Papers by Author: Nobuyuki Watanabe

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Authors: Nobuyuki Watanabe, Kozo Taguchi
Abstract: Biological cell could be trapped by a single laser beam from an optical fiber end inserted at an angle to a sample chamber. We have already developed an optical trapping system. A temperature stabilized 1480nm cw diode laser was used as the light source. The fiber end had a hemispherical micro-lens with 5μm radius of curvature for focusing the laser beam. These trapping fibers were inserted into a sample cell at an angle. The microsphere, 10μm diameter particle (refractive index 1.4), could be trapped. We theoretically analyzed the optical forces exerted on a microsphere by laser beams. The optical force on a microsphere divides itself into two components, the force in the beam axial direction of the light and a transverse force. The transverse optical force acted to pull the sphere back. We investigated the relation between the pulling force and the inserted angle of an optical fiber into a sample chamber. The microsphere is trapped at the point where the horizontal directed optical forces are balanced. We theoretically verified that the inserted angle of an optical fiber into a sample chamber was important parameter. It was found that a small inserted angle produced a weak pulling force.
1053
Authors: Kozo Taguchi, Jun Okada, Nobuyuki Watanabe
Abstract: A novel single fiber optic tweezers was proposed for cell isolation. Fiber tips were fabricated by dynamic chemical etching. The mechanically cleaved bare single mode fiber was dipped into Hydrofluoric acid containing a protective layer of Toluene at the top. By moving the fiber at variable speeds, a variety of tip shapes could be created. In our experiments, tip angle could be adjusted from 7deg to 55deg. Three-dimensional optical trap of a yeast cell could be formed by the fiber tip with less than 23deg tip.
1065
Authors: Nobuyuki Watanabe, Kozo Taguchi
Abstract: Optical trapping is a technique that is used to capture, translate, and manipulate microscopic particles, such as dielectric microspheres and cells. This cell manipulation and examination technology can be integrated on a Lab-on-a-Chip device. We have already developed an optically vibration system. The optical vibration system was formed using a temperature stabilized 1480nm cw diode laser. The output of laser light was coupled into optical fibers, which had optical connectors at these fiber ends. The fiber end had a hemispherical micro-lens with 5μm radius of curvature for focusing the laser beam emerging from the optical fiber end. These trapping fibers were attached to xyz manipulators and were inserted into a sample cell at an angle of 35 degrees. The trapped microsphere, 10μm diameter polystyrene particle (refractive index 1.59), could be optically vibrated by controlling laser power emerging from optical fibers. We theoretically analyzed the optical forces exerted on a microsphere by laser beams. Its operating principle is based upon the conservation of photon momentum carried by the incident laser light on a trapped microsphere. From these theoretical results, we verified that our proposed optical manipulation technique was useful for the manipulation of biological cells.
1059
Authors: Nobuyuki Watanabe, Kozo Taguchi
Abstract: In this paper, we proposed an optical vibration and circulation technique of a microsphere using plural optical flat-top fibres, mounted horizontally on the bottom of a sample chamber, and verify that an optically trapped object can be circulated by controlling laser power emerging from optical fibres without moving the optical fibres. We theoretically analyzed the optical forces exerted on a microsphere, a 10μm diameter polystyrene particle (refractive index 1.59), by laser beams. From these theoretical results, we verify that our proposed optical manipulation technique is useful for the manipulation of biological cells.
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