1,720,963 research outputs found
Integrated microlenses and multimode interference devices for microflow cytometers
No full textThe convergence of microfabrication technologies, novel materials systems, and techniques for chemical and biochemical analysis is enabling the realisation of lab-on-a-chip technology. Products incorporating such technologies are expected to find widespread use, for example in personal medicine, food safety, water management and security. This research is driven by the demand for fast, low-cost, small, and automated chemical analysis using minimal sample and reagent volumes, in a multiplicity of applications including interrogation of individual particles such as biological cells or molecules by µflow cytometry.Several promising optical detection methods are still in their infancy in terms of integration on to a single chip and improvements can be made to existing integrated methods. Manipulation of a free optical beam in microfluidic channels is identified as a major need to be able to realise more complex µflow cytometry detection systems. To achieve this, the integrated optics requires substantial advances. The approach in this thesis was to produce a microfluidic device with improved integrated optics, primarily for fluorescence and scattering particle detection, which can provide a platform from which to build more complex fully automated optical detection devices not yet realised. To manipulate the free beam, optical components such as waveguide lenses, both refractive and diffractive, were analytically designed and numerically simulated. An alternative device, the multimode interference device (MMI), which makes use of the self-imaging phenomenon in multimode waveguides, was also studied due to its less stringent fabrication tolerances. Optical components including channel waveguides, to route light on chip, were realised and integrated with microfluidic channels with a fabrication comprising a two-mask process developed in silica-based glass to integrate both optics and microfluidics on to a single chip. Spotsizes as low as 5.6 µm for paraxial kinoform lenses and 2.6 µm for MMIs have been measured at foci as far as 29.2 µm and 56.0 µm in a microfluidic channel. These devices pave the way to the full integration of more robust and complex microfluidic µflow cytometers
Kinoform microlenses for focusing into microfluidic channels
No full textOptical detection in microflow cytometry requires a tightly focused light beam within a microfluidic channel for effective microparticle analysis. Integrated planar lenses have demonstrated this function, but their design is usually derived from the conventional spherical lens. Compact, efficient, integrated planar kinoform microlenses are proposed for use in microflow cytometry. A detailed design procedure is given and several designs are simulated. A paraxial kinoform lens integrated with a microfluidic channel was then fabricated in a silicate glass material system and characterized for focal position and spotsize, in comparison with light emerging directly from a channel waveguide. Focal spotsizes of 5.6 µm for kinoform lenses have been measured at foci as far as 56 µm into the microfluidic channel
Integrated lenses for microfluidic systems
No full textGreater integration of optical devices is required in microfluidic systems for on-chip functionality, with lenses being key components. In this paper several candidate lens types are compared and simulations are presented which show that the paraxial kinoform lens offers optimum performance for efficiency and compactness in weak guiding system
Optofluidic integration for microanalysis
No full textThis review describes recent research in the application of optical techniques to microfluidic systems for chemical and biochemical analysis. The "lab-on-a-chip" presents great benefits in terms of reagent and sample consumption, speed, precision, and automation of analysis, and thus cost and ease of use, resulting in rapidly escalating adoption of microfluidic approaches. The use of light for detection of particles and chemical species within these systems is widespread because of the sensitivity and specificity which can be achieved, and optical trapping, manipulation and sorting of particles show significant benefits in terms of discrimination and reconfigurability. Nonetheless, the full integration of optical functions within microfluidic chips is in its infancy, and this review aims to highlight approaches which may contribute to further miniaturisation and integration
Microfluidic multimode interference device
No full textA multimode interference device has been fabricated using a novel ultra-precision micromachining technique. The micromachining technique defines the interfaces of the device by cutting microfluidic channels into a silica-on-silicon substrate. Changing the refractive index of fluid within these microfluidic channels is shown to alter the optical characteristics of the device
Multimode interference devices for focusing in microfluidic channels
Full text linkLow-cost, compact, automated optical microsystems for chemical analysis, such as microflow cytometers for identification of individual biological cells, require monolithically integrated microlenses for focusing in microfluidic channels, to enable high-resolution scattering and fluorescence measurements. The multimode interference device (MMI), which makes use of self-imaging in multimode waveguides, is shown to be a simple and effective alternative to the microlens for microflow cytometry. The MMIs have been designed, realized, and integrated with microfluidic channels in a silica-based glass waveguide material system. Focal spot sizes of 2.4 µm for MMIs have been measured at foci as far as 43.7 µm into the microfluidic channel
WEIGHTED PARTIAL MATCHING UNDER HOMOMORPHIC ENCRYPTION
No full textVarious embodiments are provided for performing weighted partial matching under homomorphic encryption in a computing environment. Selected data may be encoded and encrypted into an encrypted query for comparison using private set intersection (PSI) under homomorphic encryption (HE). An encrypted score may be determined according to data blocks of the selected data and a set of weights for each of the data blocks of the selected data to identify matches between the data and the encrypted query. The encrypted score may be decrypted and decoded to identify matches between the encrypted query with the selected data
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
DATASET - Integrated optical waveguides and inertial focussing microfluidics in silica for microflow cytometry applications
No full textA platform for microflow cytometry is presented comprising monolithically integrated waveguides and deep microfluidics in a rugged silica chip. Integrated waveguides deliver excitation light to an etched microfluidic channel and also collect transmitted light. The fluidics are designed to employ inertial focusing to reduce signal variation by bringing the flowing beads onto the same plane as the excitation light beam. A fabrication process is described which exploits microelectronics mass production techniques including: sputtering, ICP etching and PECVD. Test devices were fabricated and the effectiveness of inertial focusing of 5.6 µm fluorescent beads was studied showing lateral and vertical confinement of flowing beads within the microfluidic channel. The fluorescence signals from flowing calibration beads were quantified and a basic analysis of beads used in an immunoassay for TNF. was performed. Finally the potential of this type of device for measuring the variation in optical transmission from input to output waveguide as beads flowed through the beam was evaluated.
Paper published in 'Integrated optical waveguides and inertial focussing microfluidics in silica for microflow cytometry applications'</span
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