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. 2011;11(2):1526-41.
doi: 10.3390/s110201526. Epub 2011 Jan 27.

Advances in SXFA-coated SAW chemical sensors for organophosphorous compound detection

Wen Wang  1 , Shitang He, Shunzhou Li, Minghua Liu, Yong Pan
Affiliations

Advances in SXFA-coated SAW chemical sensors for organophosphorous compound detection

Wen Wang et al. Sensors (Basel). 2011.

Abstract

A polymer-coated surface acoustic wave (SAW)-based chemical sensor for organophosphorous compound sensing at extremely low concentrations was developed, in which a dual-delay-line oscillator coated with fluoroalcoholpolysiloxane (SXFA) acted as the sensor element. Response mechanism analysis was performed on the SXFA-coated chemical sensor, resulting in the optimal design parameters. The shear modulus of the SXFA, which is the key parameter for theoretical simulation, was extracted experimentally. New designs were done on the SAW devices to decrease the insertion loss. Referring to the new phase modulation approach, superior short-term frequency stability (±2 Hz in seconds) was achieved from the SAW oscillator using the fabricated 300 MHz delay line as the feedback element. In the sensor experiment on dimethylmethylphosphonate (DMMP) detection, the fabricated SXFA-coated chemical sensor exhibited an excellent threshold detection limit up to 0.004 mg/m(3) (0.7 ppb) and good sensitivity (∼485 Hz/mg/m(3) for a DMMP concentration of 2∼14 mg/m(3)).

Keywords: SAW chemical sensor; oscillator; response mechanism; threshold detection limit.

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Figures

Figure 1.
Figure 1.
The schematic and principle of the polymer-coated SAW chemical sensor.
Figure 2.
Figure 2.
The schematic of the sensor structure and coordination system in this study.
Figure 3.
Figure 3.
(a) Change in attenuation. (b) Velocity shift from SXFA on vapor adsorption.
Figure 4.
Figure 4.
(a) Change in attenuation, and (b) velocity shift from frequency effect.
Figure 5.
Figure 5.
Measured S12 from SAW device with (a) Cr/Au, and (b) Al/Au electrodes.
Figure 6.
Figure 6.
Frequency stability testing of oscillator using (a) Cr/Au, and (b) Al/Au electrode.
Figure 7.
Figure 7.
The SEM picture of (a) uncoated-surface, and (b) coated-surface of the delay line.
Figure 8.
Figure 8.
The measured effect of SXFA thickness on sensor response.
Figure 9.
Figure 9.
The temperature effect on sensor response and on response and recovery time.
Figure 10.
Figure 10.
Repeatability testing of sensor responses to 1,000 mg/m3 DMMP.
Figure 11.
Figure 11.
Sensor responses in terms of vapor concentration at (a) high, and (b) low DMMP concentrations
See this image and copyright information in PMC

References

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