Visualizing the transient electroosmotic flow and measuring the zeta potential of microchannels with a micro-PIV technique

2006 ◽  
Vol 124 (2) ◽  
pp. 021103 ◽  
Author(s):  
Deguang Yan ◽  
Nam-Trung Nguyen ◽  
Chun Yang ◽  
Xiaoyang Huang
Keyword(s):  
Zeta Potential ◽  
Electroosmotic Flow ◽  
Micro Piv ◽  
Piv Technique

Measurement of Transient Electrokinetic Flow in Microchannels Using Micro-PIV Technique

2006 ◽  
Author(s):  
Deguang Yan ◽  
Chun Yang ◽  
Nam-Trung Nguyen ◽  
Xiaoyang Huang
Keyword(s):  
Zeta Potential ◽  
Measurement Data ◽  
Ccd Camera ◽  
Electrokinetic Flow ◽  
Full Field ◽  
Micro Piv ◽  
Piv Technique ◽  
Piv Measurement ◽  
Electrokinetic Flows ◽  
Electroosmotic Velocity

Measurement of the steady-state electroosmotic velocity distributions in microchannels has been reported in the literature. Characterizing time-dependent electrokinetic flows is of importance to the development of microfluidic devices such as rapid capillary electrophoretic separation systems, AC pumps, novel micromixers etc. In this paper, we report a novel technique for studying and quantifying the transient electrokinetic flow phenomena in microchannels using the micro-PIV system with an ordinary PIV CCD camera. This is achieved by synchronizing different trigger signals for the laser, CCD camera, and custom high-voltage switch. Using the transient micro-PIV technique, we further propose a method to determine the electrophoretic component in the particle velocity and the zeta potential of the channel wall. Then the time evolution of the full-field, electroosmotic velocity distributions in both open- and closed-end rectangular microchannels is obtained from the micro-PIV measurement data. Using the slip velocity approach and the measured channel zeta potential, the theoretical predictions of the transient electroosmotic flow in the open- and closed-end microchannels are obtained, and they are found in good agreement with the experimental results.

Deviation of Electroosmotic Flow From Plug-Like Profile: The Effect of Reservoir Size

2007 ◽  
Author(s):  
Deguang Yan ◽  
Chun Yang ◽  
Xiaoyang Huang
Keyword(s):  
Size Effects ◽  
Electroosmotic Flow ◽  
Flow Characteristics ◽  
Microfluidic Devices ◽  
Time Dependent ◽  
Microfluidic Channels ◽  
Rectangular Microchannel ◽  
Micro Piv ◽  
Piv Technique ◽  
Proposed Model

In electrokinetically-driven microfluidic applications, reservoirs are indispensable and have finite sizes. During operating processes, as the liquid level in reservoirs keeps changing as time elapses, a backpressure is generated. Thus, the flow in microfluidic channels actually exhibits a combination of the electroosmotic flow and the time-dependent induced backpressure-driven flow. In this paper, a model is presented to describe the effect of the finite reservoir size on electroosmotic flow in a rectangular microchannel. Important parameters that describe the effect of finite reservoir size on flow characteristics are discussed. A new concept termed as “effective pumping period” is introduced to characterize the reservoir size effect. The proposed model identifies the mechanisms of the finite-reservoir size effects and is verified by experiment using the micro-PIV technique. The results reported in this study can be used for facilitating the design of microfluidic devices.

scholarly journals Numerical Analysis of the Heterogeneity Effect on Electroosmotic Micromixers Based on the Standard Deviation of Concentration and Mixing Entropy Index

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1055
Author(s):  
Alireza Farahinia ◽  
Jafar Jamaati ◽  
Hamid Niazmand ◽  
Wenjun Zhang
Keyword(s):  
Reynolds Number ◽  
Zeta Potential ◽  
Electroosmotic Flow ◽  
Molecular Diffusion ◽  
Slip Surface ◽  
Reynolds Numbers ◽  
Mixing Efficiency ◽  
Slip Coefficient ◽  
Mixing Rate ◽  
Heterogeneous Distribution

One approach to achieve a homogeneous mixture in microfluidic systems in the quickest time and shortest possible length is to employ electroosmotic flow characteristics with heterogeneous surface properties. Mixing using electroosmotic flow inside microchannels with homogeneous walls is done primarily under the influence of molecular diffusion, which is not strong enough to mix the fluids thoroughly. However, surface chemistry technology can help create desired patterns on microchannel walls to generate significant rotational currents and improve mixing efficiency remarkably. This study analyzes the function of a heterogeneous zeta-potential patch located on a microchannel wall in creating mixing inside a microchannel affected by electroosmotic flow and determines the optimal length to achieve the desired mixing rate. The approximate Helmholtz–Smoluchowski model is suggested to reduce computational costs and simplify the solving process. The results show that the heterogeneity length and location of the zeta-potential patch affect the final mixing proficiency. It was also observed that the slip coefficient on the wall has a more significant effect than the Reynolds number change on improving the mixing efficiency of electroosmotic micromixers, benefiting the heterogeneous distribution of zeta-potential. In addition, using a channel with a heterogeneous zeta-potential patch covered by a slip surface did not lead to an adequate mixing in low Reynolds numbers. Therefore, a homogeneous channel without any heterogeneity would be a priority in such a range of Reynolds numbers. However, increasing the Reynolds number and the presence of a slip coefficient on the heterogeneous channel wall enhances the mixing efficiency relative to the homogeneous one. It should be noted, though, that increasing the slip coefficient will make the mixing efficiency decrease sharply in any situation, especially in high Reynolds numbers.

