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

在该项目中，将开发一种紧凑、轻便的小颗粒传感器，可以收集和分析大气化学中的三种重要离子：硫酸盐、硝酸盐和铵。该仪器预计将具有与现有仪器相当的灵敏度和精度，但提供高时间分辨率，体积和重量小，使其成为轻型飞机，无人机（UAV）和研究气球上应用的理想选择。它将能够在无法使用现有仪器的大气区域进行大气成分测量。该项目建立在NSF支持的先前工作的基础上，为该设备构建原型。该新方法将采用数字微流体技术，该方法允许将微升和纳升体积的液体作为离散液滴进行操作。本研究计划的具体目标如下：（1）设计一种微芯片，该芯片集成了颗粒收集和提取、试剂储存以及硫酸盐、硝酸盐和铵的比色检测区域;（2）开发与数字微流控平台兼容的微纳升比色测定硝酸盐和铵的配方（3）微调液滴致动条件，用于从各种气溶胶基质中有效提取目标化合物;以及（4）表征采样和分析步骤期间的颗粒收集效率和潜在干扰和伪像，以及测试芯片在飞机研究中的适用性。该装置的使用将能够对大气成分进行更彻底和高时间分辨率的表征。

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.