Velocity Dependence of Nanoscale Friction

Within this framework, the increase in friction force with velocity simply reflects the fact that at higher sliding speeds, the system has less time to overcome the activation 

On hydrophilic surfaces under ambient conditions, the formation of a water meniscus by capillary condensation (see Chapter 5) may strongly influence the friction behavior. A logarithmic decrease in friction with increasing velocity was observed when a sapphire ball was slided on a silicon wafer with native oxide layer [1025]. Such dependence was also found for AFM tips sliding on hydrophilic CrN surfaces by Riedo et al. [1026] and explained the kinetics of capillary condensation. 

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