Influence of capillary condensation of water in nanoscale friction

Abstract

When in ambient air, the contact between an atomic force microscope tip and a sample is usually wetted due to the capillary condensation of water. This water layer affects both the normal force at the nanoasperity contacts by the effect of a meniscus loading force and the friction force by the meniscus kinetics. In this work, the influence of the water condensation, at the tip surface contact, on the friction force is studied for hydrophilic, partially hydrophilic, and hydrophobic surfaces. It is shown that the surface wettability plays an important role on the dependence of friction with the normal force and scanning velocity.

Powder Technology and Pharmaceutical Development: Particle Size and Particle Adhesion

“…The behavior of the cantilever has been found to be consistent with the classical theories of friction but is additionally influenced by adsorbed layers of water when surfaces are studied in air [74][75] .…”

On the modified Tabor parameter for the JKR–DMT transition in the presence of a liquid meniscus

“…In an ambient environment (45% RH), the Kelvin radius is about 0.66 nm. Any roughness smaller than this gives the appearance of single asperity contact [52,53] due to capillary condensation. Furthermore, repeated sliding results in smoother surfaces due to dislocation nucleation and accumulation and annihilation activities [54].…”

“…In the cited papers it is pointed out that there are problems in using AFM to determine the surface tension accurately due to the surface roughness, uncertainty in calibration and heterogeneity issues. The surface roughness can be solved by transferring a small amount of liquid to the tip in order to obtain a smoother surface [52,53,62]. The second problem can be solved by directly calibrating the sensor beam in situ [67,68].…”

Effect of Normal Contact Vibration on Nano-Scale Friction

“…For the SiO x -tip, we set R tip = 7 nm in agreement with the manufacturer's data. The effect of water condensate on the adhesion and friction between hydrophilic and hydrophobic partners has been investigated in detail (see, for example, References [44][45][46]). In an early study, the authors in Reference [44] used bidirectional force microscopy to determine the effect of capillary condensation and humidity on friction and adhesion between a tungsten tip and a hydrophilic silicon surface, and less hydrophilic amorphous carbon and lubricated silicon oxide surfaces.…”