1
|
Tavari T, Nazari M, Meamardoost S, Tamayol A, Samandari M. A systematic overview of electrode configuration in electric‐driven micropumps. Electrophoresis 2022; 43:1476-1520. [DOI: 10.1002/elps.202100317] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Revised: 02/18/2022] [Accepted: 03/22/2022] [Indexed: 11/07/2022]
Affiliation(s)
- Tannaz Tavari
- Department of Mechanical and Mechatronics Engineering Shahrood University of Technology Shahrood Iran
| | - Mohsen Nazari
- Department of Mechanical and Mechatronics Engineering Shahrood University of Technology Shahrood Iran
| | - Saber Meamardoost
- Department of Chemical and Biological Engineering University at Buffalo Buffalo New York USA
| | - Ali Tamayol
- Department of Biomedical Engineering University of Connecticut Health Center Farmington Connecticut USA
| | - Mohamadmahdi Samandari
- Department of Biomedical Engineering University of Connecticut Health Center Farmington Connecticut USA
| |
Collapse
|
2
|
Travelling-Wave Dipolophoresis: Levitation and Electrorotation of Janus Nanoparticles. MICROMACHINES 2021; 12:mi12020114. [PMID: 33499203 PMCID: PMC7910911 DOI: 10.3390/mi12020114] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/22/2020] [Revised: 01/11/2021] [Accepted: 01/14/2021] [Indexed: 11/20/2022]
Abstract
We present a theoretical study of the hydrodynamic and electrokinetic response of both metallic spherical polarized colloids as well as metallodielectic Janus particles, which are subjected to an arbitrary non-uniform ambient electric field (DC or AC forcing). The analysis is based on employing the linearized ‘standard’ model (Poisson–Nernst–Planck formulation) and on the assumptions of a ‘weak’ field and small Debye scale. In particular, we consider cases of linear and helical time-harmonic travelling-wave excitations and provide explicit expressions for the resulting dielectrophoretic and induced-charge electrophoretic forces and moments, exerted on freely suspended particles. The new analytic expressions thus derived for the linear and angular velocities of the initially uncharged polarizable particle are compared against some available solutions. We also analyze the levitation problem (including stability) of metallic and Janus particles placed in a cylindrical (insulating or conducting) pore near a powered electrode.
Collapse
|
3
|
Nagai M, Kato K, Soga S, Santra TS, Shibata T. Scalable Parallel Manipulation of Single Cells Using Micronozzle Array Integrated with Bidirectional Electrokinetic Pumps. MICROMACHINES 2020; 11:mi11040442. [PMID: 32331468 PMCID: PMC7231381 DOI: 10.3390/mi11040442] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/21/2020] [Revised: 04/17/2020] [Accepted: 04/22/2020] [Indexed: 12/27/2022]
Abstract
High throughput reconstruction of in vivo cellular environments allows for efficient investigation of cellular functions. If one-side-open multi-channel microdevices are integrated with micropumps, the devices will achieve higher throughput in the manipulation of single cells while maintaining flexibility and open accessibility. This paper reports on the integration of a polydimethylsiloxane (PDMS) micronozzle array and bidirectional electrokinetic pumps driven by DC-biased AC voltages. Pt/Ti and indium tin oxide (ITO) electrodes were used to study the effect of DC bias and peak-to-peak voltage and electrodes in a low conductivity isotonic solution. The flow was bidirectionally controlled by changing the DC bias. A pump integrated with a micronozzle array was used to transport single HeLa cells into nozzle holes. The application of DC-biased AC voltage (100 kHz, 10 Vpp, and VDC: -4 V) provided a sufficient electroosmotic flow outside the nozzle array. This integration method of nozzle and pumps is anticipated to be a standard integration method. The operating conditions of DC-biased AC electrokinetic pumps in a biological buffer was clarified and found useful for cell manipulation.
Collapse
Affiliation(s)
- Moeto Nagai
- Department of Mechanical Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan; (K.K.); (S.S.); (T.S.)
- Correspondence: ; Tel.: +81-532-44-6701
| | - Keita Kato
- Department of Mechanical Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan; (K.K.); (S.S.); (T.S.)
| | - Satoshi Soga
- Department of Mechanical Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan; (K.K.); (S.S.); (T.S.)
| | - Tuhin Subhra Santra
- Department of Engineering Design, Indian Institute of Technology Madras, Tamil Nadu 600036, India;
| | - Takayuki Shibata
- Department of Mechanical Engineering, Toyohashi University of Technology, Toyohashi, Aichi 441-8580, Japan; (K.K.); (S.S.); (T.S.)
| |
Collapse
|
4
|
Liu W, Ren Y, Tao Y, Yan H, Xiao C, Wu Q. Buoyancy-Free Janus Microcylinders as Mobile Microelectrode Arrays for Continuous Microfluidic Biomolecule Collection within a Wide Frequency Range: A Numerical Simulation Study. MICROMACHINES 2020; 11:mi11030289. [PMID: 32164333 PMCID: PMC7142959 DOI: 10.3390/mi11030289] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/03/2020] [Revised: 02/24/2020] [Accepted: 03/09/2020] [Indexed: 11/16/2022]
Abstract
We numerically study herein the AC electrokinetic motion of Janus mobile microelectrode (ME) arrays in electrolyte solution in a wide field frequency, which holds great potential for biomedical applications. A fully coupled physical model, which incorporates the fluid-structure interaction under the synergy of induced-charge electroosmotic (ICEO) slipping and interfacial Maxwell stress, is developed for this purpose. A freely suspended Janus cylinder free from buoyancy, whose main body is made of polystyrene, while half of the particle surface is coated with a thin conducting film of negligible thickness, will react actively on application of an AC signal. In the low-frequency limit, induced-charge electrophoretic (ICEP) translation occurs due to symmetric breaking in ICEO slipping, which renders the insulating end to move ahead. At higher field frequencies, a brand-new electrokinetic transport phenomenon called "ego-dielectrophoresis (e-DEP)" arises due to the action of the localized uneven field on the inhomogeneous particle dipole moment. In stark contrast with the low-frequency ICEP translation, the high-frequency e-DEP force tends to drive the asymmetric dipole moment to move in the direction of the conducting end. The bidirectional transport feature of Janus microspheres in a wide AC frequency range can be vividly interpreted as an array of ME for continuous loading of secondary bioparticles from the surrounding liquid medium along its direction-controllable path by long-range electroconvection. These results pave the way for achieving flexible and high-throughput on-chip extraction of nanoscale biological contents for subsequent on-site bioassay based upon AC electrokinetics of Janus ME arrays.
