Dissertations / Theses on the topic 'Optical Tweezers'
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Simpson, Neil B. "Optical spanners and improved optical tweezers." Thesis, University of St Andrews, 1998. http://hdl.handle.net/10023/14884.
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This thesis describes the experimental and theoretical work that investigated the transfer of orbital angular momentum from light to matter. This was achieved by combining two established areas of laser physics which were "optical tweezers" and Laguerre-Gaussian laser modes. The optical tweezers are essentially a tightly focussed laser beam from a high numerical aperture microscope objective lens, which traps particles in three dimensions just below the beam focus. By incorporating a Laguerre- Gaussian laser mode into the tweezers system, the trapping efficiency was doubled. These improved optical tweezers have been successfully demonstrated both theoretically and experimentally. In addition to the spin angular momentum which is associated with the polarisation state, the Laguerre-Gaussian laser modes also possess orbital angular momentum. The "optical spanners" utilised this property by transferring orbital angular momentum from the laser beam to the trapped particle, causing it to rotate whilst being held in the optical trap. This effect was theoretically modelled and experimentally observed. Using the optical spanners, the spin angular momentum of the laser was used to directly cancel the orbital angular momentum in the beam, which was observed as a cessation in rotation of the trapped particle. This demonstrated the mechanical equivalence of the spin and orbital components of angular momentum in a light beam, and gave experimental evidence for the well defined nature of the orbital angular momentum present in Laguerre-Gaussian laser modes.
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Sinclair, Gavin. "Experiments using holographic optical tweezers." Thesis, University of Glasgow, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.428751.
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Wan, Chenchen. "Optical Tweezers Using Cylindrical Vector Beams." University of Dayton / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1353515022.
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Stevenson, Olivia. "Investigating myosin kinetics using optical tweezers." Thesis, King's College London (University of London), 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416433.
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Stuart, Dustin L. "Manipulating single atoms with optical tweezers." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:ab99e851-3c66-4688-8725-b7d1588c5db0.
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Single atoms are promising candidates for physically implementing quantum bits, the fundamental unit of quantum information. We have built an apparatus for cooling, trapping and imaging single rubidium atoms in microscopic optical tweezers. The traps are formed from a tightly focused off-resonant laser beam, which traps atoms using the optical dipole force. The traps have a diameter of ~1 μm and a depth of ~1 mK. The novelty of our approach is the use a digital mirror device (DMD) to generate multiple independently movable tweezers from a single laser beam. The DMD consists of an array of micro-mirrors that can be switched on and off, thus acting as a binary amplitude modulator. We use the DMD to imprint a computer-generated hologram on the laser beam, which is converted in to the desired arrangement of traps in the focal plane of a lens. We have developed fast algorithms for calculating binary holograms suitable for the DMD. In addition, we use this method to measure and correct for errors in the phase of the wavefront caused by optical aberrations, which is necessary for producing diffraction-limited focal spots. Using this apparatus, we have trapped arrays of up to 20 atoms with arbitrary geometrical arrangements. We exploit light-assisted collisions between atoms to ensure there is at most one atom per trapping site. We measure the temperature of the atoms in the traps to be 12 μK, and their lifetime to be 1.4 s. Finally, we demonstrate the ability to select individual atoms from an array and transport them over a distance of 14μm with laser cooling, and 5 μm without.
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Mahamdeh, Mohammed. "High Resolution Optical Tweezers for Biological Studies." Doctoral thesis, Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2012. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-81918.
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In the past decades, numerous single-molecule techniques have been developed to investigate individual bio-molecules and cellular machines. While a lot is known about the structure, localization, and interaction partners of such molecules, much less is known about their mechanical properties. To investigate the weak, non-covalent interactions that give rise to the mechanics of and between proteins, an instrument capable of resolving sub-nanometer displacements and piconewton forces is necessary. One of the most prominent biophysical tool with such capabilities is an optical tweezers.
Optical tweezers is a non-invasive all-optical technique in which typically a dielectric microsphere is held by a tightly focused laser beam. This microsphere acts like a microscopic, three-dimensional spring and is used as a handle to study the biological molecule of interest. By interferometric detection methods, the resolution of optical tweezers can be in the picometer range on millisecond time scales. However, on a time scale of seconds—at which many biological reactions take place—instrumental noise such as thermal drift often limits the resolution to a few nanometers. Such a resolution is insufficient to resolve, for example, the ångstrom-level, stepwise translocation of DNA-binding enzymes corresponding to distances between single basepairs of their substrate. To reduce drift and noise, differential measurements, feedback-based drift stabilization techniques, and ‘levitated’ experiments have been developed. Such methods have the drawback of complicated and expensive experimental equipment often coupled to a reduced throughput of experiments due to a complex and serial assembly of the molecular components of the experiments.
We developed a high-resolution optical tweezers apparatus capable of resolving distances on the ångstrom-level over a time range of milliseconds to 10s of seconds in surface-coupled assays. Surface-coupled assays allow for a higher throughput because the molecular components are assembled in a parallel fashion on many probes. The high resolution was a collective result of a number of simple, easy-to-implement, and cost-efficient noise reduction solutions. In particular, we reduced thermal drift by implementing a temperature feedback system with millikelvin precision—a convenient solution for biological experiments since it minimizes drift in addition to enabling the control and stabilization of the experiment’s temperature. Furthermore, we found that expanding the laser beam to a size smaller than the objective’s exit pupil optimized the amount of laser power utilized in generating the trapping forces. With lower powers, biological samples are less susceptible to photo-damage or, vice versa, with the same laser power, higher trapping forces can be achieved. With motorized and automated procedures, our instrument is optimized for high-resolution, high-throughput surface-coupled experiments probing the mechanics of individual biomolecules. In the future, the combination of this setup with single-molecule fluorescence, super-resolution microscopy or torque detection will open up new possibilities for investigating the nanomechanics of biomolecules.
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Cheng, Jen-Hao. "Construction and characterization of an optical tweezers." FIU Digital Commons, 2003. http://digitalcommons.fiu.edu/etd/2156.
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Optical tweezers is a new technique for research in biological and physical sciences by using the radiation pressure. In this thesis, a diode laser, A = 785nm, maximum power=50mW, was used as the light source and a microscope was used for trapping and imaging. The laser pass through an anamorphic prism and provide an ideal Gaussian laser profile. Before reflecting the laser beam into the microscope, a beam expander and a convex lens expand and change the divergent angle of the laser beam for maximum power delivery and matching the imaging plane of the microscope. The trapped object was illuminated by the condenser and formed an image on a charge-coupled device (CCD) through a hot mirror. A laser line filter put in front of the CCD to avoid the exposure saturation by the laser light. The images from the CCD were monitored on the screen and trapped with a recorder.
We have built and tested an optical tweezers system, which successfully trapped latex particles and yeast of radius ranging from 1 to 20 μm. And we also achieved dual trap optical tweezers to trap and rotate two particles at the same time.
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Keen, Stephen Alexander Juhani. "High-speed video microscopy in optical tweezers." Thesis, University of Glasgow, 2009. http://theses.gla.ac.uk/1436/.
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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.
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Jordan, Pamela Ann. "Optical tweezers for signal detection and micromanipulation." Thesis, University of Glasgow, 2005. http://theses.gla.ac.uk/1728/.
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The work presented in this thesis explores new multi-disciplinary applications of optical tweezers in the physical and biological sciences. Firstly, the three dimensional trapping of partially silvered sphere in a standard TEM00 optical trap was characterised. These spheres were then coated with an azo dye such that surface-enhanced resonance Raman (SERRS) measurements could be made on a single bead whilst it was simultaneously trapped in 532 nm optical tweezers. The length of time over which the SERRS signal could be recorded was increased, from milli-seconds to minutes, by using 1064 nm optical tweezers and introducing second harmonic light, generated via a frequency doubling crystal, for the excitation of the SERRS signal. In addition to trapping single particles, a spatial light modulator (SLM) was introduced into the optical tweezers to produce holographic optical tweezers. The SLM allowed the creation and manipulation of several optical beams both simultaneously and independently of each other. Three dimensional trapping and manipulation of multiple micron-sized spheres were achieved using the SLM in the Fourier plane of the traps. This ability to trap and manipulate objects, such as fluorescent spheres and E. coli, in 3D was extended to create permanent 3D structures that were set within a polymer matrix. These objects could be created, permanently set and imaged ex-situ. A summary of conclusions and ideas for future work are included.
