Optical manipulation of nanoscale objects is studied with particular emphasis on the role of plasmon resonance for enhancement of optical forces. The thesis provides an introduction to plasmon resonance and its role in confinement of light to a sub-diffraction volume. The strong light confinement and related enhancement of optical forces is then theoretically studied for a special case of nanoantenna supporting plasmon resonances. The calculation of optical forces, based on the Maxwell stress tensor approach, reveals relatively weak optical forces for incident powers that are used in typical realisations of trapping with nanoantenna. The optical forces are so weak that other non-optical effects should be considered to explain the observed trapping. These effects include heating induced convection, thermoporesis and chemical binding. The thesis also studies the optical effects of plasmon resonances for a fundamentally different application - size-based optical sorting of gold nanoparticles. Here, the plasmon resonances are not utilised for sub-diffraction light confinement but rather for their ability to increase the apparent cross-section of the particles for their respective resonant sizes. Exploiting these resonances, we realise sorting in a system of two counter-propagating evanescent waves, each at different wavelength that selectively guide gold nanoparticles of different sizes in opposite directions. The method is experimentally demonstrated for bidirectional sorting of gold nanoparticles of either 150 or 130 nm in diameter from those of 100 nm in diameter within a mixture. We conclude the thesis with a numerical study of the optimal beam-shape for optical sorting applications. The developed theoretical framework, based on the force optical eigenmode method, is able to find an illumination of the back-focal plane of the objective such that the force difference between nanoparticles of various sizes in the sample plane is maximised.

Over the last few decades, the use of light to control and manipulate microscopic particles has become widespread. These methods are enabling new areas of research to flourish across the physical and biological sciences. This thesis describes investigations into both optical trapping and the closely related field of optical sorting. It documents the development of a variety of new techniques. The thesis begins with a short review of optical trapping and existing methods for sorting mixtures of microscopic particles. The first half of this chapter highlights some of the reasons behind optical trapping's rapid growth in popularity. By reviewing an array of methods for sorting particles and discussing the relative merits of each, the case for optical sorting is established. The second chapter describes research into using a spatial light modulator to create three-dimensional optically trapped colloidal structures using the time-sharing technique. Limiting factors inherent in the technology are discussed in detail. The third chapter reviews a sophisticated particle-tracking software package that has proved to be a considerable success. It was developed explicitly with colloidal microscopy in mind and experimental plots produced by the software are used throughout the thesis. Experimental studies have been performed into the behaviour of microscopic particles moving under the influence of two classes of propagation-invariant beams: Mathieu beams and Bessel beams. The Bessel beam studies have been complimented by a theoretical model and have led ultimately to a new method for the static optical sorting of both solid particles and biological cells, with particular emphasis on human blood. The fifth and final chapter describes how re-configurable optical devices can be implemented to spatially separate different colloidal species. A new method for creating arbitrary optical landscapes using an acousto-optic modulator is reported. This new technique is then used to optically sort four particle species simultaneously - the first experimental demonstration of polydisperse optical fractionation. Additionally, experiments are reported that demonstrate controlled, static optical sorting using a spatial light modulator.

Integration and miniaturisation in electronics has undoubtedly revolutionised the modern world. In biotechnology, emerging lab-on-a-chip (LOC) methodologies promise all-integrated laboratory processes, to perform complete biochemical or medical synthesis and analysis encapsulated on small microchips. The integration of electrical, optical and physical sensors, and control devices, with fluid handling, is creating a new class of functional chip-based systems. Scaled down onto a chip, reagent and sample consumption is reduced, point-of-care or in-the-field usage is enabled through portability, costs are reduced, automation increases the ease of use, and favourable scaling laws can be exploited, such as improved fluid control. The capacity to manipulate single cells on-chip has applications across the life sciences, in biotechnology, pharmacology, medical diagnostics and drug discovery. This thesis explores multiple applications of optical manipulation within microfluidic chips. Used in combination with microfluidic systems, optics adds powerful functionalities to emerging LOC technologies. These include particle management such as immobilising, sorting, concentrating, and transportation of cell-sized objects, along with sensing, spectroscopic interrogation, and cell treatment. The work in this thesis brings several key applications of optical techniques for manipulating and porating cell-sized microscopic particles to within microfluidic chips. The fields of optical trapping, optical tweezers and optical sorting are reviewed in the context of lab-on-a-chip application, and the physics of the laminar fluid flow exhibited at this size scale is detailed. Microfluidic chip fabrication methods are presented, including a robust method for the introduction of optical fibres for laser beam delivery, which is demonstrated in a dual-beam optical trap chip and in optical chromatography using photonic crystal fibre. The use of a total internal reflection microscope objective lens is utilised in a novel demonstration of propelling particles within fluid flow. The size and refractive index dependency is modelled and experimentally characterised, before presenting continuous passive optical sorting of microparticles based on these intrinsic optical properties, in a microfluidic chip. Finally, a microfluidic system is utilised in the delivery of mammalian cells to a focused femtosecond laser beam for continuous, high throughput photoporation. The optical injection efficiency of inserting a fluorescent dye is determined and the cell viability is evaluated. This could form the basis for ultra-high throughput, efficient transfection of cells, with the advantages of single cell treatment and unrivalled viability using this optical technique.

