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Wednesday, November 2, 2011

Picoliter rheology of gaseous media using a rotating optically trapped birefringent microparticle

Yoshihiko Arita , Andrew W. McKinley , Michael Mazilu , Halina Rubinsztein-Dunlop , and Kishan Dholakia

An optically trapped birefringent microparticle is rotated by a circularly polarized beam in a confined gaseous medium. By recording the terminal rotation velocity and the change in polarization of the incident trapping beam, we determine the viscosity by probing a picolitervolume of air, carbon dioxide and argon in the vicinity of the microparticle. We also characterize the optical force acting on a trapped particle in air using the generalized Lorenz-Mie theory taking into account the aberrations present. This opens up a new potential application of optical tweezers for the accurate measurement of gas viscosity in confined geometries.

DOI

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