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Tahmasebi A, Habibi S, Collins JL, An R, Dehdashti E, Minerick AR. pH Gradients in Spatially Non-Uniform AC Electric Fields around the Charging Frequency; A Study of Two Different Geometries and Electrode Passivation. MICROMACHINES 2023; 14:1655. [PMID: 37763818 PMCID: PMC10534923 DOI: 10.3390/mi14091655] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2023] [Revised: 08/15/2023] [Accepted: 08/16/2023] [Indexed: 09/29/2023]
Abstract
Dielectrophoresis (DEP), a precision nonlinear electrokinetic tool utilized within microfluidic devices, can induce bioparticle polarization that manifests as motion in the electric field; this phenomenon has been leveraged for phenotypic cellular and biomolecular detection, making DEP invaluable for diagnostic applications. As device operation times lengthen, reproducibility and precision decrease, which has been postulated to be caused by ion gradients within the supporting electrolyte medium. This research focuses on characterizing pH gradients above, at, and below the electrode charging frequency (0.2-1.4 times charging frequency) in an aqueous electrolyte solution in order to extend the parameter space for which microdevice-imposed artifacts on cells in clinical diagnostic devices have been characterized. The nonlinear alternating current (AC) electric fields (0.07 Vpp/μm) required for DEP were generated via planar T-shaped and star-shaped microelectrodes overlaid by a 70 μm high microfluidic chamber. The experiments were designed to quantify pH changes temporally and spatially in the two microelectrode geometries. In parallel, a 50 nm hafnium oxide (HfO2) thin film on the microelectrodes was tested to provide insights into the role of Faradaic surface reactions on the pH. Electric field simulations were conducted to provide insights into the gradient shape within the microelectrode geometries. Frequency dependence was also examined to ascertain ion electromigration effects above, at, and below the electrode charging frequency. The results revealed Faradaic reactions above, at, and below the electrode charging frequency. Comparison experiments further demonstrated that pH changes caused by Faradaic reactions increased inversely with frequency and were more pronounced in the star-shaped geometry. Finally, HfO2 films demonstrated frequency-dependent properties, impeding Faradaic reactions.
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Affiliation(s)
- Azade Tahmasebi
- Department of Chemical Engineering, Michigan Technological University, Houghton, MI 49931, USA
| | - Sanaz Habibi
- Department of Chemical Engineering, University of Michigan, Ann Arbor, MI 48109, USA
| | - Jeana L Collins
- Department of Chemical Engineering, Michigan Technological University, Houghton, MI 49931, USA
| | - Ran An
- Department of Chemical Engineering, University of Houston, Houston, TX 77204, USA
| | - Esmaeil Dehdashti
- Department of Chemical Engineering, Michigan Technological University, Houghton, MI 49931, USA
| | - Adrienne Robyn Minerick
- Department of Chemical Engineering, Michigan Technological University, Houghton, MI 49931, USA
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2
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Wang K, Leville S, Behdani B, Silvera Batista CA. Long-range transport and directed assembly of charged colloids under aperiodic electrodiffusiophoresis. SOFT MATTER 2022; 18:5949-5959. [PMID: 35920440 DOI: 10.1039/d2sm00631f] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Faradaic reactions often lead to undesirable side effects during the application of electric fields. Therefore, experimental designs often avoid faradaic reactions by working at low voltages or at high frequencies, where the electrodes behave as ideally polarizable. In this work, we show how faradaic processes under ac fields can be used advantageously to effect long-range transport, focusing and assembly of charged colloids. Herein, we use confocal microscopy and ratiometric analysis to confirm that ac fields applied in media of low conductivity induce significant pH gradients below and above the electrode charging frequency of the system. At voltages above 1 Vpp, and frequencies below 1.7 kHz, the pH profile becomes highly nonlinear. Charged particles respond to such conditions by migrating towards the point of highest pH, thereby focusing tens of microns away from both electrodes. Under the combination of oscillating electric fields and concentration gradients of electroactive species, particles experience aperiodic electrodiffusiophoresis (EDP). The theory of EDP, along with a mass transport model, describes the dynamics of particles. Furthermore, the high local concentration of particles near the focusing point leads to disorder-order transitions, whereby particles form crystals. The position and order within the levitating crystalline sheet can be readily tuned by adjusting the voltage and frequency. These results not only have significant implications for the fundamental understanding of ac colloidal electrokinetics, but also provide new possibilities for the manipulation and directed assembly of charged colloids.