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Brandt, Lukas. "Trapping of rubidium atoms using optical tweezers." Thesis, University of Oxford, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.558210.
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This thesis describes the realisation of a novel dipole force trapping method for cold neutral atoms, the optical tweezers. They are formed by imaging a spatial light modulator onto a mirror surface, by an aspherical lens. The spatial light modulator, a digital mirror device, consists of an array 1024 by 768 of micro-mirrors, which can individually be switched between the on and off position with a full frame refresh rate of 4 kHz and hence can create arbitrary light patterns in real time. Atoms are trapped through the dipole force in them. The optical tweezers have a potential depth on the order of 1 mK. A magneto-optical surface-trap cools and traps Rubidium atoms close to the mirror surface. Unlike a normal magneto-optical trap, which traps atoms in free space, this trap incorporates a mirror, above which the atoms are trapped and then loaded into the optical tweezers. I will show that we managed to load atoms into the dipole traps with a variety of different potential landscapes and observe them with a highly sensitive CCD-camera through fluorescence imaging. . . Furthermore I study a scheme to use a high powered, but spatial multimode diode laser for atom trapping. An optical diffuser smoothes out the otherwise poor quality profile, to make the high power diode laser applicable for optical tweezers.
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Mitchell, Steven James. "Measurement of colloidal dynamics using optical tweezers." Thesis, University of Bristol, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.393924.
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Lee, Michael Peter. "Techniques for optical tweezers and SLM microscopy." Thesis, University of Glasgow, 2014. http://theses.gla.ac.uk/5552/.
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With the development of pixelated liquid crystal displays, a new paradigm has emerged in the field of optics. Essentially, these displays enable interfacing a computer program with light, and therefore allow a wide range of light beams to be created. In this thesis, I shall be using liquid crystal displays to create phase diffraction patterns and, in this case, the displays are more commonly referred to as Spatial Light Modulators (SLMs). One area where SLMs have shown particular promise is that of optical microscopy. Here, they have been used in two different applications, namely holographic optical tweezers and SLM microscopy; this thesis concerns both. The aim of the thesis is to explore and develop new techniques combining SLMs with microscopy. The first part of this thesis goes into results of the experiments I have carried out in holographic optical tweezers. Hydrodynamic interactions play an important role in many physical and biological processes. I present experimental evidence for the partial synchronisation of the stochastic oscillations of two spheres in a bistable optical trap. This experiment showed that, even in the absence of an external driving force, a degree of synchronisation still exists due to the Brownian motion alone. I then describe a new procedure to protect the optical trap from contamination in sensitive samples. Microrheology using optical tweezers requires lengthy position measurements in order to obtain the linear viscoelastic properties of fluids and this measurement is often compromised by freely diffusing material entering the trap. I then apply rotational Doppler velocimetry to a particle spinning in an optical tweezers. This is the first time that structured illumination has been used to determine rotation rate in the micro regime. The second part describes the development of an SLM microscope and a series of experiments I carried out with it. The set up of the microscope is described and images are characterised in terms of the point spread function. I also demonstrate the multimodal capabilities by diffracting three different images, each with a unique spatial frequency filter, onto a single camera chip. Next, I report the development of some new frequency filters, namely holographic stereo microscopy and three variations, including stereo with defocus which mimics human binocular vision where we have two eyes (views) of the world, each having its own lens. I used 3D particle tracking to investigate sedimentation in a confined microscope sample. This experiment brought together SLM microscopy and optical tweezers to create a new technique for particle sizing, or study surface effects. This thesis describes several new applications of SLMs in microscopy, with the common theme being that the SLM is placed in the Fourier plane of the sample. Both holographic optical tweezers and SLM microscopy have been expanded by the techniques I have developed. In future, this work will serve as foundation for the combination for 3D particle tracking and visualisation with SLM microscopy, whilst microrheology will benefit from the new approaches.
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Yu, Ling Yao. "Optical and mechanical analysis on a biological cell in optical tweezers." Doctoral thesis, Université Laval, 2016. http://hdl.handle.net/20.500.11794/26747.
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La réponse mécanique d'une cellule à une force externe permet d'inférer sa structure et fonction. Les pinces optiques s'avèrent une approche particulièrement attrayante pour la manipulation et caractérisation biophysique sophistiquée des cellules de façon non invasive. Cette thèse explore l’utilisation de trois types de pinces optiques couramment utilisées : 1) statiques (static), 2) à exposition partagée (time-sharing) et 3) oscillantes (oscillating). L’utilisation d’un code basé sur la méthode des éléments finis en trois dimensions (3DFEM) nous permet de modéliser ces trois types de piégeage optique afin d’extraire les propriétés mécaniques cellulaires à partir des expériences. La combinaison des pinces optiques avec la mécanique des cellules requiert des compétences interdisciplinaires. Une revue des approches expérimentales sur le piégeage optique et les tests unicellulaires est présentée. Les bases théoriques liant l’interaction entre la force radiative optique et la réponse mécanique de la cellule aussi. Pour la première fois, une simulation adaptée (3DFEM) incluant la diffusion lumineuse et la distribution du stress radiatif permet de prédire la déformation d’une cellule biconcave –analogue aux globules rouges—dans un piège statique double (static dual-trap). À l’équilibre, on observe que la déformation finale est donnée par l’espacement entre les deux faisceaux lasers: la cellule peut être étirée ou même comprimée. L’exposition partagée (time-sharing) est la technique qui permet de maintenir plusieurs sites de piégeage simultanément à partir du même faisceau laser. Notre analyse quantitative montre que, même oscillantes, la force optique et la déformation sont omniprésentes dans la cellule : la déformation viscoélastique et la dissipation de l’énergie sont analysées. Une autre cellule-type, la tige cubique, est étudiée : cela nous permet d’élucider de nouvelles propriétés sur la symétrie de la réponse mécanique. Enfin, l’analyse de la déformation résolue en temps dans un piége statique ou à exposition partagée montre que la déformation dépend simultanément de la viscoélasticité, la force externe et sa forme tridimensionnelle. La technique à force oscillante (oscillating tweezers) montre toutefois un décalage temporel, entre la force et la déformation, indépendant de la forme 3D; cette approche donnerait directement accès au tenseur viscoélastique complexe de la cellule.The mechanical response of a cell to external forces carries information about its structure and function. Because cell manipulation should ideally be non-invasive while performing sophisticated biophysical characterization, the radiation force of optical tweezers has become highly attractive. In this thesis, we explore three types of recently-developed optical tweezers: 1) static, 2) time-sharing and 3) oscillating. Using a full three-dimensional finite element method (3DFEM), modeling of each of these regimes allows us to fit experiments and access the cell mechanical properties. Combining optical trapping with cell mechanics requires interdisciplinary efforts. A survey of the various experimental approaches for optical trapping and measurements on isolated cells is presented. We then lay the theoretical background linking the interaction of optical fields to the cell’s mechanical response. We are the first to implement a 3DFEM calculation including light scattering and the radiation stress distribution to predict the deformation of a biconcave cell –emulating a red blood cell– in static dual-trap optical tweezers. At equilibrium, the final deformation is given by the separation distance of the two trapping beams, revealing how the cell can be elongated or shrunk. Time-sharing optical tweezers realize multiple traps to manipulate objects ranging from macromolecules to biological cells. Our quantitative analysis shows how, although jumping, the local stress and strain is omnipresent in the cell. The viscoelastic object deformation and internal energy dissipation are analyzed. Another cell shape, a cubic rod, is also studied, elucidating novel symmetrical properties of the mechanical response. Finally, the analysis of the time-dependent deformation –creep testing– of a cell in static and time-sharing optical tweezers, shows that deformation of the object depends altogether on the object’s viscoelasticity, significantly on its 3D shape and the mechanical loading. However, dynamic testing with oscillating optical tweezers surprisingly shows a phase shift between the loading stress (external force) and strain (deformation) independent on the 3D cell shape. This is a novel avenue giving access to the cell’s viscoelasticity dynamic complex modulus directly in the time-domain.
