Miniaturized Sensors for Monitoring of Atmospheric Trace Gases using Multiple Deployment Platforms

Daylight Solutions proposes a miniaturized sensor package based on ECqcL<SUP>TM</SUP> and QEPAS technology that were independently developed by Daylight Solutions (San Diego, California) and the Laser Science Group Laboratory at Rice University (Houston, Texas)ECqcL<SUP>TM</SUP> lasers and QEPAS detectors have been successfully combined into table-top experiments, and the detection of several atmospheric gases in the low ppb range has been demonstrated. ECqcL<SUP>TM</SUP> based portable sensors have also been used to demonstrate the detection of 12CO2 and 13CO2 isotopologues at atmospheric CO2 concentrations.The ECqcL<SUP>TM</SUP>-QEPAS technique involves tightly focusing an infrared laser beam between the prongs of a commercial quartz tuning fork (QTF). Absorption of the laser emission by the sample heats up the gas between the prongs of the QTF. The resulting pressure spike is detected as an electrical signal due to a deformation of the prongs that results in a charge separation on electrodes deposited on the QTF prongs. Acoustically a QTF is a quadrupole, which results in excellent environmental noise immunity.By scanning the laser over a wide tuning range, the spectra of multiple atmospheric gas species can be recorded using only a single laser. The QEPAS technique does not require a sample chamber and air volumes as small as 1 mm3 containing atmospheric concentrations of 12CO2, 13CO2, CO, CH4, NO2, H2O2, H2CO, O3, and bromine oxides can be measured with ppb sensitivity.

Both QEPAS and ECqcL<SUP>TM</SUP> technologies are amenable to miniaturization, monolithic construction, and mass production following a straightforward engineering path using established MEMS technologies. The result would be a small, battery-operated, rugged sensor package that can be mass produced at low cost. The sensor would be insensitive to environmental factors and deployment platform independent. Wireless communication, self-calibration, and remote servicing are inherent components of such a miniaturized monolithic sensor package.