scholarly journals Electroosmotic Flow Hysteresis for Fluids with Dissimilar pH and Ionic Species

Micromachines ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1031
Author(s):  
An Eng Lim ◽  
Yee Cheong Lam
Keyword(s):  
Zeta Potential ◽  
Electroosmotic Flow ◽  
Flow Direction ◽  
Velocity Model ◽  
Ionic Species ◽  
Dependent Behavior ◽  
Nacl Concentration ◽  
Solution Pair ◽  
Current Monitoring ◽  
Ion Species

Electroosmotic flow (EOF) involving displacement of multiple fluids is employed in micro-/nanofluidic applications. There are existing investigations on EOF hysteresis, i.e., flow direction-dependent behavior. However, none so far have studied the solution pair system of dissimilar ionic species with substantial pH difference. They exhibit complicated hysteretic phenomena. In this study, we investigate the EOF of sodium bicarbonate (NaHCO3, alkaline) and sodium chloride (NaCl, slightly acidic) solution pair via current monitoring technique. A developed slip velocity model with a modified wall condition is implemented with finite element simulations. Quantitative agreements between experimental and simulation results are obtained. Concentration evolutions of NaHCO3–NaCl follow the dissimilar anion species system. When NaCl displaces NaHCO3, EOF reduces due to the displacement of NaHCO3 with high pH (high absolute zeta potential). Consequently, NaCl is not fully displaced into the microchannel. When NaHCO3 displaces NaCl, NaHCO3 cannot displace into the microchannel as NaCl with low pH (low absolute zeta potential) produces slow EOF. These behaviors are independent of the applied electric field. However, complete displacement tends to be achieved by lowering the NaCl concentration, i.e., increasing its zeta potential. In contrast, the NaHCO3 concentration has little impact on the displacement process. These findings enhance the understanding of EOF involving solutions with dissimilar pH and ion species.

Micro PIV Measurement of Electroosmotic Flow

2002 ◽  
pp. 374-376
Author(s):  
Haruyuki Kinoshita ◽  
Marie Oshima ◽  
Jong Wook Hong ◽  
Teruo Fujii ◽  
Tetsuo Saga ◽  
...  
Keyword(s):  
Electroosmotic Flow ◽  
Micro Piv ◽  
Piv Measurement

Chaotic Electroosmotic Flow

2002 ◽  
Author(s):  
Shizhi Qian ◽  
Haim H. Bau
Keyword(s):  
Zeta Potential ◽  
Electroosmotic Flow ◽  
Analytic Solution ◽  
Microfluidic Devices ◽  
Chaotic Advection ◽  
Uniform Electric Field ◽  
Periodic Modulation ◽  
Chaotic Flows ◽  
Zeta Potentials ◽  
Series Convergence

Two dimensional, time-independent and time-dependent electroosmotic flows driven by a uniform electric field in rectangular cavities with uniform and non-uniform zeta potential distributions along the cavities’ walls are investigated theoretically. The time-independent flow fields are computed with the aid of Fourier series. The series’ convergence is accelerated so that highly accurate solutions are obtained with just a few (<10) terms in the series. The analytic solution is used to compute flow patterns for various distributions of the zeta potential along the cavities’ boundaries. It is demonstrated that by time-wise periodic modulation of the zeta potentials, one can induce chaotic advection in the cavities. Such chaotic flows may be used to stir and mix fluids in microfluidic devices.

scholarly journals Velocity field measurements in an evaporating sessile droplet by means of micro-PIV technique

2016 ◽  
Vol 84 ◽  
pp. 00042 ◽  
Author(s):  
Anna Yagodnitsyna ◽  
Artur Bilsky ◽  
Mina Roudgar ◽  
Joël De Coninck ◽  
Oleg Kabov
Keyword(s):  
Velocity Field ◽  
Field Measurements ◽  
Sessile Droplet ◽  
Micro Piv ◽  
Piv Technique

scholarly journals In vitro Experiment of Blood Flow Using Micro PIV Technique

2003 ◽  
Vol 23 (Supplement1) ◽  
pp. 305-308
Author(s):  
Remi OKUDA ◽  
Yasuhiko SUGII ◽  
Koji OKAMOTO
Keyword(s):  
Blood Flow ◽  
Vitro Experiment ◽  
In Vitro Experiment ◽  
Micro Piv ◽  
Piv Technique
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