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Cui, Liyong. "An investigation into some novel areas of optical manipulation." HKBU Institutional Repository, 2017. http://repository.hkbu.edu.hk/etd_oa/436.
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Since its inception in 1970, optical manipulation has evolved into a versatile tool across many fields of science. Notably, the now widely employed optical tweezers invented in 1986 is a good example, which is in essence a strongly focused fundamental Gaussian beam. Although the optical tweezers remained as an important tool in optical manipulation, the shaped structured light such as an optical vortex beam also provides unusual light patterns and promotes exciting discoveries. This thesis is devoted to some unsolved theoretical aspects of optical manipulation. Since optical force acting on a micro-particle is typically on the order of pN and seldom larger than nN, it is a common belief that optical force is relevant in particle manipulation only when all other forces are comparable or smaller than the optical force. In chapter 2, surprisingly we showed that this is not always the case. Here, we find that under appropriate condition, optical vortices can make a sphere orbit around the beam center owing to the non-conservative optical force. If the sphere is attached to a mechanical spring, the spring can be stretched significantly even when the mechanical spring is orders of magnitude stronger than the optical force. Since its inception in 1970, optical manipulation has evolved into a versatile tool across many fields of science. Notably, the now widely employed optical tweezers invented in 1986 is a good example, which is in essence a strongly focused fundamental Gaussian beam. Although the optical tweezers remained as an important tool in optical manipulation, the shaped structured light such as an optical vortex beam also provides unusual light patterns and promotes exciting discoveries. This thesis is devoted to some unsolved theoretical aspects of optical manipulation. Since optical force acting on a micro-particle is typically on the order of pN and seldom larger than nN, it is a common belief that optical force is relevant in particle manipulation only when all other forces are comparable or smaller than the optical force. In chapter 2, surprisingly we showed that this is not always the case. Here, we find that under appropriate condition, optical vortices can make a sphere orbit around the beam center owing to the non-conservative optical force. If the sphere is attached to a mechanical spring, the spring can be stretched significantly even when the mechanical spring is orders of magnitude stronger than the optical force
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Guo, Yabin. "Mechanical unfolding and folding studies by optical tweezers." Thesis, University of British Columbia, 2017. http://hdl.handle.net/2429/61185.
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As a single molecule technique, optical tweezers technique proves to be a powerful tool to investigate the physical and chemical properties of DNA/RNA and protein molecules. In this thesis, optical tweezers are applied to two studies. In the first study, we directly investigated the unfolding and folding pathways and kinetics of the wild-type Top7 with optical tweezers. The existence of a folding intermediate state is confirmed. The unfolding process also occasionally shows non-cooperative behavior which has not been observed before. To identify if the mechanical stability of an isolated fragment of Top7 is responsible for the non-cooperative unfolding and folding behavior of Top7, we purified the C-fragment of Top7 and found that it reaches equilibrium at low applied forces, which indicates that Top7’s C-fragment could unfold and fold independently, but the unfolding and folding behavior of Top7 depends on the mutual assistance of both N-terminal and C-terminal residues. Illuminated by computational simulation methods, six residues were mutated aiming at improving the folding cooperativity of Top7. The results show that the folding cooperativity is improved significantly, while the unfolding intermediate appears more frequently. The possible influence of pathways on the frequency of occurrence of unfolding/folding intermediate state is discussed. In the second study, the two-step unfolding behavior of rubredoxin is revealed by optical tweezers. The reversible unfolding/folding behavior under force pressure and chemical pressure are further studied. Optical tweezers technique is proved to be well suited for mechanical unfolding/folding studies of metalloproteins.Science, Faculty of
Chemistry, Department of
Graduate
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Carberry, David Michael, and dave_carberry@yahoo com au. "Optical Tweezers: Experimental Demonstrations of the Fluctuation Theorem." The Australian National University. Research School of Chemistry, 2006. http://thesis.anu.edu.au./public/adt-ANU20060410.122727.
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In the late 19th and early 20th centuries famous scientists like Boltzmann, Loschmidt, Maxwell and Einstein tried, unsuccessfully, to find the link between the time-reversible equations of motion of individual molecules and irreversible thermodynamics. The solution to this puzzle was found in 1993, and the link is now known as the Fluctuation Theorem (FT). In the decade that followed theory and computer simulation tested the FT and, in 2002, an experiment indirectly demonstrated the FT.¶
This thesis describes original experiments that demonstrate the FT directly using Optical Tweezers. A related expression, known as the Kawasaki Identity, is also experimentally demonstrated. These experimental results provide a rigorous demonstration that irreversible dynamics can be obtained from a system with time-reversible dynamics.
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Zhou, Zhaokun. "Magneto-optical tweezers with super-resolution fluorescence microscopy." Thesis, University of York, 2017. http://etheses.whiterose.ac.uk/18771/.
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This thesis describes the design, construction and application of a novel magneto-optical tweezers with super-resolution fluorescence microscopy for manipulation, force/torque measurement and imaging of single biomolecules. The optical tweezers component offers force or position clamping in three dimensions. The 3D-printed magnetic tweezers is designated for rotation in the vertical plane. The separation of rotation from force transduction results in the capability of precise torque measurement. The filamentous biomolecules to be used in the device will lie in a transverse direction in the imaging plane to allow fluorescence imaging with techniques including Blinking assisted Localisation Microscopy (BaLM) and total internal reflection fluorescence microscopy (TIRF). Also included are features such as acousto-optic deflection and multiplexing of laser traps, interferometry based tracking with quadrant photodiode and piezoelectric actuated nanostage for active feedback. These tweezers have been developed to enable direct observation of molecular topological transformation and protein binding event localisation with mechanical perturbation, which traditional tweezers could not achieve.
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Theofanidou, Eirini. "Design, construction and biophysical applications of optical tweezers." Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/11461.
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The first part of this work is dedicated to technical issues and system developments; the design and construction of an open microscope which forms the base for an optical tweezers set-up, is described. Subsequently the creation of a generic optical tweezers set-up is presented. This set-up was used in combination with two photon fluorescence to investigate the deteriorating of the quality of the trap due to optical aberrations. It is shown that using adaptive optics (i.e. a deformable membrane), the aberrations are partially corrected. Furthermore, it was demonstrated that using the deformable membrane one can achieve the axial-position control of the trapped particle. The same open microscope was used in combination with a ferroelectric liquid crystal spatial light modulator to construct multiple trap tweezers. The fast switching speeds of the ferroelectric device, compared to the conventional nematic systems, is shown to enable very rapid reconfiguration of trap geometries, controlled, high speed particle movement, and the firs tweezers array multiplexing. The second part of the work focuses on biophysical applications. A commercial microscope combined with fluorescence imaging is used to analyse the stretching and unwinding of DNA, as well as DNA condensation. Stretching and unwinding of polymers under flow is a very important phenomenon associated with the rheological properties of dilute polymer solutions. Scaling theory predicts two broad regimes for the overall shape of the deformed DNA molecule: the ‘trumpet’ regime at low flow velocities and a ‘stem and flower’ regime at high flow velocities. I studied the DNA shape at different velocities using optical trapping of single DNA molecules tethered on polystyrene beads. The results show clearly the two theoretically predicted regimes of ‘trumpet’ and ‘stem and flower’.
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Carberry, David Michael. "Optical tweezers : experimental demonstrations of the fluctuation theorem /." View thesis entry in Australian Digital Theses Program, 2005. http://thesis.anu.edu.au/public/adt-ANU20060410.122727/index.html.
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Yin, Munan. "Haptic optical tweezers with 3D high-speed tracking." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066003/document.