Collapse
Affiliation(s)
- Weiyu Liu
- School of Electronics and Control Engineering, Chang’an University, Middle-Section of Nan’er Huan Road, Xi’an 710064, China; (W.L.); (C.X.); (Q.W.)
| | - Yukun Ren
- State Key Laboratory of Robotics and System, Harbin Institute of Technology, West Da-zhi Street 92, Harbin 150001, China;
- Correspondence: (R.Y.); (H.Y.); Tel.: +86-0451-8641-8028 (Y.R.)
| | - Ye Tao
- State Key Laboratory of Robotics and System, Harbin Institute of Technology, West Da-zhi Street 92, Harbin 150001, China;
| | - Hui Yan
- School of Mechatronics Engineering, Harbin Institute of Technology, West Da-zhi Street 92, Harbin 150001, China
- Correspondence: (R.Y.); (H.Y.); Tel.: +86-0451-8641-8028 (Y.R.)
| | - Congda Xiao
- School of Electronics and Control Engineering, Chang’an University, Middle-Section of Nan’er Huan Road, Xi’an 710064, China; (W.L.); (C.X.); (Q.W.)
| | - Qisheng Wu
- School of Electronics and Control Engineering, Chang’an University, Middle-Section of Nan’er Huan Road, Xi’an 710064, China; (W.L.); (C.X.); (Q.W.)
| |
Collapse
|
5
|
Multifrequency Induced-Charge Electroosmosis. MICROMACHINES 2019; 10:mi10070447. [PMID: 31277290 PMCID: PMC6680487 DOI: 10.3390/mi10070447] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 06/27/2019] [Accepted: 07/01/2019] [Indexed: 01/31/2023]
Abstract
We present herein a unique concept of multifrequency induced-charge electroosmosis (MICEO) actuated directly on driving electrode arrays, for highly-efficient simultaneous transport and convective mixing of fluidic samples in microscale ducts. MICEO delicately combines transversal AC electroosmotic vortex flow, and axial traveling-wave electroosmotic pump motion under external dual-Fourier-mode AC electric fields. The synthetic flow field associated with MICEO is mathematically analyzed under thin layer limit, and the particle tracing experiment with a special powering technique validates the effectiveness of this physical phenomenon. Meanwhile, the simulation results with a full-scale 3D computation model demonstrate its robust dual-functionality in inducing fully-automated analyte transport and chaotic stirring in a straight fluidic channel embedding double-sided quarter-phase discrete electrode arrays. Our physical demonstration with multifrequency signal control on nonlinear electroosmosis provides invaluable references for innovative designs of multifunctional on-chip analytical platforms in modern microfluidic systems.
Collapse
|
6
|
Ren Y, Song C, Liu W, Jiang T, Song J, Wu Q, Jiang H. On hybrid electroosmotic kinetics for field-effect-reconfigurable nanoparticle trapping in a four-terminal spiral microelectrode array. Electrophoresis 2018; 40:979-992. [DOI: 10.1002/elps.201800325] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2018] [Revised: 09/09/2018] [Accepted: 09/22/2018] [Indexed: 01/16/2023]
Affiliation(s)
- Yukun Ren
- State Key Laboratory of Robotics and System; Harbin Institute of Technology; Harbin Heilongjiang P. R. China
- The State Key Laboratory of Nonlinear Mechanics (LNM); Institute of Mechanics; Chinese Academy of Sciences; Beijing P. R. China
| | - Chunlei Song
- State Key Laboratory of Robotics and System; Harbin Institute of Technology; Harbin Heilongjiang P. R. China
| | - Weiyu Liu
- School of Electronics and Control Engineering, and School of Highway; Chang'an University; Xi'an Shaanxi P. R. China
| | - Tianyi Jiang
- State Key Laboratory of Robotics and System; Harbin Institute of Technology; Harbin Heilongjiang P. R. China
| | - Jingni Song
- School of Electronics and Control Engineering, and School of Highway; Chang'an University; Xi'an Shaanxi P. R. China
| | - Qisheng Wu
- School of Electronics and Control Engineering, and School of Highway; Chang'an University; Xi'an Shaanxi P. R. China
| | - Hongyuan Jiang
- State Key Laboratory of Robotics and System; Harbin Institute of Technology; Harbin Heilongjiang P. R. China
| |
Collapse
|
7
|
Booth WA, Edwards B, Jo K, Timperman A, Schiffbauer J. Diffusion layer formation drives zone migration in travelling wave electrophoresis. Analyst 2018; 142:1554-1561. [PMID: 28375420 DOI: 10.1039/c6an01268j] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
COMSOL finite element modeling software is used to simulate 2D traveling-wave electrophoresis for microfluidic separations and sample concentration. A four-phase AC potential is applied to a periodic interdigitated four-electrode array to produce a longitudinal electric wave that travels through the channel. Charged particles are carried along with the electric wave or left behind, depending on their mobilities. A simplified model of asymmetric electrode reactions resolves the issue of electric double layer shielding at the electrodes. Selective reactions allow for the formation of diffusion layers of charged particles which follow the traveling electric wave. These diffusion layers determine the transport of charged species through the system. Our model reproduces experimental separations of charged species based on mobility. With easy control over the frequency and direction, one may employ this method for concentrating and/or separating charged particles.