För att kunna uppnå de tuffare materialåtervinningsmålen som börjar gälla i Sverige år 2020 måste utsorteringen av bland annat plast-, papper- och metallförpackningar öka. Hushållsavfall beskrivs som en av de mest miljöpåverkande kategorin av avfall men samtidigt den kategori där det finns mest potential för förbättringar genom bättre hantering. Plockanalyser från 67 procent av Sveriges kommuner mellan åren 2013 och 2016 visar att ett svenskt villahushålls restavfall innehåller 34,5 procent förpackningar och returpapper som skulle kunna sorteras ut för materialåtervinning. Ett sätt att öka utsorteringen av producentansvarsmaterial från restavfallet och då kunna uppnå materialåtervinningsmålen är att kommuner erbjuder enklare samt ökad service i form av källsortering närmare hushållen. Tidigare studier har jämfört systemen optisk sortering och fyrfackskärl, som båda innebär källsortering närmare hushållen, med det vanligaste systemet i Sverige idag, tvåkärl, som inte innebär en ökad service genom kvalitativa metoder. Systemen har inte jämförts med kvantitativa metoder utifrån ekonomi eller miljö och inte heller med ett nytt koncept som heter Kvartersnära insamling. Den här rapporten har därför jämfört de fyra systemen utifrån aspekterna miljö och ekonomi med hjälp av verktygen livscykel- och livscykelkostnadsanalys som applicerades i ett område i Kristinehamns kommun för att på så sätt komma närmare verkligheten. Resultatet visar att systemet kvartersnära insamling har lägst miljöpåverkan i de undersökta miljöpåverkanskategorierna och därefter fyrfackskärl, optisk sortering och högst miljöpåverkan har systemet tvåkärl utifrån förutsättningarna och antagandena som har applicerats i studien. Livscykelanalysen visar att miljönyttan med materialåtervinningen överväger konsekvenserna av ökade transporter. Systemet med lägst livscykelkostnad är tvåkärl och sedan kvartersnära insamling, optisk sortering och dyrast livscykelkostnad har fyrfackskärl utifrån antaganden och de förutsättningar som använts i studien. En slutsats från rapporten är att det är viktigt att även undersöka andra aspekter förutom ekonomi och miljö vid val av insamlingssystem då resultatet till stor del beror på andra aspekter bland annat användarens uppfattning om systemet. / To achieve the stricter material recycling goals in Sweden in 2020 plastic-, metallic- and paper packages need to be better sorted from the household waste. Household waste might have the highest environmental impact compared with other sorts of waste but household waste has the highest potential to lower its impact. Waste pick-up analysis from 67 percent of Sweden's municipalities between 2013 and 2016 show that a Swedish household waste contains 34.5 percent packaging and recycled paper that could be sorted for recycling. The producers of that material have the responsibility to collect it but it does not work as well as planned because of different circumstances. One way to increase the recycling of the material from the household waste and then achieve the material recycling goals is that municipalities offer simpler and increased service in the form of source sorting closer to the households. Previous studies have compared the systems of optical sorting and multi compartment bin, which offer separation at sources closer to the households. Moreover, those systems have been compared with the most common system in Sweden today, two bins, which do not involve increased service. The systems have not been compared with quantitative methods based on economics or the environment, nor with a new concept called district collection. This report has compared the four systems. The aspects that have been compared are the environmental aspects and economical aspects by using the tools lifecycle assessment and lifecycle cost assessment. Moreover, the systems have been fictive studied in an area in the municipality of Kristinehamn, in order to get closer to reality. The results indicate that the collection system district collection had the lowest environmental impact followed by multi compartment bin and then optical sorting. Moreover, the system with two bins has the highest impact in the studied environmental impact categories according to the assumptions that have been applied in the study. The lifecycle assessment indicates that the benefits with material recycling is higher than the environmental impacts of increased transportation. The system with lowest lifecycle cost is the system with two bins and then the district collection. The system with highest lifecycle cost is the system optical sorting and the system with the second highest cost is multi compartment bin according to the assumptions that have been applied in the study. One conclusion from the study is that it is important to investigate more aspects than environmental impact and costs when to decide collection system. It is because the results depends on the other aspects as well like the users experience about the system.