This research presents the development of an advanced, state-of-the-art optical trap for use in biological materials and nanosystems investigation. An optical trap is an instrument capable of manipulating microscopic particles using the inherent momentum of light. First introduced by Askin et al., the single beam gradient optical trap is capable of generating small forces (~1-100 pN) in a noninvasive manner. As a result, the optical trap is often used to manipulate biological specimen. This research presents the process for the construction of a custom optical trap, the methods to build a controllable optical trap through a traditional fixed gain controller as well as an adaptive controller, and also enables the application of torque to trapped particles. A method of using adaptive techniques for system identification and calibration is also presented. This research has the potential to use forces and torques to affect our understanding of the mechanics of single molecules and motor proteins. This instrument provides a more precise means of manipulating biological specimen as well as a tool for nanofabrication and has the potential to expand the knowledge base of DNA, chromosomes, biomotors, motor proteins, reversible polymers, and can be used to control chemical reactions. The research presented here documents the creation of an optical trap that is sensitive for applications requiring precise displacements and forces, adaptable to a variety of current and future research applications, and useable by anyone interested in researching micro- and nanosytems. / Dissertation

Integrated microfluidic devices for biomedical analysis attract lots of interest in the MEMS (Micro-Electro-Mechanical-Systems) research field. However, the characteristic Reynolds number for liquids flowing in these microchannels is very small (typically less than 10). At such low Reynolds numbers, turbulent mixing does not occur and homogenization of the solutions occurs through diffusion processes alone. Hence, a satisfactory mixing performance generally requires the use of extended flow channels and takes longer to accomplish such that the practical benefits of such devices are somewhat limited. Consequently, accomplishing the goal of u¡VTAS requires the development of enhanced mixing techniques for microfluidic structures. This study first presents a microfluidic mixer utilizing alternatively switching electroosmotic flow and proposes two microchannel designs of T-form and double-T-form micromixer. Switching DC field is used to generate the electroosmotic force to drive the fluid and also used for mixing of the fluids simultaneously, such that moving parts in the microfluidic device and delicate external control system are not required for the mixing purpose. Furthermore, this study also proposed a novel pinched-switching mode in the T-form microfluidic mixer, which could be effectively increase the perturbation within the fluid to promote the mixing efficiency. In this study, computer simulation for the operation conditions is used to predict the mixing outcomes and the mixing performance is also confirmed experimentally. Result shows the mixing performance can be as larger as 95% within the mixing distance of 1 mm downstream the common boundary between the different sample fluids. The novel method proposed in this study can be used for solving the mixing problem in a simple way in the field of micro-total-analysis-systems. Furthermore, in order to demonstrate the proposed micromixer is feasible for on-line bio-reaction, this study designs a fully integrated device for demonstration of DNA/enzyme reaction within the microfluidic chip. The microchip device contains a pre-column concentrating region, a micro mixer for DNA-enzyme mixing, an adjustable temperature control system and a post-column concentration channel. The integrated microfluidic chip has been used to implement the DNA digestion and extraction. Successfully digestion of £f-DNA using EcoRI restriction enzyme in the proposed device is demonstrated utilizing large-scale gel electrophoresis scheme. Results show that the reaction speed doubled while using the microfluidic system. In addition, on-line DNA digestion and capillary electrophoresis detection is also successfully demonstrated using a standard DNA-enzyme system of $X-174 and Hae III. Finally, this reasearch also proposes a novel cell/microparticle manipulation platform by integrating an optical tweezer system and a micro flow cytometer. During operation, electrokinetically driven sheath flows are utilized to focus microparticles to flow in the center of the sample stream then pass through an optical manipulation area. An IR diode laser is focused to generate force gradient in the optical manipulation area to manipulate the microparticles in the microfluidic device. Moving the particles at a static condition is demonstrated to confirm the feasibility of the home-built optical tweezer. The trapping force of the optical tweezer is measured using a novel method of Stocks-drag equilibrium. The proposed system can continuously catch moving microparticles in the flowing stream or switch them to flow into another sample flow within the microchannel. Target particles can be separated from the sample particles with this high efficient approach. More importantly, the system demonstrates a continuously manipulation of microparticles using non-contact force gradient such that moving parts and delicate fabrication processes can be excluded. The proposed system is feasible of high-throughput catching, moving, manipulation and sorting specific microparticles/cells within a mixed sample and results in a simple solution for cell/microparticle manipulation in the field of micro-total-analysis-systems. In this thesis, low-cost soda-lime glass substrates are adopted for the microchip fabrication using a simple and reliable fabrication process. Three kinds of novel microfluidic devices including an electrokinetically-driven microfluidic mixer, a high throughput DNA/enzyme reactor and an optically cell manipulation platform are successfully demonstrated. It is the author¡¦s believes that the results of this study will give important contributions in the development of micro-total-analysis-systems in the future. With the success of this study, we have a further step approaching to the dream of lab-on-a-chip system for bio-analytical applications.