Collapse
|
8
|
Ren Y, Liu W, Tao Y, Hui M, Wu Q. On AC-Field-Induced Nonlinear Electroosmosis next to the Sharp Corner-Field-Singularity of Leaky Dielectric Blocks and Its Application in on-Chip Micro-Mixing. MICROMACHINES 2018; 9:E102. [PMID: 30424036 PMCID: PMC6187378 DOI: 10.3390/mi9030102] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 02/24/2018] [Accepted: 02/24/2018] [Indexed: 11/16/2022]
Abstract
Induced-charge electroosmosis has attracted lots of attention from the microfluidic community over the past decade. Most previous researches on this subject focused on induced-charge electroosmosis (ICEO) vortex streaming actuated on ideally polarizable surfaces immersed in electrolyte solutions. Starting from this point, we conduct herein a linear asymptotic analysis on nonlinear electroosmotic flow next to leaky dielectric blocks of arbitrary electrical conductivity and dielectric permittivity in harmonic AC electric fields, and theoretically demonstrate that observable ICEO fluid motion can be generated at high field frequencies in the vicinity of nearly insulating semiconductors, a very low electrical conductivity, of which can evidently increase the double-layer relaxation frequency (inversely proportional to the solid permittivity) to be much higher than the typical reciprocal RC time constant for induced double-layer charging on ideally polarizable surfaces. A computational model is developed to study the feasibility of this high-frequency vortex flow field of ICEO for sample mixing in microfluidics, in which the usage of AC voltage signal at high field frequencies may be beneficial to suppress electrochemical reactions to some extent. The influence of various parameters for developing an efficient mixer is investigated, and an integrated arrangement of semiconductor block array is suggested for achieving a reliable mixing performance at relatively high sample fluxes. Our physical demonstration with high-frequency ICEO next to leaky dielectric blocks using a simple channel structure offers valuable insights into the design of high-throughput micromixers for a variety of lab-on-a-chip applications.
Collapse
Affiliation(s)
- Yukun Ren
- State Key Laboratory of Robotics and System, Harbin Institute of Technology, West Da-zhi Street 92, Harbin 150001, China.
| | - Weiyu Liu
- School of Electronics and Control Engineering, Chang'an University, Middle-Section of Nan'er Huan Road, Xi'an 710064, China.
| | - Ye Tao
- State Key Laboratory of Robotics and System, Harbin Institute of Technology, West Da-zhi Street 92, Harbin 150001, China.
| | - Meng Hui
- School of Electronics and Control Engineering, Chang'an University, Middle-Section of Nan'er Huan Road, Xi'an 710064, China.
| | - Qisheng Wu
- School of Electronics and Control Engineering, Chang'an University, Middle-Section of Nan'er Huan Road, Xi'an 710064, China.
| |
Collapse
|
9
|
García-Sánchez P, Loucaides NG, Ramos A. Pumping of electrolytes by electrical forces induced on the diffusion layer: A weakly nonlinear analysis. Phys Rev E 2017; 95:022802. [PMID: 28297906 DOI: 10.1103/physreve.95.022802] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Indexed: 06/06/2023]
Abstract
Pumping of electrolytes in microchannels can be achieved with the use of microelectrodes subjected to AC potentials. Experiments have shown an influence of Faradaic currents in the pumping performance, and theoretical studies for asymmetric electrolytes suggest that induced charges in the diffusion layer play an important role. In this work we consider the case of a diffusion layer induced by an array of electrodes subjected to a traveling wave potential and we include Faradaic currents. Previous theoretical studies considered the case of very small applied voltages, which allowed for two major simplifications: (i) Butler-Volmer (B-V) equation was linearized, and (ii) the presence of gradients in ion concentration was neglected. We extend previous results and used the full nonlinear B-V equation. A comparison with the linear limit shows that the flow rate in both cases coincides for voltages around and below ≈0.25 V. For voltages larger than this, the nonlinear equations show that gradients in ion concentration appear and have an important influence, therefore, the predictions deviate from the linear model. We show that the electrical force in the diffusion layer can induce pumping either in the same or the opposite direction of the applied traveling-wave potential and it could be responsible for the reversal of the flow as observed in experiments.
Collapse
Affiliation(s)
- Pablo García-Sánchez
- Depto. Electrónica y Electromagnetismo, Facultad de Física, Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012, Sevilla, Spain
| | - Neophytos G Loucaides
- Depto. Electrónica y Electromagnetismo, Facultad de Física, Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012, Sevilla, Spain
| | - Antonio Ramos
- Depto. Electrónica y Electromagnetismo, Facultad de Física, Universidad de Sevilla, Avda. Reina Mercedes s/n, 41012, Sevilla, Spain
| |
Collapse
|
10
|
Wu X, Ramiah Rajasekaran P, Martin CR. An Alternating Current Electroosmotic Pump Based on Conical Nanopore Membranes. ACS NANO 2016; 10:4637-43. [PMID: 27046145 DOI: 10.1021/acsnano.6b00939] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Electroosmotic flow (EOF) is used to pump solutions through microfluidic devices and capillary electrophoresis columns. We describe here an EOF pump based on membrane EOF rectification, an electrokinetic phenomenon we recently described. EOF rectification requires membranes with asymmetrically shaped pores, and conical pores in a polymeric membrane were used here. We show here that solution flow through the membrane can be achieved by applying a symmetrical sinusoidal voltage waveform across the membrane. This is possible because the alternating current (AC) carried by ions through the pore is rectified, and we previously showed that rectified currents yield EOF rectification. We have investigated the effect of both the magnitude and frequency of the voltage waveform on flow rate through the membrane, and we have measured the maximum operating pressure. Finally, we show that operating in AC mode offers potential advantages relative to conventional DC-mode EOF pumps.
Collapse
Affiliation(s)
- Xiaojian Wu
- Department of Chemistry, University of Florida , Gainesville, Florida 32611-7200, United States
| | | | - Charles R Martin
- Department of Chemistry, University of Florida , Gainesville, Florida 32611-7200, United States
| |
Collapse
|
11
|
Jivani RR, Lakhtaria GJ, Patadiya DD, Patel LD, Jivani NP, Jhala BP. Biomedical microelectromechanical systems (BioMEMS): Revolution in drug delivery and analytical techniques. Saudi Pharm J 2016; 24:1-20. [PMID: 26903763 PMCID: PMC4719786 DOI: 10.1016/j.jsps.2013.12.003] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2013] [Accepted: 12/14/2013] [Indexed: 01/19/2023] Open
Abstract
Advancement in microelectromechanical system has facilitated the microfabrication of polymeric substrates and the development of the novel class of controlled drug delivery devices. These vehicles have specifically tailored three dimensional physical and chemical features which together, provide the capacity to target cell, stimulate unidirectional controlled release of therapeutics and augment permeation across the barriers. Apart from drug delivery devices microfabrication technology’s offer exciting prospects to generate biomimetic gastrointestinal tract models. BioMEMS are capable of analysing biochemical liquid sample like solution of metabolites, macromolecules, proteins, nucleic acid, cells and viruses. This review summarized multidisciplinary application of biomedical microelectromechanical systems in drug delivery and its potential in analytical procedures.
