Contact mode Casimir and capillary force measurements

PhD ceremony: Mr. P.J. van Zwol, 14.45 uur, Academiegebouw, Broerstraat 5, Groningen

Title: Contact mode Casimir and capillary force measurements

Promotor(s): prof. T.T.M. Palstra

Faculty: Mathematics and Natural Sciences

The Casimir effect is said to be a “force from nothing”. Like the Lamb-Shift it is a consequence of the Heisenberg uncertainty principle for energy and time. Therefore the Casimir effect is fundamentally important. But it is also a background force in the search for new forces at microscopically small distances. The force becomes strong for nanoscale separations and affects the motion of parts in mechanical nanodevices, which is the reason that this thesis is written. Here the typical strength of the Casimir force for such systems was measured with an Atomic Force Microscope. Theory and experiments to probe the effect off roughness and optical reflectance on the force are discussed. The results of this analysis are not only important for nanodevices but also for theory that accurately describes the force for real materials. On the other hand the Casimir force may also be put to good use. For example in this thesis it is shown that the force can be modulated using switchable materials that are typically used in DVDs. In some special cases, when a fluid replaces the vacuum, the Casimir force can be made repulsive. A way of maximizing this repulsion is presented here. Casimir repulsion can be important for lowering friction between surfaces as it prevents them from touching.