Structural anisotropy and orientation-induced Casimir repulsion in fluids (original) (raw)
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Reviews of Modern Physics, 2009
The physical origin of the Casimir force is connected with the existence of zero-point and thermal fluctuations. The Casimir effect is very general and finds applications in various fields of physics. This review is limited to the rapid progress at the intersection of experiment and theory that has been achieved in the last few years. It includes a critical assessment of the proposed approaches to the resolution of the puzzles arising in the applications of the Lifshitz theory of the van der Waals and Casimir forces to real materials. All the primary experiments on the measurement of the Casimir force between macroscopic bodies and the Casimir-Polder force between an atom and a wall that have been performed in the last decade are reviewed, including the theory needed for their interpretation. The methodology for the comparison between experiment and theory in the force-distance measurements is presented. The experimental and theoretical results described here provide a deeper understanding of the phenomenon of dispersion forces in real materials and offer guidance for the application of Lifshitz theory for the interpretation of the measurement results.
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Physical Review Letters, 2007
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Physical Review Letters, 2002
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Influence of random roughness on the Casimir force at small separations
Physical Review B, 2008
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%. PACS numbers: 68.55.Jk, 68.37.Ps, 85.85.+j, 78.68.+m * Corresponding author: g.palasantzas@rug.nl 2 When the proximity between material objects becomes of the order of nanometers up to a few microns, a regime is entered where forces quantum mechanical in nature, namely, van der Waals and Casimir forces, become operative [1]. Historically, the Casimir force has been considered to result from the perturbation of zero point vacuum fluctuations by conducting plates [1]. Because of its relatively short range, the Casimir force is now starting to take on technological importance in the operation of micro/nanoelectromechanical systems (MEMS/NEMS) at separations <200 nm, e.g., micro oscillator devices, micro/nano switches, nanoscale tweezers or actuators [2-9]. Moreover, from a fundamental point of view the Casimir force plays important role in the search of hypothetical forces beyond the standard model [6]. The early force measurements by Sparnaay and van Blockland and Overbeek [1] gave evidense on the existence of the Casimir force. Higher accuracy measurements by Lamoreaux with the use of torsion pendulum [7] initiated further detailed investigations of the Casimir force. It was also measured accurately by other groups in the plate-sphere setup with the Atomic Force Microscope (AFM), and micro oscillator devices . Other geometries were also investigated, e.g., crossed cylinders [10], and parallel plates .
Physical Review Letters, 2002
We discuss repulsive Casimir forces between dielectric materials with non trivial magnetic susceptibility. It is shown that considerations based on naive pair-wise summation of Van der Waals and Casimir Polder forces may not only give an incorrect estimate of the magnitude of the total Casimir force, but even the wrong sign of the force when materials with high dielectric and magnetic response are involved. Indeed repulsive Casimir forces may be found in a large range of parameters, and we suggest that the effect may be realized in known materials. The phenomenon of repulsive Casimir forces may be of importance both for experimental study and for nanomachinery applications.