Collapse
Affiliation(s)
- Rishad R Jivani
- Department of Pharmaceutics, C. U. Shah College of Pharmacy & Research, Surendranagar, Wadhwan, Gujarat, India
| | - Gaurang J Lakhtaria
- Department of Pharmaceutics, C. U. Shah College of Pharmacy & Research, Surendranagar, Wadhwan, Gujarat, India
| | - Dhaval D Patadiya
- Department of Pharmaceutics, C. U. Shah College of Pharmacy & Research, Surendranagar, Wadhwan, Gujarat, India
| | - Laxman D Patel
- Department of Pharmaceutics, C. U. Shah College of Pharmacy & Research, Surendranagar, Wadhwan, Gujarat, India
| | - Nurrudin P Jivani
- Department of Pharmaceutics, C. U. Shah College of Pharmacy & Research, Surendranagar, Wadhwan, Gujarat, India
| | - Bhagyesh P Jhala
- Department of Pharmaceutics, C. U. Shah College of Pharmacy & Research, Surendranagar, Wadhwan, Gujarat, India
| |
Collapse
|
12
|
Hrdlička J, Patel NS, Šnita D. Traveling wave electroosmosis: The influence of electrode array geometry. Electrophoresis 2014; 35:1790-4. [DOI: 10.1002/elps.201300614] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 03/14/2014] [Accepted: 03/17/2014] [Indexed: 11/11/2022]
Affiliation(s)
- Jiří Hrdlička
- Department of Chemical Engineering; Institute of Chemical Technology Prague; Prague Czech Republic
| | - Niketan S. Patel
- Department of Chemical Engineering; Institute of Chemical Technology Prague; Prague Czech Republic
| | - Dalimil Šnita
- Department of Chemical Engineering; Institute of Chemical Technology Prague; Prague Czech Republic
| |
Collapse
|
13
|
Lin SC, Lu JC, Sung YL, Lin CT, Tung YC. A low sample volume particle separation device with electrokinetic pumping based on circular travelling-wave electroosmosis. LAB ON A CHIP 2013; 13:3082-3089. [PMID: 23753015 DOI: 10.1039/c3lc50343g] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Particle separation is a crucial step in sample preparation processes. The preparation of low volume samples is especially important for clinical diagnosis and chemical analysis. The advantages of microfluidic techniques have lead them to become potential candidates for particle separation. However, existing microfluidic devices require external pumping sources and extensive geometric patterns to attain high separation efficiency, which is disadvantageous when handling low volume samples. This paper presents a low sample volume particle separation microfluidic device with low voltage electrokinetic pumping based on circular travelling-wave electroosmosis (TWEO). Computational numerical software was utilized to simulate two electrokinetic mechanisms: circular TWEO and dielectrophoresis (DEP). The circular TWEO shear flow generates a velocity gradient in the radial direction which causes a shear stress-induced force to drag particles into the center region of the device. In contrast, the non-parallel electrodes induce negative DEP forces which push polystyrene beads towards the peripheral regions; the magnitude of the DEP forces are dependent on the sizes of the polystyrene beads. We used particles of various sizes to experimentally prove the concept of particle separation. Our experiments show that 15 μm beads are dragged into the center region due to the shear stress-induced force, and 1 μm beads move towards the outer region because of the large negative DEP force. The results show a separation purity of 94.4% and 80.0% for 15 μm and 1 μm beads respectively. We further demonstrated particle isolation from a sample of containing a small proportion of 6 μm beads mixed with 1 μm beads at a concentration ratio of 1 : 300. Therefore, the innovative device developed in this paper provides a promising solution to allow particle separation in sample volumes as low as 50 nL.
Collapse
Affiliation(s)
- Shiang-Chi Lin
- Graduate Institute of Electronics Engineering, National Taiwan University, Taipei 10617, Taiwan
| | | | | | | | | |
Collapse
|
14
|
Williams SJ. Enhanced electrothermal pumping with thin film resistive heaters. Electrophoresis 2013; 34:1400-8. [DOI: 10.1002/elps.201200377] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2012] [Revised: 01/21/2013] [Accepted: 02/06/2013] [Indexed: 11/10/2022]
Affiliation(s)
- Stuart J. Williams
- Department of Mechanical Engineering; University of Louisville; Louisville; KY; USA
| |
Collapse
|
15
|
Ferris RJ, Lin S, Therezien M, Yellen BB, Zauscher S. Electric double layer formed by polarized ferroelectric thin films. ACS APPLIED MATERIALS & INTERFACES 2013; 5:2610-2617. [PMID: 23484485 DOI: 10.1021/am3031954] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Ferroelectric surfaces can have very high surface charge densities that can be harnessed for manipulation of charged colloidal particles and soft matter in aqueous environments. Here, we report on the electrical double layer (EDL) formed by polarized ultrasmooth lead zirconium titanate (US-PZT) thin films in dilute electrolyte solutions. Using colloidal probe force microscopy (CPFM) measurements, we show that the ion distribution within the double layer can be changed by reversing the ferroelectric polarization state of US-PZT. The interaction force in dilute 1:1 electrolyte solution between the negatively charged probe and a positive surface charge (upward polarized) US-PZT thin film is attractive, while the interaction force is repulsive for a negative surface charge (downward polarized) film. We modeled these interactions with a constant-potential EDL model between dissimilar surfaces with the inclusion of a Stern layer. We report the surface potentials at the inner and outer-Helmholtz planes both for polarization states and for a range of ionic strength solutions. Effects of free-charge carriers, limitations of the analytical model, and effects of surface roughness are discussed.
