Surface acoustic wave microsensors based on cyclodextrin coatings

Cyclodextrin thin films were applied to surface acoustic wave (SAW) devices as receptors for detecting organic vapors. Self-assembled monolayers (SAMs) and sol–gel techniques were used in fabricating chemical sensing layer thin films on SAW microsensors. The cyclodextrin coatings on the surface of SAW resonators (200 MHz) were studied as a method of tracking organic toxins in gas phase. The mass loading of cyclodextrin coatings on SAW resonators gave frequency shifts corresponding to a coverage of a typical monolayer for SAM method and “multilayer” for sol–gel techniques. Subsequent exposure of the coated SAW resonators to organic vapors at various concentrations, typically 5000 parts per million (ppm) down to 50 parts per billion (ppb) by mole, gave responses indicating middle-ppb-sensitivity (∼50 ppb) for those sensor-host receptors and organic-toxin pairs with optimum mutual matching of polarity, size, or structural properties.