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Biomedical subjects

Eiichiro Tamaki

Publications and source records attributed to Eiichiro Tamaki.

6 recordsLinked to original sources
PubMed2006

Pressure-driven flow control system for nanofluidic chemical process.

We developed a novel flow control system for a nanofluidic chemical process. Generally, flow control in nanochannels is difficult because of its high-pressure loss with very small volume flow rate. In our flow control method, liquid pressure in a microchannel connected to the nanochannels is regulated by utilizing a backpressure regulator. The flow control method was verified by using simple structured microchip, which included parallel nanochannels. We found that the observed flow rate was three times lower than the value expected from Hagen-Poiseuille's equation. That implied a size-dependent viscosity change in the nanochannels. Then, we demonstrated mixing of two different fluorescent solutions in a Y-shaped nanochannel and also a proton exchange reaction in the Y-shaped nanochannel. The flow control method will contribute to further integration of nanochemical systems.

Microfluidics↗
PubMed2006

Liquid filling method for nanofluidic channels utilizing the high solubility of CO2.

We developed a fabrication method and a liquid filling method for a nano chemical reactor that used Y-shaped nanochannels specially designed for mixing and reacting. In order to reduce the pressure loss and to utilize the characteristics of the nanochannel, inlet microchannels were fabricated just beside the nanochannels. We investigated an initial liquid filling method into the nanochannels that ensured there were no air bubbles that could cause a flow stack due to the capillary pressure. In our method, the micro- and nanochannels were filled with carbon dioxide and any remaining air during the initial liquid introduction was dissolved utilizing the high solubility of carbon dioxide. We propose that chemical reactions in nanospaces can be realized by utilizing these fabrication and liquid introduction techniques.

Journal Article↗
PubMed2005

Grazing-exit and micro X-ray fluorescence analyses for chemical microchips.

Grazing-exit x-ray fluorescence (GE-XRF) and micro x-ray fluorescence (micro-XRF) methods were applied to chemical microchips as a detection method. Since an energy-dispersive x-ray detector was used, the simultaneous detection of multiple elements was possible. An analyzing region was especially designed on the microchip so that a sample solution could be dried and concentrated in a suitable area corresponding to the size of the primary x-ray beam. Finally, it was confirmed that both analytical methods could be combined well for use with a microchip. In GE-XRF, the background intensity in the XRF spectrum was reduced at grazing-exit angles. In addition, a good relationship between the x-ray fluorescence intensities and the concentrations of standard solutions that were introduced into the microchip was obtained. This indicates that the GE-XRF method is feasible for trace elemental analysis in chemical microchip systems. In micro-XRF, an attempt was made to concentrate and dry the analyte within a small analyzing region. The preliminary results indicated that the micro-XRF method could be applied for the analysis of microchips.

Journal Article↗
PubMed2003

Microchannel-assisted thermal-lens spectrometry for microchip analysis.

Microchannel-assisted thermal lens spectrometry (MATLS) was developed for microchip analysis. This method utilized a photothermal effect in a very small space and rapid thermal conduction between a solid-liquid interface to produce a temperature gradient in the microchannel. In order to examine the mechanism experimentally, we constructed a detection system of laser defocus setup in which an excitation beam was not tightly focused, but it irradiated the microchannel homogeneously. The signal intensity dependence on modulation frequency of excitation and on solvent was investigated with the laser defocusing setup. The results of this investigation indicated that the mechanism of MATLS worked as expected. Since the mechanism of MATLS does not require directivity and coherence of the laser beam, other incoherent lightsources can be used as excitation light for sensitive detections. Finally, we considered some future applications utilizing the mechanism.

Semiconductors↗
PubMed2002

Single-cell analysis by a scanning thermal lens microscope with a microchip: direct monitoring of cytochrome c distribution during apoptosis process.

We developed a microsystem for cell experiments consisting of a scanning thermal lens microscope detection system and a cell culture microchip. The microchip system was good for liquid control in microspace, and this results in secure cell stimulation and coincident in vivo observation of the cell responses. The system could detect nonfluorescent biological substances with extremely high sensitivity without any labeling materials and had a high spatial resolution of approximately 1 microm. This system was applied to monitoring of cytochrome c distribution in a neuroblastoma-glioma hybrid cell cultured in the microflask (1 mm x 10 mm x 0.1 mm; 1 microL) fabricated in a glass microchip. Cytochrome c release from mitochondria to cytosol during the apoptosis process was successfully monitored with this system. The cytochrome c detected with this system was estimated to be approximately 10 zmol. We concluded that the system was suitable for measuring the distribution of chemical substances in a single cell because the microchip is good for liquid handling in microspace and the thermal lens microscope has high sensitivity and spatial resolution.

Apoptosis↗