Regensburg 2010 – scientific programme

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SYNT: Symposium Nanotribology

SYNT 1: Symposium Nanotribology

SYNT 1.2: Invited Talk

Friday, March 26, 2010, 10:45–11:15, H1

Layering and Squeeze-out Damping in Confined Liquid Films — •Frieder Mugele — University of Twente, Physics of Complex Fluids, Enschede (The Netherlands)

Liquid films confined between solid surfaces play a crucial role as lubricants reducing friction and wear in a wide range of tribological contacts ranging from biological joints to engineering bearings. For separations between the solid surfaces of just a few nanometers, the properties of the fluid deviate substantially from their macroscopic behaviour. Due to the presence of the solid surfaces the liquid arranges itself in well-defined molecular layers, which gives rise to pronounced forces between the solid surfaces, oscillating between attractive and repulsive as a function of the distance between the surfaces. The structural reorganization also affects the dissipation during flow. Compared to the oscillatory conservative forces, however, the effect of confinement on the dissipation has been much more challenging to quantify. Recent experiments using both laterally wide slit pores with atomically smooth surfaces in a surface forces apparatus (SFA) as well as atomic force microscopy (AFM) experiments with nanoscale single asperity contacts indicate that the effect of the structural reorganization is relatively small. Except for the molecular layers in direct contact with the solid surfaces, the effective viscosity of confined liquids remains close to its bulk value within approximately one order of magnitude.