title: Optical torque wrench: angular trapping, rotation, and torque detection of quartz microparticles.
abstract: We describe an apparatus that can measure the instantaneous angular displacement and torque applied to a quartz particle which is angularly trapped. Torque is measured by detecting the change in angular momentum of the transmitted trap beam. The rotational Brownian motion of the trapped particle and its power spectral density are used to determine the angular trap stiffness. The apparatus features a feedback control that clamps torque or other rotational quantities. The torque sensitivity demonstrated is ideal for the study of known biological molecular motors.
authors.affiliation: Department of Physics, Laboratory of Atomic and Solid State Physics, Cornell University, Ithaca, New York 14853, USA.
authors.forename: Arthur
authors.initials: A
authors.lastname: La Porta
authors.forename: Michelle D
authors.initials: MD
authors.lastname: Wang
mesh_terms: D055095:Optics and Photonics / Q000295:instrumentation; D010316:Particle Size; D011791:Quartz / Q000737:chemistry*; D019415:Torque
chemical_list: D011791:Quartz