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Affiliation(s)
- Kun Wang
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, USA.
| | - Samuel Leville
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, USA.
| | - Behrouz Behdani
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, USA.
| | - Carlos A Silvera Batista
- Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, TN, USA.
- Vanderbilt Institute for Nanoscale Science and Engineering, Vanderbilt University, Nashville, TN, USA
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3
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Habibi S, Lee HY, Moncada-Hernandez H, Minerick AR. Induction and suppression of cell lysis in an electrokinetic microfluidic system. Electrophoresis 2022; 43:1322-1336. [PMID: 35306692 DOI: 10.1002/elps.202100310] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2021] [Revised: 12/23/2021] [Accepted: 01/24/2022] [Indexed: 01/26/2023]
Abstract
The ability to strategically induce or suppress cell lysis is critical for many cellular-level diagnostic and therapeutic applications conducted within electrokinetic microfluidic platforms. The chemical and structural integrity of sub-cellular components is important when inducing cell lysis. However, metal electrodes and electrolytes participate in undesirable electrochemical reactions that alter solution composition and potentially damage protein, RNA, and DNA integrity within device microenvironments. For many biomedical applications, cell viability must be maintained even when device-imposed cell-stressing stimuli (e.g., electrochemical reaction byproducts) are present. In this work, we explored a novel and tunable method to accurately induce or suppress device-imposed artifacts on human red blood cell (RBC) lysis in non-uniform AC electric fields. For precise tunability, a dielectric hafnium oxide (HfO2 ) layer was used to prevent electron transfer between the electrodes and the electric double layer and thus reduce harmful electrochemical reactions. Additionally, a low concentration of Triton X-100 surfactant was explored as a tool to stabilize cell membrane integrity. The extent of hemolysis was studied as a function of time, electrode configuration (T-shaped and star-shaped), cell position, applied non-uniform AC electric field, with uncoated and HfO2 coated electrodes (50 nm), and absence and presence of Triton X-100 (70 µM). Tangible outcomes include a parametric analysis relying upon literature and this work to design, tune, and operate electrokinetic microdevices to intentionally induce or suppress cellular lysis without altering intracellular components. Implications are that devices can be engineered to leverage or minimize device-imposed biological artefacts extending the versatility and utility of electrokinetic diagnostics.
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Affiliation(s)
- Sanaz Habibi
- Department of Chemical Engineering, Michigan Technological University, Houghton, Michigan, USA
| | - Hwi Yong Lee
- Department of Chemical Engineering, Michigan Technological University, Houghton, Michigan, USA
| | | | - Adrienne R Minerick
- Department of Chemical Engineering, Michigan Technological University, Houghton, Michigan, USA
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4
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Shen C, Jiang Z, Li L, Gilchrist JF, Ou-Yang HD. Frequency Response of Induced-Charge Electrophoretic Metallic Janus Particles. MICROMACHINES 2020; 11:mi11030334. [PMID: 32213879 PMCID: PMC7142510 DOI: 10.3390/mi11030334] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/15/2020] [Revised: 03/19/2020] [Accepted: 03/21/2020] [Indexed: 12/23/2022]
Abstract
The ability to manipulate and control active microparticles is essential for designing microrobots for applications. This paper describes the use of electric and magnetic fields to control the direction and speed of induced-charge electrophoresis (ICEP) driven metallic Janus microrobots. A direct current (DC) magnetic field applied in the direction perpendicular to the electric field maintains the linear movement of particles in a 2D plane. Phoretic force spectroscopy (PFS), a phase-sensitive detection method to detect the motions of phoretic particles, is used to characterize the frequency-dependent phoretic mobility and drag coefficient of the phoretic force. When the electric field is scanned over a frequency range of 1 kHz-1 MHz, the Janus particles exhibit an ICEP direction reversal at a crossover frequency at ~30 kH., Below this crossover frequency, the particle moves in a direction towards the dielectric side of the particle, and above this frequency, the particle moves towards the metallic side. The ICEP phoretic drag coefficient measured by PFS is found to be similar to that of the Stokes drag. Further investigation is required to study microscopic interpretations of the frequency at which ICEP mobility switched signs and the reason why the magnitudes of the forward and reversed modes of ICEP are so different.
