Collaborative Research: Development of a Digital Microfluidic Impactor for One Minute Measurements of Main Inorganic Aerosol Species

Duke University, Durham NC

Investigators

Abstract

In this project, a compact and lightweight small particle sensor will be developed that can collect and analyze three important ions in atmospheric chemistry: sulfate, nitrate and ammonium. The instrument is expected to have the sensitivity and accuracy comparable to existing instruments, but provide high time resolution and have low volume and weight making it ideal for applications on light aircraft, unmanned aerial vehicles (UAVs), and research air balloons. It will enable atmospheric composition measurements in areas of the atmosphere where existing instrumentation cannot be used. This project builds on prior work supported by NSF to build a proto-type for this device. The novel method will employ the use of digital microfluidics, a method that allows manipulation of micro- and nano-liter volumes of liquids as discrete droplets. The specific objectives of this research proposal are as follows: (1) Design a micro-chip that incorporates areas for particle collection and extraction, reagent storage, and colorimetric detection of sulfate, nitrate and ammonium; (2) Develop micro/nanoliter colorimetric assay formulations for nitrate and ammonium detection that are compatible with the digital microfluidic platform (the sulfate assay has been developed in previous work); (3) Fine-tune droplet actuation conditions for efficient extraction of target compounds from a variety of aerosol matrixes; and (4) Characterize particle collection efficiency and potential interferences and artifacts during the sampling and analysis steps, as well as test applicability of the chip for aircraft studies. The use of this device will enable a more thorough and high time resolution characterization of atmospheric composition.