Optical torque wrench: angular trapping, rotation, and torque detection of quartz microparticles

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...

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Bibliographic Details
Published inPhysical review letters Vol. 92; no. 19; p. 190801
Main Authors La Porta, Arthur, Wang, Michelle D
Format Journal Article
LanguageEnglish
Published United States 14.05.2004
Subjects
Optics and Photonics - instrumentation
Particle Size
Quartz - chemistry
Torque
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Summary: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.
ISSN:0031-9007
DOI:10.1103/physrevlett.92.190801