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Affiliation(s)
- Chong Shen
- Department of Physics, Lehigh University, Bethlehem, PA 18015, USA; (C.S.); (Z.J.); (L.L.)
- Emulsion Polymers Institute, Lehigh University, Bethlehem, PA 18015, USA
| | - Zhiyu Jiang
- Department of Physics, Lehigh University, Bethlehem, PA 18015, USA; (C.S.); (Z.J.); (L.L.)
- Emulsion Polymers Institute, Lehigh University, Bethlehem, PA 18015, USA
| | - Lanfang Li
- Department of Physics, Lehigh University, Bethlehem, PA 18015, USA; (C.S.); (Z.J.); (L.L.)
- Emulsion Polymers Institute, Lehigh University, Bethlehem, PA 18015, USA
| | - James F. Gilchrist
- Department of Chemical & Biomolecular Engineering, Lehigh University, Bethlehem, PA 18015, USA;
| | - H. Daniel Ou-Yang
- Department of Physics, Lehigh University, Bethlehem, PA 18015, USA; (C.S.); (Z.J.); (L.L.)
- Emulsion Polymers Institute, Lehigh University, Bethlehem, PA 18015, USA
- Department of Bioengineering, Lehigh University, Bethlehem, PA 18015, USA
- Correspondence:
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5
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S Iliescu F, Sim WJ, Heidari H, P Poenar D, Miao J, Taylor HK, Iliescu C. Highlighting the uniqueness in dielectrophoretic enrichment of circulating tumor cells. Electrophoresis 2019; 40:1457-1477. [PMID: 30676660 DOI: 10.1002/elps.201800446] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2018] [Revised: 01/19/2019] [Accepted: 01/20/2019] [Indexed: 12/14/2022]
Abstract
Circulating tumor cells (CTCs) play an essential role in the metastasis of tumors, and thus can serve as a valuable prognostic factor for malignant diseases. As a result, the ability to isolate and characterize CTCs is essential. This review underlines the potential of dielectrophoresis for CTCs enrichment. It begins by summarizing the key performance parameters and challenges of CTCs isolation using microfluidics. The two main categories of CTCs enrichment-affinity-based and label-free methods-are analysed, emphasising the advantages and disadvantages of each as well as their clinical potential. While the main argument in favour of affinity-based methods is the strong specificity of CTCs isolation, the major advantage of the label-free technologies is in preserving the integrity of the cellular membrane, an essential requirement for downstream characterization. Moving forward, we try to answer the main question: "What makes dielectrophoresis a method of choice in CTCs isolation?" The uniqueness of dielectrophoretic CTCs enrichment resides in coupling the specificity of the isolation process with the conservation of the membrane surface. The specificity of the dielectrophoretic method stems from the differences in the dielectric properties between CTCs and other cells in the blood: the capacitances of the malignantly transformed cellular membranes of CTCs differ from those of other cells. Examples of dielectrophoretic devices are described and their performance evaluated. Critical requirements for using dielectrophoresis to isolate CTCs are highlighted. Finally, we consider that DEP has the potential of becoming a cytometric method for large-scale sorting and characterization of cells.
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Affiliation(s)
| | - Wen Jing Sim
- Department of Biochemistry, Yong Loo Lin School of Medicine, National University of Singapore, Singapore.,NUS Synthetic Biology for Clinical and Technological Innovation (SynCTI), National University of Singapore, Singapore
| | - Hossein Heidari
- Department of Mechanical Engineering, University of California, Berkeley, CA, USA
| | - Daniel P Poenar
- VALENS-Centre for Bio Devices and Signal Analysis, Nanyang Technological University, Singapore
| | - Jianmin Miao
- School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore
| | - Hayden K Taylor
- Department of Mechanical Engineering, University of California, Berkeley, CA, USA
| | - Ciprian Iliescu
- Biomedical Institute for Global Health Research & Technology (BIGHEART), National University of Singapore, Singapore
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6
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Abstract
Electroosmotic flow (EOF) or electro-osmosis has been shown to exhibit a hysteresis effect under displacement flow involving two solutions with different concentrations, i.e. the flow velocity for a high-concentration solution displacing a low-concentration solution is faster than the flow velocity in the reverse direction involving the same solution pair. On the basis of our recent numerical analysis, a pH change initiated at the interface between the two solutions has been hypothesized as the cause for the observed anomalies. We report the first experimental evidence of EOF hysteresis induced by a pH change in the bulk solution. pH-sensitive dye was employed to quantify the pH changes in the microchannel during EOF. The electric-field gradient across the boundary of two solutions generates an accumulation or depletion of a minority of pH-governing ions such as hydronium (H3O+) ions, thus inducing pH variations across the microchannel. When a high-concentration solution displaced a lower-concentration solution, a pH increase was observed, while the flow in the reverse direction induced a decrease in pH. This effect causes significant changes to the zeta potential and flow velocity. The experimental results show good quantitative agreement with numerical simulations. This work presents the experimental proof which validates the hypothesis of a pH change during electroomostic flow hysteresis as predicted by numerical analysis. The understanding of pH changes during EOF is crucial for accurate flow manipulation in microfluidic devices and maintenance of constant pH in biological and chemical systems under an electric field.