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La micromanipulation a un grand potentiel pour révolutionner la recherche biologique et les soins médicaux. À petite échelle, microrobots peuvent effectuer des tâches médicales avec peu invasive, et d'explorer la vie à un niveau fondamental. Pinces optiques sont l'une des techniques les plus populaires pour la manipulation biologique. La production de petits lots qui exige une grande flexibilité repose principalement sur le processus de téléopération. Cependant, le niveau limité d'intuitivité rend de plus en plus difficile de conduire efficacement les tâches de manipulation et d'exploration dans le micromonde complexe. Dans de telles circonstances, des chercheurs pionniers ont proposé d'incorporer l'haptique dans la boucle de contrôle du système OTs, qui vise à gérer les tâches de micromanipulation de manière plus flexible et plus efficace. Cependant, la solution n'est pas encore complète, et il ya deux défis principaux à résoudre dans cette thèse: Détection de force 3D, qui doit être précis, rapide et robuste dans un espace de travail suffisamment grand; Haute vitesse jusqu'à 1 kHz force de rétroaction, ce qui est indispensable pour permettre une sensation tactile fidèle et d'assurer la stabilité du système. Dans la micromanipulation des pinceaux optiques, la vision est un bon candidat pour l'estimation de la force puisque le modèle force-position est bien établi. Cependant, le suivi de 1 kHz dépasse la vitesse des procédés de traitement classiques. La discipline émergente de l'ingénierie biomorphe visant à intégrer les comportements de vie dans le matériel informatique ou le logiciel à grande échelle rompt le goulot d'étranglement. Le capteur d'image asynchrone basé sur le temps (ATIS) est la dernière génération de prototype de rétine de silicium neuromorphique qui enregistre seulement les changements de contraste de scène sous la forme d'un flux d'événements. Cette propriété exclut le fond redondant et permet la détection et le traitement des mouvements à grande vitesse. La vision événementielle a donc été appliquée pour répondre à l'exigence de la rétroaction de force 3D à grande vitesse. Le résultat montre que les premières pinces optiques haptiques 3D à grande vitesse pour une application biologique ont été obtenues. La réalisation optique et les algorithmes de suivi événementiel pour la détection de force 3D à grande vitesse ont été développés et validés. L'exploration reproductible de la surface biologique 3D a été démontrée pour la première fois. En tant que puissant capteur de force 3D à grande vitesse, le système de pinces optiques développé présente un potentiel important pour diverses applicationsMicromanipulation has a great potential to revolutionize the biological research and medical care. At small scales, microrobots can perform medical tasks with minimally invasive, and explore life at a fundamental level. Optical Tweezers are one of the most popular techniques for biological manipulation. The small-batch production which demands high flexibilities mainly relies on teleoperation process. However, the limited level of intuitiveness makes it more and more difficult to effectively conduct the manipulation and exploration tasks in the complex microworld. Under such circumstances, pioneer researchers have proposed to incorporate haptics into the control loop of OTs system, which aims to handle the micromanipulation tasks in a more flexible and effective way. However, the solution is not yet complete, and there are two main challenges to resolve in this thesis: 3D force detection, which should be accurate, fast, and robust in large enough working space; High-speed up to 1 kHz force feedback, which is indispensable to allow a faithful tactile sensation and to ensure system stability. In optical tweezers micromanipulation, vision is a sound candidate for force estimation since the position-force model is well established. However, the 1 kHz tracking is beyond the speed of the conventional processing methods. The emerging discipline of biomorphic engineering aiming to integrate the behaviors of livings into large-scale computer hardware or software breaks the bottleneck. The Asynchronous Time-Based Image Sensor (ATIS) is the latest generation of neuromorphic silicon retina prototype which records only scene contrast changes in the form of a stream of events. This property excludes the redundant background and allows high-speed motion detection and processing. The event-based vision has thus been applied to address the requirement of 3D high-speed force feedback. The result shows that the first 3D high-speed haptic optical tweezers for biological application have been achieved. The optical realization and event-based tracking algorithms for 3D high-speed force detection have been developed and validated. Reproducible exploration of the 3D biological surface has been demonstrated for the first time. As a powerful 3D high-speed force sensor, the developed optical tweezers system poses significant potential for various applications
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Hay, Rebecca. "Optimising optical tweezers for tracking and force measurement experiments." Thesis, University of Glasgow, 2017. http://theses.gla.ac.uk/8624/.
Full textAbstract:
Optical Tweezers are a useful tool in many aspects of biology, including cell manipulation and microrheology. They are often used as piconewton force transducers, and are an effective tool for measuring forces acting upon optically trapped particle. To measure such forces, knowledge of the displacement of the particle from the trap centre is always needed. However, due to Brownian motion, a trapped particle is constantly moving and never at rest. In this case, one must track a bead over a set time, so as to gain an average displacement. In this thesis, we have improved and optimised this tracking procedure for biological samples in different ways. In Chapter 1 we discuss how Optical Tweezers work, how they are set up, and how we measure forces using them. In Chapter 2 we redesign a commercial Optical Tweezer Product to improve tracking data results. We also incorporate fluorescence imaging using a compact, low cost, LED illumination source. In Chapter 3 we combine fluorescence microscopy with state of the art Scientific cameras, to increase tracking frame rates and potentially improve our tracking data of fluorescent stained cells. This was part of a collaboration, where I helped to build the setup, took the data (using programs produced by one of my collaborators), and was part of the team to analyse it. In Chapter 4, we look at Low Reynolds number environments and discuss the benefits of viscous forces, and how it may be possible to make non-invasive, less harmful traps for biological samples. Again, this was part of a collaboration, where I was in charge of the experimental part. Here, I built in the static tweezer trap into a tweezer system, took position data and analysed it. A collaborator took control of analysing velocity data. Finally, in Chapter 5, we measure the accuracy of tracking in three dimensions using a stereomicroscope, by placing a Spatial Light Modulator (SLM) at the Fourier plane in the imaging arm. Again, this was a collaboration. I designed and manufactured the illumination head, helped design an acquisition program, and took the data. We discuss how all of these could optimise and advance the tracking of optically trapped particles, especially biological samples. Despite the obvious applications in biology, to allow a fair evaluation of the different tracking techniques, all of our experiments used samples of spherical beads, as they have known specifications, including fluorescence excitation and emission wavelengths, size, and amount of fluorophore stain.
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Nascimento, Jaclyn Marie. "Analysis of sperm motility and physiology using optical tweezers." Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2008. http://wwwlib.umi.com/cr/ucsd/fullcit?p3291333.
Full textAbstract:
Thesis (Ph. D.)--University of California, San Diego, 2008.Title from first page of PDF file (viewed February 14. 2008). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references.
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Preece, Daryl. "Novel uses of spatial light modulators in optical tweezers." Thesis, University of Glasgow, 2011. http://theses.gla.ac.uk/2619/.
Full textAbstract:
In recent years spatial light modulators (SLMs) have become an integral part of many optical trapping experiments. Yet their usefulness, which stems from their flexibility, is often under exploited. In this thesis I seek to demonstrate how it is possible to expand the range of optical trapping applications that may benefit from the use of spatial light modulators. From exploring the benefits of increased resolution to demonstrating novel applications like position clamping and polarization control, I show how SLMs are a resource which can benefit optical trapping in new and unconventional ways. The optical properties of liquid crystals have long been known however it is only recently that they have been applied to optical tweezers. The physics and operation of spatial light modulators are discussed in chapter 1, with specific attention paid to those aspects of operation which are of pertinent practical use to optical trapping. In chapter 2 it is shown how phase only modulation can be used to create effective holographic optical tweezers systems which are capable of manipulating micron scale particles and measuring pico-Newton forces. Chapter 3 charts the development and characterization of a 4 Mega-pixel spatial light modulator which was created as an improvement on current SLM technology. The role of SLMs in utilising lights angular momentum as a tool for creating rotational torque is discussed in chapter 4. In chapter 5 describes how SLMs can be used to create torques based the application of spin angular momentum to birefringent particles. We show, in chapter 6 how with suitable software engineering it is possible to both move optical traps and track particles in real time. Since the use of SLMs has been previously been limited by their bandwidth constraints we discuss in chapter 7 the use spatial light modulators in closed loop systems. We finish with a discussion of the use of SLMs in a new technique that may be applied to microrheology.
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Abdosamadi, Mohammad K., Anita Jannasch, and Erik Schäffer. "Resonant optical tweezers with anti-reflection coated titania microspheres." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-183282.