Collapse
Affiliation(s)
- Robert J Ferris
- Department of Mechanical Engineering and Material Science, Duke University, 144 Hudson Hall, Durham, North Carolina 27708, United States
| | | | | | | | | |
Collapse
|
16
|
Hrdlička J, Cervenka P, Přibyl M, Snita D. Zig-zag arrangement of four electrodes for ac electro-osmotic micropumps. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 84:016307. [PMID: 21867304 DOI: 10.1103/physreve.84.016307] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Indexed: 05/31/2023]
Abstract
This paper deals with the mathematical modeling of traveling-wave ac electro-osmotic micropumps with a zig-zag arrangement of microelectrodes. A mathematical model based on the Poisson-Nernst-Planck-Navier-Stokes description is used in this study within the physically relevant ranges of the model parameters. We present an extensive set of parametrical studies concerning the dependence of the net velocity on a variety of parameters. We also demonstrate limits of the validity of the commonly used Capacitor-Resistor-Capacitor model. In order to achieve high net velocities, we found that there are the optimal values of the electrode length, the shift between the top and bottom electrode arrays, and the signal frequency. Performance of the zig-zag micropumps is evaluated by the means of back-pressure loads. The suggested zig-zag design brings two main benefits: (i) it allows an easier construction of four-phase traveling-wave micropumps without the need of spatially complicated electrode connections, and (ii) the zig-zag pumps can provide higher flow rates than those with single-sided coplanar arrangements. Another robust feature of the proposed zig-zag system is that a single flow reversal is observed at the ac frequency approximately six times higher than the reciprocal resistor-capacitor time even in low-amplitude regimes.
Collapse
Affiliation(s)
- J Hrdlička
- Department of Chemical Engineering, Institute of Chemical Technology Prague, Prague, Czech Republic
| | | | | | | |
Collapse
|
17
|
Yeh HC, Yang RJ, Luo WJ. Analysis of traveling-wave electro-osmotic pumping with double-sided electrode arrays. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2011; 83:056326. [PMID: 21728666 DOI: 10.1103/physreve.83.056326] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/07/2010] [Indexed: 05/31/2023]
Abstract
In this paper, a series of numerical simulations was performed to investigate the pumping performance of electro-osmotic micropumps containing electrode arrays patterned on the upper and lower sides of a microchannel. The simulations have been analyzed with a linear electro-osmotic model based upon the Debye-Hückel theory of the double layer. The potential drop across the diffuse layer is assumed to be less than 25 mV (k(B)T/e), and there is a linear response between the surface charge and the voltage drop across the double layer. The double layer is not resolved but is lumped into effective parameters that are imported from the Debye-Hückel and Stern layers. We examined the effects of the relative positioning of the electrodes in the opposing arrays (i.e., symmetrical or staggered), and the phase lag and the angular frequency of the alternating current (ac) signals applied to the electrodes within the two arrays. A critical height of the microchannel was observed, below which the interactions of the applied electrical potentials on the walls became significant. The optimum pumping effect was obtained when the electrode arrays were symmetrical to one another around the centerline of the channel and were activated by ac potentials with a 0° phase shift. The corresponding angular frequency of the maximum pumping velocity for different phase shifts of the applied ac signals was also determined. Overall, the simulation results presented in this paper provide a useful insight into the optimal design parameters and operating conditions for micropumps containing two arrays of microelectrodes on the microchannel walls.
Collapse
Affiliation(s)
- Hung-Chun Yeh
- Department of Engineering Science, National Cheng Kung University, Tainan 701, Taiwan
| | | | | |
Collapse
|
18
|
Dhont JKG, Kang K. Electric-field-induced polarization and interactions of uncharged colloids in salt solutions. THE EUROPEAN PHYSICAL JOURNAL. E, SOFT MATTER 2010; 33:51-68. [PMID: 20924635 DOI: 10.1140/epje/i2010-10656-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/12/2010] [Accepted: 09/14/2010] [Indexed: 05/30/2023]
Abstract
The electric-field-induced charge distribution and potential around a colloidal sphere and rod in salt solutions are analyzed. The resulting field-induced colloid-colloid interactions are calculated for specific orientations. The colloids are assumed to be uncharged (or very weakly charged), such that the deflection of ion fluxes by the cores of the colloids is the dominant polarization mechanism (which is referred to as volume-polarization). Explicit expressions are derived for the frequency-dependent charge distribution and the potential in case of a symmetric electrolyte. It is shown that colloid-colloid interactions due to the induced charge distributions can be much larger than the thermal energy, and are therefore sufficiently strong to give rise to electric-field-induced phase transitions. The present study is a first step towards a quantitative description of field-induced transitions for systems where volume-polarization is the dominant polarization mechanism.
Collapse
Affiliation(s)
- J K G Dhont
- Forschungszentrum Jülich, Institute für Festkörper Forschung (IFF), Weiche Materie, D-52425 Jülich, Germany.
| | | |
Collapse
|
19
|
Højgaard Olesen L, Bazant MZ, Bruus H. Strongly nonlinear dynamics of electrolytes in large ac voltages. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 82:011501. [PMID: 20866619 DOI: 10.1103/physreve.82.011501] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/02/2009] [Revised: 05/12/2010] [Indexed: 05/29/2023]
Abstract
We study the response of a model microelectrochemical cell to a large ac voltage of frequency comparable to the inverse cell relaxation time. To bring out the basic physics, we consider the simplest possible model of a symmetric binary electrolyte confined between parallel-plate blocking electrodes, ignoring any transverse instability or fluid flow. We analyze the resulting one-dimensional problem by matched asymptotic expansions in the limit of thin double layers and extend previous work into the strongly nonlinear regime, which is characterized by two features--significant salt depletion in the electrolyte near the electrodes and, at very large voltage, the breakdown of the quasiequilibrium structure of the double layers. The former leads to the prediction of "ac capacitive desalination" since there is a time-averaged transfer of salt from the bulk to the double layers, via oscillating diffusion layers. The latter is associated with transient diffusion limitation, which drives the formation and collapse of space-charge layers, even in the absence of any net Faradaic current through the cell. We also predict that steric effects of finite ion sizes (going beyond dilute-solution theory) act to suppress the strongly nonlinear regime in the limit of concentrated electrolytes, ionic liquids, and molten salts. Beyond the model problem, our reduced equations for thin double layers, based on uniformly valid matched asymptotic expansions, provide a useful mathematical framework to describe additional nonlinear responses to large ac voltages, such as Faradaic reactions, electro-osmotic instabilities, and induced-charge electrokinetic phenomena.
