A simple method to determine the surface charge in microfluidic channels

Mampallil, Dileep; Ende, Dirk van den; Mugele, Friedrich Gunther

doi:10.1002/elps.200900603

Cited by 15 publications

(25 citation statements)

References 17 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It is assumed that the surface charge density is constant regardless of the concentrations of the solutions during the course of the two-fluid displacement flow. 27 Table VI shows the surface charge densities r s that are prescribed on the channel wall for different solution pairs.…”

Section: B Boundary and Initial Conditionsmentioning

confidence: 99%

“…Mampallil et al 27 have proposed a technique to measure the surface charge of a microchannel based on electroosmotic displacement flow of two solutions with different concentrations. The zeta potentials of the two solutions and the surface charge were obtained by fitting the current-time curve (obtained from the current monitoring experiment) to a theoretical expression.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Electroosmotic flow hysteresis for dissimilar ionic solutions

Lim

Lam

2015

Biomicrofluidics

View full text Add to dashboard Cite

Electroosmotic flow (EOF) with two or more fluids is commonly encountered in various microfluidics applications. However, no investigation has hitherto been conducted to investigate the hysteretic or flow direction-dependent behavior during the displacement flow of solutions with dissimilar ionic species. In this investigation, electroosmotic displacement flow involving dissimilar ionic solutions was studied experimentally through a current monitoring method and numerically through finite element simulations. The flow hysteresis can be characterized by the turning and displacement times; turning time refers to the abrupt gradient change of current-time curve while displacement time is the time for one solution to completely displace the other solution. Both experimental and simulation results illustrate that the turning and displacement times for a particular solution pair can be directional-dependent, indicating that the flow conditions in the microchannel are not the same in the two different flow directions. The mechanics of EOF hysteresis was elucidated through the theoretical model which includes the ionic mobility of each species, a major governing parameter. Two distinct mechanics have been identified as the causes for the EOF hysteresis involving dissimilar ionic solutions: the widening/sharpening effect of interfacial region between the two solutions and the difference in ion concentration distributions (and thus average zeta potentials) in different flow directions. The outcome of this investigation contributes to the fundamental understanding of flow behavior in microfluidic systems involving solution pair with dissimilar ionic species. V C 2015 AIP Publishing LLC. [http://dx

show abstract

Section: B Boundary and Initial Conditionsmentioning

confidence: 99%

mentioning

confidence: 99%

Electroosmotic flow hysteresis for dissimilar ionic solutions

Lim

Lam

2015

Biomicrofluidics

View full text Add to dashboard Cite

show abstract

“…Assuming the surface charge s 0 is constant over different concentrations, which is a good first-order approximation for low potentials and dilute systems [7,36,37] we can use well-known Grahame's equation to obtain Electrophoresis 2011, 32, 3295-3304 the nondimensionalz…”

Section: Nondimensionalized Equationsmentioning

confidence: 99%

“…Recently, Rodriguez [29] extended these studies to account for the effects of electrolysis. Furthermore, Mugele and coworkers [7] proposed a straightforward solution for the case of buffers having a large differences in concentration. However, to date, there has been no extension of these methods to the case of heterogenous surfaces.…”

Section: Introductionmentioning

confidence: 99%

“…In general, theoretical characterization of wall properties in fluidic channels is difficult, due to the sensitivity of the zeta potential z to small differences in chemistry and surface treatments [7]. Measurements of z under various experimental conditions and for different ion varieties is a vast field with many pioneering works [8][9][10][11][12].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Method to determine the effective ζ potential in a microchannel with an embedded gate electrode

et al. 2011

View full text Add to dashboard Cite

We present a theoretical model to determine the effective zeta potential ζ(eff) in microfluidic channels where an embedded, insulated gate electrode allows for external tuning of a portion of the channel surface charge. In addition, we derive a method to determine ζ(eff) in such channels, for any value of salt concentration, using the solution displacement technique. To do so, we simulate typical current-monitoring measurements using our model, and highlight the experimental parameters that lead to inaccurate results using this procedure with an heterogenous channel. Our method corrects for such inaccuracies by using our model with experimental data to find the correct value of ζ(eff) . Finally, we perform experiments to demonstrate our method and the use of our model with a silica-PMDS microchannel system with an embedded Ti-Au-Ti gate electrode that covers 50% of the bottom surface of the channel. We show that our theory captures the salient features of our experiments, thereby offering a useful tool to predict effective zeta potential in channels with a nonuniform zeta potential.

show abstract

Silicon insulator‐based dielectrophoresis devices for minimized heating effects

Zellner¹,

Agah

2012

Electrophoresis

View full text Add to dashboard Cite

Concentration of biological specimens that are extremely dilute in a solution is of paramount importance for their detection. Microfluidic chips based on insulator-based DEP (iDEP) have been used to selectively concentrate bacteria and viruses. iDEP biochips are currently fabricated with glass or polymer substrates to allow for high electric fields within the channels. Joule heating is a well-known problem in these substrates and can lead to decreased throughput and even device failure. In this work, we present, for the first time, highly efficient trapping and separation of particles in DC iDEP devices that are fabricated on silicon using a single-etch-step three-dimensional microfabrication process with greatly improved heat dissipation properties. Fabrication in silicon allows for greater heat dissipation for identical geometries and operating conditions. The 3D fabrication allows for higher performance at lower applied potentials. Thermal measurements were performed on both the presented silicon chips and previously published PDMS devices comprised of microposts. Trapping and separation of 1 and 2 μm polystyrene particles was demonstrated. These results demonstrate the feasibility of high-performance silicon iDEP devices for the next generation of sorting and concentration microsystems.

show abstract

A simple method to determine the surface charge in microfluidic channels

Cited by 15 publications

References 17 publications

Electroosmotic flow hysteresis for dissimilar ionic solutions

Electroosmotic flow hysteresis for dissimilar ionic solutions

Method to determine the effective ζ potential in a microchannel with an embedded gate electrode

Silicon insulator‐based dielectrophoresis devices for minimized heating effects

Contact Info

Product

Resources

About