Electroosmotic flow and mixing in microchannels with the lattice Boltzmann method

Tang, G.H.; Li, Zhuo; Wang, J. K.; He, Yingli; Wu, Tao

doi:10.1063/1.2369636

Cited by 46 publications

(23 citation statements)

References 53 publications

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“…This flow phenomenon was observed experimentally by Stroock et al (2000). In later studies, these induced localized circulations in the steady flow field were successfully employed to improve species mixing in a microchannel (Erickson and Li 2002;Chang and Yang 2004;Fushinobu and Nakata 2005;Wang et al 2005a;Tang et al 2006) or a curved microchannel (Lin et al 2006). However, chaotic mixing was absent in the proposed mixers since the zeta potential was time-independent and hence the induced circulations were closed and steady in two-dimensional flow systems.…”

Section: Heterogeneous Surface Charge Patterning Enhanced Electroosmomentioning

confidence: 92%

“…Recently, the lattice Boltzmann (LB) equation has been proven useful for the description of mesosystems with complicated geometry and composition (Succi 2001). Hence, it also has been widely used over the past years to describe the electrokinetic flow field and mixing (Tian et al 2005;Wang et al 2005aWang et al , 2006aTang et al 2006), which is solved through the so-called lattice Boltzmann method (LBM).…”

Section: Basic Methodologymentioning

confidence: 99%

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Electrokinetic mixing in microfluidic systems

Chang

Yang

2007

Microfluid Nanofluid

268

150

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The applications of electrokinetics in the development of microfluidic devices have been widely attractive in the past decade. Electrokinetic devices generally require no external mechanical moving parts and can be made portable by replacing the power supply by small battery. Therefore, electrokinetic-based microfluidic systems can serve as a viable tool in creating a lab-on-a-chip (LOC) or micro-total analysis system (TAS) for use in biological and chemical assays. Mixing of analytes and reagents is a critical step in realizing lab-on-a-chip. This step is difficult due to the flow in microscale devices which are typically limited to low Reynolds numbers, turbulence does not readily occur. The mixing of two or more fluid streams in a simple microchannel is dominated by the molecular diffusion effect. The diffusive mixing time is given by t m ~ w 2 /D and the mixing length (l m ) along the downstream channel increases linearly with the Péclet number (i.e. l m ~ Pe×w), where w and D are the channel width and molecular diffusivity. However, the rate of diffusive mixing in microscale channels is very slow compared to the convection of the fluid along the channel since the Péclet number of typical microchannel flows is very high due to biomolecules (e.g. DNA and protein) with relatively low molecular diffusivities. To reduce the mixing time and length, various schemes to enhance micro-mixing have been proposed in the past years. This review reports recent developments in the micro-mixing schemes based on DC and AC electrokinetics. The overview given in this article provides a potential user or researcher of electrokinetic-based technology to select the most favorable mixing scheme for applications in the field of micro-total analysis systems. Mixing principle and chaotic mixingAlthough it is difficult to induce turbulence (so-called Eulerian chaos) in microchannels, an effective mixing in low Reynolds number flow regimes can be obtained by the chaotic advection mechanism (or so-called Lagrangian chaos or laminar chaos), which provides an effective increase in the interfacial contact area and concentration gradient due to reduction of the striation thickness (i.e. diffusion length).In this way, mixing time and length can be considerably reduced. If an exponential reduction of striation thickness should occur, the mixing time and mixing length can be reduced down to t m ~ ln(Pe) and l m ~ ln(Pe), respectively, for chaotic flows in the limit of large Pe. An effective mixing always requires repeated stretching and folding of fluid elements, e.g blanking vortex models. Blinking vortex models are similar to the link twist map (LTM) strategy which is based on a dynamic system theory described in the literature [1]. An LTM is often obtained when the dynamic system has a structure such that the motion can be described by the repeated application of two twist maps. Over the past few years, many effective micromixers have been designed according to the LTM strategy. Micro-mixing based on electrokinetics