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Shepherd, Jack William. "Manipulating DNA with magneto-optical tweezers and multiscale simulation." Thesis, University of York, 2018. http://etheses.whiterose.ac.uk/22040/.
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González, Rubio Ricardo S. M. Massachusetts Institute of Technology. "Tools to study the kinesin mechanome using optical tweezers." Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/61241.
Full textAbstract:
Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Biological Engineering, 2009.Cataloged from PDF version of thesis.
Includes bibliographical references (p. 108-111).
Molecular motors play an important role in driving some of the most complex and important tasks in biological systems, ranging from transcribing RNA from a DNA template (Polymerases) to muscle contraction (Myosin) and propelling bacteria (Flagellum). Key to the understanding of the fundamental principles and designs by which molecular motor function has been the kinesin family. Missing, however, is a clear understanding of the series of events that take place at the atomistic level when kinesin walks on a microtubule and generates force. Recent MD simulations have identified the force-generating mechanism in kinesin, the cover-neck bundle, and strongly suggest that the formation of the CNB by the N-terminal cover strand and the C-terminal neck linker of the motor head are responsible for force generation. In this thesis we present tools developed in the Lang Laboratory to further elucidate the stepping motion and force generation mechanism of kinesin using Drosophila kinesin as a model system. We demonstrate the function of a force clamp specifically designed for the laboratory and show traces of WT kinesin walking under constant load. We also purified and tested kinesin mutants running under a force load. We present two assays specifically designed to study the interaction between kinesin and the last 10-18 C-terminal residues of a-p tubulin, the E-hook. We were unable to observe kinesin - e-hook interactions, such as those suggested by the formation of tethers, when the e-hook was bound to the surface. In the case of e-hook in solution, our results indicate that 2G kinesin was still functional and its stall force approximately 3 pN just as for the case when no e-hook is present. We also propose ways that the work in this thesis can be expanded. The force clamp can be easily adapted to study novel kinesin mutants under constant load in 2D. In addition, the force clamp can be used to probe the kinesin - e-hook interactions by looking at kinesin walking over microtubules with cleaved e-hooks. The e-hook assays presented in this thesis can also be expanded to include higher concentrations of e-hook or be performed using labeled e-hook to assess single molecule interactions and concentrations.
by Ricardo González Rubio.
S.M.
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Muldoon, Cecilia. "Control and manipulation of cold atoms in optical tweezers." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:920933c8-441c-4d59-a4f4-87f8c799a820.
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The ability to address and manipulate individual information carriers in a deterministic, coherent, and scalable manner is a central theme in quantum information processing. Neutral atoms trapped by laser light are amongst the most promising candidates for storing and processing information in a quantum computer or simulator, so a scalable and flexible scheme for their control and manipulation is paramount. This thesis demonstrates a fast and versatile method to address and dynamically control the position (the motional degrees of freedom) of neutral atoms trapped in optical tweezers. The tweezers are generated by using the direct image of a Spatial Light Modulator (SLM) which can control and shape a large number of optical dipole-force traps. Trapped atoms adapt to any change in the potential landscape, such that one can re-arrange and randomly access individual sites within atom-trap arrays. A diffraction limited imaging system is used to map the intensity distribution of the SLM onto a cloud of cold atoms captured and cooled using a Magneto Optical Surface Trap (MOST).
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Abdosamadi, Mohammad K., Anita Jannasch, and Erik Schäffer. "Resonant optical tweezers with anti-reflection coated titania microspheres." Diffusion fundamentals 20 (2013) 61, S. 1, 2013. https://ul.qucosa.de/id/qucosa%3A13638.
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Brady, Kyle T. "ENHANCED NANOPORE DETECTION VIA DIFFUSION GRADIENTS AND OPTICAL TWEEZERS." VCU Scholars Compass, 2015. http://scholarscompass.vcu.edu/etd/3798.
Full textAbstract:
Nanopore-based resistive pulse sensing represents an important class of single-molecule measurements. It provides information about many molecules of interest (i.e. DNA, proteins, peptides, clusters, polymers, etc.) without the need for labeling. Two experiments that are especially well suited for studying with nanopore sensors are DNA sequencing and DNA-protein force measurements. This thesis will describe progress that has been made in both areas.
DNA sequencing has become an active area of research for stochastic single-molecule sensing, with many researchers striving for the ultimate goal of single-molecule de novo DNA sequencing. One intriguing method towards that goal involves the use of a DNA exonuclease or polymerase enzyme, which when attached close to the mouth of a pore, leads to cleavage of individual DNA nucleotide bases for loading into the pore for sensing. Though this method seems promising, the end goal has been elusive because the nucleotide motion is dominated by diffusion over the relevant length scales. This limits the likelihood of the cleaved nucleotide entering the pore to be characterized. The first part of this thesis will describe a method for addressing this problem, where it is shown that increasing the nucleotide capture probability can be achieved by lowering the bulk diffusion coefficient relative to the pore diffusion coefficient.
The second part of this thesis will describe the design and implementation of a new type of sensor that combines a biological nanopore experimental apparatus with optical tweezers. The goal of this apparatus is to develop a means to independently measure the force on a charged molecule inside of the pore. The setup will be thoroughly described, and preliminary results showing that it is possible to optically trap a micron sized bead within a few microns of an isolated biological nanopore while simultaneously making current measurements through that pore will be presented. This will enable force measurements on DNA molecules tethered to the bead, which opens the door for the study of molecular force interactions between DNA and biological nanopores, DNA-bound protein interactions that cause diseased states, and controlled translocation of DNA through biological nanopores.
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Català, i. Castro Frederic. "Implementation of the direct force measurement method in optical tweezers." Doctoral thesis, Universitat de Barcelona, 2018. http://hdl.handle.net/10803/665757.
Full textAbstract:
Mechanics is the branch of physics that studies movement and force, and plays an evident role in life. The swimming dynamics of bacteria in search of nutrients, organelle transport by molecular motors or sensing different kinds of stimuli by neurons, are some of the processes that need to be explained in terms of mechanics.
At a human scale, distance and force can be measured with a ruler and a calibrated spring. However, assessing these magnitudes may become an important challenge at a micron scale. Among several techniques, optical tweezers stand out as a non-invasive tool that is capable of using light to grab micron-sized particles and measuring position and force with nanometer (10(-9) and femto-Newton (10(-15) accuracy. Small specimens, such as a bacterium or a cell membrane, can be trapped and effectively manipulated with a focused laser beam. Light momentum exchanged with the trapped sample can be used for eventually measuring the otherwise inaccessible forces that govern biological processes.
Optical tweezers have enabled, after trapping cell vesicles in vivo, to measure the pulling force exerted by molecular motors, such as kinesin. Flagellar propulsion forces and energy generation have been investigated by optically trapping the head of a bacterium. Cell membranes have been deformed with optical tweezers and the underlying tension determined.
However, the exact forces exerted by optical tweezers are difficult to measure beyond the in vitro approach. In order to calibrate the optical traps, the trapped samples often need to be spherical or present some degree of symmetry, it is important to bear information on the experimental parameters, and one needs high control of several variables that determine the trapping dynamics, such as medium homogeneity and temperature.
A cutting-edge method, developed in the Optical Trapping Lab – BiOPT, from the Universitat de Barcelona, targets the light-momentum change as a direct reading of the force exerted by an optical trap. This frees experiments from the necessity of calibrating the optical traps, and makes possible to perform accurate force measurement experiments in vivo and involving irregular samples.
In my PhD thesis, the direct force detection method for optical tweezers has been implemented and tested in some of such situations. I first give a technical description of the set-up used for the experiments. The use of a spatial light modulator (SLM) for holographic optical tweezers (HOTs), a piezo-electric platform to induce drag forces, and the trapping laser emission characteristics, are explained in detail.
The light-momentum set-up is tested against certain situations deviating from the ideal performance and some steps for optimization of several effects are analyzed. Backscattering light loss is quantified through experiments and numerical simulations and finally assessed to account for an average ±5% uncertainty in force measurements.
Then, the method is used to measure forces on irregular samples. First, arbitrary systems composed of microspheres of different kinds are collectively treated as irregular samples, in which the global momentum exchanged with the trapping beam coincides with the total Stokes-drag force. Second, pairs of optical tweezers are used to stably trap cylinders of sizes from 2 milimicras to 50 milimicras and measure forces in accordance with slender-body hydrodynamic theory.
