A multi-resolution passive SAW chemical sensor

Referring to the technology of SAW wireless identification systems, a passive SAW element for analyte sensing is developed. The sheet substrate is cut out of piezoelectric single crystal. One interdigital transducer (IDT) and several reflectors are manufactured on the surface of the substrate. When the sensing element is interrogated by a high-frequency modulated burst, the IDT transforms the signal into a SAW, which propagates on the surface of the substrate and is reflected by the reflectors. Thus, the information for the surface state is contained in the echoed wave. When the echoed wave is back to the IDT and transduced back into an electromagnetic signal, it can be received and processed by the interrogation unit. Therefore, when the surface is coated with analyte-sensitive film, a novel chemical SAW sensor can be implemented. Some attractive properties of the sensing system, which is quite different from the conventional SAW sensor, are theoretically predicted and experimentally verified.