Formation and Transport Dynamics of High Speed Gas-Liquid Droplet Microfluidics

该项目的目标是了解气态微流体系统中液滴的形成和传输动力学，包括可压缩性效应。了解液滴在气体微通道中的形成和运输将对液滴微流动的一般领域产生重大影响，特别是对于气体取样和干颗粒气溶胶的产生。所获得的知识将对下一代便携式气体生化诊断和传感应用中的微流体系统以及更大规模的喷雾和雾化系统产生重大影响。丰富的工程，物理和材料的挑战在这里解决代表了一个伟大的跨学科项目，为学生参与。该项目的成果将为PI教授的课程提供新的课堂材料，并为小学观众提供外联活动。东北大学（Northeastern University）将设立一项针对代表性不足的大一/大二学生的本科暑期实习项目，将他们培养成未来工程挑战的多学科领导者。在不同的几何形状和流动条件下，液滴形成、分离、输运以及与连续气相流动的相互作用背后的控制物理将被研究和分析。一项多任务研究计划将到位，包括液滴形成、分离和传输相互作用的液压和光学诊断特征，以及这些过程的数值模拟。具体研究内容如下：(1)针对不同的流动条件和几何形状，包括三维微流体流动结构，对滴灌和喷射两种流态下的液滴形成进行实验和数值模拟。在这两种状态之间转换的条件和可能的滞后效应也将被探讨。(2)对液滴形成和分离后的空气动力学进行表征和控制，包括基于静电的控制策略。液滴蒸发、蒸汽种类的吸收、液滴内部流动动力学和混合特性也将被讨论。(3)从流动加速度和激波的存在两方面评价气相可压缩性的影响。将评估由于这些影响而引起的流态和过渡的变化以及液滴传输动力学。同样，微通道中液滴与驻波的相互作用也将被研究。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

The goal of this project is to understand liquid droplet formation and transport dynamics in gaseous microfluidic systems, including compressibility effects. Understanding liquid droplet formation and transport in gaseous microchannels will have significant impact on the general area of droplet microflows, particularly for gas sampling and dry particle aerosol generation. The knowledge gained will have major implications for next generation microfluidic systems in portable gaseous biochemical diagnostics and sensing applications, as well as in larger scale spray and atomization systems. The rich engineering, physics, and materials challenges tackled here represent a great cross-disciplinary project for the students involved. The results of the project will provide new classroom materials for courses that the PI teach, as well as outreach activities geared towards elementary school audiences. An undergraduate summer internship program aimed at underrepresented Northeastern University freshmen/sophomores will be established to prepare them as multidisciplinary leaders of future engineering challenges.The governing physics behind the liquid droplet formation, detachment, transport, and interaction with the continuous gas phase flow for different geometries and flow conditions will be studied and analyzed. A multi-task research program will be put in place that includes hydraulic and optical diagnostics characterization of droplet formation, detachment and transport interactions, alongside numerical simulations of these processes. The research program includes the following specific thrusts: (1) Experiments and numerical simulation of droplet formation in the dripping and jetting regimes will be conducted for different flow conditions and geometries, including 3D microfluidic flow architectures. The conditions for transition between these two regimes and possible hysteresis effects will also be explored. (2) Characterization and control of the aerodynamics of droplet transport will be conducted after formation and detachment, including electrostatic based control strategies. Droplet evaporation, absorption of vapor species, and internal flow dynamics and mixing characteristics of the droplets will also be addressed. (3) An assessment will be made of the gas phase compressibility effects in terms of flow acceleration and the presence of shock waves. Changes in flow regimes and transitions as well as the droplet transport dynamics due to these effects will be assessed. Similarly, droplet interaction with standing shock waves in the microchannel will be studied.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.