Flow Connecting Type SH-SAW Methanol Concentration Sensor for Direct Methanol Fuel Cells ������������������ SH-SAW ����� �����

With expanding functions of mobile IT gadgets, such as smart phones, their battey duration time has been continuing to shorten. In addion to these situations, due to the tremendous earthquake on March 11, 2011 in eastern Japan, necessity of wide variety of electric power generating methods have been realized. A direct methanol fuel cell (DMFC) is one of the most promising candidates of next generation mobile power sources. Methanol, which provides electricity to DMFC, preserves electricity more efficient than conventional lithium-ion battery in same weight. The energy preserving efficiency is quite important. Energy storage efficiency brings long-lasting and/or lighter power source to final products. In order to operate DMFCs at optimal electricity generating efficiency, maintaining the concentration of methanol in the fuel is absolutely imperative. In case lower concentration fuel, generating electricity can be reduced. On the other hand, higher concentration causes a methanol cross-over, which is a fuel consumption without electricity generation. The cross-over leads not only unwanted fuel waste, but also shortening DMFC’s lifetime. While optimal concentraion value vary among configuration of DMFC, around 1M (~3% by weight) is widely used [1]. For the purpose of monitoring methanol concentrations, wide variety of sensing method has been developed [2]. Though proposed methods has respective advantages, ultimate device which satisfies all of the requirement from DMFC does not exist. Surface acoustic wave based methanol concentration sensor has been developed as one of the promising technology for DMFC’s fuel control. SAW based device suits massproduction, because SAW technologies have been widely used in the communication industory for over the past several decades and well established production technologies. Thease SAW advantages bring significant benefits to DMFC in price reduction. A purpose of our study is to provide SH-SAW methanol concentration sensors to DMFC manufacturs in reasonable price and easy-to-use configuration.