Fundamental study on multi-mode quartz crystal gas sensors

A quartz crystal microbalance (QCM) gas sensor using multiple resonant modes is studied. In this QCM sensor the absorbent is not fully deposited onto the plate surface as in the general QCM gas sensors. The absorbent is coated on the plate surface where the external-stress sensitivity difference between the two modes used is greatest. The external-stress sensitivity is measured by a semiconductor pulsed-laser system. To perform the fundamental experiments, that is, determining effectiveness of using external-stress sensitivity measuring in the design and fabrication of multi-mode QCM devices, a polyimide thin film is used as the adsorbent of carbon dioxide, and an 11 MHz AT-cut quartz resonator is used.