An idealized system composed of two parallel, semiconducting boundaries separated by an empty gap of variable width is considered. A gedanken experiment is discussed to show that, in general, the total work done by the Casimir force along a closed path that includes appropriate transformations does not vanish. It is shown that, in the limit of an engine cycle bringing the two boundaries to a relatively small distance, positive net exchange of energy associated with the Casimir force field could quite possibly be achieved. Viable technological implementations of this idealized system are analyzed in some quantitative detail, in particular, in the case of doped and undoped $c-\mathrm{Si}$ boundaries. For the purpose of direct experimentation, measurements with both macroscopic and microelectromechanical devices are suggested. A full theoretical and experimental study of systems of this kind on every scale will greatly contribute to a much deeper understanding of the nature of the Casimir force and associated concepts, including the possible manipulation of semiconducting nanostructures and the noninvasive optical characterization of semiconducting samples. In the event of no other alternative explanations, one should conclude that major technological advances in the area of endless, by-product free-energy production could be achieved.

• Received 28 May 1999

DOI:https://doi.org/10.1103/PhysRevB.60.14740