NER: Developing a Nanoscale Strain Gauge

这个项目的目标是开发一种纳米级的“应变计”来测量界面上的流动诱导应力。这种分子探针将从一种灵活的大分子发展而来，例如两端都连接有荧光团的单链DNA。一端系在相界面上，另一端自由伸展进入变形阶段。在流体流动存在的情况下，分子将根据局部流体动力改变构型。这种变化将通过荧光共振能量转移(FRET)来测量，该技术为测量两个荧光团之间的距离提供了一把纳米尺度的“尺子”。FRET提供了一种灵敏的方法来测量间距为1-9 nm的荧光团之间的距离。这项技术最初的发展是为了绘制紧邻界面的流场图，作为研究流动和/或变形对界面性质的影响的一种手段。然而，这项技术也将有助于研究自组装单分子膜和系链大分子中的流动效应。它还将通过提供对宏观作用力的分子尺度响应的准确测量来帮助验证多尺度建模技术。本科生和研究生都将直接参与这项技术的发展，并将接受材料科学、荧光显微镜应用和生物结合技术方面的培训。这项研究的结果还将通过提供流动/边界相互作用的可视化示例来增强学生在流体力学等课程中的课堂体验。

The objective of this project is to develop a nanoscale "strain-gauge" to measure flow-induced stresses at an interface. This molecular probe will be developed from a flexible macromolecule such as a single-strand DNA with fluorophores conjugated to each end. One end will be tethered to the phase interface and the other will extend freely into the deforming phase. In the presence of fluid flow, the molecule will change configuration, based on the local hydrodynamic forces. This change will be measured by fluorescent resonance energy transfer (FRET), which provides a nanoscale "ruler'" for measuring the distance between two fluorophores. FRET provides a sensitive means to measure distances between fluorophores that are 1-9 nm apart.This technique will initially be developed to map the flow field immediately adjacent to an interface as a means to study the effect of flow and/or deformation on interfacial properties. However, the technique will also be useful in studying the effects of flow in self-assembled monolayers and tethered macromolecules. It will also help verify multiscale modeling techniques by providing accurate measurements of molecular-scale response to macroscopic forces. Both undergraduate and graduate students will be directly involved in the development of the technique and will be trained in material science applications of fluorescent microscopy and in bioconjugate techniques. Results from the this study will also enhance the classroom experience for students in courses such as fluid mechanics by providing a visual example of flow/boundary interaction.