Collapse
Affiliation(s)
- Laurits Højgaard Olesen
- Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech Building 345 East, DK-2800 Kongens Lyngby, Denmark
| | | | | |
Collapse
|
20
|
|
21
|
González A, Ramos A, García-Sánchez P, Castellanos A. Effect of the combined action of Faradaic currents and mobility differences in ac electro-osmosis. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2010; 81:016320. [PMID: 20365473 DOI: 10.1103/physreve.81.016320] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2009] [Indexed: 05/29/2023]
Abstract
In this work, we extend previous analyses of ac electro-osmosis to account for the combined action of two experimentally relevant effects: (i) Faradaic currents from electrochemical reactions at the electrodes and (ii) differences in ion mobilities of the electrolyte. In previous works, the ac electro-osmotic motion has been analyzed theoretically under the assumption that only forces in the diffuse (Debye) layer are relevant. Here, we first show that if the ion mobilities of a 1-1 aqueous solution are different, the charged zone expands from the Debye layer to include the diffusion layer. We later include the Faradaic currents and, as an attempt to explore both factors simultaneously, we perform a thin-layer, low-frequency, linear analysis of the system. Finally, the model is applied to the case of an electrolyte actuated by a traveling-wave signal. A steady liquid motion in opposite direction to the applied signal is predicted for some ranges of the parameters. This could serve as a partial explanation for the observed flow reversal in some experiments.
Collapse
Affiliation(s)
- A González
- Departamento Física Aplicada III, Universidad de Sevilla, Sevilla, Spain.
| | | | | | | |
Collapse
|
22
|
Towards an understanding of induced-charge electrokinetics at large applied voltages in concentrated solutions. Adv Colloid Interface Sci 2009; 152:48-88. [PMID: 19879552 DOI: 10.1016/j.cis.2009.10.001] [Citation(s) in RCA: 427] [Impact Index Per Article: 28.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 09/29/2009] [Accepted: 10/01/2009] [Indexed: 11/22/2022]
Abstract
The venerable theory of electrokinetic phenomena rests on the hypothesis of a dilute solution of point-like ions in quasi-equilibrium with a weakly charged surface, whose potential relative to the bulk is of order the thermal voltage (kT/e approximately 25 mV at room temperature). In nonlinear electrokinetic phenomena, such as AC or induced-charge electro-osmosis (ACEO, ICEO) and induced-charge electrophoresis (ICEP), several V approximately 100 kT/e are applied to polarizable surfaces in microscopic geometries, and the resulting electric fields and induced surface charges are large enough to violate the assumptions of the classical theory. In this article, we review the experimental and theoretical literatures, highlight discrepancies between theory and experiment, introduce possible modifications of the theory, and analyze their consequences. We argue that, in response to a large applied voltage, the "compact layer" and "shear plane" effectively advance into the liquid, due to the crowding of counterions. Using simple continuum models, we predict two general trends at large voltages: (i) ionic crowding against a blocking surface expands the diffuse double layer and thus decreases its differential capacitance, and (ii) a charge-induced viscosity increase near the surface reduces the electro-osmotic mobility; each trend is enhanced by dielectric saturation. The first effect is able to predict high-frequency flow reversal in ACEO pumps, while the second may explain the decay of ICEO flow with increasing salt concentration. Through several colloidal examples, such as ICEP of an uncharged metal sphere in an asymmetric electrolyte, we show that nonlinear electrokinetic phenomena are generally ion-specific. Similar theoretical issues arise in nanofluidics (due to confinement) and ionic liquids (due to the lack of solvent), so the paper concludes with a general framework of modified electrokinetic equations for finite-sized ions.
Collapse
|
23
|
Mathematical modeling of AC electroosmosis in microfluidic and nanofluidic chips using equilibrium and non-equilibrium approaches. J APPL ELECTROCHEM 2009. [DOI: 10.1007/s10800-009-9966-3] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
|
24
|
Gregersen MM, Andersen MB, Soni G, Meinhart C, Bruus H. Numerical analysis of finite Debye-length effects in induced-charge electro-osmosis. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2009; 79:066316. [PMID: 19658603 DOI: 10.1103/physreve.79.066316] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2009] [Indexed: 05/28/2023]
Abstract
For a microchamber filled with a binary electrolyte and containing a flat unbiased center electrode at one wall, we employ three numerical models to study the strength of the resulting induced-charge electro-osmotic (ICEO) flow rolls: (i) a full nonlinear continuum model resolving the double layer, (ii) a linear slip-velocity model not resolving the double layer and without tangential charge transport inside this layer, and (iii) a nonlinear slip-velocity model extending the linear model by including the tangential charge transport inside the double layer. We show that, compared to the full model, the slip-velocity models significantly overestimate the ICEO flow. This provides a partial explanation of the quantitative discrepancy between observed and calculated ICEO velocities reported in the literature. The discrepancy increases significantly for increasing Debye length relative to the electrode size, i.e., for nanofluidic systems. However, even for electrode dimensions in the micrometer range, the discrepancies in velocity due to the finite Debye length can be more than 10% for an electrode of zero height and more than 100% for electrode heights comparable to the Debye length.
Collapse
Affiliation(s)
- Misha Marie Gregersen
- Department of Micro- and Nanotechnology, Technical University of Denmark, DTU Nanotech, DK-2800 Kongens Lyngby, Denmark
| | | | | | | | | |
Collapse
|
25
|
García-Sánchez P, Ramos A, González A, Green NG, Morgan H. Flow reversal in traveling-wave electrokinetics: an analysis of forces due to ionic concentration gradients. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:4988-97. [PMID: 19320476 DOI: 10.1021/la803651e] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Pumping of electrolytes using ac electric fields from arrays of microelectrodes is a subject of current research. The behavior of fluids at low signal amplitudes (<2-3 V(pp)) is in qualitative agreement with the prediction of the ac electroosmosis theory. At higher voltages, this theory cannot account for the experimental observations. In some cases, net pumping is generated in the direction opposite to that predicted by the theory (flow reversal). In this work, we use fluorescent dyes to study the effect of ionic concentration gradients generated by Faradaic currents. We also evaluate the influence of factors such as the channel height and microelectrode array shape in the pumping of electrolytes with traveling-wave potentials. Induced charge beyond the Debye length is postulated to be responsible for the forces generating the observed flows at higher voltages. Numerical calculations are performed in order to illustrate the mechanisms that might be responsible for generating the flow.
