High-speed video microscopy in optical tweezers

Keen, Stephen Alexander Juhani (2009) High-speed video microscopy in optical tweezers. PhD thesis, University of Glasgow.

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Optical tweezers have become an invaluable tool for measuring and exerting forces in the pico-Newton regime. Force measurements have in the past concentrated on using only one trapped particle as a probe, partly due to the difficulties in tracking more than one par- ticle at high enough frame rate. Recent advances in video camera technology 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 involving the 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. The camera was used in a Shack-Hartmann sensor setup to determine rapidly and non-ambiguously the sign and magnitude of the orbital angular momentum of a helically-phased beam light beam, as an alternative to interferometric techniques. Chapter 4 presents a di- rect comparison of a CCD high-speed video camera with a quadrant photodiode to track particle position. Particle tracking was possible at high enough accuracy and bandwidth to allow convenient trap calibration by thermal analysis. Chapter 5 reports an investigation of the resulting change in trap stiffness during the update of trap positions in holographic optical tweezers. Chapter 6 presents the re- sults from using a high-speed camera to successfully track multiple particles in a microfluidic channel to measure the viscosity at sev- eral points simultaneously. The last three chapters investigate the hydrodynamic interactions between trapped particles under different conditions and comparisons were made with theory.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: optical tweezers,high-speed camera,hydrodynamics
Subjects: Q Science > QC Physics
Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
Funder's Name: UNSPECIFIED
Supervisor's Name: Padgett, Prof. M.J.
Date of Award: 2009
Depositing User: Mr Stephen Alexander Juhani Keen
Unique ID: glathesis:2009-1436
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 19 Jan 2010
Last Modified: 10 Dec 2012 13:39
URI: http://theses.gla.ac.uk/id/eprint/1436

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