Evanescent Wave-Based Particle Tracking Velocimetry for Nanochannel Flows

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• 作者：Yutaka Kazoe ; Keizo Iseki ; Kazuma Mawatari ; Takehiko Kitamori
• 刊名：Analytical Chemistry
• 出版年：2013
• 出版时间：November 19, 2013
• 年：2013
• 卷：85
• 期：22
• 页码：10780-10786
• 全文大小：341K
• 年卷期：v.85,no.22(November 19, 2013)
• ISSN：1520-6882

文摘

Understanding fluid flows in 10鈥?000 nm space, which we call extended nanospace, is important for novel nanofluidic devices in analytical chemistry. This study therefore developed a particle tracking velocimetry for measuring velocity distribution in nanochannel flows, by using the evanescent wave illumination. 64 nm fluorescent nanoparticles were used as flow tracer. The particle position was determined from fluorescent intensity by the evanescent wave field, with a spatial resolution smaller than light wavelengths. The time resolution of 260 渭s was achieved to make error by the Brownian diffusion of the tracer small to be neglected. An image processing by multitime particle tracking was established to detect the tracer nanoparticles of weak fluorescent intensity. Though the measurement region was affected by nonuniform particle distribution with the electrostatic interactions, pressure-driven flows of water in a nanochannel of 50 渭m width and 410 nm depth were successfully measured. The results of the velocity distribution in the depth-wise direction approximately showed agreement with the fluid dynamics with the bulk liquid properties from the macroscopic view, however, suggested slip velocities even in the hydrophilic channel. We suggest a possibility of appearance of molecular behavior in the fluid near the wall within 10 nm-order scale.