Investigation of SH-SAW sensors for toxic heavy metal detection

In this study, a guided shear horizontal mode surface acoustic wave (SH-SAW) sensor with 64° YX-LiNbO₃ based piezoelectric substrate and gold (Au) interdigitated electrodes (IDE) was used for the detection of toxic heavy metal compounds. A flow cell, with a reservoir volume of 3 μl, which employs inlet and outlet valves for the microfluidic chamber and polydimethylsiloxane (PDMS) based microfluidic channels, was also designed and fabricated using an acrylic material. As the SAW propagates through the substrate between input and output IDEs, a change in the velocity of the wave due to the varying concentrations of the test analytes, causes a change in the resonant frequency. This frequency based response of the SAW sensor towards mercury sulfide (HgS) and lead sulfide (PbS) demonstrated the capability of the system to detect picomolar level concentrations. The response of the SAW sensor is analyzed and presented in this paper.