Published online by Cambridge University Press: 28 February 2011
New experimental techniques are described for measuring both the static and dynamic interactions of very thin liquid films between two molecularly smooth surfaces as they are moved normally or laterally relative to each other. Film thickness can be measured and controlled to IA. Results are presented of how the properties of liquid films only one, two, or three molecular layers thick differ from those of bulk liquids. When close together, two molecularly smooth surfaces slide (shear) past each other while separated by a discrete number of liquid layers. The critical shear stress required to initiate motion for simple spherical molecules is “quantized” with the number of layers. Another important characteristic of molecular thin liquid films undergoing shear is the phenomenon of “stick-slip” or “intermit-tent” motion. Both of these phenomena have been studied as a function of driving velocity, area of contact, and number of molecular layers.