Sensing of Airborne Nanoparticles Using Miniaturized Whipple Double Condenser

Abstract

We have demonstrated the sensing of airborne nanoparticles using a miniaturized Whipple double condenser (MWDC). Each condenser (17 mm long, 2.2 mm wide, and 1 mm tall) was fabricated using photolithography and copper electroplating. The MWDC was theoretically shown to function within the laminar flow regime and capable of detecting 10- and 20-nm particles at a flow rate of 0.3 LPM. Monodispersed isopropyl alcohol and oleic acid airborne nanoparticles (10 and 20 nm) were generated using a TSI Model 9302 Single Jet Atomizer and TSI 3080 Electrostatic Classifier, and were electrically charged with 85Kr isotope. The calculated and experimental particle pass through ratio (PPR) agreed reasonably well. Using a Keithley 616 electrometer, similar threshold condenser voltage (maximum second condenser current) was observed in both experimental PPR as well as the second condenser current versus condenser voltage plot. The MWDC also displayed characteristic Whipple curves in its experimental I/V versus $\text{k}_{c}$ plots. These data demonstrate the feasibility of the microfabricated double condenser design as the basis of a miniaturized nanoparticle sizing and counting device.