This paper studies the structural design of the wireless-electrodeless quartz crystal microbalance (QCM) sensor, which has a rectangular AT-cut quartz oscillator installed in the microchannel fabricated by nanoimprint lithography. The quartz oscillator was supported by the micropillars in the microchannel, and by optimizing the micropillar arrangement, it was found that the structural damping could be significantly reduced by performing the finite elemental piezoelectric analysis. This behavior was then confirmed by the experiments using the evaluation chips. By supporting the four corners of the quartz oscillator with the micropillars, the structural damping could be reduced, achieving a high-quality factor (Q-factor) of about 24700. This high Q-factor was also realized in the experiments, and we investigated its application to a hydrogen-gas sensor. We succeeded in detecting hydrogen gas with an extremely low concentration of 10 ppm.

The hydrogen energy, which is environmentally friendly and does not emit carbon dioxide, has been attracting attention as an alternative fuel to the fossil fuel. In the shift to a hydrogen energy society, the highly sensitive hydrogen gas sensor has been required for the storage and management of hydrogen gas. In this research, we propose a film deposition method to induce the in-plane plastic deformation in the thin film, and apply it to a hydrogen gas sensor, where the palladium film formed by this method is deposited on a thin quartz resonator. It is found that the sensor chip with the plastically deformed palladium film is about 1.5 times more sensitive than the conventional sensor chip and has high-speed response. The developed sensor is a novel device that can be used in an oxygen-free environment without any temperature compensation and constant heating.