Stand-Off Chemical Detection Using Photoacoustic Sensing Techniques—From Single Element to Phase Array

Abstract

Abstract:Technologies that can detect harmful chemicals, such as explosive devices, harmful gas leaks, airborne chemicals or/and biological agents, are heavily invested in by the government to prevent any possible catastrophic consequences. Some key features of such technology are, but not limited to, effective signal-to-noise ratio (SNR) of the detected signal and extended distance between the detector and target. In this work, we describe the development of photoacoustic sensing techniques from simple to more complex systems. These techniques include passive and active noise filters, parabolic sound reflectors, a lock-in amplifier, and beam-forming with an array of microphones; using these techniques, we increased detection distance from a few cm in an indoor setting to over 41 feet in an outdoor setting. We also establish a theoretical mathematical model that explains the underlying principle of how SNR can be improved with an increasing number of microphone elements in the phase array. We validate this model with computational simulations as well as experimental results.

Standoff Chemical Detection Using Laser Absorption Spectroscopy: A Review

“…Subsequently, the research group demonstrated a signal-enhancement and noise-reduction approach experimentally by means of acoustic beam-former technology with multiple microphone/reflector system, as well as with an array of multiple microphones and one reflector [144,145]. A standoff detection distance of 41 feet in an outdoor setting has been achieved for safely detecting chemicals, such as IPA, RDX, and TNT, with high signal sensitivity [146]. Most recently, Ramesh C. Sharma et al developed a QCL based standoff LPAS with for detection of hazardous molecules contaminants/adsorbed on surfaces, such as plastic and cloth, from short standoff distances [147].…”

Nanoporous Silica-Dye Microspheres for Enhanced Colorimetric Detection of Cyclohexanone

“…In the past decade, a large number of analytical methods for trace explosive screening have been investigated, including gas chromatography-mass spectrometry (GC-MS) [7][8][9][10], electronic noses [11][12][13][14], ion mobility spectrometry [5,[15][16][17][18], surface acoustic wave devices [19][20][21] and fluorimetry [22][23][24][25]. Some effective approaches, such as solid-phase microextraction (SPME) [26][27][28], have been extensively explored for ultrasensitive gaseous detection of non-volatile explosives at the ppb or ppt level.…”

Nanoporous Silica-Dye Microspheres for Enhanced Colorimetric Detection of Cyclohexanone

“…In the past decade, a large number of analytical methods for trace explosive screening have been investigated, including GC-MS [7][8][9][10], electronic noses [11][12][13][14], ion mobility spectrometry [5,[15][16][17][18], surface acoustic wave devices [19][20][21] and fluorimetry [22][23][24][25]. Some effective approaches, such as solid-phase microextraction (SPME) [26][27][28], have been extensively explored for ultrasensitive gaseous detection of non-volatile explosives at ppb or ppt level.…”