Vol.4 No.2 2011

Research paper : Thermoelectric hydrogen gas sensor (W. Shin et al.)−103−Synthesiology - English edition Vol.4 No.2 (2011) bound by their expertise, encouraging the members to propel their corresponding special jobs. To direct them to a single goal keeping every core technology of each member is not easy, but it is possible to align their vector if the scenario is shared. In developing thermoelectric sensors, with all the members understanding the technological domains of others while holding firmly their own technological specialties, the organic collaboration between the members was achieved. There is a concept called agile type often used in software development. As the waterfall type development is considered to be difficult to have communication among the staff, the agile type is currently widely used from the point of emphasizing communication among the members. Our research progress was close to the agile type but was not the same. A negative aspect of the agile type is the risk that the progress becomes slow dragged by too much discussion among members. We, however, built up the scenario at an early stage, and the whole image of development could be shared by the members. For example, the supply and installation of the equipment, process and test facilities for the overall research period were carried out following the plan written in the proposal at the start. The leader of the project continuously showed the clear vision of the results after five years and also the five-year scenario to all the members. His work is similar to an orchestra conductor. The essential part is to share all the possible information and visions together.4 How to make synthesis4.1 Elements and boundary conditionsA simple combination of elemental technologies cannot make synthesis. Figure 5 shows the schematic plan of synthetic integration of each element. Natural phenomena and engineering components are listed on the left, and the observations and analysis are related tools to quantify their characteristics. It is important to bring out the full features of each element, resulting in performance which has an engineering or scientific value. When one integrates them into a new synthesis, specific and detailed boundary conditions are necessary. The boundary conditions are the various social demands.For example, if you configure a catalyst and thermoelectric material for the applications to a generator and to a gas sensor, the conditions of configuration are largely different. For synthesis of the generator, it is important to obtain large electric voltage and current by high-calorie combustion. A catalytic material which can endure high temperature combustion needs to be selected and the device needs a complex flow channel for efficient fuel combustion. A large thermal capacity of the whole system is desired. Therefore, it is necessary to design a thermoelectric device that allows large electric current flow. For the synthesis of a gas sensor detecting a wide range of gas from a few ppm to a few percent, ensuring reliable, linear sensor output, extremely high catalytic activity of the combustor is required which enables combustion even with low concentration gas. In order to detect slight temperature changes, a thermoelectric device which generates high voltage is required with a sensor structure of easy fast gas diffusion and sensor elements of minimized heat capacity for fast response. In our sensor development, we configured and integrated the elemental technologies with the boundary conditions based on social demands as illustrated in Fig. 5. The conditions on the right such as high sensitivity, stability, Fig. 4 Scenario of thermoelectric hydrogen sensor developmentIn FY2000, the operation of the new sensor was started with the NEDO grant, and the full development of hydrogen sensor technology was carried out under the national project of developing hydrogen infrastructure, FY2003-07. micro-heaterABFY2000 FY2007FY2003FY2008FY2010New researchProposal of ISOstandardStandardizationof H2 sensor (ISO)Mass production・Full automation facilities・Communication between staffsTest for varioususer demandsBreath analysisResearch period of synthesisTesting sensor・Testing working principle・Social receptivity・Mass productionLeak tester etc.Commercialization(Venture company)Application researchMedical devices developmentDesigning Lab Microfabricationreducing the thermalcapacity of sensor isessential for highsensitivity.Verifying the workingprinciple of the sensorby IR camera⇒ voltage signal (⊿V)Heat (⊿T) x Seebeck effectUnexpectedSensing performanceCatalystSiGe thermoelectric film


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