Mercury vapor detection with a self-sensing, resonating piezoelectric cantilever

A microcantilever with an integrated piezoelectric film is demonstrated as a mercury vapor detector. The cantilever is self-sensing and self-actuating, and therefore does not need alignment of an external, optical detection system. This gives the new sensor system an advantage in array applications. Mercury vapor, when adsorbed onto gold on the cantilever, causes the stiffness, and therefore the natural frequency, of the cantilever to increase as a result of mercury gold amalgamation. This shift is detected using the piezoelectric portion of the cantilever in conjunction with a bridge circuit and amplifier. A mercury concentration of 93 ppb in nitrogen is detected.