Research Introduction　

Marine environment measurement system using microfluidic channels

The importance of international efforts to continuously monitor global warming and environmental destruction over a wide range of global environmental changes is increasing. Satellite observations with a variety of instruments for climate, atmosphere, ocean, etc. are now being carried out, and the technology to continuously acquire data over a wide area is being established. In addition, the data can be calibrated by comparing them with the data measured in the field, which enables more accurate analysis. The integration of in-situ measurements and satellite observation data is a challenge to develop an in-situ measurement method to regularly monitor environmental changes over a wide area. Among the observed items, carbon dioxide has been measured at many fixed points in the atmosphere because its increase is considered to be a cause of global warming. On the other hand, it is known that about 30% of carbon dioxide in the atmosphere is absorbed by seawater. Observation of carbon dioxide concentration in seawater is as important as that in the atmosphere because it can lead to the estimation of the global amount of carbon dioxide and the prediction of climatic changes. In order to regularly observe carbon dioxide concentrations over a wide area of the ocean, ocean surface carbon dioxide sensors that can be attached to surface drifting buoys are being developed. 　Our research group aims to reduce the size and mass production of conventional ocean surface carbon dioxide sensors in order to increase the number of observation stations and to reduce operational costs, measurement solutions and materials, as well as to increase the integration of instruments mounted on surface drifting buoys.
小野里 勇太, 朴 鍾淏, 柳田 保子, 中野 善之, 三輪 哲也, 初澤 毅, マイクロ流路式海洋二酸化炭素センサーの特性評価, 精密工学会学術講演会講演論文集A巻, p. 81-82 (2016)

　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　

Intraoral Monitoring Using Ion-Selective Electrodes

According to a global survey conducted from 1990 to 2015, the number of oral diseases is reported to be increasing, and it is important to understand the oral condition before oral diseases such as tooth decay develop from the viewpoint of disease prevention. In order to monitor the oral condition, the measurement of metabolites and ions contained in saliva is considered to be an effective method. Currently, all-solid-state ion selective electrode (SC-ISE) is used as a method to measure ion concentrations. Ionophores are used as ion selective membranes. The ionophores are responsible for transporting specific ions in the biomembrane. Therefore, by installing multiple types of ionophores on the ISE and parallelizing them, an ISE sensor array that can simultaneously measure multiple types of ions can be created. It is a recent issue that SC-ISE is easily affected by foreign ions other than target ions. Our research group is developing a device that can reduce the influence of foreign ions and measure the concentration of target ions with high accuracy by using multivariate analysis.

Cell Evaluation System Using Bio-MEMS

In the study of cells, it is important to perform passaging culture. The periodic detachment and dilution of sufficiently proliferated cells is called passaging, which allows us to maintain a constant cell culture environment in terms of space and nutrients. In the past, the detachment of cells during passaging was generally performed using enzymatic reagents, but since the cells were forcibly detached by enzymatic degradation of the extracellular matrix, damage to the cell membrane was unavoidable. On the other hand, with the development of tissue engineering, cell sheet detachment and recovery methods using temperature-responsive polymers such as PNIPAAm (poly-N-isopropyl acrylamide) have been widely investigated. However, the polymerization of polymers onto substrates is mainly done by electron beam irradiation or plasma polymerization, both of which are not easy and require expensive equipment, and therefore, have not been widely used.　Our research group has developed a new method to fabricate temperature-responsive substrates by using spin-coating technology and applying the cell sheet recovery method to passaging to suppress cell membrane damage, We are also investigating a new method of cell passaging that does not require complicated manipulations.
木下 裕美子, 柳田 保子, 初澤 毅, 朴 鍾淏, 温度応答性高分子を用いたデバイスによる細胞継代培養法, 精密工学会学術講演会講演論文集A巻, p. 897-898 (2013)

Development of Portable Solid Oxide Fuel Cells

Necessary elements for next-generation energy are 1) high energy efficiency, 2) high energy density, and 3) few restrictions on the types of energy fuels. A candidate for satisfying these elements is a solid oxide fuel cell that can operate at high temperatures and is being commercialized as a stationary power source. We are developing portable solid oxide fuel cells by applying novel material synthesis, flow path, and device fabrication technologies. Tetsuya Yamada et al., ACS Applied Nano Materials, 2019. Fig.　Synthesis of Zirconia Nanosheets as Potential Electrolytes for Solid Oxide Fuel Cells

Exploration of Solid Oxide Electrocatalysts Using Microreactors

In order to achieve carbon neutrality, it is essential to develop a technology to reduce carbon dioxide to methane, carbon monoxide, and other forms of carbon dioxide using natural surplus energy, and effectively utilize them as energy and materials. The focus is on solid oxide electrolysis, which can reduce CO2 with high efficiency by driving a solid oxide fuel cell in the reverse direction. The problem with solid oxide electrolysis is that catalyst materials that can operate at sufficiently high temperatures have not yet been developed. Therefore, we have developed an original reaction vessel using microfluidic channels and microreactors to search for catalysts that are active at high temperatures in a safe and high-throughput manner.

Application of Nano-Periodic Structures to Bioinstrumentation

In recent years, on-site measurement of biomolecules such as DNA is required for home medical diagnosis, intraoperative diagnosis, and borderline countermeasures against infectious diseases. Traditionally, fluorescence measurement using fluorescent dyes has been used to measure biomolecules. However, the large size of the fluorescence measurement device used for the measurement is said to make it unsuitable for on-site measurement. Therefore, we believe that miniaturizing the fluorescence measurement device and enabling on-site measurement will lead to early detection and early treatment of diseases by using it for home medical diagnosis and intraoperative diagnosis. We believe that the downsizing of fluorescence measurement devices is possible by using photonic crystals, which are optical elements, to measure fluorescence spectra in a controlled manner. Photonic crystals are characterized by their ability to amplify wavelengths in a specific region, but because they depend on the lattice constant and size of the photonic crystal, it is necessary to fabricate a new device every time the measurement object is changed. Therefore, by using a temperature-responsive polymer as a material for photonic crystals, we have devised a method to fabricate photonic crystals whose structure can be changed by temperature change, and the wavelength range of amplification can be arbitrarily changed. Our research group has verified the effect of changes in the lattice constant of the photonic crystal on the peak wavelength of the emitted light, as well as the transfer to the thermoresponsive polymer, We are also examining the possibility of miniaturizing the fluorescence measurement system by transferring it to temperature-responsive polymers.
櫻井 友紀也, 朴 鍾淏, 初澤 毅, 柳田 保子, 温度応答性高分子を用いたフォトニック結晶の作製, 精密工学会学術講演会講演論文集A巻,  p. 901-902 (2017)