Equipment Grant for Interfacial Velocimetry and 3D Liquid-Phase Thermometry in Microfluidic Devices

该奖项是根据2009年美国复苏和再投资法案（公法111-5）资助的。微流体“芯片上的实验室”通过将分析化学实验室的内容缩小到几平方厘米，已经改变了各种各样的生化分析。进一步缩小规模，最终在单分子水平上进行分析，需要对界面传输有基本的了解。在这些尺度下，整个流动将在距离壁面1微米以内，表面作用力（如静电）变得显著。PI的小组在开发非侵入式光学技术来研究界面输运方面处于领先地位，使用基于倏逝波的光学技术，如粒子图像测速（PIV）和双示踪荧光测温（DFT）来测量距离壁面400nm内的速度和温度场。最近，他们使用多层纳米PIV （MnPIV）测量了通过亲水和疏水涂层微通道的泊泽维尔流的速度梯度（即壁剪切应力）和滑移长度，并表明微尺度PIV技术中使用的胶体颗粒示踪剂的不均匀分布会显著影响滑移长度的估计。PI的小组还开发了一种DFT技术，可以测量水溶液中的温度场，其空间分辨率（平面内n）小至3微米，灵敏度是以前DFT方法的三倍多。这笔小型设备拨款将通过支持购买“下一代”电子倍增CCD相机来扩展PI小组的微尺度传输诊断能力，该相机可以在最短曝光时间内为MnPIV成像40 nm（及更小）示踪剂，以最大限度地减少布朗效应；此外，在现有的显微镜上安装旋转盘共聚焦装置，可以“实时”获取由70 × 512 × 512个样品组成的三维温度场，空间分辨率小至1.3微米。该设备将支持目前由美国国家科学基金会和海军研究办公室资助的两个研究项目，用于亚微米尺度的速度和温度测量。这些研究项目将通过提高微尺度速度测量技术的精度和空间分辨率，特别是在近壁区域，以及首次开发一种温度测量技术，可以获得三维液相温度场，其空间分辨率足以用于微流体装置，从而促进对微尺度输运的认识和理解。最后，该设备将支持全国最大的机械工程项目的研究生和本科生研究人员的教育，并且（基于2008年的数据）是非裔美国人和西班牙裔工程师教育的领导者之一。该奖项与CBET的TTP项目共同资助。

0933360YodaThis award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5). Microfluidic 'Labs on a Chip' have transformed a wide variety of biochemical assays by shrinking the contents of an analytical chemistry laboratory down to a few square centimeters. Scaling down even further, ultimately to assays at the single-molecule level, requires a fundamental understanding of interfacial transport. At these scales, the entire flow will be well within 1 micron of the wall, surface (e.g. electrostatic) forces become significant. The PI's group has led in developing non-intrusive optical techniques to study interfacial transport, using evanescent wave-based optical techniques such as particle image velocimetry (PIV) and dual-tracer fluorescence thermometry (DFT) to measure velocity and temperature fields within 400 nm of the wall. Recently, they have used multilayer nano-PIV (MnPIV) to measure velocity gradient (i.e., wall shear stress) and slip length in Poiseuille flows through hydrophilic and hydrophobically coated microchannels, and shown that the nonuniform distribution of the colloidal particle tracers used in microscale PIV techniques can significantly affect estimates of slip length. The PI's group has also developed a DFT technique that can measure temperature fields in aqueous solutions with a(n in-plane) spatial resolution as small as a 3 micron with a sensitivity more than triple that of previous DFT methods. This small equipment grant will extend the microscale transport diagnostic capabilities of the PI's group by supporting the acquisition of a 'next generation' electron multiplying CCD camera to image 40 nm (and smaller) tracers for MnPIV over the brief exposures required to minimize Brownian effects; and a spinning-disk confocal attachment for an already existing microscope to acquire three-dimensional temperature fields in 'real time' consisting of up to 70 × 512 × 512 samples with a spatial resolution as small as 1.3 micron. This equipment will support two current research projects funded by NSF and the Office of Naval Research for velocity and temperature measurement at sub-micron scales. These research projects will advance knowledge and understanding of microscale transport by improving the accuracy and spatial resolution of microscale velocimetry techniques, especially in the near-wall region, and by developing, for the first time, a thermometry technique that can obtain 3D liquid-phase temperature fields with a spatial resolution fine enough for microfluidic devices. Finally, this equipment will support the education of graduate students and undergraduate researchers at the largest Mechanical Engineering program in the nation and (based on 2008 data) one of the leaders in educating African-American and Hispanic engineers.This award is cofunded with the TTP program in CBET.