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

在这个项目中，将开发一种紧凑、轻便的小颗粒传感器，可以采集和分析大气化学中的三种重要离子：硫酸盐、硝酸盐和铵。预计该仪器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，体积和重量都很小，因此非常适合在轻型飞机、无人机(UAV)和研究气球上应用。它将能够在不能使用现有仪器的大气层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，为该设备建立原型。新方法将使用数字微流控技术，这是一种允许将微升和纳升体积的液体作为离散液滴进行操纵的方法。本研究方案的具体目标如下：(1)设计一种集硫酸盐、硝酸盐和铵的颗粒收集和提取、试剂存储和比色检测为一体的微芯片；(2)开发与数字微流控平台兼容的硝酸盐和铵的微纳升比色分析配方(硫酸盐分析已在以前的工作中开发)；(3)微调液滴驱动条件，以有效地从各种气溶胶基质中提取目标化合物；以及(4)表征采样和分析步骤中的颗粒收集效率和潜在的干扰和伪影，以及该芯片在飞机研究中的测试适用性。该装置的使用将使大气成分的表征更加全面和更高的时间分辨率。

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.