Imaging high-speed friction at the nanometer scale

Abstract

Friction is a complicated phenomenon involving nonlinear dynamics at different length and time scales. Understanding its microscopic origin requires methods for measuring force on nanometer-scale asperities sliding at velocities reaching centimetres per second. Despite enormous advances in experimental technique, this combination of small length scale and high velocity remain elusive. We present a technique for rapidly measuring the frictional forces on a single asperity over a velocity range from zero to several centimetres per second. At each image pixel we obtain the velocity dependence of both conservative and dissipative forces, revealing the transition from stick-slip to smooth sliding friction. We explain measurements on graphite using a modified Prandtl–Tomlinson model, including the damped elastic deformation of the asperity. With its improved force sensitivity and small sliding amplitude, our method enables rapid and detailed surface mapping of the velocity dependence of frictional forces with less than 10 nm spatial resolution.

Lyapunov estimation for high-speed demodulation in multifrequency atomic force microscopy

“…Intermodulation AFM is a novel extension to the bimodal method that focuses on the mixing products of a slightly below and above resonance bimodal drive. It has been shown to achieve increased image contrast [ 17 ] and lead to further insights into nanomechanical properties [ 18 ]. Regardless of which particular MF-AFM method is employed, they each require the demodulation of amplitude and phase to form observables for the characterization of nanomechanical properties.…”

A review of demodulation techniques for multifrequency atomic force microscopy

“…In addition, this zeroing characteristic can provide strong attenuation of unwanted harmonics and intermodulation products. This has lead to the multifrequency coherent demodulator being successfully applied to intermodulation AFM [26,27].…”

“…Compared to higher-harmonic AFM, this technique has more enhanced nonlinear interactions [25]. Intermodulation products present in the cantilevers motion have been shown to be sensitive to material and chemical contrast [16,26], leading to enhanced nanomechanical insights [27]. Regardless of which MF-AFM technique is performed, the demodulator is an essential component for acquiring observables to characterize the sample.…”

Friction Determination by Atomic Force Microscopy in Field of Biochemical Science

“…However, there is little application for lateral force measurements (such as friction force) [ 29 , 30 , 31 , 32 ]; thus, there is not much comprehensive systematic review on friction determination by AFM. This article is based on the measurement of friction by AFM at the single molecule level in the field of biochemical science.…”