(589a) Invited Talk: Role of Interfacial Water in Adhesion and Friction

A thin layer of water confined between two contacting surfaces control the adhesion and friction. I will present direct measurements of the structure of this thin confined water layer between two surfaces of different wettability using infrared-visible sum frequency generation spectroscopy (SFG). SFG signals are a function of orientation and concentration of interfacial molecules. Although there is a common consensus on the binding of water to the polar head groups, there is no direct experimental knowledge of the structure of this thin water layer between two surfaces with varying hydrophilicity. The changes in the structure of this interface upon contact and during sliding will be discussed. Understanding the contact interface is important in understanding the role of interstitial water in controlling hydration and hydrophobic interactions.