Another aspect of the thesis deals with the temperature change induced by water absorption of IR light, which is one of the major concerns within the optical trapping community. As main reasons, accurate knowledge of local temperature is needed for understanding thermally-driven processes, as well as eventual damage to live specimens. Here we use direct force measurements to detect changes in viscosity that are due to laser heating, and compare the results with heat transport simulations to discuss the main conclusions on this effect.
The last goal of my thesis has been the implementation of the method inside tissue. The laser beam is affected by the scattering structures present in vivo, such as refractive index mismatches throughout different cells, nuclei, cell membranes or vesicles. As a primary result, despite the trapping beam is captured beyond 95%, I quantified this effect to result in an increase in the standard deviation of force measurements around ±20%. The approach has consisted in comparing the trapping force profiles of spherical probes in vitro (water) and in vivo (zebrafish embryos).
To conclude, I here demonstrate that the direct force measurement method can be applied in an increasing number of experiments for which trap calibration becomes intricate or even impossible. Quantitative measurements become feasible in samples with unknown properties, the more important examples being arbitrary, non-spherical samples and the interior of an embryonic tissue.Les pinces òptiques són una eina que permet la manipulació d'objectes de mida micromètrica mitjançant llum làser. En no ser necessari el contacte mecànic directe sobre una mostra, els dóna la característica de ser una eina no invasiva, fet que obre moltes aplicacions en nombrosos camps de la biologia, com ara en estudis de mecànica cel·lular en teixits. A més a més, una pinça o trampa òptica pot emprar-se per tal de realitzar mesures quantitatives, com ara posicions i forces amb precisió de nanòmetres (10-9) i femto- Newtons (10-15). D'aquesta manera, magnituds que altrament foren inaccessibles, com ara la força en un contacte cel·lular, poden obtenir-se i engegar així una nova dimensió en la recerca en biomecànica. El mètode de mesura directa de forces analitza els canvis en el moment lineal dels fotons que conformen el feix per tal de mesurar forces òptiques. Aquest mètode permet de mesurar forces sense dependre d’un alt control experimental, cosa que fa possible la mesura de forces, per exemple, en objectes irregulars. Per contra, això és gràcies a un disseny experimental capaç de capturar tota la llum que crea la pinça òptica i de mesurar-ne els canvis de moment. En la meva tesi doctoral, demostrem l’aplicabilitat del mètode en situacions en què la força no es pot obtenir de manera indirecta a partir de tècniques de calibració. En primer lloc, analitzem les millores tècniques que fan del mètode de detecció de moment una eina robusta per tal de realitzar mesures de força en un ampli ventall de situacions experimentals. Seguidament, emprem pinces òptiques controlades hologràficament per tal d’atrapar objectes irregulars, com ara sistemes de múltiples esferes i micro-cilindres, i mostrem la capacitat de mesurar l’intercanvi de moment entre el feix i les partícules que dóna lloc a les forces òptiques. Un altre aspecte àmpliament analitzat gràcies a aquesta tècnica de mesura és l’escalfament que origina una pinça òptica sobre el medi que envolta la partícula atrapada. Finalment, ens endinsem en la biologia de teixits per esbrinar com la dispersió a través d’aquests afecta el moment del feix i, per tant, les mesures. Les meves conclusions demostren l’aplicabilitat del mètode de mesura en situacions en què la calibració in situ pot esdevenir-se molt complicada o, fins i tot, impossible. Podem considerar que, per tant, el camp d’aplicació de les pinces òptiques anirà creixent i trobarà nous experiments en què s’elucidaran alguns dels interrogants més importants de la biologia.
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Phillips, David Benjamin. "Applications of closed-loop feedback control with holographic optical tweezers." Thesis, University of Bristol, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.570860.
Full textAbstract:
SINCE their invention, optical tweezers have found a host of applications, primarily as micro- manipulation tools and sensitive force transducers. The development of techniques such as holographic optical tweezers has enabled the manipulation of multiple particles in three dimensions. Recent advances in computation power and display technologies have afforded the opportunity to explore applications of real-time manipulation and particle tracking, utilising closed-loop feedback control, the principle aim of this work. We begin by investigating the use of holographic optical tweezers as an autonomous micro- fabrication device, to construct three dimensional colloidal crystals. We develop a bespoke microfluidic construction environment, and demonstrate tracking and control algorithms to iden- tify, capture and manipulate microspheres into required arrangements. Our algorithm calculates the paths of particles from any desired initial to final configurations, and avoids inter-particle collisions, and the undiffracted beam. The development of multiple trap systems has also increased interest in the trapping and tracking properties of lower symmetry structures. In this light, we investigate the behaviour of multiply trapped silica micro-rods, and demonstrate real-time tracking in two dimensions. The precision of our method is estimated, and the translational and rotational stiffness coefficients are evaluated using thermal motion analysis and Stokes' drag. We measure the variation of these stiffness coefficients relative to the displacement of the traps from the ends of the micro-rods, and find good agreement with theory. We go on to use our micro-rod probes to image the surface of an oil droplet in a manner analogous to scanning probe microscopy, with closed-loop feedback control of the micro-rod's position. As. the resolution of our surface images is limited by the tracking accuracy of the micro-rods, we investigate the imaging capability of another form of high aspect-ratio probe - a cigar shaped, silica shelled form of Diatom algae. This probe is held using two optical traps centered at least lOμm from its tip, enabling highly curved and strongly scattering samples to be imaged. We demonstrate the advantages of this technique by imaging the surface of the soft alga Pseudopediastrum, while it is alive and unadhered to the surface. The resolution is currently equivalent to confocal microscopy, but as it is not diffraction limited, there is scope for significant improvement by reducing the tip diameter and limiting the thermal motion of the probe. Motivated by improving our imaging technique, we further investigate the degree of control that can be exercised over our Diatom probe. By position clamping translational and rotational modes in different ways, we are able to dramatically improve the position resolution, with no reduction in force sensitivity. We also demonstrate control over rotational-translational coupling, and exhibit a mechanism whereby the average centre of rotation of our probe can be displaced away from its centre, a feature that could potentially be used to damp existing couplings within the motion of more complex optically trapped structures. Finally, we explore three dimensional tracking of our Diatom probes using stereo-microscopy. The full five degree of freedom stiffness matrix is used to calculate forces and torques exerted at the probe tip. Together, we hope the techniques demonstrated in this thesis. represent a step towards a novel and flexible form of all optical scanning probe microscopy.
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Bugiel, Michael, Elisa Böhl, and Erik Schäffer. "Diffusive protofilament switching of kinesin-8 investigated with optical tweezers." Universitätsbibliothek Leipzig, 2015. http://nbn-resolving.de/urn:nbn:de:bsz:15-qucosa-182342.
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Hui, Jeremy R. (Jeremy Ryan) 1977. "Optical tweezers using the Texas Instruments' Digital Micromirror Device(tm)." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/86699.
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Thesis (M.Eng. and S.B.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2001.Includes bibliographical references.
by Jeremy R. Hui.
M.Eng.and S.B.
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Ta, Jenny 1982. "Antibody-Antigen assay design for combined optical tweezers and fluorescence." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/32789.
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Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (p. 37).
The recent development in combined optical trapping and fluorescence technology promises to enable unbindinig force studies of receptor-ligand interactions, whose specificity play a crucial role in the function of many biological systems. This thesis focuses on the development of assay designs for the study of antibody-antigen binding interactions using combined optical trapping and single molecule fluorescence. The assays create the necessary linkage geometry between the antibody-antigen system under study to an optically trapped bead, enabling force probing of the antibody-antigen binding interaction. In particular, two tether materials and fluorophores were studied: polyethylene glycol (PEG) with Cy-2, and dsDNA with fluorescein. We demonstrate tether formation in the dsDNA-fluorescein antibody-antigen linkage system with preliminary optical trapping data.
by Jenny Ta.
S.B.
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Rebane, Aleksander. "Exploring Free Energy Landscapes of SNARE Assembly Using Optical Tweezers." Thesis, Yale University, 2018. http://pqdtopen.proquest.com/#viewpdf?dispub=10957335.
