Vacuum Fluctuation Induced Torque on Liquid Crystal Molecules

University Of Maryland, College Park, College Park MD

Investigators

Abstract

The goal of this project is to search for a new effect that is predicted to rotate small objects on the micro-scale without the use of traditional forces like gravity or electrostatics. According to quantum mechanics, i.e. the study of how nature works on the ultra-small-scale, "empty space" is actually teeming with activity. Even when all particles are removed from a region of space, fluctuating electromagnetic waves are found to persist. If two uncharged metal plates are brought near each other in "empty space," these electromagnetic waves exert a force, which pushes the two plates together, much like two ships in choppy water. This force that pushes the metal plates together is known as the Casimir force, and is purely a result of quantum mechanics. Could the fluctuating fields in empty space cause objects to rotate? According to quantum mechanics, the answer is yes! For that, the objects need to have reflective properties that vary with orientation so that the force would cause these objects to rotate rather than just be pushed together. This rotation could be used to help design more efficient and useful micro-electro-mechanical systems (MEMS), like the ones found in airbags and cell phones. The principal investigator aims to perform the first measurement of this rotational effect, the so-called Casimir torque, which will be carried out on a system consisting of liquid crystal molecules near a bulk crystal. In additional, this work will advance our understanding of quantum mechanics and our knowledge of how it can be used to improve small-scale devices, which have become ubiquitous. When optically anisotropic materials are placed in close proximity, the boundary conditions imposed by the materials on the zero-point electromagnetic fluctuations will cause an angle dependent energy density. In order to minimize the total energy for the system, the objects will rotate. The principal investigator aims to measure the rotation of an optically anisotropic liquid crystal in close proximity to a birefringent plate using an all-optical measurement technique. Incident light will propagate through the liquid crystal, whose orientation is twisted as a result of the Casimir torque, and the final polarization state of the light will be measured upon exiting the system. The light intensity will be used to determine the torque experienced by the liquid crystal resulting from the Casimir torque at various separations from the birefringent plate. The separation is controlled by an isotropic spacer layer deposited between the birefringent crystal and the liquid crystal. The measurement technique avoids the need for detection of mechanical motion, which both simplifies the detection and improves the measurement sensitivity.