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Affiliation(s)
- Chun Yee Lim
- School of Mechanical and Aerospace Engineering, Nanyang Technological University , 50 Nanyang Avenue, Singapore 639798
| | - An Eng Lim
- School of Mechanical and Aerospace Engineering, Nanyang Technological University , 50 Nanyang Avenue, Singapore 639798
| | - Yee Cheong Lam
- School of Mechanical and Aerospace Engineering, Nanyang Technological University , 50 Nanyang Avenue, Singapore 639798
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7
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Wu Y, Ren Y, Tao Y, Hou L, Hu Q, Jiang H. A novel micromixer based on the alternating current-flow field effect transistor. LAB ON A CHIP 2016; 17:186-197. [PMID: 27934980 DOI: 10.1039/c6lc01346e] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Induced-charge electroosmosis (ICEO) phenomena have been attracting considerable attention as a means for pumping and mixing in microfluidic systems with the advantage of simple structures and low-energy consumption. We propose the first effort to exploit a fixed-potential ICEO flow around a floating electrode for microfluidic mixing. In analogy with the field effect transistor (FET) in microelectronics, the floating electrode act as a "gate" electrode for generating asymmetric ICEO flow and thus the device is called an AC-flow FET (AC-FFET). We take advantage of a tandem electrode configuration containing two biased center metal strips arranged in sequence at the bottom of the channel to generate asymmetric vortexes. The current device is manufactured on low-cost glass substrates via an easy and reliable process. Mixing experiments were conducted in the proposed device and the comparison between simulation and experimental results was also carried out, which indicates that the micromixer permits an efficient mixing effect. The mixing performance can be further enhanced by the application of a suitable phase difference between the driving electrode and the gate electrode or a square wave signal. Finally, we performed a critical analysis of the proposed micromixer in comparison with different mixer designs using a comparative mixing index (CMI). The novel methods put forward here offer a simple solution to mixing issues in microfluidic systems.
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Affiliation(s)
- Yupan Wu
- School of Mechatronics Engineering, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, 150001 PR China.
| | - Yukun Ren
- School of Mechatronics Engineering, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, 150001 PR China. and State Key Laboratory of Robotics and System, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, 150001 PR China
| | - Ye Tao
- School of Mechatronics Engineering, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, 150001 PR China.
| | - Likai Hou
- School of Mechatronics Engineering, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, 150001 PR China.
| | - Qingming Hu
- School of Mechatronics Engineering, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, 150001 PR China.
| | - Hongyuan Jiang
- School of Mechatronics Engineering, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, 150001 PR China. and State Key Laboratory of Robotics and System, Harbin Institute of Technology, West Da-zhi Street 92, Harbin, Heilongjiang, 150001 PR China
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8
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Boymelgreen A, Yossifon G, Miloh T. Propulsion of Active Colloids by Self-Induced Field Gradients. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:9540-7. [PMID: 27611819 DOI: 10.1021/acs.langmuir.6b01758] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
Previously, metallodielectric Janus particles have been shown to travel with their dielectric hemisphere forward under low frequency applied electric fields as a result of asymmetric induced-charge electroosmotic flow. Here, it is demonstrated that at high frequencies, well beyond the charge relaxation time of the electric double layer induced around the particle, rather than the velocity decaying to zero, the Janus particles reverse direction, traveling with their metallic hemisphere forward. It is proposed that such motion is the result of a surface force, arising from localized nonuniform electric field gradients, induced by the dual symmetry-breaking of an asymmetric particle adjacent to a wall, which act on the induced dipole of the particle to drive net motion even in a uniform AC field. Although the field is external, since the driving gradient is induced on the particle level, it may be considered an active colloid. We have thus termed this propulsion mechanism "self-dielectrophoresis", to distinguish from traditional dielectrophoresis where the driving nonuniform field is externally fixed and the particle direction is restricted. It is demonstrated theoretically and experimentally that the critical frequency at which the particle reverses direction can be characterized by a nondimensional parameter which is a function of electrolyte concentration and particle size.