Full textAbstract:
Scientists have long sought to understand the working principles of protein machinery. A decisive step towards this goal has been the development of the Gibbs free energy landscape of protein folding. However, measurement of energy landscapes has remained challenging, particularly when folding occurs over one or more intermediates. An important example is soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) complex assembly, in which the energetics and kinetics of multiple assembly steps are coupled to distinct stages of vesicle maturation and membrane fusion in synaptic exocytosis. As a result, a quantitative test of this fundamental biophysical mechanism remains outstanding. In recent years it has become possible to measure energy landscapes of proteins in the presence of force using a single-molecule manipulation technique called optical tweezers (OT). However, derivation of energy landscapes in the absence of force from OT data has remained difficult. Here, we present a comprehensive OT data analysis method that uses information from high-resolution protein structures to derive a simplified energy landscape of protein folding at zero force by model fitting of the experimental measurements. We apply our method to derive the energetics, kinetics, and intermediate conformations of SNARE assembly for the wild-type complex and a number of mutants with known phenotypes. We characterize how the steps in SNARE assembly function in the respective stages of synaptic exocytosis and provide quantitative verification of the coupling mechanism. Finally, we investigate the mechanism by which two SNARE mutations cause severe neurological disease. In sum, our work provides a complete methodology to measure energy landscapes to reveal the underlying mechanisms of protein function.
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Bugiel, Michael, Elisa Böhl, and Erik Schäffer. "Diffusive protofilament switching of kinesin-8 investigated with optical tweezers." Diffusion fundamentals 20 (2013) 26, S. 1, 2013. https://ul.qucosa.de/id/qucosa%3A13593.
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Guo, Qing. "Single Molecule Optical Magnetic Tweezers Microscopy Studies of Protein Dynamics." Bowling Green State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1435334948.
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Selvam, Sangeetha. "Molecular Population Dynamics of DNA Tetraplexes using Magneto-Optical Tweezers." Kent State University / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=kent1516742116760289.
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Sudhakar, Swathi [Verfasser]. "Germanium nanospheres as high precision optical tweezers probes / Swathi Sudhakar." Tübingen : Universitätsbibliothek Tübingen, 2021. http://d-nb.info/1236994094/34.
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Seol, Yeonne. "Study of stochastic processes and RNA elasticity using optical tweezers." Diss., The University of Arizona, 2004. http://hdl.handle.net/10150/280567.
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Our main research project is to develop an experimental system to understand the ribosomes as molecular motors. For this purpose, we designed and developed the single molecule ribosome motility assay. In this thesis, we discuss the related steps which we have taken to develop this assay: the instrumentation and four experiments. In the introduction, we illustrate the current experimental scheme and show the preliminary data of the single molecule ribosome translation. In the first two chapters, we discuss two interesting experiments dealing with stochastic problems. In the first chapter, we introduce the idea that the noise can be reduced in certain conditions. We show that the noise can be really reduced but only if added fluctuations have to drive the input into states with reduced intrinsic noise. In the second chapter, we investigate two-state processes experimentally using a simple physical system in which a microscopic bead is trapped in a double-well potential. We discuss how we can control the characteristics of the escape process by adding a periodic force and illustrate the characteristics in terms of the residence time distribution and the escape phase. As last two chapters, we discuss the elastic and structural properties of homopolymeric RNA, polyadenylic acids (poly(A)), polycytidylic acids (poly(C)), and polyuridylic acids (poly(U)). First, we investigate the elastic property of poly(U) as a random coil. We find that the force-extension data is well predicted by a classic worm-like chain model at high Na⁺ concentrations, whereas at low such concentrations the introduction of a scale-dependent persistence length is required. As single-stranded helices, poly(A) and poly(C) are studied. We stretch the molecules to induce the conformational transition from folded states to unfolded states and use the elastically coupled two-state model to acquire their structural information (about 9 bases per turn and 8 bases per turn, for poly(A) and poly(C) respectively, at neutral pH and 500 mM [Na⁺]) and the free energy differences between two states (20 pN·nm for poly(A) and 17.5 pN·nm for poly(C)).
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Brau, Ricardo R. (Ricardo Rafael) 1979. "Exploring the mechanome with optical tweezers and single molecule fluorescence." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/43795.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Biological Engineering Division, February 2008.Includes bibliographical references (p. 213-231).
The combination of optical tweezers and single molecule fluorescence into an instrument capable of making combined, coincident measurements adds an observable dimension that allows for the examination of the localized effects of applied forces on biological systems. This technological advance had remained elusive due to the accelerated photobleaching of fluorophores in the presence of the high photon flux of the optical trap. This problem was circumvented by alternately modulating the trapping and fluorescence excitation laser beams, a technique named IOFF. Results show that our solution extends the longevity of Cy3 fluorophores by a factor of 20 without compromising the stiffness of the optical trap. This versatile arrangement can be extended to other fluorophores and was applied to unzip a 15 base pair region of dsDNA and to induce reversible conformational changes in a dsDNA hairpin labeled with a FRET pair. Next, this work developed an immobilization strategy and two single molecule assays for the CIpX ATPase, an enzyme capable of unfolding substrates that have been targeted for proteolytic degradation. In the first assay, which employs single molecule fluorescence, CIpX was found to unfold and translocate pre-engaged GFP substrates with a time constant of 22 s at saturating ATP concentrations, a rate that is 8-fold faster than bulk measurements clouded by binding and unbinding events. The second assay measured the strength of the ClpX-substrate interaction with optical tweezers. Results show that CIpX holds on to its substrates with forces on the order of 55 pN regardless of the nature and concentration of the nucleotide in solution.
(cont.) Finally, optical tweezers were used to characterize the rheological properties of methylcellulose and polarized cells, to quantify the mechanical properties of bacteriophage, and to measure the forces generated by a cellular actin spring.
by Ricardo R. Brau.
Ph.D.
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Garbin, Valeria. "Optical tweezers for the study of microbubble dynamics in ultrasound." Doctoral thesis, Università degli studi di Trieste, 2007. http://hdl.handle.net/10077/3220.
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2005/2006Optical tweezers enable for non-destructive, contact-free manipulation of ultrasound contrast agent (UCA) microbubbles, which are used in medical imaging for enhancing the echogenicity of the blood pool and to quantify organ perfusion. Understanding the dynamics of ultrasound-driven contrast agent microbubbles from a fundamental physical standpoint is a first step for exploiting their acoustical properties and to develop new diagnostic and therapeutic applications. However, experiments on bubble dynamics presently suffer from a lack of control on bubble position, because of buoyancy, microstreaming and bubble clustering. In this respect, optical tweezers can be used to study UCA microbubbles under controlled and repeatable conditions, by positioning them away from interfaces and from neighboring bubbles. In addition, an ultra-high speed imaging system is required to record the dynamics of UCA microbubbles in ultrasound, as their oscillations occur on the nanoseconds timescale. In this thesis, optical tweezers and an ultra-high speed camera are integrated into an experimental setup to control the boundary conditions and record the oscillations of the microbubbles. Optical tweezers are commonly obtained by focusing a laser beam through a microscope objective, as the high intensity gradient in the focal region causes dielectric microparticles to be attracted in the focus. In the special case of microbubbles, which exhibit a lower refractive index than the surrounding liquid, the opposite situation arises: they are pushed away from the region of maximum intensity. Nevertheless, microbubbles can be trapped in the dark core of a donut-shaped trap, which can be obtained e.g. by focusing a Laguerre-Gaussian beam. In our setup, a Gaussian beam is converted to a Laguerre-Gaussian mode by using diffractive optical elements implemented on a spatial light modulator. This allows to trap and manipulate single or multiple microbubbles, and to control the distance from interfaces as well as the bubbleto- bubble distance. The “Brandaris 128” ultra-high speed camera is used, in combination with the optical tweezers, to recorded the bubble oscillations at a frame rate of 15 million frames per second. The influence of a rigid wall on the resonance frequency and oscillation amplitude was experimentally investigated. An experimental phospholipid-coated agent (BR-14, Bracco Research S.A., Geneva, Switzerland) was used throughout the experiments. A resonance frequency curve was recorded for the same bubble positioned at the wall and at controlled distance from the wall. The experiments show a drop in the resonance frequency for the bubble close to the ii Abstract wall, as expected from the theoretical models. These results are highly relevant for molecular imaging applications, where the response of targeted microbubbles needs to be discriminated from that of freely flowing ones. We also quantify the bubble-to-bubble interaction, in two ways: first, we compare the change of the radial oscillations of one bubble with and without a neighboring bubble. Second, we resolve the change in distance between two bubbles during ultrasonic insonation. This results from an acoustical, generally attractive, interaction force between the bubbles, termed secondary Bjerknes force. To understand this rich two-bubble dynamics, we couple a recent single-bubble model, accounting for both gas and monolayer properties with a model quantifying the mutual interaction of bubbles in their translation and oscillations. Experiments where optical tweezers are used as a force sensor to measure the binding force in an antigen-antibody complex at the single molecule level are also presented. In the future, the possibility of combining optical micromanipulation with the force-sensing capabilities of optical tweezers will open the way to a new class of experiments which will give us a deeper insight into fundamental bubble phenomena and find direct application to new ultrasound-assisted targeting strategies.
