Antisymmetric-mode lamb wave methanol sensor with edge reflectors for fuel cell applications

A Lamb wave sensor to measure the concentration of methanol solution in direct methanol fuel cell (DMFC) systems was designed, fabricated and evaluated. The sensor piezoelectrically generates the lowest antisymmetric mode (A0-mode) Lamb wave on a suspended thin AlN/SiO
₂
/Si composite membrane, and confines a standing wave with edge reflectors. The fabricated sensor showed an almost constant sensitivity of 510 ppm/% in methanol concentration from 0 % to 100 %. The temperature coefficient of frequency (TCF) was found to be -31 ppm/K, which might approach zero by using a 1 ¿m thick buried oxide (BOX) layer.