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On-chip analysis of atmospheric ice-nucleating particles in continuous flow.
Lab on a Chip ( IF 6.1 ) Pub Date : 2020-07-08 , DOI: 10.1039/d0lc00251h
Mark D Tarn 1 , Sebastien N F Sikora 2 , Grace C E Porter 1 , Bethany V Wyld 2 , Matan Alayof 3 , Naama Reicher 3 , Alexander D Harrison 2 , Yinon Rudich 3 , Jung-Uk Shim 4 , Benjamin J Murray 2
Affiliation  

Ice-nucleating particles (INPs) are of atmospheric importance because they catalyse the freezing of supercooled cloud droplets, strongly affecting the lifetime and radiative properties of clouds. There is a need to improve our knowledge of the global distribution of INPs, their seasonal cycles and long-term trends, but our capability to make these measurements is limited. Atmospheric INP concentrations are often determined using assays involving arrays of droplets on a cold stage, but such assays are frequently limited by the number of droplets that can be analysed per experiment, often involve manual processing (e.g. pipetting of droplets), and can be susceptible to contamination. Here, we present a microfluidic platform, the LOC-NIPI (Lab-on-a-Chip Nucleation by Immersed Particle Instrument), for the generation of water-in-oil droplets and their freezing in continuous flow as they pass over a cold plate for atmospheric INP analysis. LOC-NIPI allows the user to define the number of droplets analysed by simply running the platform for as long as required. The use of small (∼100 μm diameter) droplets minimises the probability of contamination in any one droplet and therefore allows supercooling all the way down to homogeneous freezing (around −36 °C), while a temperature probe in a proxy channel provides an accurate measure of temperature without the need for temperature modelling. The platform was validated using samples of pollen extract and Snomax®, with hundreds of droplets analysed per temperature step and thousands of droplets being measured per experiment. Homogeneous freezing of purified water was studied using >10 000 droplets with temperature increments of 0.1 °C. The results were reproducible, independent of flow rate in the ranges tested, and the data compared well to conventional instrumentation and literature data. The LOC-NIPI was further benchmarked in a field campaign in the Eastern Mediterranean against other well-characterised instrumentation. The continuous flow nature of the system provides a route, with future development, to the automated monitoring of atmospheric INP at field sites around the globe.

中文翻译:

连续流中大气冰核颗粒的片上分析。

冰核颗粒(INPs)在大气中具有重要意义,因为它们催化过冷云滴的冻结,从而强烈影响云的寿命和辐射特性。有必要提高对INP的全球分布,其季节性周期和长期趋势的了解,但是我们进行这些测量的能力有限。大气中INP浓度通常是使用冷阶段涉及的液滴阵列的测定法确定的,但此类测定法通常受限于每个实验可分析的液滴数,通常涉及手动处理(例如吸取液滴),并且容易受到污染。在这里,我们介绍了一种微流体平台,即LOC-NIPI(通过沉浸式粒子仪器进行的芯片实验室成核),用于油包水液滴的产生以及当它们通过冷板时以连续流动的方式冻结用于大气INP分析。LOC-NIPI允许用户通过简单运行平台所需的时间来定义所分析的液滴数量。使用较小的液滴(直径约为100μm)可将任何一个液滴中的污染物的可能性降到最低,因此可以一直进行过冷直至均匀冻结(-36°C左右),而代理通道中的温度探头可提供精确的无需温度建模即可测量温度。该平台已使用花粉提取物和Snomax®样品进行了验证,每个温度步骤分析数百个液滴,每个实验测量数千个液滴。研究了使用> 10000滴,温度增量为0.1°C的纯净水的均质冷冻。结果是可重现的,与测试范围内的流速无关,并且数据与常规仪器和文献数据进行了很好的比较。LOC-NIPI在东地中海的野外战役中与其他功能完备的仪器进一步进行了基准测试。该系统的连续流动特性为未来的发展提供了一条在全球范围内自动监测大气INP的途径。10000个液滴,温度增量为0.1°C。结果是可重现的,与测试范围内的流速无关,并且数据与常规仪器和文献数据进行了很好的比较。LOC-NIPI在东地中海的野外战役中与其他功能完备的仪器进一步进行了基准测试。该系统的连续流动特性为未来的发展提供了一条在全球范围内自动监测大气INP的途径。10000个液滴,温度增量为0.1°C。结果是可重现的,与测试范围内的流速无关,并且数据与常规仪器和文献数据进行了很好的比较。LOC-NIPI在东地中海的野外战役中与其他功能完备的仪器进一步进行了基准测试。该系统的连续流动特性为未来的发展提供了一条在全球范围内自动监测大气INP的途径。
更新日期:2020-08-11
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