Influence of random roughness on the Casimir force at small separations

Abstract

The influence of random surface roughness of Au films on the Casimir force is explored with atomic force microscopy in the plate-sphere geometry. The experimental results are compared to theoretical predictions for separations ranging between 20 and 200 nm. The optical response and roughness of the Au films were measured and used as input in theoretical predictions. It is found that at separations below 100 nm, the roughness effect is manifested through a strong deviation from the normal scaling of the force with separation distance. Moreover, deviations from theoretical predictions based on perturbation theory can be larger than 100%.

Roughness correction to the Casimir force at short separations: Contact distance and extreme value statistics

“…(23), the continuous (blue) line] is compared to measured force data [from Ref. 27, the open (red) circles], which were obtained with an AFM setup. The same figure includes the result for a smooth surface [Eq.…”

“…The total Casimir force becomes approximately 46 nN near contact, which is an order of magnitude larger than what has been found for the rougher samples. 27 However, this estimate still needs experimental verification, because presently it is not trivial to measure the force at separations below 10 nm.…”

“…This distinction gives a reliable estimate of the Casimir force at short separations. It was introduced in a recent letter, 26 where it was shown to reproduce experimental results 27 for one gold sample. In the present paper, the method will be discussed in more detail, and results for multiple gold samples will be shown.…”

“…28 Just before the final section with the conclusions, we will evaluate the results and compare them to experimental data from Ref. 27.…”

Design of a Casimir-driven parametric amplifier

“…An integrated MEMS device may enable significant improvements in the sensitivity of Casimir experiments. This could shed light on experiments studying material, surface topology [47,48] and metamaterials [49,50], an understanding of which is crucial for stabilizing nano-structures subjected to the Casimir force. Ultimately, using parametrically driven MEMS may even enable high precision measurements of non-Newtonian forces acting on short length scales [51].…”