Johnsen–Rahbek effect

Johnsen - Rahbek effect of a electrostatic attraction effect between the surface of a slightly conductive material and a metal when an electrical voltage. The strength of the attractive force depends on the voltage and the materials used.

The effect is named after the Danish engineers Alfred Frederik Johnsen (1887-1930) and Knud Rahbek ( 1891-1971 ). They described in their article published in 1923, how can use the effect for the construction of electrically controlled clutches. To this end, they harnessed a metal strip on a rotating cylinder of porous material impregnated with an electrolyte. Using an electrical current between the tape and cylinder, the friction of the metal strip could be controlled. In this way, speakers and amplifiers in telephone networks were built to a limited extent. For this application, the effect Rahbek and Johnsen had in 1919 filed a patent. Recent studies dealing with the application of the effect for holding semiconductor wafers during the manufacturing process.

A theoretical model for the effect empirically found by Johnsen and Rahbek was published in 1925 by Albino Antinori. An extended model was established by R. Atkinson. It takes account of the imperfections of the surface, on the other, the interface is modeled as a capacitor, on which a field emission occurs.