Device for measuring the force and separation between two surfaces down to molecular separations

We present an apparatus for measuring the force as a function of distance between surfaces at separations down to the order of molecular dimensions. The device is a simplified yet improved version of the surface force apparatus first developed by Israelachvili and Adams [J. Chem. Soc. Faraday Trans. 1, 74, 975 (1978)]. It gives the same measurement resolution and has the same possibilities of studying various phenomena in thin films such as friction, viscosity, adhesion, and phase transitions. It offers improved performance with regard to control of surface separation and increased versatility by virtue of variable chamber dimensions and geometry.