Authors: S Jin P Huang J Park J Y Yoo K S Breuer
Publish Date: 2004/10/23
Volume: 37, Issue: 6, Pages: 825-833
Abstract
Total internal reflection velocimetry TIRV is used to measure particle motion in the nearwall region of a microfluidic system TIRV images are illuminated with the evanescent field of an incident laser pulse and contain only particles that are very close to the channel surface Submicronsized fluorescent particles suspended in water are used as seed particles and their images are analyzed with a particle tracking velocimetry PTV algorithm to extract information about apparent slip velocity At relatively low shear rates less than 2500 s1 a velocity proportional to the shear rate was observed The statistical difference between velocities measured over hydrophilic and hydrophobic surfaces was found to be minimal The results suggest that the slip length if present is less than 10 nm but uncertainty regarding the exact character of the illumination field prevents a more accurate measurement at this time Numerical simulations are presented to help understand the results and to provide insight into the mechanisms that result in the experimentally observed distributions Issues associated with the accuracy of the experimental technique and the interpretations of the experimental results are also discussedThe authors would like to thank Thomas Powers for his discussion on issues regarding the simulation of Brownian motion in shear flow MinJun Kim for assistance in channel fabrication and the rest of the Brown University Microfluidics Lab for their support Two authors SJ and JYY acknowledge support from the Brain Korea 21 Project and the Micro Thermal System Research Center Seoul National University
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