Coupled evanescent field molecular tagged velocimetry for nanofluidics

本提案中要求的仪器涉及一种创新的非侵入式微/纳米级设备流量测量技术，该技术将分子标记测速法（MTV）与倏逝波场相结合。这将使我们能够量化距离通道壁几百纳米（nm）内的速度场，其中滑移、壁电荷相互作用等现象占主导地位。 这样的速度测量将是重要的，以验证近壁现象的理论模型，并将大大提高我们对微通道和纳米通道中的流体流动的理解。现有技术依赖于直径通常约为100 - 200 nm的晶种颗粒，因此不能准确地解析壁处的流场。通过使用所提出的倏逝波场，一种被限制在所研究的表面的几百纳米内并且依赖于光源的全内反射的现象，结合现有的MTV系统，将使我们能够解决这样的流场。这种耦合将通过采购高数值孔径物镜和相关的光学器件和光束转向机制来实现，然后将其与现有的“内部”开发的MTV系统集成，从而为微流体应用创造一种独特的测量技术。

The instrument requested in this proposal relates to an innovative non-intrusive flow measurement technique for micro/nano-scale devices which combines the molecular tagging velocimetry (MTV) with evanescent wave field. This will allow us to quantify the velocity field within a few hundred nanometers (nm) from the channel walls where phenomena like slip, wall charge interactions, etc. are dominant. Such velocity measurements will be important to validate the theoretical models for the near wall phenomena and will substantially improve our understanding of fluid flow in micro and nanochannels. Existing techniques rely on seed particles which are typically around 100 - 200 nm in diameter and hence are not able to accurately resolve the flow field at the wall. By using the proposed evanescent wave field, a phenomenon which is confined within a few hundred nanometers of the investigated surface and relies on the total internal reflection of the light source, in conjunction with the existing MTV system will allow us to resolve such flow fields. This coupling will be rendered by procuring a high numerical aperture objective and related optics and beam steering mechanisms, which will then be integrated with the existing "in-house" developed MTV system, thereby creating a unique measurement technique for microfluidics applications.