付記する学位プログラム名: 京都大学卓越大学院プログラム「先端光・電子デバイス創成学」 / 京都大学 / 新制・課程博士 / 博士(理学) / 甲第24123号 / 理博第4851号 / 新制||理||1694(附属図書館) / 京都大学大学院理学研究科物理学・宇宙物理学専攻 / (主査)教授 高橋 義朗, 教授 石田 憲二, 教授 田中 耕一郎 / 学位規則第4条第1項該当 / Doctor of Science / Kyoto University / DFAM

The development of ultrasound contrast agents, or microbubbles, over the past 40 years has increased the possibilities for diagnostic imaging, although, more recently they have been proposed as a new vehicle for delivery of drugs and genes. However, there yet remains a considerable lack of fundamental understanding of microbubble behaviour under ultrasound excitation which has restricted their translation to therapeutic use. This project focussed on three key areas relating to the generation, observation, and bioeffects of microbubbles and the ultrasound used in their excitation. The experimental endeavour involved first, a full characterisation of the performance of a rotating mirror high-speed camera (Cordin 550-62) that was previously used by our group [and others] to investigate microbubble dynamics. Specifically, the investigation begins with an assessment of the frame-rate reporting accuracy of the system, a key aspect to the robustness of quantitative measurements extracted from recorded image sequences. This is then followed by the demonstration of a novel method of analysis for examining the image formation process in this type of camera, which facilitates a sensor-by-sensor assessment of performance that was not previously realised. Consolidating with previous work from within the group, this new analysis method was used to clarify previous data, and in the process suggested the presence of a temporal anomaly embedded within recorded images. In addition, the analysis also revealed empirical evidence for the mechanisms leading to this anomaly. Following on, a holographic optical tweezer system was developed for the purpose of exercising precise spatial control over microbubbles within their experimental environment. By positioning microbubbles in specific arrangements, interesting behaviours that were not previously achieved experimentally in the context of shelled microbubbles, were observed. Furthermore, by careful positioning of microbubbles within the imaging plane, it was possible to exploit the temporal anomaly present in the camera to greatly improve the integrity of data recorded, and to also operate in an enhanced imaging mode. Group aspirations to accelerate the development of therapeutic microbubbles had previously generated some early work on the in-house generation of bespoke bubble populations using microfluidic lab-on-a-chip techniques. In order to facilitate further development in this area, a finite-element computational model was herein developed to aid next generation chip design. Finally, in a slightly different context, considering not only the mechanical effect a microbubble may effect in a therapeutic treatment, a single biological cell assay was developed in order to probe any mechanical effects that were induced by the excitation ultrasound itself. Capitalising on the precise force control possible with atomic force spectroscopy, the elastic moduli of cells pre- and post-ultrasound insonation (sans microbubbles) were recorded. These new developments have extended the group capability and expertise in the areas of high-speed imaging, experimental observations of microbubble dynamics and with microfluidic generation of microbubbles. Additionally, the insights garnered have both served to consolidate the group's previous and as yet unpublished data, opening the way for circulation with absolute confidence in the integrity of that data.

abstract: In the frenzy of next generation genetic sequencing and proteomics, single-cell level analysis has begun to find its place in the crux of personalized medicine and cancer research. Single live cell 3D imaging technology is one of the most useful ways of providing spatial and morphological details inside living single cells. It provides a window to uncover the mysteries of protein structure and folding, as well as genetic expression over time, which will tremendously improve the state of the fields of biophysics and biomedical research. This thesis project specifically demonstrates a method for live single cell rotation required to image them in the single live cell CT imaging platform. The method of rotation proposed in this thesis uses dynamic optical traps generated by a phase-only spatial light modulator (SLM) to exert torque on a single mammalian cell. Laser patterns carrying the holographic information of the traps are delivered from the SLM through a transformation telescope into the objective lens and onto its focal plane to produce the desired optical trap "image". The phase information in the laser patterns being delivered are continuously altered by the SLM such that the structure of the wavefront produces two foci at opposite edges of the cell of interest that each moves along the circumference of the cell in opposite axial directions. Momentum generated by the motion of the foci exerts a torque on the cell, causing it to rotate. The viability of this method was demonstrated experimentally. Software was written using LabVIEW to control the display panel of the SLM. / Dissertation/Thesis / M.S. Bioengineering 2013

