Particle Tracking Techniques for Electrokinetic Microchannel Flows

• Published in: Analytical chemistry (Washington) Vol. 74; no. 15; pp. 3704 - 3713
• Main Authors: Devasenathipathy, Shankar, Santiago, Juan G, Takehara, Kohsei
• Format: Journal Article
• Language: English
• Published: Washington, DC American Chemical Society 01-08-2002
• Subjects: Analysis; Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; Kinetics; Other chromatographic methods; Particle physics; Capillary electrophoresis; Electroosmosis; Electrophoretic mobility; Geometrical configuration; Numerical simulation; Particle image velocimetry; Velocity distribution; Calibration; Microfluidics
• ISSN: 0003-2700; 1520-6882
• DOI: 10.1021/ac011243s

We have applied particle tracking techniques to obtain spatially resolved velocity measurements in electrokinetic flow devices. Both micrometer-resolution particle image velocimetry (micro-PIV) and particle tracking velocimetry (PTV) techniques have been used to quantify and study flow phenomena in electrokinetic systems applicable to microfluidic bioanalytical devices. To make the flow measurements quantitative, we performed a series of seed particle calibration experiments. First, we measure the electroosmotic wall mobility of a borosilicate rectangular capillary (40 by 400 μm) using current monitoring. In addition to this wall mobility characterization, we apply PTV to determine the electrophoretic mobilities of more than 1000 fluorescent microsphere particles in aqueous buffer solutions. Particles from this calibrated particle/buffer mixture are then introduced into two electrokinetic flow systems for particle tracking flow experiments. In these experiments, we use micro-PIV, together with an electric field prediction, to obtain electroosmotic flow bulk fluid velocity measurements. The first example flow system is a microchannel intersection where we demonstrate a detailed documentation of the similitude between the electrical fields and the velocity fields in an electrokinetic system with uniform zeta potential, ζ. In the second system, we apply micro-PIV to a microchannel system with nonuniform ζ. The latter experiment provides a simultaneous measurement of two distinct wall mobilities within the microchannel.