Localized Collection of Airborne Analytes: A Transport Driven Approach to Improve the Response Time of Existing Gas Sens
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Localized Collection of Airborne Analytes: A Transport Driven Approach to Improve the Response Time of Existing Gas Sensor Designs including SERS based Detection of Small Molecules Jun Fang1, Se-Chul Park1, Leslie Schlag2, Thomas Stauden2, Joerg Pezoldt2 and Heiko O. Jacobs2 1 Electrical and Computer Engineering, University of Minnesota 200 Union St. SE, Minneapolis, MN 55455, USA 2 Fachgebiet Nanotechnologie, Technische Universität Ilmenau Gustav-Kirchhoff-Strasse 1, D-98693 Ilmenau, Germany ABSTRACT The detection of single molecular binding events has been a recent trend in sensor research introducing various sensor designs where the active sensing elements are nanoscopic in size. Currently, diffusion-only-transport is often used and it becomes increasingly unlikely for an analyte molecule to “find” and interact with sensing structures where the active area is shrunk in size, trading an increased sensitivity with a long response time. This report introduces electrodynamic nanolens based analyte concentration concepts to transport airborne analytes to nanoscopic sensing points to improve the response time of existing gas sensor designs. In all cases we find that the collection rate is several orders of magnitudes higher than in the case where the collection is driven by diffusion. INTRODUCTION The desire to detect and identify trace amounts of airborne analytes, including combustible or toxic gases, small molecules, particles, viruses or bacteria with ever increasing sensitivity and selectivity continues to be one of the main drivers in sensor research and analytical science [1-3]. While the variety of sensing principles continues to grow, most principles share a common feature which is the requirement that the analyte adsorbs on the sensor surface or interacts chemically or physically with the sensing element for signal transduction to take place [4-7]. A recent trend has been to increase the sensitivity to a point where it is possible to detect single binding events. While it is possible to detect single binding events through the introduction of these highly miniaturized sensing points, the efficient transport of the airborne analytes to point-like structures has been a critical factor to improve the response time. Instead of relying on diffusion-only-transport, this report evaluates the use of a directed force to overcome this problem and to transport the analyte from a distance away to predetermined sensing points at a higher rate. The approach is inspired in part by prior research in the aerosol community which has developed transport strategies to collect airborne particles using convection [8], thermophoretic [9], magnetic [10] and Coulomb forces [11,12]. Specifically we introduce a new general approach which uses a corona discharge based analyte charging method in combination with an electrodynamic lens based analyte collection concept to
transport airborne analytes to precise points on a surface to improve the response time of existing gas sensor designs by several orders of magnitude. This approach has
