We show that the power dissipated into field excitations and the associated friction force depend on how the atom is boosted from being initially at rest to a configuration in which it is moving at constant velocity v parallel to the planar interface. View PDF. Save to Library. Create Alert.
Share This Paper. Figures and Topics from this paper. Citations Publications citing this paper. Milton , Johan S. Nonequilibrium atom-surface interaction with lossy multi-layer structures. Quantum friction in arbitrarily directed motion Juliane Klatt , M. Bel'en Farias , D. Dalvit , Stefan Yoshi Buhmann.
Spatial dispersion in atom-surface quantum friction Daniel Reiche , Diego A. I have proposed that this challenge can be overcome by exploiting the fact that the optical properties of nanotubes are dominated by excitons —electron-hole pairs bound to the curved nanotube surface. As shown experimentally by Chunlei Yang and collaborators, then at the Hong Kong University of Science and Technology, laser illumination generates a gas of free charges in the nanotube wall—referred to as photogenerated charges —which affects the excitonic spectra and the reflectivity of the nanotube.
In bulk semiconductors, any effects on the Casimir force due to excitons were shown in by Raul Esquivel- Sirvent and his collaborators at the Universidad Nacional Autonoma de Mexico to be relatively small; in the case of nanotubes, however, simply partially illuminating the nanotube outer walls can yield a net dispersion force on the embedded shuttle capable to overcome static friction. A phased application of this mechanism can be used to maintain shuttle oscillations against the extremely low intershell friction.
The ejection of the shuttle can therefore be controlled; one of its ends can be partially exposed for tapping tools, much like an atomic force microscope, or for use in sensors. In addition, Vesselin N. Shanov, Mark J.
Schulz, and their group at the University of Cincinnati have successfully demonstrated the synthesis of nanotubes with lengths exceeding 1 centimeter. Therefore it is possible to consider repeating the boosting process over thousands of acceleration stages, leading to shuttle ejection speeds exceeding 10 to kilometers per second. This is the principle behind a novel nonelectromagnetic, neutral nanoparticle accelerator I proposed, which, if scaled up from a single nanotube to a dense array, could serve as a high performance nanothruster for space applications.
The nanotube shuttles in the thruster could be shot out at high speeds to propel a small satellite or other device, obviating the need to store a chemical propellant. Therefore, the net energy exchanged with all external heat reservoirs over a cycle vanishes, but the total mechanical work done by dispersion forces does not, in apparent violation of the First Law of Thermodynamics.
A hypothetical dispersion force engine cycle top is shown with the analogy of a pulley lifting a weight. Shown clockwise, the two parallel plates at rest 1 are illuminated by an external light 2; a to b on graph , adding energy that draws the plates together and lifts a load 3; b to c. Once the light shuts off, waste energy leaves the system 4 , and the cycle returns to its starting point d to a.
The net result is that a weight is permanently lifted to a higher position. The graph displays the Casimir pressure as a function of gap width during the thermodynamical cycle. With the Casimir effect, this idea goes back to the first mention of zero-point energy. However, extracting that energy in any useful manner is another matter. Robert L. If the net energy exchanged is equal to the work done, this result would preserve the First Law. Several other issues still require clarification, including the generalization of the Lifshitz theory to real-world geometries different than the usual two-slab system, such as the surface of pollen grains or biological cells.
With such rough surfaces, the force is expected to become quite complex and in some cases it could even become repulsive. Controlling when the Casimir effect is attractive or repulsive would be a major advance for MEMS devices, because stiction could be overcome. Research by Jeremy N. Munday, Federico Capasso, and V. Adrian Parsegian in demonstrated that the Casimir force can be made repulsive in some regimes if the gap between the materials is filled with a carefully selected substance with appropriate optical properties. Another challenge is that calculating the Casimir force between two oddly shaped objects is very difficult with current methods.
The system can only be approximated with a grid of points, rather than a continuous solution. A substantial step forward was taken in by Alejandro Rodriguez and his colleagues at MIT, who proved that finite-difference approaches standard in numerical electromagnetism can be successfully adapted to the task. Without such accurate numerical solutions, we may know the origin of the source physically, but its behavior remains unknown quantitatively.
Dispersion Forces II
Another exciting research subfield is that of dispersion forces in the presence of gravitation, which could eventually see applications in increasing understanding of black holes, gravitational wave detection, and other aspects of cosmology. In practice, because a typical two-plate system has its own positive, mechanical mass and the negative Casimir energy mass-equivalent is smaller than one proton mass under any realistic conditions, this mass decrease is extremely challenging to detect.
But devices called atomic gravimeters can measure the change in gravity affecting an atom and achieve relative sensitivities of the order of 10 Therefore I decided instead to concentrate on the measurement of the gravitational equivalent mass of the van der Waals energy between individual atoms confined in cold traps, which can be shown to be within present-day experimental capabilities.
This gravitational mass decrease can be further magnified by several orders of magnitude by exciting the trapped atoms to high-energy states, referred to as Rydberg states. The average distance of an excited electron from the nucleus in a Rydberg atom is much larger than in ground-state atoms with radii around picometers , in some cases becoming comparable to the size of a virus, about nanometers in diameter. In these conditions, an atom is extremely fragile and far more easily deformed by external fields, corresponding to a vastly enhanced atomic polarizability and far better prospects for successful detection of this gravitational effect.
An intriguing connection between Casimir forces in gravitational fields and in metamaterials has also been uncovered.
Because their optical response is described by dielectric functions equivalent to those that formally correspond to gravitational fields, metamaterials can be used to mimic Casimir forces in gravitational fields inaccessible in the laboratory, such as in black holes and in cosmology.
This approach has led to the suggestion by Tian-Ming Zhao and Rong-Min Miao of the University of Science and Technology of China in that the Casimir force in such structures may be enhanced by stunning factors as large as 10 11 by a metamaterial based implementation of the narrow frequency-band strategies previously discussed. Dispersion force engines should be capable of actuating nanosurgical robots deep inside the human body or powering next-generation thrusters in space.
If indeed we are able to alter the vacuum, then because the vacuum is ever present and everywhere, our microscopic world of elementary particles would become inextricably connected to the macroscopic world of the cosmos. View the discussion thread. Skip to main content.
Login Register. Engines Powered by the Forces Between Atoms By Fabrizio Pinto By manipulating van der Waals forces, it may be possible to create novel types of friction-free nanomachines, propulsive systems, and energy storage devices. Page DOI: For I am induced by many reasons to suspect that they may all depend upon certain forces by which the particles of bodies, by some causes hitherto unknown, are either mutually impelled towards each other and cohere in regular figures, or are repelled and recede from one another; which forces being unknown, philosophers have hitherto attempted the search of Nature in vain.
Casimir–Polder Potential of a Driven Atom
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[PDF] Friction forces on atoms after acceleration. - Semantic Scholar
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