Optimization of a BSP3-Coated Surface Acoustic Wave Chemical Sensor

The optimization of fluorinated bisphenol-containing polymer (BSP3)-coated surface acoustic wave (SAW) chemical sensor was performed for sensing organophosphorous compounds with trace concentration in this contribution. First, the response mechanism was characterized using the classical perturbational approach. Optimal sensitive film thickness and operation frequency are determined theoretically to achieve a relative linear characteristic response and a high gas sensitivity. Next, to improve of the corrosion resistance and frequency response characteristics of the sensor chip, Al/Au electrodes are used to form the resonator acted as the feedback element for oscillator. In addition, the substantial improvement is obtained in frequency stability of the resonator–oscillator referring to phase modulation approach. The measured short-term frequency stability of the oscillator at the operation frequency of 300 MHz is up to 2 Hz/s. The theoretical predictions are confirmed by the measured responses from the BSP3-coated SAW sensor for dimethylmethylphosphonate (DMMP) detection. Excellent threshold detection limit less than 0.004 mg/
$\text{m}^{3}$
and good sensitivity (
$\sim 3.09$
kHz/mg/
$\text{m}^{3})$
were achieved from the developed BSP3-coated SAW chemical sensor in the DMMP detection.