In this thesis, an approach for developing single-photon sources at the 1550nm wavelength will be demonstrated, based on optical trapping of luminescent upconverting nanoparticles. A single-photon source is a source that emits a single photon at a time, and hence it is a source of quantum bits that constitutes the basic building units in quantum computers and quantum communications. The approach exploits the plasmonic properties of gold films and the waveguiding characteristics of single mode optical fibers (SMFs). We start by planar nanofabrication of subwavelength nanoapertures in a thin gold film based on finite difference time domain simulations for a peak transmission at the wavelength in question. Subsequently, using ultraviolet curable epoxy adhesion material, a nanoaperture patterned on a gold film can be transferred to an SMF tip forming a nanoantenna enhanced optical fiber tweezer (NAFT). As a final step in building the optical tweezer, a test of the capability of the integrated optical fiber tweezer to trap 20 nm, and 30nm polystyrene nanospheres, as well as luminescent upconverting nanoparticles (UCNPs), has been experimentally realized with encouraging results. In addition to the optical trapping of the luminescent nanoparticles, the nano aperture antenna can improve light coupling into the low loss optical fiber guiding channel. Also, it could have a positive influence on enhancing the photon emission rate through the Purcell effect. Furthermore, we have combined NAFT with a low insertion loss wave splitter, a wavelength-division multiplexer (WDM), to allow measuring the 1550nm photon-emission statistics on a cooled superconducting nanowire single-photon detector (SNSPD) at ~ 2.4o K. Eventually, nanoantenna enhanced optical fiber tweezers can play an essential role in optical trapping towards developing single-photon sources and the emerging technology of quantum information processing, computation, and cryptography. / Graduate

[pt] Optomecânica, o estudo de forças induzidas pela luz sobre a matéria, teve grandes avanços nos últimos anos com diversas implicações sobre todas as ciências naturais. Pinças ópticas, por exemplo, são amplamente usadas na física, química e biologia para aprisionar nano e micropartículas com índice de refração maior do que o meio que a cerca usando, em geral, feixes Gaussianos. Generalizando essa técnica, trabalhos recentes começaram a explorar estados de ordem maior dos feixes eletromagnéticos e suas superposições para aprisionamento óptico, criando feixes com fase, modo e amplitude ajustáveis. Esses novos graus de liberdade permitem o uso de potenciais arbitrários e até mesmo forças dependentes do tempo capazes de induzir movimento controlado no objeto aprisionado. Nesse contexto de feixes estruturados, nós podemos explorar não apenas as forças atrativas entre luz e matéria, mas também as forças repulsivas que ocorrem quando o índice de refração da partícula é menor que o do meio circundante. Neste trabalho vamos explorar ambos cenários a partir da criação de feixes holográficos com um Modulador Espacial de Luz (SLM). Mais especificamente, vamos focar na implementação do feixe de foco escuro, ou feixe de garrafa, onde as partículas encontram equilíbrio em uma região sem incidência de luz. Resultados experimentais são apresentados e comparados com simulações numéricas baseadas na teoria de Lorentz-Mie e possíveis aplicações dessas pinças óticas inversas são discutidas em optomecânica e biologia. / [en] Optomechanics, the study of light-induced forces upon matter, has seen tremendous advances in recent years with broad implications to all natural sciences. Optical tweezers, for instance, are now widely used in physics, chemistry and biology to trap nano- and micro-objects with a refractive index greater than of its surrounding medium using typically Gaussian laser beams. Generalizing these techniques, recent works began to explore higher-order states of the electromagnetic field and its superpositions for optical trapping, creating beams with customized phase, mode and amplitude. These new degrees of freedom allows for optical potentials beyond the harmonic approximation, enabling virtually arbitrary potential forms and even time-dependent forces capable of inducing controlled motion on the trapped object. Within this context of structured light beams, we can explore not only the attractive forces between light and matter but the repulsive ones that arise when the particle s refractive index is smaller than that of its medium. In this work we explore both scenarios by creating holographic beams with a Spatial Light Modulator (SLM). Specifically, we focus on the implementation of the dark focus beam, or optical bottle beam, where particles may find equilibrium in a region with no incidence of light. Experimental results are presented and compared to Lorentz-Mie numerical simulations and possible applications of these inverted optical tweezers in optomechanics and biology are discussed.

