NER: Developing a Nanoscale Strain Gauge

该项目的目标是开发一种纳米尺度的“应变计”来测量界面上的流动诱发应力。这种分子探针将由一种灵活的大分子发展而来，如单链DNA，其两端共轭有荧光团。一端将被拴在相界面上，另一端将自由地延伸到变形相。在流体存在的情况下，分子会根据局部水动力改变构型。这种变化将通过荧光共振能量转移（FRET）来测量，它提供了一个纳米尺度的“尺子”来测量两个荧光团之间的距离。FRET提供了一个敏感的手段，以测量距离1-9纳米之间的荧光团。这项技术最初将用于绘制与界面相邻的流场，作为研究流动和/或变形对界面特性影响的一种手段。然而，该技术也将有助于研究自组装单层和系住大分子的流动影响。它还将通过提供对宏观力的分子尺度反应的精确测量，帮助验证多尺度建模技术。本科生和研究生都将直接参与该技术的开发，并将接受荧光显微镜和生物偶联技术的材料科学应用方面的培训。这项研究的结果还将通过提供流动/边界相互作用的视觉例子，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.