BRIGE: Computational Studies of Droplet Motion in Digital Microfluidics

1032514王项目总结我们建议通过发展稳定电场中界面动力学的全三维谱边界元方法来对数字微流体中的液滴运动进行基础研究。数字微流控技术在生物医学研究和临床研究中有着重要的应用，包括酶分析、DNA分析和疾病诊断。十多年来，人们一直在努力设计可靠、经济和方便的数字微流控设备。然而，由于对液滴在流体流动和电场影响下的运动缺乏基本的了解，目前的数字微流控系统必须借助昂贵的光学或电子成像设备来操作。实验中的流体动力学控制是凭经验实现的，对于新的流体系统来说，这是非常耗时的。如果开发一种全面的计算工具来描述微流控装置中液滴运动的物理过程，上述问题就可以得到解决。我们预计，拟议的计算工作能够为液滴动力学提供基本的了解，预测装置的运行，并进一步为装置的设计和优化奠定坚实的基础，从而产生可靠、负担得起、操作方便的新一代微流控装置。1)微流体稳恒电场中液滴动力学的三维谱边界元方法的发展和应用具有创新性。该研究为研究流体流动和电场共同作用下微流体中液滴的运动提供了全面的信息。它不像现有方法那样设定轴对称、均匀电场或静态液滴界面等假设。2)首次将谱方法(即高阶插值法)应用于电场作用下的数字微流体中的液滴动力学研究。所提出的计算方法将克服其他数值方法由于其低阶插值法而存在的障碍(在效率和精度方面)。3)这也是首次对微流体中液滴的动力学进行全三维研究。十年前，由于微流体系统中三维流体动力学聚焦实验的困难，人们对微流体的三维数值模拟提出了更高的要求，这项工作对科学、推广和教育都产生了广泛的影响。虽然这项研究的重点是数字微流控中的液滴运动，但对界面动力学的研究总体上可以应用于药物输送、燃料电池、三次采油和水过滤技术等，因此这项研究将有助于医疗保健、能源和环境补救措施。这项研究将通过以下方式实现更广泛的参与。PI计划通过北达科他州EPSCoR支持的培育美国部落本科生研究和教育(自然)计划，在部落大学举办研究研讨会并发表关于数字微流体的演讲。PI将为美洲原住民学生提供参与其实验室研究活动的机会，为他们提供夏季研究助学金。国际学生协会将作为一名残疾高中生的研究导师，指导他/她在国际学生协会的实验室进行研究。该协会鼓励本科生，尤其是女本科生参与微流体学的研究。她计划招募女本科生担任研究助理。国际学生联合会还计划说服一名代表不足的少数族裔学生加入她的研究小组，担任研究生研究助理。代表不足的少数族裔学生、残疾人和女学生的上述研究工作将得到布里奇基金的支持。为了增加本科生和研究生公开展示研究工作的机会，并改善微流体学的教育，PI计划在南洋理工大学组织和举办一年一度的微尺度流体动力学和传输现象学生研讨会。此外，拟议的研究工作将纳入作为互动教学软件教授的本科生和研究生课程。

1032514WangProject SummaryWe propose to perform a fundamental investigation of the droplet motion in digital microfluidics via the development of a fully three-dimensional Spectral Boundary Element Method for interfacial dynamics in a steady electric field. Digital microfluidics, in which an electric field is applied to manipulate droplet motion, has significant applications in biomedical research and clinical studies, including enzymatic analysis, DNA analysis and disease diagnosis. Great efforts have been made for over a decade to design reliable, affordable and convenient digital microfluidic devices. However, due to the lack of fundamental understanding of droplet motion under the influence of fluid flow and electric field, current digital microfluidic systems have to be operated with the assistance of expensive optical or electronic imaging devices. The control of fluid dynamics in experiments is achieved empirically and is extremely time consuming for new fluid systems. If a comprehensive computational tool is developed to describe the physics of droplet motion in microfluidic devices, the afore-mentioned problems can be resolved. We envision that the proposed computational work is able to provide fundamental understanding for the droplet dynamics, predict the operation of the device, and further create a solid foundation for the device design and optimization which can lead to a new generation of reliable, affordable, and operationally convenient microfluidic devices.The intellectual merit of the proposed study lies in the following aspects. 1) The development and application of a 3D Spectral Boundary Element Method for droplet dynamics in a steady electric field in microfluidics is new and innovative. The study can provide comprehensive information for the droplet motion in microfluidics under a joint influence of fluid flow and electric force. It does not make assumptions such as axisymmetry, uniform electric field, or static droplet interface, as existing methods do. 2) It will be the first time that a Spectral method (i.e. high-order interpolation scheme) is applied for droplet dynamics in digital microfluidics under the influence of electric field. The proposed computational method will overcome the obstacles (in terms of efficiency and accuracy) of other numerical methods due to their low-order interpolation schemes. 3) It will also be the first time that a fully three-dimensional study is carried out for the dynamics of droplets in microfluidics. It was pointed out a decade ago that three-dimensional numerical simulations are in demand for microfluidics due to the difficulties in 3D hydrodynamics focusing experiments in microfluidic system.The proposed work has a broad impact on science, outreach, and education. Although this study is focused on droplet motion in digital microfluidics, the insight gained for interfacial dynamics in general can be applied in drug delivery, fuel cells, tertiary oil recovery and water filtration technologies, etc. This research will thus contribute in health care, energy and environmental remedies. A broader participation of this research will be realized in the following ways. The PI plans to hold research workshops and give presentations on digital microfluidics at tribal colleges via the Nurturing American Tribal Undergraduate Research and Education (NATURE) program supported by North Dakota EPSCoR. The PI will provide opportunities for Native American students to participate the research activities in her laboratory by creating research assistantships for them in summers. The PI will act as a research mentor for a disabled high school student and guide him/her to conduct research in the PI's laboratory. The PI encourages undergraduate students, especially female undergraduates, to take part in research in Microfluidics. She plans to recruit female undergraduates as research assistants. The PI also plans to convince an underrepresented minority student to join her research group as a graduate research assistant. The afore-mentioned research work by underrepresented minority students, persons with disabilities and female students will be supported by the BRIGE funding. To increase the opportunities for undergraduates and graduate students to present research work in public, and to improve education in microfluidics, the PI plans to organize and hold an annual Student Symposium in Micro-scale Fluid Dynamics and Transport Phenomena at NDSU. In addition, the proposed research work will be integrated into both undergraduate and graduate courses that the PI teaches as interactive instructional software.