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

随着低于微米尺度的工程系统变得更加适用于生物和化学分析和检测，液-固界面处的边界条件在流体流动和纳米颗粒的运输中起着越来越重要的作用。 使用量子点（QD）成像作为一种工具，在纳米通道内的流动和纳米颗粒的运输和扩散的审讯，我们利用结合实验和计算方法的基础上分子动力学（MD）模拟研究液体流动，扩散和限制在纳米通道的基本原理。 具体而言，其目的是询问固-液滑移边界条件的基础上的QD纳米颗粒的扩散运动，并在同一时间回答以下问题：（1）约束如何影响纳米颗粒的热扩散运动在平衡和剪切流的存在？(2)表面特性（纳米粗糙度和润湿性）如何影响受限几何形状中的滑移流和纳米颗粒的局部流动性？这些问题的答案是很重要的设计化学和生物传感技术，涉及微和nano-fluidics.Intellectual优点：拟议的研究是专注于解决的基本问题，通过使用纳米颗粒的热运动的测量在纳米通道作为一种敏感的方法探测流体在表面滑移的程度，关于固液边界条件。这里提出的量子点成像方法介绍了一种强大的方法，用于获得有关纳米通道内流动和传输的定量信息。实验和分子动力学模拟的集成是独特的，因为模拟用于通过识别和隔离影响流体流动和QD纳米颗粒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物理和工程领域的广泛研究人员，他们研究并希望在微米和纳米尺度上控制流体传输特性。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朝向位于通道壁处的传感器的运输的限制。从拟议的工作中获得的基础知识将直接影响解决这些检测限的方法的设计。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的沿着。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广泛的跨学科接触纳米尺度流动物理，现代实验，大规模计算和光学诊断来教育我们的学生。除了教育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的高中科学教师举办为期两天的纳米级研究研讨会？的教师认证计划，为他们提供激励自己的高中生在现代研究的当前推力，以及他们如何与基础科学和工程的想法。在这项研究计划中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育材料。一个新的研究生课程将被设计为教育我们的学生在计算方法的基础上蒙特卡罗和分子动力学。拟议研究的科学进展将通过技术会议和期刊出版物传播。此外，我们计划为这个项目开发一个网站，提供简单的模拟和解释纳米尺度的流动。

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.