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YOUSAFZAI, MUHAMMAD SULAIMAN. "Cancer cell mechanics and cell microenvironment: An optical tweezers study." Doctoral thesis, Università degli Studi di Trieste, 2016. http://hdl.handle.net/11368/2908097.
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Since cancer metastasis is a complex process, lot of research has been carried out to identify different hallmarks for its diagnosis and cure. Mechanical alterations in cancer cells during cell spreading to adjacent tissues and other organs of the body emerged as a prominent hallmark in the last decade.
In this thesis we employed a mechanistic approach and used stiffness (elasticity) as a marker to study cell’s mechanical response in varying microenvironmental conditions. Cell– microenvironment mechanical interaction is a blend of cell-matrix and cell-cell interactions. Therefore we adopted an approach to study cells in the presence of their neighbouring cells as well as on compliant substrates at small forces (<10pN) using optical tweezers. The elastic modulus was calculated using the Hertz-model.
We considered three breast cell lines as model, showing three phases of cancer progression: MDA-MB-231, a highly aggressive cell line belonging to the Basal cell-like phenotype; MCF-7, a less aggressive cancer cell line, belonging to the Luminal A cell-like phenotype; and HBL-100, a non-neoplastic cell line, derived from the milk of a Caucasian woman, normal control for breast basal-myoepithelial cells.
Cell elasticity can be locally measured by pulling membrane tethers, stretching or indenting the cell using optical tweezers. We introduce a simple approach to perform cell indentation by axially moving the cell against a trapped microbead. Our scheme is similar to the AFM vertical cell indentation approach and can help to compare the quantitative results and thus complement AFM in a low force regime and loading rates.
The elasticity trend of the three cell lines in isolated conditions showed that the aggressive MDA-MB-231 cells are significantly softer as compared to HBL-100 and MCF-7 cells.
We demonstrate that stiffness measurements are sensitive to the cellular sub-regions as well as the interacting microenvironment. We probed the cells at three cellular sub regions: central (above nucleus), intermediate (cytoplasm) and near the leading edge. In isolated condition, all cells showed a significant regional variation in stiffness: higher at the center and fading toward the leading edge. However, the regional variation become statistical insignificant when the cells were in contact with other neighboring cells. We found that neighboring cells significantly alter cell stiffness: MDA-MB-231 becomes stiffer when in contact, while HBL-100 and MCF-7 exhibit softer character.
Furthermore, we have studied the influence of substrate stiffness on cell elasticity by seeding the cells on Collagen and Polydimethylsiloxane (PDMS) coated substrates with varying stiffnesses to mimic extracellular (ECM) rigidities in vitro. PDMS polymer to crosslinker ratio was adjusted to 15:1, 35:1 and 50:1 corresponds to 173kPa, 88kPa and 17kPa respectively. These results show that cells adapt their stiffness to that of the substrate. Flexible substrates leads to reduced cell spreading morphological changes. Cells on complaint substrates are softer as compared to stiffness substrates. Our results demonstrates that the substrate stiffness influence not only cell spreading and motility, but also cell elasticity.
Finally, from the 3D tracking of the bead probe we analyzed the lateral forces arising during the vertical indentation of the cell membrane during cell-bead interaction. We calculated and compared the elastic moduli resulting from the total and vertical forces for two breast cancer cell lines: MDA-MB-231 and HBL-100, showing that the differences are important and the total force should be considered.
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Wray, John. "INVESTIGATING THE POTENTIAL APPLICATIONS OF A RAMAN TWEEZER SYSTEM." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/3135.
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This thesis describes the construction of an Optical Tweezer apparatus to be used in conjunction with a confocal Raman spectrometer. The tweezer utilizes an infrared (λ=1064 nm) laser directed into an inverted microscope with NA=1.4 oil immersion 100x objective lens that strongly focuses the laser light into a sample to function as a single-beam gradient force trap. The long term goal of this research program is to develop a single molecule Raman tweezers apparatus that allows one to control the position of a Raman nanoplasmonic amplifier. This thesis describes the construction of the Raman tweezer apparatus along with several Raman spectra obtained from optically trapped samples of polystyrene fluorescent orange, amine-modified latex beads. In addition, I explored the Raman spectra of bulk cytochrome c mixed with or injected onto Ag aggregates for SERs enhancement.
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Latinovic, Olga S. "Structural and micromechanical properties of soft materials : An optical tweezers study /." Diss., [Free access to full dissertation available to Lehigh users only.], 2005. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3203821.
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Shirdel, Mariam. "Probing protein - Pili interactions by optical tweezers and 3D molecular modelling." Thesis, Umeå universitet, Institutionen för fysik, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-68747.
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Wang, Na 1982. "System of measuring mechanical properties of colloidal gels with optical tweezers." Thesis, McGill University, 2006. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=101662.
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Due to the unique rheological properties of colloidal gels, gelation of colloidal suspensions has become increasingly important to fundamental investigations, as well as to technological applications. Recent experimental approaches are mainly focused on the bulk properties of colloidal gels, using methods of static and dynamic light scattering and shear rheometry. This thesis describes the development of a system for measuring the mechanical properties of colloidal gels with optical tweezers.We make colloidal gels out of polystyrene beads of two different sizes, diameters of 3.5mum or 62nm respectively. Investigation of the colloidal gels under the light microscope shows the fractal nature of the gel structure while macroscopic study confirms that the gelation process of the smaller polystyrene beads is faster than that of the bigger polystyrene beads. We were also able to generate a phase diagram of the gelation process.
We successfully assembled the main instrument, a time-sharing single beam optical tweezers, and calibrated the lateral stiffness of the optical trap. Our optical tweezers setup is used to study the polystyrene gel and it has many more applications in colloidal samples. The strong 3D optical trapping highlights the optical tweezers as a powerful technique suitable for further investigation of colloidal samples.
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Orta, Alberto. "Development and automation of optical tweezers for single biomolecule force measurements." Thesis, University of Nottingham, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493322.
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Zhang, Hanqing. "Construction of an Optical Tweezers Instrumentation and Validation of Brownian motion." Thesis, Umeå universitet, Institutionen för fysik, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:umu:diva-94771.
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We constructed a standalone optical trapping system that was steerable in three dimensions and allowed for sufficient imaging of one цm particles with a CCD camera. The motion of the trapped particles was monitored by both a position sensitive detector as well with the CCD camera. The trap stiffness was evaluated by the power spectrum method and the equipartition theorem. For calibration of the stiffness of the trap, we found that the power spectrum method with data assessed by the PSD was most straightforward and accurate. The equipartition method was compromised by noise, low resolution and the bandwidth of the detector. With a HeNe laser run at 10 mW output power the trap strength of our system reached ~2 pN/um. The results also showed a decrease in the trap stiffness and particle's position variance when the size of trapped particles increased.
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Buajarern, Jariya. "Fundamental studies of inorganic and organic aqueous aerosols using optical tweezers." Thesis, University of Bristol, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439956.
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