AVS 50th International Symposium
    Homeland Security Topical Conference Wednesday Sessions
       Session HS+MM-WeA

Paper HS+MM-WeA2
Development of a Piezoelectric Microphone for Trace Gas Detection

Wednesday, November 5, 2003, 2:20 pm, Room 309

Session: Detection of Explosives and Other Chemicals for Homeland Security
Presenter: R.G. Polcawich, U.S. Army Research Laboratory
Authors: R.G. Polcawich, U.S. Army Research Laboratory
P. Pellegrino, U.S. Army Research Laboratory
Correspondent: Click to Email
Escalating environmental awareness has led to more restrictive regulations on air quality in both the workplace and the environment in general. As a result, there is an increasing desire to have portable trace gas analyzers especially for chemical and biological agent detection. To meet these goals, a gas detection system must be miniaturized allowing large scale production of affordable small sensing systems. Initial examination of the scaling principles associated with photoacoustic spectroscopy (PAS) in respect to microelectromechanical system (MEMS) dimensions indicate the photoacoustic signals would remain at similar or greater sensitivities commonly found in macro-scale devices.@footnote 1@ Several other issues including: increased stability, noise avoidance, small source-to-detector distances and monolithic sensor construction support the idea that a MEMS photoacoustic chemical sensor can be realized.@footnote 2@ Our current research efforts have focused on fabrication of a piezoelectric microphone for trace gas sensing using a MEMS PAS. Using lead zirconate titanate (PZT) thin films as the piezoelectric sensor, 500 to 2000 micrometer diameter acoustic sensors have been fabricated and have an unamplified sensitivity of 0.1 to 1.0 µmV/Pa, depending on geometry. Using a limit of detection determined from the noise floor of the PZT microphone, it is anticipated that a PZT based acoustic sensor should detect SF@sub 6@ at slightly less than 1 ppb. Our presentation will cover the fabrication, packaging, and testing of a piezoelectric microphone for use in a MEMS based PAS detector. @FootnoteText@ @footnote 1@ S.L. Firebaugh, K.F. Jensen, and M.A. Schmidt, Miniaturization and integration of photoacoustic detection, J. Appl. Phys., vol 92, pp.1555-1563 (2002).@footnote 2@ P. Pellegrino and R. Polcawich, Evaluation of a MEMS Photoacoustic Sensor, submitted to 2002 Joint Service Scientific Conference Chemical Biological Defense Research, Hunt Valley.