Influence of Confinement on Flow, Diffusion, and Boundary Conditions in Nano Channels: A Combined Quantum Dot Imaging and Molecular Dynamics Simulations Approach

随着微米级以下的工程系统在生物和化学分析和检测方面的可行性越来越高，液固界面的边界条件在纳米颗粒的流动和传输中起着越来越重要的作用。利用量子点（QD）成像作为研究纳米通道内流动和纳米颗粒传输和扩散的工具，我们利用基于分子动力学（MD）模拟的实验和计算相结合的方法来研究纳米通道中液体流动、扩散和限制的基本原理。具体而言，目的是询问基于量子点纳米颗粒扩散运动的固液滑移边界条件，同时回答以下问题：(1)约束如何影响平衡状态和剪切流存在下纳米颗粒的热扩散运动？(2)表面特性（纳米粗糙度和润湿性）如何影响纳米颗粒在受限几何结构中的滑动流动和局部迁移率？这些问题的答案对于设计涉及微和纳米流体的化学和生物传感技术非常重要。智力优势：本研究的重点是通过测量纳米颗粒在纳米通道中的热运动，作为探测表面流体滑移程度的灵敏方法，来解决关于固液边界条件的基本问题。本文提出的量子点成像方法为获得纳米通道内流动和输运的定量信息提供了一种强有力的方法。实验和分子动力学模拟的结合是独特的，因为模拟被用来通过识别和分离影响量子点纳米颗粒流体流动和动力学的各种物理效应来帮助解释实验结果。更广泛的影响：本提案中开发的实验和计算方法将有利于研究并希望在微纳米尺度上控制流体传输特性的物理和工程领域的广泛研究人员。在微流体中的许多化学和生物传感应用中，化学/生物试剂的检测受到其向位于通道壁的传感器的传输的限制。从拟议的工作中获得的基本知识将直接影响解决这些检测极限的方法的设计。这项工作的一个重要影响将是两名博士生的教育，以及本科生早期参与研究。pi的技术重点及其计算和实验纳米尺度研究的方法将通过提供纳米尺度流动物理，现代实验，大规模计算和光学诊断的广泛跨学科接触来教育我们的学生。除了培养研究生作为未来的教育工作者和研究人员，我们的计划将包括本科生研究人员每年夏天。pi计划为密歇根州立大学（MSU）注册的密歇根州中部高中科学教师举办为期两天的纳米级研究研讨会。美国教师资格认证计划，为他们提供一些想法，以激励他们自己的高中生参与当前现代研究的重点，以及如何将它们与基础科学和工程联系起来。本研究计划所开发的量子点成像方法，将为我们现有的流体动力学实验方法研究生课程增加教材。一个新的研究生课程将被设计来教育我们的学生基于蒙特卡罗和分子动力学的计算方法。拟议研究的科学进展将通过技术会议和期刊出版物加以传播。此外，我们计划为这个项目开发一个网站，对纳米尺度的流动进行简单的模拟和解释。

As engineered systems below the micron scale become more viable for biological and chemical analysis and detection, the boundary condition at the liquid-solid interface plays an increasingly important role in fluid flow and transport of nanoparticles. Using quantum dot (QD) imaging as a tool for interrogation of flow and nanoparticle transport and diffusion within nano channels, we utilize a combined experimental and computational approach based on molecular dynamics (MD) simulations to investigate the fundamental principles of liquid flow, diffusion, and confinement in nano channels. Specifically, the aim is to interrogate the solid-liquid slip boundary condition based on the diffusive motion of QD nano-particles and at the same time answer the following questions: (1) How does confinement affect the thermal diffusive motion of a nanoparticle in equilibrium and in the presence of shear flow? (2) How do surface characteristics (nanoroughness and wetting) affect the slip flow in a confined geometry and the local mobility of a nanoparticle? Answers to these questions are important to designing chemo- and bio-sensing technologies that involve micro- and nano-fluidics.Intellectual Merit: The proposed research is focused on addressing the fundamental questions regarding the solid-liquid boundary condition by using the measurement of the thermal motion of nanoparticle in a nano channel as a sensitive method of probing the degree of fluid slip at the surface. The quantum dot imaging method proposed here introduces a powerful approach for obtaining quantitative information about flow and transport within nano channels. The integration of experiments and molecular dynamics simulations is unique, in that the simulations are used to help interpret the experimental results by identifying and isolating the various physical effects that influence the fluid flow and the dynamics of QD nanoparticles. Broader Impacts: The experimental and computational methods developed in this proposal will be beneficial to a broad range of researchers in physics and engineering who investigate and wish to control fluid transport properties at micro and nano scales. In many chemo- and bio-sensing applications in microfluidics, the detection of a chemo/bio agent is limited by its transport towards the sensor located at the channel wall. The fundamental knowledge gained from the proposed work will directly impact the design of methods to address these detection limits. An important impact of this work will be the education of two PhD students, along with the early involvement of undergraduate students in research. The technical focus of the PIs and their approaches to computational and experimental nano-scale research will educate our students by providing a broad interdisciplinary exposure to nano-scale flow physics, modern experimentation, large-scale computations, and optical diagnostics. In addition to educating graduate students as future educators and researchers, our program will include undergraduate student researchers each summer. The PIs plan to give a two-day workshop on their nano-scale research to mid-Michigan high school science teachers enrolled in MSU?s teacher certification program, to provide them with ideas for stimulating their own high-schoolers in the current thrusts of modern research and how they relate to basic science and engineering. The quantum dot imaging methods developed in this research program will add educational material to our existing graduate level course in experimental methods in fluid dynamics. A new graduate course will be designed to educate our students in computational methods based on Monte Carlo and molecular dynamics. The scientific progress of the proposed research will be disseminated through technical conferences and journal publications. In addition, we plan to develop a website for this project with simple simulations and explanation of nano-scale flows.