Kozo Taguchi

Three-Dimensional Optical Trapping for Cell Isolation Using Tapered Fiber Probe by Dynamic Chemical Etching

In this paper, chemically etched fiber probe was proposed for laser trapping and manipulation of cells. We fabricated tapered fiber probe by dynamic chemical etching technique. Three-Dimensional optical trap of a yeast cell dispersed in water solution could be formed by the fiber tip with 17deg tip. Optical forces were sufficient to move the yeast cell for trapping and manipulation. From these experimental results, it was found that our proposed tapered fiber tip was a promising tool for cell isolation.

Theoretical Study of Optical Vibration and Circulation of a Microsphere

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.

Dual-Beam Trapping Method for an Object with Large Relative Refractive Index

A novel dual-beam trapping method was proposed and discussed for the three-dimensional optical trapping of an object. We theoretically studied the optical forces on a sphere by the laser beams from plural optical fiber ends inserted into a sample cell at an angle. There was only one stable point of equilibrium located below the beam-crossing point and significantly enhanced stability was obtained. Furthermore, we revealed the feasibility of trapping an object with large relative refractive index.

Two-Dimensional Cell Trapping Using Single Axicon Fiber without Physical Contact

Chemically etched axicon fiber was proposed for two-dimensional cell trapping. We fabricated axicon micro lenses on a single-mode bare optical fiber by selective chemical etching technique. The laser beam from fiber axicon microlens was strongly focused and optical forces were sufficient to move a microorganisms and biological cells without physical contact. The apex angle of the chemically etched fiber axicon microlens was very important parameter for laser trapping. From these experimental results, it was found that our proposed method was a promising tool for the isolation of microorganisms.

Observation of Biological Tissues Using Common Path Optical Coherence Tomography with Gold Coated Conical Tip Lens Fiber

In this paper, we proposed a high lateral resolution common-path Fourier domain optical coherence tomography(OCT) system with the use of a chemically etched single mode fiber. In our experiments, single mode optical fiber for 1310nm was used for preparing the tapered tips. Our system used a conical microlens that was chemically etched by selective chemical etching technique using an etching solution of buffered hydrofluoric acid (BHF). From experimental results, we verified that our proposed optical coherence tomography system could operate as a common-path Fourier domain OCT system and conical tip lens fiber was very useful for a high lateral resolution common-path Fourier domain OCT system. Furthermore, we could observe a surface of paramecium bursaria and symbiotic chlorella in the paramecium bursaria using gold coated conical-tip fiber in the water.

A Study of Ion Beam Etching of Polymethylmethacrylate Using N_2 and N_2/O_2-Mixtures

The influence of process parameters such as gas composition, kinetic energy of the ions and sample temperatures was studied in order to discuss the dry etching mechanism of polymers. First, we investigated polymer dry etching using N2 gas and verified that the heating temperature was the critical parameter in the case of polymer dry etching. Next, polymer dry etching was carried out using N2–O2 gas for obtaining smooth vertical side walls. The experimental results revealed that the generation of neutralized reactive species needed to be suppressed to form smooth vertical side walls.

Efficient Evaluation Method of Cell’s Viability Using Dielectrophoresis

We used Dielectrophoresis (DEP) to discover healthy cells and estimate the cells activity and viability. In the first experiment, we mixed dead cells with methylene blue solution. We applied voltage of 4V, frequency of 10 kHz and 15 MHz to the electrode [1], and observed the movement of the cells. This experiment proved that DEP could also be used to judge cell’s viability. In the next experiment, we used viable cells and raised water temperature rapidly to apply damage. Temperature of water was fixed at 30 degrees, 40 degrees, 50degrees, 60degrees, and 70 degrees. And we observed the cells movement while changing the frequency. We mixed methylene blue solution with the sample to confirm whether the yeast cells were dead or alive when water temperature was from 50 degrees to 70 degrees. These experiments proved that it was possible to measure the activity of cells by changing the DEP frequency.

Efficient Selective Dismantlement of Protoplast Cell with Femtosecond Laser

We made the protoplast cell of red cabbage. And we irradiated to the protoplast cell with continues-wave laser. It is impossible to break down the protoplast cell. On the other hand we use the slide evaporated gold thin film, it is possible to break down a few protoplast cell. We use the femtosecond laser, it is possible to break down almost protoplast cell. The femtosecond laser used in experiment is mode-locked fiber ring laser. It also has 300fs pulse width, 52kW peak power and 4.773MHz pulse repetition frequency. Experiments show it is possible to break down the protoplast cell on an electrode.

Photocatalytic Activity and Visible-Light Response of TiO 2 Thin Film Doped with Nitrogen by Using Urea

TiO2 has become a widely investigated photocatalyst because of its low cost, low toxicity and high photocatalytic activity under UV irradiation that causes photocatalytic decomposition of organic compounds. Impurities dopant and metal are often used to acquire impurities doped or metal doped TiO2 powder by a sol-gel method. In this paper, we made nitrogen doped TiO2 by a simple process. TiO2 (P25) thin films with 80 % of anatase and 20 % of rutile were fabricated on FTO glass by electrophoretic deposition (EPD). These were then doped with nitrogen by using urea and sintered in electric furnace at 500 and 600 degrees Celsius. EPD was superior for film formation at dispersibility. We calculated absorbance spectra of nitrogen doped TiO2 thin film fabricated on FTO glass. As the result, 600 degrees Celsius is superior sintering temperature at absorbance under visible light than 500 degrees Celsius. Moreover, when the samples sintered at 600 degrees Celsius, each additive amount had different increment of absorbance in specific visible light range. This result indicates the improvement in visible-light response on TiO2 by the simple process. To further research, it is essential to make nitrogen doped TiO2 under pressure and measure the photodegradation reaction.

Investigation of the Effect of Ultrasound on Cell Growth

Several studies have been made on cell growth by the ultrasound irradiation. It is important to change the output, irradiation time and duty cycle for cell growth. The duty cycle determined the proportion of the time that the ultrasound was “on”. We can control cell growth by changing these three terms. The purpose of this study is to find the optimum conditions for cell growth and examine a new factor to influence cell growth. Cell concentration was determined by measuring the absorbance with a spectrophotometer. In this study, the absorbance became highest on 10min ultrasound irradiation and the duty cycle of 67% in experimental conditions. However, when 30 min ultrasound irradiation and the duty cycles of 86%, the absorbance became close to the highest value too. The results suggested that, in addition to the duty cycle, the off time of ultrasound might also affect the cell growth.