Hiroyuki Kawada

Kagawa University, Takamatsu-shi, Kagawa-ken, Japan

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Publications (5)6.98 Total impact

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    ABSTRACT: Here we propose a collision-free sorting method for optically controlled dynamic micro-arrays. The beads forming a two-dimensional M×N lattice array can be sorted in arbitrary order by the collision-free cyclic shifts of four beads and six beads. A mathematical proof based on group theory and the experimental result with the time-sharing optical tweezers are described.
    No preview · Article · Jan 2011
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    ABSTRACT: Dynamic microarrays have great flexibility and potential as tools for advancing research in diagnostics and biomedical fields. In contrast with static microarrays such as DNA-chip using micro-spots of the bio-molecules, dynamic microarrays use a mobile substrate, usually micro-beads coated with bio-molecules. To realize the dynamic microarray, micro-bead handling techniques are essential, allowing us to transport the selected bead, and immobilize them for signal detection. Laser manipulation, known as optical tweezers, is one of the most suitable techniques for arranging and handling micro-beads. We have developed a multi-arm laser manipulation system with an excellent user-interface and realtime image processing functions. In this paper, we report a new approach for fully-automated assembly of a versatile dynamic micro-bead array. The beads, dispersed in a pipetted liquid on a cover glass, can be simultaneously trapped and sorted into a desired order, using multiple optical tweezers to transport the beads along collision-less paths guided by both computer vision and knowledge database techniques. Two typical examples are demonstrated. One is the fully-automated assembly of a 3x3 micro-bead array and its handling in 3D space. The other is the collision-free sorting of an array’s elements. We also describe the experimental apparatus used in these demonstrations. KeywordsOptical tweezers–Micromanipulation–Dynamic microarray–μ-TAS–Hough Transform
    No preview · Chapter · Jan 2010
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    ABSTRACT: Dynamic micro-bead arrays offer great flexibility and potential as sensing tools in various scientific fields. Here we present a software-oriented approach for fully automated assembly of versatile dynamic micro-bead arrays using multi-beam optical tweezers combined with intelligent control techniques. Four typical examples, including the collision-free sorting of array elements by bead features, are demonstrated in real time. Control algorithms and experimental apparatus for these demonstrations are also described.
    Full-text · Article · Dec 2009 · Optics Express
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    ABSTRACT: Automated optical trapping of non-spherical objects offers great flexibility as a non-contact micromanipulation tool in various research fields. Computer vision control enables fruitful applications of automated manipulation in biology and material science. Here we demonstrate fully-automated, simultaneous, independent trapping and manipulation of multiple non-spherical objects using multiple-force optical clamps. Customized real-time feature recognition and trapping beam control algorithms are also presented.
    Full-text · Article · Oct 2008 · Optics Express
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    ABSTRACT: Laser trapping, which was first demonstrated in 1970 by Ashkin and is well-known as optical tweezers, is a powerful micro- or nano-manipulation tool suitable for a closed working space such as a Lab-on-a-Chip, since it enables the manipulation of micron-sized objects without physical contact, in contrast to a mechanical micro-manipulator using a glass capillary. However, the control and vision systems of a conventional laser trapping system are insufficient to manipulate the objects in 3-dimensional space, if the intention is to dexterously or automatically manipulate the objects in real-time. We have developed an optical tweezers system with an excellent user-interface and real-time image processing functions. In the present paper, a concept of automated noncontact micromanipulation based on visual information and fields suitable for its application are proposed, and the system configuration of the developed system is described. The results of several demonstrations, namely the automated arrangement of micro-beads and micron-sized non-spherical objects, are also described. In our automated manipulation experiment, the micro-beads dispersed in water are detected by a real-time image processing technique, and then trapped and transported to be arranged in desired patterns. In the other experiments, whiskers and diatoms of non-spherical shape suspended in water are automatically detected and stably trapped by the simultaneous irradiation with multiple trapping beams.
    No preview · Article · Jan 2008