LaserSPECks: LaserSPECtroscopic Trace-Gas Sensor Networks -SensorIntegration andApplications

General Terms We introduce a novellaser spectroscopic trace-gas sensor Performance, Design platform, LaserSPECks thatintegrates recently developed miniature quartz-enhanced photoacoustic spectroscopy (QE- Keywords PAS)gassensing technology. Thisuniversal platform uses infrared laser spectroscopy detect andquantify numerous gasspecies atpart-per-million topart-per-billion (ppm-ppb) 1.INTRODUCTION concentrations [2]. Traditional gassensing devices capable of thesamesensitivity andspecificity areseveral orders ofmag- Thedetection andquantification oftrace-gases provide a nitude larger insize, cost, andpowerconsumption. Thus, diverse setofreal-world applications. Inthispaper, we rehighresolution gassensing technology hasbeendifficult to portthefirst successful design andimplementation ofahighintegrate intosmall, low-power, replicated sensors suitable performance miniature gassensorintegrated within theWSN forwireless sensor networks (WSNs). Thispaperpresents methodology. Theminiature gassensorimplements quartztheprinciples behindlaser basedtracegasdetection, de- enhanced photoacoustic spectroscopy (QEPAS), a technolsignissues, andoutlines theimplementation ofaminiatur- ogyrecently developed atRiceUniversity [6]. Theplatform izedtrace-gas sensor fromcommerical-off-the-shelf (COTS) isuniversal sincedetection andquantification ofanygas components. We report onanearly prototype asaproof- typeispossible, aslong asthelaser cantunetothespeof-concept forintegration intoWSN applications. We also cific wavelengths ofaparticular trace-gas species. Theseopdescribe anumberofongoing collaborations inutilizing the tical techniques haveextremely highspecificity ascompared platform inairpollution andcarbon fluxquantification, in- tosemiconductor/metal-oxide gassensors(previously intedustrial plant control, explosives detection, andmedical di- grated intoWSNs)whichsuffer fromhighfalse positive and agnosis. Furthermore, wediscuss experimental performancenegative rates(undesirable insecurity andmedical applicaevaluations toexaminegeneral platform requirements for tions). Thus,QEPASsensorscan bepractically deployed thesetypes ofsensors.Theresults ofourevaluation illustratethatourprototype improves uponprevious gassensingtechnology bytwoorders ofmagni'tude inmeasuresof powerconsumption, size, andcost, without sacrificing sensor performance. Ourdesign andexperiments reveal thatlaserbasedtrace-gas sensorsbuilt fromCOTS canbesuccessfully implemented andintegrated within WSN nodestoenable a widerangeofnewandimportant sensing applications.