Digital Microfluidics for the Detection of Selected Inorganic Ions in Aerosols
Digital Microfluidics for the Detection of Selected Inorganic Ions in Aerosols
复制标题
DOI：
10.3390/s20051281
复制
发表时间：
2020-03-01
期刊：
影响因子：
3.9
通讯作者：
Fair, Richard B.
中科院分区：
文献类型：
--
作者：
Huang, Shuquan;Connolly, Jessica;Fair, Richard B.
提出了一种原型气溶胶检测系统，旨在准确、快速地测量大气中选定无机离子的浓度。该气溶胶检测系统将数字微流体技术、气溶胶冲击和化学检测集成在同一芯片上。目标化合物是主要的无机气溶胶成分：硫酸盐、硝酸盐和铵。数字微流体系统由夹有流体层的顶板和底板组成。用于惯性冲击器的喷嘴根据已知的缩放原理内置于顶板中。沉积的空气颗粒密集地集中在底板上的清晰沉积物中，底板上的固定区域包含芯片的液滴驱动电极。对于直径大于100 nm的颗粒物的气溶胶收集效率高于95%。收集阶段结束后，沉积物溶解成扫描液滴。由于液滴尺寸为亚微升，因此获得的提取物高度浓缩。然后，液滴穿过芯片上的空气/油界面，使用放置在芯片两块板之间的光纤通过分光光度法进行比色分析。为了为每种分析物创建标准曲线，为每次分析选择了六种不同浓度的液体标准品，并从芯片上的储液器中分配。液滴混合在几秒钟内完成，混合完成后最终液滴被输送到检测位置。最终液滴的检测限 (LOD) 确定为：硫酸盐为 11 ppm，铵为 0.26 ppm。对于硝酸盐，不可能获得稳定的测量结果。硫酸盐的片上测量结果的 LOD 接近使用 Tecan 光谱仪通过片外方法获得的结果。铵的片上方法的 LOD 比片外方法获得的 LOD 大约五倍。对于当前撞击器收集空气流量 (1 L/min) 和 1 小时收集时间，空气中换算的 LOD 为：硫酸盐为 0.275 mu g/m(3)，铵为 6.5 ng/m(3)，足以满足大多数环境空气监测应用。
A prototype aerosol detection system is presented that is designed to accurately and quickly measure the concentration of selected inorganic ions in the atmosphere. The aerosol detection system combines digital microfluidics technology, aerosol impaction and chemical detection integrated on the same chip. Target compounds are the major inorganic aerosol constituents: sulfate, nitrate and ammonium. The digital microfluidic system consists of top and bottom plates that sandwich a fluid layer. Nozzles for an inertial impactor are built into the top plate according to known, scaling principles. The deposited air particles are densely concentrated in well-defined deposits on the bottom plate containing droplet actuation electrodes of the chip in fixed areas. The aerosol collection efficiency for particles larger than 100 nm in diameter was higher than 95%. After a collection phase, deposits are dissolved into a scanning droplet. Due to a sub-microliter droplet size, the obtained extract is highly concentrated. Droplets then pass through an air/oil interface on chip for colorimetric analysis by spectrophotometry using optical fibers placed between the two plates of the chip. To create a standard curve for each analyte, six different concentrations of liquid standards were chosen for each assay and dispensed from on-chip reservoirs. The droplet mixing was completed in a few seconds and the final droplet was transported to the detection position as soon as the mixing was finished. Limits of detection (LOD) in the final droplet were determined to be 11 ppm for sulfate and 0.26 ppm for ammonium. For nitrate, it was impossible to get stable measurements. The LOD of the on-chip measurements for sulfate was close to that obtained by an off-chip method using a Tecan spectrometer. LOD of the on-chip method for ammonium was about five times larger than what was obtained with the off-chip method. For the current impactor collection air flow (1 L/min) and 1 h collection time, the converted LODs in air were: 0.275 mu g/m(3) for sulfate, 6.5 ng/m(3) for ammonium, sufficient for most ambient air monitoring applications.