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Section: Heterogeneous Surface Charge Patterning Enhanced Electroosmomentioning

confidence: 92%

Section: Basic Methodologymentioning

confidence: 99%

Electrokinetic mixing in microfluidic systems

Chang

Yang

2007

Microfluid Nanofluid

268

150

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“…For example, numerical simulations by Tang et al (2006) indicate that a proper combination of electroosmotic flow and pulsatile flow can achieve complete mixing of two microchannel flows. Stroock et al (2002) and Glasgow and Aubry (2003) observed that inertial effects become important for microfluidic mixing for Re ) 1, which is the case studied here.…”

Section: Introductionmentioning

confidence: 98%

Measurement and modeling of pulsatile flow in microchannel

Tikekar

Singh

Agrawal

2010

Microfluid Nanofluid

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An experimental study of pulsatile flow in microchannel is reported in this paper. Such a study is important because time-varying flows are frequently encountered in microdevices. The hydraulic diameter of the microchannel is 144 lm and deionized water is the working fluid. The pressure drop across the microchannel as a function of time is recorded, from which the average and r.m.s. pressure drops are obtained. The experiments have been performed in the quasi-steady flow regime for a wide range of flow rate, frequency of pulsations, and duty cycle. The results suggest that the pressure with pulsations lies between the minimum and maximum steady state pressure values. The average pressure drop with pulsation is approximately linear with respect to the flow rate. The theoretical expression for pressure has also been derived wherever possible and the experimental data is found to lie below the corresponding theoretical values. The difference with respect to the theoretical value increases with an increase in frequency and a decrease in flow rate, with a maximum difference of 32.7%. This is attributed to the small size of the microchannel. An increase in frequency of square waveform leads to a larger reduction in pressure drop as compared to rectangular waveform, irrespective of the duty cycle. The results can be interpreted with the help of a firstorder model proposed here; the model results are found to compare well against the experimental results. A correlation for friction factor in terms of the other non-dimensional governing parameters is also proposed. Experimental study of mass-driven pulsatile flow in microchannel is being conducted for the first time at these scales and the results are of both fundamental and practical importance. Keywords Microchannel Á Pulsatile flow Á Microfluidics Á Flow modeling Á Microscale flow Á Pressure drop List of symbols A Area of cross-section of channel (m 2 ) C Capacitance (F) D h Hydraulic diameter of the channel (=4A/perimeter) (m) f Average friction factor pD h 1 2 qv 2 L À Á f rms Friction factor r.m.s p rms D h 1 2 qv 2 L À Á F Dimensionless form of frequency ¼ D h ðt N þt F Þa i Current (A) L Length of the microchannel (m) m F Minimum flow rate (kg/s) m N Maximum flow rate (kg/s) p Pressure (Pa) p Time-averaged pressure drop (Pa) p rms Root mean square value of the pressure drop (Pa) Q Volumetric flow rate (m 3 /s) R Resistance (ohm) Re Reynolds number ¼ vD h a À Á Re N On-time Reynolds number ¼ v N D h a À Á t Time (s) t F Off-time. Time for which minimum flow (m F ) occurs (s) t N On time. Time for which maximum flow (m N ) occurs (s) T Duty cycle or ratio of on-time to off-time (t N /t F ) u Streamwise velocity (m/s) v Time-averaged velocity of the flow over the crosssection (m/s), normalized voltage V Voltage (V) v F Average velocity over the cross-section, during the state of minimum flow (m/s) v N Average velocity over the cross-section, during the state of maximum flow (m/s) x Streamwise coordinate (m) a Kinematic viscosity of the fluid (m 2 /s) b Womersley para...

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“…However, for the pressure-driven flow, the entire cross section of the channel experiences the pressure-driven force. As noted in our previous work [24], the velocity profile for Newtonian flow behaves plug-like when the ratio of the channel height to the Debye length is larger than about 10. It can also be observed from Fig.…”

Section: Electroosmotic Channel Flowmentioning

confidence: 77%

“…The following discrete lattice Boltzmann evolution equation for the electric potential has been derived by [9,24] g i (r + c i ı t , t + ı t )…”

Section: The Lattice Boltzmann Equation For Electric Potentialmentioning

confidence: 99%