As a new and safe reduction method for copper oxide, we propose the use of water vapor plasma at low pressure instead of conventional hydrogen plasma. Although hydrogen plasma is the established method to reduce copper oxide at low temperature, hydrogen is flammable and requires safety equipment. In this study, oxidized copper film was treated with water vapor plasma and its reduction process was compared with hydrogen plasma's. Surface, cross-section structure and thickness of oxidized and reduced copper film were measured and analyzed by FE-SEM (Field Emission-Scanning Electron Microscope), FIB (Focused Ion Beam), XRD (X-Ray Diffraction) and XPS (X-ray Photoelectron Spectroscopy). Using water vapor plasma, oxidized copper film was reduced without any oxygen remaining. During the reduction process, induction period and S-shaped curve were observed to be the same as hydrogen plasma. Furthermore, the reduction rate of water vapor plasma was more than twice that of hydrogen plasma.
Bio-chemical sensors are used for discrimination of bio-chemical species, concentration measurement, and so on. Because metamaterial responds to slight changes in the ambient refractive index, it is possible to realize ultra-sensitive bio-chemical sensors. We designed and fabricated refractive index sensors using polarization independent metamaterial and examined their application as bio-chemical sensors. Refractive index sensitivity, concentration measurement, and DNA detection were carried out.
In this paper, we developed a quartz oscillator based liquid concentration sensor for contactless monitoring of solution in bottle. This sensor is composed of the sensing capacitor (SC) and quartz crystal resonator (QCR). This sensor has advantages such as high stability and it can measure the frequency dependence on liquid concentration. We succeeded in measuring the hardness of the mineral water and the carbonate aqueous solution in bottle. Because this contactless capacitive sensor is low-priced, we can expect the use for the liquid management of various fields.
Recently, self-driving cars, small spacecraft, and unmanned aerial vehicles have been widely developed, which requires small size and high performance of IMUs. We have developed the high performance MEMS gyroscope for small size IMUs. This paper described experimental results performed to improve the performance of MEMS gyroscope. By means of mode-matched and bias corrected operations named MPC correction, angle random walk of 0.0069 deg/√h, bias instability of 0.027 deg/h and rate ramp of 0.051 deg/h/h have been achieved.
This paper reports a highly sensitive MEMS silicon-hair device with novel functions of hair follicle. Human hairy skin has peculiar receptor called hair follicle. Therefore, a highly sensitive sensor reproducing the function of hair follicle is demanded in order to quantify peculiar sense in hairy skin such as wind, static electricity, and perception of the liquid surface. The developed device in this study has fine silicon-hair with 10µm width and 5mm length. Moreover, it detects 2-axis force and 1-axis moment applied to silicon-hair by piezoresistors. The MEMS silicon-hair device has realized resolutions of 5µN axial force, 1µN shear force, and 3nN･m moment. Also, the device in this study precisely acquired surface tension close to the physical property of water and ethanol water solution. In addition, the MEMS silicon-hair device was successful in detecting 0.1µN electrostatic attraction. Resolutions of shear force and moment have been improved by tenfold using the resonance-drive of silicon-hair.
We newly introduced sensor system for applying tube type of flow sensor to respiration and heartbeat measurement in baby. An adaptor was developed and the flow sensor was integrated into slip joint of tracheal tube. In animal experiments, the airflow of rat was measured and we confirmed the sensor system could detect both respiration and heartbeat.
We developed a technique for producing and separating micrometer-size vesicles from human lymphocytes using microholes. Using cell-anchoring molecules, lymphocytes were immobilized on a microhole array formed in a silicon nitride (SiN) membrane. Then, the cells were chemically stimulated with sodium butyrate, and the vesicle production was induced near the microholes with the assistance of the cell-anchoring molecules. This resulted in the vesicle production inside the microholes, and the vesicles finally passed through the microholes. We tested microholes having 3 different diameters of 2, 4, and 7.5 µm, and counted the number of fluorescently-stained vesicles and cells which passed through microholes of each diameter. The number of vesicles increased with increasing diameter of microholes, but the number of invading cells also increased. In case of microholes 4 µm in diameter, a relatively large number of vesicles were obtained, and the cell invasion rate was below 1%, which was the best result in the present experiment. Also, we succeeded in drastically increasing the number of vesicles in case of microholes 2 µm in diameter by preventing vesicles from adhering to the back side of a SiN membrane.
A coating type clay insulating layer was successfully fabricated on a stainless steel surface by dip coating of an aqueous paste of hectorite clay followed by calcination at 600℃. A surface roughness and electrical characteristics of the clay layer were evaluated. Cr-N thin film strain sensors on the clay insulating layer and stainless steel substrate were fabricated and the output properties of them were investigated. It is considered that the clay layer is expected as a candidate of lower-cost insulating materials.
Liver organoids hold a great potential to understand liver development and contribute for drug screening and toxicological testing. However, conventional methods to generate organoids provide insufficient liver functions and less reproducibility, due to lack of controllability of cellular microenvironmental cues. To tackle these issues, we focus on one of the environmental cues, pressure stimuli by heart beating, and develop a microfluidic-based cell culture platform integrating a fluidic capacitor to produce pressure stimuli with hydrostatic pressure. Furthermore, we demonstrate a numerical simulation based on equivalent circuit model for designing the device parameters with sufficient accuracy. This device concept will provide insights into physical micro-environmental regulation on organoid development.
Pretreatment using Ar or O2 plasma was investigated for wafer-scale room-temperature bonding using ultrathin Au films in ambient air. The main difference between Ar plasma and O2 plasma is their surface activation mechanism: physical etching and chemical reaction, respectively. Bonding strength of samples obtained by Ar plasma treatment was strong enough to be broken from Si substrates, while that of samples obtained by O2 plasma treatment was only about 0.1 J/m2.