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Affiliation(s)
- Alicia Boymelgreen
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion - Israel Institute of Technology , Haifa 32000, Israel
| | - Gilad Yossifon
- Faculty of Mechanical Engineering, Micro- and Nanofluidics Laboratory, Technion - Israel Institute of Technology , Haifa 32000, Israel
| | - Touvia Miloh
- School of Mechanical Engineering, University of Tel-Aviv , Tel-Aviv 69978, Israel
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9
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Park S, Yossifon G. Induced-charge electrokinetics, bipolar current, and concentration polarization in a microchannel-Nafion-membrane system. Phys Rev E 2016; 93:062614. [PMID: 27415327 DOI: 10.1103/physreve.93.062614] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/30/2014] [Indexed: 06/06/2023]
Abstract
The presence of a floating electrode array located within the depletion layer formed due to concentration polarization across a microchannel-membrane interface device may produce not only induced-charge electro-osmosis (ICEO) but also bipolar current resulting from the induced Faradaic reaction. It has been shown that there exists an optimal thickness of a thin dielectric coating that is sufficient to suppress bipolar currents but still enables ICEO vortices that stir the depletion layer, thereby affecting the system's current-voltage response. In addition, the use of alternating-current electro-osmosis by activating electrodes results in further enhancement of the fluid stirring and opens new routes for on-demand spatiotemporal control of the depletion layer length.
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Affiliation(s)
- Sinwook Park
- Micro- and Nanofluidics Laboratory, Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, Technion City 32000, Israel
| | - Gilad Yossifon
- Micro- and Nanofluidics Laboratory, Faculty of Mechanical Engineering, Technion-Israel Institute of Technology, Technion City 32000, Israel
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10
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An R, Massa K, Wipf DO, Minerick AR. Solution pH change in non-uniform alternating current electric fields at frequencies above the electrode charging frequency. BIOMICROFLUIDICS 2014; 8:064126. [PMID: 25553200 PMCID: PMC4272385 DOI: 10.1063/1.4904059] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/29/2014] [Accepted: 12/02/2014] [Indexed: 05/23/2023]
Abstract
AC Faradaic reactions have been reported as a mechanism inducing non-ideal phenomena such as flow reversal and cell deformation in electrokinetic microfluidic systems. Prior published work described experiments in parallel electrode arrays below the electrode charging frequency (fc ), the frequency for electrical double layer charging at the electrode. However, 2D spatially non-uniform AC electric fields are required for applications such as in plane AC electroosmosis, AC electrothermal pumps, and dielectrophoresis. Many microscale experimental applications utilize AC frequencies around or above fc . In this work, a pH sensitive fluorescein sodium salt dye was used to detect [H(+)] as an indicator of Faradaic reactions in aqueous solutions within non-uniform AC electric fields. Comparison experiments with (a) parallel (2D uniform fields) electrodes and (b) organic media were employed to deduce the electrode charging mechanism at 5 kHz (1.5fc ). Time dependency analysis illustrated that Faradaic reactions exist above the theoretically predicted electrode charging frequency. Spatial analysis showed [H(+)] varied spatially due to electric field non-uniformities and local pH changed at length scales greater than 50 μm away from the electrode surface. Thus, non-uniform AC fields yielded spatially varied pH gradients as a direct consequence of ion path length differences while uniform fields did not yield pH gradients; the latter is consistent with prior published data. Frequency dependence was examined from 5 kHz to 12 kHz at 5.5 Vpp potential, and voltage dependency was explored from 3.5 to 7.5 Vpp at 5 kHz. Results suggest that Faradaic reactions can still proceed within electrochemical systems in the absence of well-established electrical double layers. This work also illustrates that in microfluidic systems, spatial medium variations must be considered as a function of experiment time, initial medium conditions, electric signal potential, frequency, and spatial position.