Collapse
Affiliation(s)
- P García-Sánchez
- Departamento de Electronica y Electromagnetismo, Facultad de Fisica, Universidad de Sevilla, 41012, Seville, Spain.
| | | | | | | | | |
Collapse
|
26
|
Wang X, Cheng C, Wang S, Liu S. Electroosmotic pumps and their applications in microfluidic systems. MICROFLUIDICS AND NANOFLUIDICS 2009; 6:145. [PMID: 20126306 PMCID: PMC2756694 DOI: 10.1007/s10404-008-0399-9] [Citation(s) in RCA: 152] [Impact Index Per Article: 10.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Electroosmotic pumping is receiving increasing attention in recent years owing to the rapid development in micro total analytical systems. Compared with other micropumps, electroosmotic pumps (EOPs) offer a number of advantages such as creation of constant pulse-free flows and elimination of moving parts. The flow rates and pumping pressures of EOPs matches well with micro analysis systems. The common materials and fabrication technologies make it readily integrateable with lab-on-a-chip devices. This paper reviews the recent progress on EOP fabrications and applications in order to promote the awareness of EOPs to researchers interested in using micro- and nano-fluidic devices. The pros and cons of EOPs are also discussed, which helps these researchers in designing and constructing their micro platforms.
Collapse
Affiliation(s)
- Xiayan Wang
- Department of Chemistry and Biochemistry, The University of Oklahoma, Norman, OK 73019, USA
| | | | | | | |
Collapse
|
27
|
García-Sánchez P, Ramos A, Green NG, Morgan H. Traveling-wave electrokinetic micropumps: velocity, electrical current, and impedance measurements. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:9361-9. [PMID: 18672919 DOI: 10.1021/la800423k] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
An array of microelectrodes covered in an electrolyte and energized by a traveling-wave potential produces net movement of the fluid. Arrays of platinum microelectrodes of two different characteristic sizes have been studied. For both sizes of arrays, at low voltages (<2 V pp) the electrolyte flow is in qualitative agreement with the linear theory of ac electroosmosis. At voltages above a threshold, the direction of fluid flow is reversed. The electrical impedance of the electrode-electrolyte system was measured after the experiments, and changes in the electrical properties of the electrolyte were observed. Measurements of the electrical current during pumping of the electrolyte are also reported. Transient behaviors in both electrical current and fluid velocity were observed. The Faradaic currents probably generate conductivity gradients in the liquid bulk, which in turn give rise to electrical forces. These effects are discussed in relation to the fluid flow observations.
Collapse
Affiliation(s)
- P García-Sánchez
- Departamento de Electrónica y Electromagnetismo, Facultad de Física, Universidad de Sevilla, 41012 Sevilla, Spain.
| | | | | | | |
Collapse
|
28
|
Storey BD, Edwards LR, Kilic MS, Bazant MZ. Steric effects on ac electro-osmosis in dilute electrolytes. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2008; 77:036317. [PMID: 18517521 DOI: 10.1103/physreve.77.036317] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2007] [Revised: 02/04/2008] [Indexed: 05/07/2023]
Abstract
The current theory of alternating-current electro-osmosis (ACEO) is unable to explain the experimentally observed flow reversal of planar ACEO pumps at high frequency (above the peak, typically 10-100 kHz), low salt concentration (1-1000 microM) , and moderate voltage (2-6 V), even taking into account Faradaic surface reactions, nonlinear double-layer capacitance, and bulk electrothermal flows. We attribute this failure to the breakdown of the classical Poisson-Boltzmann model of the diffuse double layer, which assumes a dilute solution of pointlike ions. In spite of low bulk salt concentration, the large voltage induced across the double layer leads to crowding of the ions and a related decrease in surface capacitance. Using several mean-field models for finite-sized ions, we show that steric effects generally lead to high-frequency flow reversal of ACEO pumps, similar to experiments. For quantitative agreement, however, an unrealistically large effective ion size (several nanometers) must be used, which we attribute to neglected correlation effects.
Collapse
Affiliation(s)
- Brian D Storey
- Franklin W Olin College of Engineering, Needham, MA 02492, USA
| | | | | | | |
Collapse
|
29
|
Gregersen MM, Olesen LH, Brask A, Hansen MF, Bruus H. Flow reversal at low voltage and low frequency in a microfabricated ac electrokinetic pump. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2007; 76:056305. [PMID: 18233754 DOI: 10.1103/physreve.76.056305] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/30/2007] [Indexed: 05/07/2023]
Abstract
Microfluidic chips have been fabricated in Pyrex glass to study electrokinetic pumping generated by a low-voltage ac bias applied to an in-channel asymmetric metallic electrode array. A measurement procedure has been established and followed carefully resulting in a high degree of reproducibility of the measurements over several days. A large coverage fraction of the electrode array in the microfluidic channels has led to an increased sensitivity allowing for pumping measurements at low bias voltages. Depending on the ionic concentration a hitherto unobserved reversal of the pumping direction has been measured in a regime, where both the applied voltage and the frequency are low, V(rms)<1.5 V and f<20 kHz , compared to previously investigated parameter ranges. The impedance spectrum has been thoroughly measured and analyzed in terms of an equivalent circuit diagram to rule out trivial circuit explanations of our findings. Our observations agree qualitatively, but not quantitatively, with theoretical electrokinetic models published in the literature.
Collapse
Affiliation(s)
- Misha Marie Gregersen
- MIC-Department of Micro and Nanotechnology, Technical University of Denmark, DTU Building 345 East, DK-2800 Kongens Lyngby, Denmark
| | | | | | | | | |
Collapse
|
30
|
Abstract
We study theoretically the effects of secondary (transverse) flows on the Taylor-Aris dispersion of pressure-driven, open column flow in a conduit with a rectangular cross section and account for the interaction of solutes with the retentive coating on the conduit's surface. A few plausible means of inducing secondary flows (that are independent of the primary, pressure-driven, axial flow) are described. The Taylor-Aris dispersion coefficient is computed as a function of the secondary flow's pattern and intensity. By inducing secondary flows, one can significantly reduce dispersion.
