Velocity Dependence of Friction for Simple Liquids in Oscillating System

Confined solid–liquid friction is a significant phenomenon in micro-electromechanical systems, and its unclear energy dissipation mechanism has attracted numerous researchers. In this work, the frictional responses of a lubricant fluid confined between two plates in an oscillating system were investigated at different shear velocities using molecular dynamics simulations. The results show that the instantaneous frictional forces at different shear velocities exhibit uniform frequency responses, and the average friction force shows a non-monotonous tendency and finally decreases to a tiny value as the shear velocity increases. The presence of resonant friction leads to the multiple friction peaks in the entire friction-velocity curve. By calculating the velocity of the lubricated fluid during shear, it is found that the velocity of the fluid near the substrate shows a decreasing trend at high velocity, leading to the decrease of interfacial viscous resistance and thus the decreased friction force at high shear velocity.