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Affiliation(s)
- Ran An
- Department of Chemical Engineering, Michigan Technological University , Houghton, Michigan 49931, USA
| | - Katherine Massa
- Department of Chemical Engineering, Michigan Technological University , Houghton, Michigan 49931, USA
| | - David O Wipf
- Department of Chemistry, Mississippi State University , Mississippi State, Mississippi 39762, USA
| | - Adrienne R Minerick
- Department of Chemical Engineering, Michigan Technological University , Houghton, Michigan 49931, USA
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11
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An R, Wipf DO, Minerick AR. Spatially variant red blood cell crenation in alternating current non-uniform fields. BIOMICROFLUIDICS 2014; 8:021803. [PMID: 24753734 PMCID: PMC3977840 DOI: 10.1063/1.4867557] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/04/2013] [Accepted: 02/24/2014] [Indexed: 05/04/2023]
Abstract
Alternating-current (AC) electrokinetics involve the movement and behaviors of particles or cells. Many applications, including dielectrophoretic manipulations, are dependent upon charge interactions between the cell or particle and the surrounding medium. Medium concentrations are traditionally treated as spatially uniform in both theoretical models and experiments. Human red blood cells (RBCs) are observed to crenate, or shrink due to changing osmotic pressure, over 10 min experiments in non-uniform AC electric fields. Cell crenation magnitude is examined as functions of frequency from 250 kHz to 1 MHz and potential from 10 Vpp to 17.5 Vpp over a 100 μm perpendicular electrode gap. Experimental results show higher peak to peak potential and lower frequency lead to greater cell volume crenation up to a maximum volume loss of 20%. A series of experiments are conducted to elucidate the physical mechanisms behind the red blood cell crenation. Non-uniform and uniform electrode systems as well as high and low ion concentration experiments are compared and illustrate that AC electroporation, system temperature, rapid temperature changes, medium pH, electrode reactions, and convection do not account for the crenation behaviors observed. AC electroosmotic was found to be negligible at these conditions and AC electrothermal fluid flows were found to reduce RBC crenation behaviors. These cell deformations were attributed to medium hypertonicity induced by ion concentration gradients in the spatially nonuniform AC electric fields.
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Affiliation(s)
- Ran An
- Department of Chemical Engineering, Michigan Technological University, Houghton, Michigan 49931, USA
| | - David O Wipf
- Department of Chemistry, Mississippi State University, Mississippi State, Mississippi 39762, USA
| | - Adrienne R Minerick
- Department of Chemical Engineering, Michigan Technological University, Houghton, Michigan 49931, USA
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12
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Islam N, Reyna J. Bi-directional flow induced by an AC electroosmotic micropump with DC voltage bias. Electrophoresis 2012; 33:1191-7. [DOI: 10.1002/elps.201100544] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Nazmul Islam
- Department of Engineering; The University of Texas at Brownsville TX; USA
| | - Jairo Reyna
- Department of Engineering; The University of Texas at Brownsville TX; USA
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13
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Yang Ng W, Ramos A, Cheong Lam Y, Rodriguez I. Numerical study of dc-biased ac-electrokinetic flow over symmetrical electrodes. BIOMICROFLUIDICS 2012; 6:12817-1281710. [PMID: 22662084 PMCID: PMC3365336 DOI: 10.1063/1.3668262] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/06/2011] [Accepted: 11/20/2011] [Indexed: 05/25/2023]
Abstract
This paper presents a numerical study of DC-biased AC-electrokinetic (DC-biased ACEK) flow over a pair of symmetrical electrodes. The flow mechanism is based on a transverse conductivity gradient created through incipient Faradaic reactions occurring at the electrodes when a DC-bias is applied. The DC biased AC electric field acting on this gradient generates a fluid flow in the form of vortexes. To understand more in depth the DC-biased ACEK flow mechanism, a phenomenological model is developed to study the effects of voltage, conductivity ratio, channel width, depth, and aspect ratio on the induced flow characteristics. It was found that flow velocity on the order of mm/s can be produced at higher voltage and conductivity ratio. Such rapid flow velocity is one of the highest reported in microsystems technology using electrokinetics.
