Measurements of and Relation Between the Adhesion and Friction of Two Surfaces Separated by Molecularly Thin Liquid Films

Abstract

A new technique is described for sliding (shearing) two molecularly smooth surfaces laterally past each other in liquids while monitoring their exact contact area, the normal and transverse forces, and the surface separation. First, we show that the elastic deformations of two initially curved surfaces in adhesive contact are the same under static and dynamic (i.e., sliding) conditions. Detailed results are then presented of how the shear properties of thin films of water and a simple nonpolar liquid are “quantized” with the number of layers. Results with water as the intervening liquid, as well as the effects of humidity on sliding in air, reveal that more complex mechanisms are operating than with simple liquids which appear to be related to the complex “hydration” forces between two surfaces in water or in aqueous salt solutions. The results suggest a close correlation between the static forces and shear properties of very thin liquid films, and the molecular structure of the liquids confined within such films.

Effect of Changing Ellipiticity Ratio on the Formation of Ultra-Thin Lubricating Film

“…This has already been shown by Matsouka and Kato [21], Al-samieh and Rahnejat [22], Alsamieh [24], Van Megen and Snook [28], Horn and Israelachvili [29], Israelachvili et al [30], Homola et al [31], Israelachvili [32], Philippe Bordarier et al [33] and Ateeque Malani and Ayappa [34]. Figures 4-7 show the total pressure distribution and the corresponding elastic film shape for the central line of contact in the direction of entraining motion for cases (16), (36), (66) and (79) of table (2).…”

“…structural force) is a surface interaction force that acts between two solid surfaces, when they approach each other to form a very small gap filled by a fluid. Van Megen and Snook [28], Horn and Israelachvili [29], Israelachvili et al [30], Homola et al [31], Israelachvili [32], Philippe Bordarier et al [33] and Ateeque Malani and Ayappa [34] have studied the solvation force in the narrow contact of contiguous bodies. They have all shown that these surface forces have generally a decaying oscillatory characteristic as a function of gap (i.e.…”

Micromechanics of friction: effects of nanometre-scale roughness

“…In general, the water layer can affect the frictional behaviour in two aspects. When the contact pressure is small, the interlayer is kept between the contacting surfaces and the water behaves like a lubricant (Homola et al 1989;Israelachvili 1992;Pertsin & Grunze 2006). This lubrication effect alters the frictional response at the molecular level significantly.…”

The interpretation of water anomalies in terms of core-softened models

“…In these nanocontacts, brication regime [24] breaks down, tion and wear between the two sur This problem would be severe in th electromechanical machines (MEMS usually used unlubricated. Careful measurements using wate two molecular layers indicate that wa well as lubricant in this regime [20], cation of its high lubricity under str derstanding these anomalous propert plest way may contribute with some of new lubricants for miniaturized eq here some qualitative considerations water is preserved under strong confi will be based -again-in the use of c qualitatively mimic the behavior of w If we squeeze a liquid film betw the liquid opposes a force, which i tion force [23,24]. When studying nanocontacts, oscillations as a funct tween solids are usually observed.…”