Design of SH-surface acoustic wave sensors for detection of ppb concentrations of BTEX in water

To address the need to protect public health from contamination of drinking water and water for recreational use, a compact sensor system for in-situ detection of fuel and oil components in water is being investigated. The system makes use of shear-horizontal surface acoustic wave (SH-SAW) sensors coated with thin chemically sensitive polymer films. For this work, the BTEX compounds (benzene, toluene, ethylbenzene, and xylenes) were selected as target analytes because they are good indicators of fuel and oil releases, but also because they include known carcinogens (benzene, ethylbenzene). Chemical selectivity is achieved by combining sensors with various polymer coatings into a sensor array, and by evaluating both steady-state and transient response information. This work focuses on the influence of interdigital transducer (IDT) design on signal distortion and rms (root-mean-square) noise level. It is demonstrated that for suitable IDT design and experimental approach, it is possible to detect all BTEX compounds at concentration levels of 100 ppb or below, and to quantify benzene concentration in binary analyte mixtures at concentrations well below 1 ppm.