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14
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SASAKI N. Recent Applications of AC Electrokinetics in Biomolecular Analysis on Microfluidic Devices. ANAL SCI 2012; 28:3-8. [DOI: 10.2116/analsci.28.3] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Affiliation(s)
- Naoki SASAKI
- Department of Chemical and Biological Sciences, Faculty of Science, Japan Women’s University
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15
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Ng WY, Ramos A, Lam YC, Wijaya IPM, Rodriguez I. DC-biased AC-electrokinetics: a conductivity gradient driven fluid flow. LAB ON A CHIP 2011; 11:4241-7. [PMID: 22052533 DOI: 10.1039/c1lc20495e] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
This paper studies the principles of fluid flow manipulation based on DC-biased AC-electrokinetics. This method makes use of planar parallel electrodes in a microfluidic channel in contact with an electrolyte solution, with a DC biased AC electrical signal applied to the electrode pair. Due to the application of DC bias, incipient Faradaic electrolytic reactions take place resulting in an increase of the ionic content of the bulk solution. The ionic content was found to be dissimilar at the cathodic and anodic sides of the channel and a conductivity difference of approximately 10% was measured for 2 V(DC). Fluid flow is generated by the action of the DC biased AC electric signal acting on the transverse conductivity gradient generated across the microchannel. The induced flow in the form of vortex was characterized experimentally and the results substantiated theoretically. The velocity of the induced flow vortex under the employed experimental conditions was ~600 to 700 μm s(-1) which is faster than those obtained in conventional AC-electroosmosis and AC-electrothermal types of flows.
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Affiliation(s)
- Wee Yang Ng
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 3 Research Link, Singapore, 117602, Singapore
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Friend J, Yeo L. Fabrication of microfluidic devices using polydimethylsiloxane. BIOMICROFLUIDICS 2010; 4:026502. [PMID: 20697575 DOI: 10.1063/1.3259624.1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 10/16/2009] [Indexed: 05/27/2023]
Abstract
Polydimethylsiloxane (PDMS) is nearly ubiquitous in microfluidic devices, being easy to work with, economical, and transparent. A detailed protocol is provided here for using PDMS in the fabrication of microfluidic devices to aid those interested in using the material in their work, with information on the many potential ways the material may be used for novel devices.
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Affiliation(s)
- James Friend
- Department of Mechanical and Aerospace Engineering, MicroNanophysics Research Laboratory, Monash University, Melbourne VIC 3800 Australia
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Friend J, Yeo L. Fabrication of microfluidic devices using polydimethylsiloxane. BIOMICROFLUIDICS 2010; 4:026502. [PMID: 20697575 PMCID: PMC2917889 DOI: 10.1063/1.3259624] [Citation(s) in RCA: 170] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/06/2009] [Accepted: 10/16/2009] [Indexed: 05/02/2023]
Abstract
Polydimethylsiloxane (PDMS) is nearly ubiquitous in microfluidic devices, being easy to work with, economical, and transparent. A detailed protocol is provided here for using PDMS in the fabrication of microfluidic devices to aid those interested in using the material in their work, with information on the many potential ways the material may be used for novel devices.
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Affiliation(s)
- James Friend
- Department of Mechanical and Aerospace Engineering, MicroNanophysics Research Laboratory, Monash University, Melbourne VIC 3800 Australia
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Yeo LY. Preface to special topic: papers from the 2009 conference on advances in microfluidics and nanofluidics, the Hong Kong university of science & technology, Hong Kong, 2009. BIOMICROFLUIDICS 2009; 3:22301. [PMID: 19693335 PMCID: PMC2717579 DOI: 10.1063/1.3167278] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Accepted: 06/11/2009] [Indexed: 05/28/2023]
Abstract
The inaugural conference on Advances in Microfluidics and Nanofluidics was held at the Hong Kong University of Science and Technology on 5-7 January 2009 and brought together leading researchers from across a wide variety of disciplines from North America, Europe, Asia, and Oceania. This Special Topic section forms the second of the two issues dedicated to original contributions covering both fundamental physicochemical aspects of microfluidics and nanofluidics as well as their applications to the miniaturization of chemical and biological systems that were presented at the conference.
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Affiliation(s)
- Leslie Y Yeo
- Department of Mechanical & Aerospace Engineering, Monash University, Clayton VIC 3800, Australia
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