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

这个项目的目标是了解液滴的形成和运输动力学的气体微流体系统，包括压缩性的影响。了解气体微通道中液滴的形成和传输将对液滴微流的一般领域产生重大影响，特别是对于气体采样和干颗粒气溶胶的产生。所获得的知识将对便携式气体生化诊断和传感应用中的下一代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。这里解决的丰富的工程，物理和材料挑战代表了相关学生的一个伟大的跨学科项目。该项目的结果将为PI教授的课程提供新的课堂材料，以及针对小学受众的外展活动。针对未被充分代表的东北大学新生/大学生的本科生暑期实习计划将建立，以培养他们成为未来工程挑战的多学科领导者。将研究和分析不同几何形状和流动条件下液滴形成，分离，运输以及与连续气相流相互作用背后的主导物理。一个多任务研究计划将到位，其中包括液滴形成，分离和运输相互作用的液压和光学诊断表征，以及这些过程的数值模拟。具体研究内容包括：（1）针对不同的流动条件和几何形状，包括三维微流控流动结构，对滴注和喷射两种工况下的液滴形成过程进行实验和数值模拟。这两个制度之间的过渡和可能的滞后效应的条件也将进行探讨。(2)液滴运输的空气动力学的表征和控制将在形成和分离后进行，包括基于静电的控制策略。液滴蒸发，吸收的蒸汽物种，和内部流动动力学和液滴的混合特性也将得到解决。(3)将根据流动加速和激波的存在对气相压缩性效应进行评估。将评估由于这些影响而引起的流态和过渡以及液滴运输动力学的变化。同样，液滴与微通道中的驻激波相互作用也将被研究。该奖项反映了NSF的法定使命，并被认为值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估来支持。

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.