No description available.

The main objective of this thesis is to present a simple and robust hands-on technology for the fabrication of a microfluidic chip in a laboratory. The purpose of this new technology is to replace the existing PDMS based microfluidic chip used for optical trapping of diverse single nano particles. It also lists the different fabrication methods attempted and the successful integration of this chip to the optical trap system which is used to study binding at the single molecular level. Microfluidics is a quickly growing field which deals with manipulating the fluids in channels whose dimensions are few tens of micrometers. Its potential has a major impact on fields like chemical analysis and synthesis techniques, biological analysis and separation techniques, and optics and information technology. One of the main application of these microfluidic chips is in optofluidics, which is the emerging field of integrated photonics with fluidics. This provides freedom to both fields and permits the realization of optical and fluidic property. It requires small volumes of fluids and connections and eventually performs better than conventional methods of robotic fluid handling. Here, the microfluidic chip is targeted for optical trapping with double nano-hole aperture to trap a single protein. The double nanoholes integrated with this microfluidic chip show that stable trapping can be achieved below flow rates of few μL/min. This has provided many possibilities of co-trapping of proteins and study their interactions. / Graduate

Dans le cadre de l’étude expérimentale des états quantiques intriqués de particules uniques, il est nécessaire de développer des systèmes compacts, robustes et polyvalents. Motivés par la miniaturisation, la stabilité et la flexibilité apportées par les fibres optiques, nous présentons deux expériences où les fibres optiques servent d’interfaces pour piéger des atomes uniques et collecter les photons uniques émis. Dans un premier temps, en combinant une fibre optique monomode avec une lentille asphérique, un faisceau dipolaire permet de piéger un atome de rubidium unique par blocage collisionnel. Le refroidissement et le taux de pertes par collisions assistées par la lumière dans le piège dipolaire sont augmentés via une modulation de l’intensité du faisceau dipolaire dont l’effet sur la durée de vie de l’atome est expliqué. Une source fibrée de photons uniques à la demande est obtenue avec ce dispositif, produisant des photons dans un mode spatial et temporel à priori bien défini. Dans un second temps, nous présentons la conception d’une expérience couplant optimalement une chaîne d’atomes uniques piégés à une cavité Fabry-Pérot fibrée combinée avec une lentille à forte ouverture numérique pour imager et adresser les atomes individuellement. Un dispositif d’ablation laser de précision submicrométrique est alors construit pour réaliser et analyser in situ les formes de miroirs voulues à l’extrémité des fibres optiques. Nous présentons ensuite les cavités fibrées doublement résonantes avec une biréfringence contrôlée réalisées. Nous décrivons également le système expérimental construit pour la production rapide d’un nuage d’atomes froids et leur transport vers la cavité. / The experimental study of entangled quantum states of single particle ensembles requires development of compact, robust and versatile systems. Motivated by miniaturization, stability and flexibility provided by optical fibers as light wave-guides, we present two experiments where optical fibers are used as interfaces for single atoms trapping and single photons collection into their guided modes. The first experiment combines a single mode fiber with an aspherical lens to produce a dipolar beam in which we trap a single rubidium atom by collisional blockade. This fiber-pigtailed optical tweezer is a simple, compact and versatile tool for single cold atom production. Cooling and light-assisted collisional loss rate in the dipole trap are increased by modulating the dipole beam intensity. The modulation and beam polarization effects on atom lifetime are presented and explained. With this setup, we realized a triggered single photon source, whose photons have a priori well defined spatial and spectral mode due to the optical fiber and the atomic transition.In a second part, we present the design of an experiment which optimally couples a trapped single atom register to a fiber Fabry-Pérot cavity and where a high numerical aperture lens allows for individual imaging and addressing. A sub-micron precision laser ablation setup is built to create and to analyze in situ desired mirror shapes on optical fiberend faces. Then, we present the produced double resonant fiber cavities with controlled birefringence. Eventually, we describe the created experimental setup for fast cold atom cloud production and transport towards the cavity.