Enhanced optical tweezing: from hydrodynamic micro-manipulation to optimised optical trapping

Būtaitė, Unė Gabrielė (2020) Enhanced optical tweezing: from hydrodynamic micro-manipulation to optimised optical trapping. PhD thesis, University of Glasgow.

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Optical tweezers, with their ability to trap particles at the focus of a laser beam and control their motion, have provided unparalleled insight into the inner workings of the micro-world of colloids, cells and biomolecules. However, not all materials yield to optical trapping, and living organisms can be damaged by direct light exposure.

Many optical tweezing experiments are performed in aqueous environments. This offers a route to indirect particle manipulation via the surrounding fluid. We develop, study, and experimentally demonstrate an approach which, by employing optically controlled micro-rotors to induce flow currents in the surrounding fluid, exerts near field hydrodynamic control over freely diffusing particles, irrespective of their material.

With our optically actuated hydrodynamic manipulation we were able to suppress the thermal motion of single sedimented micro-sized target particles of various materials in both translational and rotational degrees-of-freedom, translate individual particles over complex local trajectories or transport them over long distances across the holding sample cell, and exert control over multiple particles simultaneously.

The biggest challenge in our hydrodynamic manipulation technique is the accuracy with which the optical tweezers can control the actuator motion. This boils down to optical trapping stiffness. We employ the generalised Wigner-Smith operators alongside an optimisation scheme to upgrade the optical trapping field from the standard Gaussian beam to a three-dimensionally stiffness-enhanced trap.

Within simulations we demonstrate light fields with an order of magnitude stiffness enhancement in all three dimensions simultaneously. Such fields, as well as the techniques used to develop them, can find applications throughout the wide community of optical trapping and manipulation.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Keywords: Optical tweezers, hydrodynamic manipulation.
Subjects: Q Science > QC Physics
Colleges/Schools: College of Science and Engineering > School of Physics and Astronomy
Funder's Name: Engineering and Physical Sciences Research Council (EPSRC)
Supervisor's Name: Taylor, Dr. Jonathan M. and Phillips, Dr. David B. and Courtial, Dr. Johannes
Date of Award: 2020
Depositing User: Une Gabriele Butaite
Unique ID: glathesis:2020-81662
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 21 Sep 2020 11:17
Last Modified: 01 Sep 2022 13:25
Thesis DOI: 10.5525/gla.thesis.81662
URI: http://theses.gla.ac.uk/id/eprint/81662
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