A method for simultaneously determining the zeta potentials of the channel surface and the tracer particles using microparticle image velocimetry technique

Abstract

The zeta potentials of channel surfaces and tracer particles are of importance to the design of electrokinetic microfluidic devices, the characterization of channel materials, and the quantification of the microparticle image velocimetry (microPIV) measurement of EOFs. A method is proposed to simultaneously measure the zeta potentials of the channel surface and the tracer particles in aqueous solutions using the microPIV technique. Through the measurement of the steady velocity distributions of the tracer particles in both open- and closed-end rectangular microchannels under the same water chemistry condition, the electrophoretic velocity of the tracer particles and the EOF field of the microchannel are determined using the expressions derived in this study for the velocity distributions of charged tracer particles in the open- and closed-end rectangular microchannels. Thus, the zeta potentials of the tracer particles and the channel surfaces are simultaneously obtained using the least-square method to fit the microPIV measured velocity distribution of the tracer particles. Measurements were carried out with a microPIV system to determine the zeta potentials of the channel wall and the fluorescent tracer particles in deionized water and sodium chloride and boric acid solutions of various concentrations.

Electrokinetically driven concentration of particles and cells by dielectrophoresis with DC-offset AC electric field

“…The general trend is that an increase in buffer concentration will lead to stronger DEP force (Fig. 2) and lower down the zeta potentials of both the PDMS channel wall and the particles (Yan et al 2006). As a result, increasing the buffer concentration is favorable to particle trapping, which is supported by the results reported in Fig.…”

Electrophoresis of concentrated colloidal dispersions in low-polar solvents

“…By measuring the electrophoretic mobility l = v/E, where v is the speed of the particle moving in an electric field of strength jEj, the surface potential and the particle charge can be determined. Electrophoretic mobilities can be measured by laser Doppler anemometry [22] but can also be determined in real space using an optical microscope [23,24]. In this paper, we use confocal laser scanning microscopy (CLSM) and particle tracking software to obtain the trajectories of individual particles moving in an electric field.…”

Effect of finite reservoir size on electroosmotic flow in microchannels

“…For analysis, we choose the following parameters: the half height and half width of the rectangular channel w = h = 150 lm, the channel length l = 4 cm, the wall zeta potential of borosilicate glass channel f = -62.3 mV (Yan et al 2006), the electric strength E = 100 V/cm, and the reservoir radii are r 1 = r 2 = 1 mm. Figure 3 presents the volumetric flow rate and the pressure gradient versus time.…”

“…To obtain the true fluid flow field, the electrophoretic component has to be subtracted from the measured particle velocity. Using micro-PIV technique reported elsewhere (Yan et al 2006), we obtained the zeta potentials of both the channel wall (-62.3 mV) and the tracer particles (-30.4 mV) in DI water. With the images processed, the flow velocity field can be obtained by removing the electrophoretic component of the tracer particles' velocity measured by micro-PIV directly.…”