High-speed video microscopy inoptical tweezers

[摘要] Optical tweezers have become an invaluable tool for measuring andexerting forces in the pico-Newton regime. Force measurements havein the past concentrated on using only one trapped particle as aprobe, partly due to the difficulties in tracking more than one par-ticle at high enough frame rate. Recent advances in video cameratechnology allow the collection of images at several kHz. However,there has been little use of high-speed cameras in optical tweezers,partly due to data management problems and affordability. This the-sis presents seven experiments carried out during my PhD involvingthe use of several different high-speed cameras.Chapter 3 presents the use of a CMOS high-speed camera with in-tegrated particle tracking built by Durham Smart Imaging. Thecamera was used in a Shack-Hartmann sensor setup to determinerapidly and non-ambiguously the sign and magnitude of the orbitalangular momentum of a helically-phased beam light beam, as analternative to interferometric techniques. Chapter 4 presents a di-rect comparison of a CCD high-speed video camera with a quadrantphotodiode to track particle position. Particle tracking was possibleat high enough accuracy and bandwidth to allow convenient trapcalibration by thermal analysis. Chapter 5 reports an investigationof the resulting change in trap stiffness during the update of trappositions in holographic optical tweezers. Chapter 6 presents the re-sults from using a high-speed camera to successfully track multipleparticles in a microfluidic channel to measure the viscosity at sev-eral points simultaneously. The last three chapters investigate thehydrodynamic interactions between trapped particles under differentconditions and comparisons were made with theory.

[发布机构] University:University of Glasgow;Department:School of Physics and Astronomy

[关键词] optical tweezers,high-speed camera,hydrodynamics