Shinichi Etoh

Fabrication of Open-Top Microchannel Plate Using Deep X-Ray Exposure Mask Made with Silicon On Insulator Substrate

We propose a high-aspect-ratio open-top microchannel plate structure. This type of microchannel plate has many advantages in electrophoresis. The plate was fabricated by deep X-ray lithography using synchrotron radiation (SR) light and the chemical wet etching process. A deep X-ray exposure mask was fabricated with a silicon on insulator (SOI) substrate. The patterned Si microstructure was micromachined into a thin Si membrane and a thick Au X-ray absorber was embedded in it by electroplating. A plastic material, polymethylmethacrylate (PMMA) was used for the plate substrate. For reduction of the exposure time and high-aspect-ratio fast wet development, the fabrication condition was optimized with respect to not the exposure dose but to the PMMA mean molecular weight (M.W.) changing after deep X-ray exposure as measured by gel permeation chromatography (GPC). Decrement of the PMMA M.W. and increment of the wet developer temperature accelerated the etching rate. Under optimized fabrication conditions, a microchannel with 50 µm width through 1000 µm PMMA plate, with a high aspect ratio over 20, was fabricated. By using a high-aspect-ratio open-top microchannel plate, high fluorescent electrophoresis was performed.

Fabrication of Taste Sensor Chip and Portable Taste Sensor System

This paper reports miniaturization on one-chip size of a receptor part of taste sensor, which can measure the taste using lipid/polymer membranes. The miniaturization was made by producing metal electrodes and making lipid/polymer membranes deposit on a glass substrate. The reference electrode also realized a miniaturization and stabilization of potential according to laminating structures of pHEMA and polymer layers. Therefore, an integration of the working and the reference electrodes was attained on the chip. By realization of this taste sensor chip, taste measurement can be easily performed now in all places, such as the distribution industry and the medicine manufacture industry, including the food industry. Moreover, we succeeded to fabricate the portable taste sensor system which unified the amplifier, a data-processing unit and an LCD display

Evaluation of the odor quality by substructures of odor molecules using integrated multi-channel odor sensor

In order to imitate the mechanism of biological odor reception, an integrated multi-channel odor sensor was developed here. In this study, we attempted to control the response characteristics of this odor sensor by the composition of the water membrane and surface modification technology. As a result, the addition of P cellulose, ion-exchange resin, to the water membrane enabled large response to ethanol, which has hydroxyl group in its structure, and the formation of benzene-patterned self-assembled monolayer (SAM) enhanced the sensitivity to benzene, which has aromatic ring in its structure. In addition, both technologies were also appropriate for the detection of phenethyl alcohol, which has both hydroxyl group and aromatic ring; consequently, these channels could recognize the molecular substructures.

Investigation of sample behaviors inside on-chip electrophoresis microcapillary using confocal laser scanning microscopy

We report the observation of sample behaviors using the confocal laser scanning microscopy (CLSM) in on-chip microcapillary. Sample loading by pinched valve injection is observed in a new cross injector shape, which has the structure added conventional cross injector to circle shape. In sample loading, because this structure causes a different electric field compared with that in conventional cross injector, high efficient sample plug injection was performed. It is important to investigate further the detailed sample profiles using the CLSM in sample loading for development of the on-chip microcapillary. We attempt the simulation of sample loading in the cross injector using the semiconductor device simulator MEDICI in order to investigate it in further detail. The sample movements in the channel turn along the Z-direction are observed using the CLSM. In order to miniaturize the microfluidic channel, it is necessarily needed to fold the channel, but then it is inevitable that sample dispersion occurs in the turn. We present sample flow profiles along the Z-direction in the turn using the CLSM and the influence on the electrophoretic separation. Also, we improve that fabrication of duct channel for exhaustion the vaporized xylene to outside the chip and the adhesion process

Mass-production fabrication of miniaturized plastic chip devices for biochemical applications

A very important aspect in the next stage of genomic research will be the study of genetic diversity originating from an individual, for example, a single nucleotide polymorphism (SNP),. For this, the base-pair sequence needs to be determined quickly and easily; along with effectively gathering the proteins that are produced from the cell and depend on each genetic design. To meet these demands, the use of a miniaturized experimental apparatus formed on a chip is suitable as it gives a very small and well-controlled space to undertake precise analyses. This type of chip device needs to be disposable, inexpensive and of uniform quality, therefore many chips should be fabricated at the same time from a low cost chip material such as plastic. A mass production fabrication process for such plastic chips was determined as follows. A thick coating type photoresist was spin-coated onto a 4-inch size Si wafer to 20 μm thickness and patterned by UV-lithography. Thick Au structures were embedded into the resist mold by microelectropolating. After removal of the resist, Au fine structures remained and were used as a metal mold for plastic casting. Plastic, polymethylmethacrylate (PMMA), beads were dissolved in acetone and the polymer solution was cast into the metal mold under vacuum heating environment producing many identical plastic chips at a thickness of 1 mm. The size of the chemical reaction channel, one of the device’s components, was 50 μm in width and 20 μm in depth.

Fast Separation of DNA Fragments in On-chip Electrophoresis Microcapillary

Separation of DNA fragments is performed in on-chip electrophoresis microcapillary fabricated on a photosensitive glass. Since the UV-irradiated part of the photosensitive glass has the etching rate 20 times higher than the other parts, we can obtain the channel structure with the high aspect ratio, which is valuable to the high-sensitivity detection of the signal. The confocal laser scanning microscopy (CLSM) is used to observe and detect the fluorescent sample plug in the on-chip electrophoresis microcapillary. The CLSM is a powerful tool to observe and detect the sample inside the channel since it can capture the fluorescence images and can vary the laser focal plane depth. In this study, Hydroethylcellurose (HEC) polymer solution is using in the electrophoresis as sieving matrix. Therefore the on-chip electrophoresis microcapillary with the short separation channel is able to separate DNA fragments.

Fabrication of open-top microchannel plate using deep x-ray exposure mask made with SOI substrate

Human genome project has now been completed. At the next stage, the analysis of the DNA diversity originated from each individual is a very important aspect. It requires a method that can determine the base-pair sequence quickly and easily for fast and effective analysis. Separating the biochemical samples by electrophoresis is one of the analysis processes. Recently, electrophoresis has been performed in the fine channel formed on various substrates. By utilizing a microchannel chip for electrophoresis, the dead volume of the reagent and detection apparatus, and energy are reduced. To improve the separation performance of microchannel chip, the width of the channel should be narrower. On the other hand, the volume of the sample that can be introduced is restricted. Then, the channel is filled with ionic solution, and the top of the substrate is covered with a plate for shallow channel, so as not to cause current leakage induced by applying high voltage during electrophoresis. But, it requires a high quality substrate-cover adhesion. technique. We propose a high-aspect-ratio open-top microchannel plate. The high-aspect-ratio structure increases the sample and reagent volume inside the channel without increasing the channel width, which results in an enhancement of the detection sensitivity. And the buffer solution is introduced only before the measurement and sequential supply from an external source is not needed. The chip is standalone. The deep channel leads to another advantage. Its deep depth prevents overflow of the solution to the uncovered channel. By avoiding the difficult sealing process, the fabrication process become easy and high-throughput is realized.