A new capacitive sensor for displacement measurement in a surface force apparatus

We present a new capacitive sensor for displacement measurement in a Surface Forces Apparatus (SFA) which allows dynamical measurements in the range of 0-100 Hz. This sensor measures the relative displacement between two macroscopic opaque surfaces over periods of time ranging from milliseconds to in principle an indefinite period, at a very low price and down to atomic resolution. It consists of a plane capacitor, a high frequency oscillator, and a high sensitivity frequency to voltage conversion. We use this sensor to study the nanorheological properties of dodecane confined between glass surfaces.Comment: 7 pages, 8 figure

The Ecole Centrale de Lyon surface force apparatus: an application overview

International audienceThe ECL (Ecole Centrale de Lyon) surface force apparatus (SFA) has been developed and refined over the last two decades. This paper reviews a number of applications of the SFA that are of interest to the tribologist. In order to predict and improve contact performance, the tribologist needs to understand and quantify the basic properties of the lubricant and the solid bodies it is separating. Previously, these important properties were the material bulk properties, or at least these properties were sufficient. This situation is no longer true, and the material properties of the solids and the lubricant are required on a scale which is small or comparable with the film thickness. Nowadays, that means a scale small or comparable with 10(-7)-10(-8) mi It is in this domain that the SFA can provide information on mechanical properties of very thin lubricant films, and on the properties of the solid material close to its surface