Nanotribology of Ultrathin Confined Liquid Films Peter T. Cummings and Yongsheng Leng, Vanderbilt University, Nashville, TN 37235 Dynamic squeeze out of hydration water: Using a newly developed liquid-vapor extended (LVE) molecular ensemble, we performed molecular dynamics (MD) simulations of the normal approach between two mica surfaces immersed in a water droplet at ambient conditions. As the dynamic squeeze out of water molecules proceeds, water confined in mica pore exhibits layered structure (see Figs A and B). Repulsive hydration force begins to develop at four hydration layers (Fig. C). Very large repulsive pressures at final two to one water layers are observed (Fig. C). These phenomena indicate that the energy barrier to squeeze out the final hydration layer is extremely high.     A C B