Dual-channel flexural acoustic wave chemical sensor

摘要

A dual channel flexural device is fabricated on a gallium arsenide (GaAs) substrate that includes a pair of elongated active vibrating (GaAs) bars formed in the substrate that serve as acoustic waveguides. One of the bars serves as a reference channel, while the other bar is covered with a chemically sensitive coating and operates as a sensing channel. A pair of pseudo-surface acoustic wave (SAW) transducers serving as input and output transducers are located at each end of the bars. Each of the transducers is comprised of discontinuous U-shaped elements having dimensions and mutual separations of one half the acoustic operating wavelength formed on one side of the substrate while ground electrodes are formed thereunder on the opposite side of the substrate. When the transducers are energized, a flexural motion in the bars is set up, causing the bars to vibrate. The vibration of the chemically coated bar changes in response to absorption of vaporous contaminants providing a device which operates in a differential mode for chemical vapor sensing.