A capacitive micromachined ultrasonic transducer (CMUT) array as a low-power multi-channel volatile organic compound (VOC) sensor

In this study we extend our work on low-power CMUT chemical sensors from a single element to an array as a way to improve selectivity to volatile organic compound (VOC) analytes. A single channel of our sensor array comprises of a polymer-functionalized CMUT resonator in the feedback loop of a Colpitts oscillator, which consumes 0.76 mW, when operated continuously. Using our anodic-bonding based fabrication process, we fabricated 6-, 8-, and 15-channel prototype arrays with a standard deviation of 1 % in the parallel resonant frequency (4.5 MHz) in a 7×9-mm2 die area. We measured the response of three channels, one uncoated, one with a polyisobutylene (PIB) layer, and one with a polyvinyl alcohol (PVA) layer, to 20-ppm toluene vapor. Initial measurements show 1:13:37 ratio in the response of reference: PVA:PIB channels.