Thesis (Ph.D.) - University of St Andrews, May 2007.

Thesis (Ph.D.)--Drexel University, 2009. / Includes abstract and vita. Includes bibliographical references (leaves 95-103).

Thesis (Ph.D.) - University of St Andrews, May 2009.

Thesis (PhD) - Swinburne University of Technology, Faculty of Engineering and Industrial Sciences, Centre for Micro-Photonics, 2007. / A thesis submitted for the degree of Doctor of Philosophy, Centre for Micro-Photonics, Faculty of Engineering and Industrial Sciences, Swinburne University of Technology, 2007. Typescript. Bibliography: p. 135-153.

Thesis (Ph.D.) - University of St Andrews, January 2007.

Thesis (Ph.D.) - University of St Andrews, April 2008.

Thesis (Ph.D.) - University of St Andrews, June 2009.

This thesis investigates the application of a variety of optical techniques for the manipulation of single cells and their local micro-environment. The methodologies developed provide enhanced control over a single cell under study affording exquisite spatial and temporal control over biological processes of interest. The work presented within the thesis can be split into three distinct categories. The first of these provides an investigation in light activated “caged” molecular probes. This work generated several new compounds which were then applied to providing control over processes involved in pain, mitochondrial intracellular signalling and memory processes in the central nervous system. Application of caged neurotransmitters then demonstrates the first in vitro wavelength orthogonal photolysis of biologically relevant substances. Such a technique has great potential in the study of fundamental interactions within the processes underpinning memory and cognitive function. Secondly the application of optical injection techniques for the introduction of membrane impermeable species of interest is presented. An exploration of laser sources and optical systems has yielded two new strategies for optical injection. The targeted introduction of fluorescent stains, nucleic acids and gold nanoparticles to the interior of live mammalian cells demonstrates the power of these techniques. Thirdly, an investigation in optical trapping and optical injection provides simplified micromanipulation techniqes for application to biological studies. The use of capillaries as reservoirs for reagents of interest has realised a procedure for the reduction of large-scale chemical assays to a single cell level in static flow. When this technique is combined with intelligent control over the trapping laser source’s temporal behaviour, the interaction with the sample under study can be tailored for biological amiability or sample ablation. In this way a single laser source can be employed for the optical trapping and nanosurgery of a biological sample. A final study is presented demonstrating initial results for the targeted optical injection of caged compounds into mammalian cells. This methodology draws on the strengths of optical injection and caging technologies and presents a significant step forward in the level of control afforded over a biological system under study by optical techniques. The studies presented highlight the level of control and flexibility afforded by the application of optical manipulation and excitation strategies. Such optical methodologies extend the photonic tools available for enhanced studies in the life sciences.

Three projects are described in this thesis that combine microfabrication techniques with optical micromanipulation. The aim of these projects is to use expertise in microlithography and optical tweezing to create new tools for Lab-on-Chip devices. The first project looks at the creation of microgears that can be moved using an optical force. The microgears include one dimensional photonic crystal that creates birefringence. This allows the transfer of angular momentum from a circularly polarised light beam to the microgear, making them spin. The microgears are simulated, fabricated and tested. Possible biological applications are suggested. The second project looks at creating microchannels to perform micromanipulation experiments in. Different methods of fabricating the microfluidic channels are compared, and the resulting chambers are used to find the maximum flow rate an optical sorting experiment can be performed at. The third project involves using a thin photoconductive layer to allow the optical control of an electrical force called dielectrophoresis. This light induced dielectrophoresis (LIDEP) allows similar control to optical tweezing but requires less irradiance than optical tweezing, allowing control over a larger area with the same input optical power. A LIDEP device is created and experiments to measure the electrical trap size that is created with a given optical spot size are performed. These three projects show different microfabrication techniques, and highlight how well suited they are for use in optical manipulation and microfluidic experiments. As the size of objects that can be optically manipulated matches well with the size of objects that can be created with microfabrication, it seems likely that many more interesting applications will develop.

This thesis describes my work on the development of optical trapping techniques for manipulating airborne particles. Although many of the basic principles are similar to those used in more conventional colloidal experiments, there are many differences which have been described and investigated in detail in this work. Basic characterisation measurements are made, such as axial Q and sample size selectivity, for a number of sample liquids in a basic optical tweezers setup. Performance at 532nm and 1064nm were compared and shown to be very similar, despite increased absorption in the infrared. A successful method was developed for the optical trapping of solid aerosol particles, allowing a direct comparison between similar particles suspended in both the gas and liquid phase. A single beam levitation trap was developed for transporting liquid aerosols to allow multiple chemical measurements to be made on a single droplet. Performance between Gaussian and Bessel beams was compared for various liquids, with guiding distances of several millimetres being achieved with the Bessel beam geometry. An experiment to demonstrate lasing within an optically tweezed droplet was also performed and spectra were taken. Although strong resonance modes were evident, the data was not conclusive. However, it is likely that a redesign of the experiment would be successful. These techniques have extended research capabilities in the areas of both optical trapping and atmospheric chemistry, allowing the detailed study of single aerosol particles in the 1-10 μm range.