Collapse
Affiliation(s)
- Hui Zhao
- Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia, Pennsylvania 19104-6315, USA
| | | |
Collapse
|
31
|
Ramos A, González A, García-Sánchez P, Castellanos A. A linear analysis of the effect of Faradaic currents on traveling-wave electroosmosis. J Colloid Interface Sci 2007; 309:323-31. [PMID: 17346725 DOI: 10.1016/j.jcis.2007.01.076] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2006] [Revised: 01/18/2007] [Accepted: 01/20/2007] [Indexed: 11/17/2022]
Abstract
Net fluid flow of electrolytic solutions induced by a traveling-wave potential applied to an array of co-planar interdigitated microelectrodes has been reported. At low applied voltages the flow is driven in the direction of the traveling-wave potential, as expected by linear and weakly nonlinear theoretical studies. The flow is driven at the surfaces of the electrodes by electrical forces acting in the diffuse electrical double layer. The pumping mechanism has been analyzed theoretically under the assumption of perfectly polarizable electrodes. Here we extend these studies to include the effect of Faradaic currents on the electroosmotic slip velocity generated at the electrode/electrolyte interface. We integrate the electrokinetic equations under the thin-double-layer and low-potential approximations. Finally, we analyze the pumping of electrolyte induced by a traveling-wave signal applied to a microelectrode array using this linear model.
Collapse
Affiliation(s)
- Antonio Ramos
- Departamento Electrónica y Electromagnetismo, Facultad de Física, Universidad de Sevilla, Avenida Reina Mercedes s/n, 41012 Seville, Spain.
| | | | | | | |
Collapse
|
32
|
Urbanski JP, Levitan JA, Burch DN, Thorsen T, Bazant MZ. The effect of step height on the performance of three-dimensional ac electro-osmotic microfluidic pumps. J Colloid Interface Sci 2007; 309:332-41. [PMID: 17346735 DOI: 10.1016/j.jcis.2007.01.095] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2006] [Revised: 01/21/2007] [Accepted: 01/26/2007] [Indexed: 10/23/2022]
Abstract
Recent numerical and experimental studies have investigated the increase in efficiency of microfluidic ac electro-osmotic pumps by introducing nonplanar geometries with raised steps on the electrodes. In this study, we analyze the effect of the step height on ac electro-osmotic pump performance. AC electro-osmotic pumps with three-dimensional electroplated steps are fabricated on glass substrates and pumping velocities of low ionic strength electrolyte solutions are measured systematically using a custom microfluidic device. Numerical simulations predict an improvement in pump performance with increasing step height, at a given frequency and voltage, up to an optimal step height, which qualitatively matches the trend observed in experiment. For a broad range of step heights near the optimum, the observed flow is much faster than with existing planar pumps (at the same voltage and minimum feature size) and in the theoretically predicted direction of the "fluid conveyor belt" mechanism. For small step heights, the experiments also exhibit significant flow reversal at the optimal frequency, which cannot be explained by the theory, although the simulations predict weak flow reversal at higher frequencies due to incomplete charging. These results provide insight to an important parameter for the design of nonplanar electro-osmotic pumps and clues to improve the fundamental theory of ACEO.
Collapse
Affiliation(s)
- John Paul Urbanski
- Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
| | | | | | | | | |
Collapse
|
33
|
Bazant MZ, Ben Y. Theoretical prediction of fast 3D AC electro-osmotic pumps. LAB ON A CHIP 2006; 6:1455-61. [PMID: 17066170 DOI: 10.1039/b608092h] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
AC electro-osmotic (ACEO) pumps in microfluidics currently involve planar electrode arrays, but recent work on the underlying phenomenon of induced-charge electro-osmosis (ICEO) suggests that three-dimensional (3D) geometries may be exploited to achieve faster flows. In this paper, we present some new design principles for periodic 3D ACEO pumps, such as the "fluid conveyor belt" of ICEO flow over a stepped electrode array. Numerical simulations of these designs (using the standard low-voltage model) predict flow rates almost twenty times faster than existing planar ACEO pumps, for the same applied voltage and minimum feature size. These pumps may enable new portable or implantable lab-on-a-chip devices, since rather fast (mm s(-1)), tuneable flows should be attainable with battery voltages (<10 V).
Collapse
Affiliation(s)
- Martin Z Bazant
- Institute of Soldier Nanotechnologies and Department of Mathematics, Massachusetts Institute of Technology, Cambridge, MA 02139-4307, USA.
| | | |
Collapse
|
34
|
Olesen LH, Bruus H, Ajdari A. ac electrokinetic micropumps: the effect of geometrical confinement, Faradaic current injection, and nonlinear surface capacitance. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2006; 73:056313. [PMID: 16803043 DOI: 10.1103/physreve.73.056313] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/09/2005] [Indexed: 05/10/2023]
Abstract
Recent experiments have demonstrated that ac electrokinetic micropumps permit integrable, local, and fast pumping (velocities approximately mm/s) with low driving voltage of a few volts only. However, they also displayed many quantitative and qualitative discrepancies with existing theories. We therefore extend the latter theories to account for three experimentally relevant effects: (i) vertical confinement of the pumping channel, (ii) Faradaic currents from electrochemical reactions at the electrodes, and (iii) nonlinear surface capacitance of the Debye layer. We report here that these effects indeed affect the pump performance in a way that we can rationalize by physical arguments.
Collapse
Affiliation(s)
- Laurits Højgaard Olesen
- MIC, Department of Micro and Nanotechnology, Technical University of Denmark, Kongens Lyngby
| | | | | |
Collapse
|
35
|
Mortensen NA, Olesen LH, Belmon L, Bruus H. Electrohydrodynamics of binary electrolytes driven by modulated surface potentials. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2005; 71:056306. [PMID: 16089648 DOI: 10.1103/physreve.71.056306] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2004] [Revised: 12/14/2004] [Indexed: 05/03/2023]
Abstract
We study the electrohydrodynamics of the Debye screening layer that arises in an aqueous binary solution near a planar insulating wall when applying a spatially modulated ac voltage. Combining this with first order perturbation theory we establish the governing equations for the full nonequilibrium problem and obtain analytic solutions in the bulk for the pressure and velocity fields of the electrolyte and for the electric potential. We find good agreement between the numerics of the full problem and the analytics of the linear theory. Our work provides the theoretical foundations of circuit models discussed in the literature. The nonequilibrium approach also reveals unexpected high-frequency dynamics not predicted by circuit models.
Collapse
Affiliation(s)
- Niels Asger Mortensen
- MIC-Department of Micro and Nanotechnology, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark
| | | | | | | |
Collapse
|