| Abstract: | Apparatus for chemical detection includes a pair of interdigitated
transducers (IDTs) formed on a piezoelectric substrate. The apparatus
includes a layer of adsorptive material deposited on a surface of the
piezoelectric substrate between the IDTs, where each IDT is conformed,
and is dimensioned in relation to an operating frequency and an acoustic
velocity of the piezoelectric substrate, so as to function as a
single-phase uni-directional transducer (SPUDT) at the operating
frequency. Additionally, the apparatus includes the pair of IDTs is
spaced apart along a propagation axis and mutually aligned relative to
said propagation axis so as to define an acoustic cavity that is resonant
to surface acoustic waves (SAWs) at the operating frequency, where a
distance between each IDT of the pair of IDTs ranges from 100 wavelength
of the operating frequency to 400 wavelength of the operating frequency. |