces, although an additional external vibration source is typically needed to excite the system. Here, by introducing a piezoelectric thin film along the contact interface, we demonstrate that friction measured by a conductive AFM probe can be significantly reduced (more than 70%) when an alternating current (AC) voltage is applied. Such real-time friction modulation is achieved owing to the localized nanoscale vibration originating from the intrinsic inverse piezoelectric effect, and is applicable for various material combinations. Assisted by analysis with the Prandtl—Tomlinson (P—T) friction model, our experimental results suggest that there exists an approximately linear correlation between the vibrational amplitude and the relative factor for perturbation of sliding energy corrugation. This work offers a viable strategy for realizing active friction modulation for small-scale interfaces without the need of additional vibration source or global excitation that may adversely impact device functionalities.

Modulating Friction by the Phase of the Vertical Vibrational Excitation at Washboard Frequency

“…It means that periodic textured surfaces and atomically flat surfaces have similar functions in terms of modulating friction force. Since our studies above and those of many others − have shown that the application of excitation at the resonant frequencies of the frictional system can reduce the friction force, here we directly fix the excitation frequency at the washboard frequency. Figure c clearly shows that the friction force changes periodically at washboard frequency as the initial phase angle φ increases gradually from 0 to 360°.…”

“…These groundbreaking experiments open the door to superlubricity, a state with a friction coefficient of less than 0.01 between two rubbing surfaces. , Shortly thereafter, superlubricity is recognized as the ultimate solution to protect various mechanical systems from malfunctions caused by friction and wear. , Recently, many researchers in the community have conducted theoretical − and experimental − investigations on superlubricity. Several techniques and experimental strategies have been proposed to achieve superlubricity, such as the incommensurate surface , and the application of mechanical vibrations. − However, there is still a scientific gap between the proposed superlubricity technology and practical engineering application due to the complexity of friction and energy dissipation involved in the buried interface …”