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Li H, Peng T, Zhong Y, Liu M, Mak PI, Martins RP, Wang P, Jia Y. pH Regulator on Digital Microfluidics with Pico-Dosing Technique. BIOSENSORS 2023; 13:951. [PMID: 37998126 PMCID: PMC10669492 DOI: 10.3390/bios13110951] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/14/2023] [Revised: 09/01/2023] [Accepted: 09/03/2023] [Indexed: 11/25/2023]
Abstract
Real-time pH control on-chip is a crucial factor for cell-based experiments in microfluidics, yet difficult to realize. In this paper, we present a flexible pH regulator on a digital microfluidic (DMF) platform. The pico-dosing technology, which can generate and transfer satellite droplets, is presented to deliver alkali/acid into the sample solution to change the pH value of the sample. An image analysis method based on ImageJ is developed to calculate the delivered volume and an on-chip colorimetric method is proposed to determine the pH value of the sample solution containing the acid-base indicator. The calculated pH values show consistency with the measured ones. Our approach makes the real-time pH control of the on-chip biological experiment more easy to control and flexible.
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Affiliation(s)
- Haoran Li
- The State Key Laboratory of Analog and Mixed-Signal VLSI, Institute of Microelectronics, University of Macau, Macau 999078, China; (H.L.); (M.L.); (P.-I.M.)
| | - Tao Peng
- Zhuhai UM Science & Technology Research Institute, Zhuhai 519085, China;
| | - Yunlong Zhong
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510120, China
| | - Meiqing Liu
- The State Key Laboratory of Analog and Mixed-Signal VLSI, Institute of Microelectronics, University of Macau, Macau 999078, China; (H.L.); (M.L.); (P.-I.M.)
| | - Pui-In Mak
- The State Key Laboratory of Analog and Mixed-Signal VLSI, Institute of Microelectronics, University of Macau, Macau 999078, China; (H.L.); (M.L.); (P.-I.M.)
- Zhuhai UM Science & Technology Research Institute, Zhuhai 519085, China;
| | - Rui P. Martins
- The State Key Laboratory of Analog and Mixed-Signal VLSI, Institute of Microelectronics, University of Macau, Macau 999078, China; (H.L.); (M.L.); (P.-I.M.)
- Faculty of Science and Technology–ECE, University of Macau, Macau 999078, China
- Instituto Superior Técnico, Unversidade de Lisboa, 1049-001 Lisboa, Portugal
| | - Ping Wang
- Department of Hepatobiliary Surgery, The First Affiliated Hospital of Guangzhou Medical University, Guangzhou 510120, China
| | - Yanwei Jia
- The State Key Laboratory of Analog and Mixed-Signal VLSI, Institute of Microelectronics, University of Macau, Macau 999078, China; (H.L.); (M.L.); (P.-I.M.)
- Faculty of Science and Technology–ECE, University of Macau, Macau 999078, China
- MoE Frontiers Science Center for Precision Oncology, University of Macau, Macau 999078, China
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2
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Wilder LM, Thompson JR, Crooks RM. Electrochemical pH regulation in droplet microfluidics. LAB ON A CHIP 2022; 22:632-640. [PMID: 35018955 DOI: 10.1039/d1lc00952d] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
We report a method for electrochemical pH regulation in microdroplets generated in a microfluidic device. The key finding is that controlled quantities of reagents can be generated electrochemically in moving microdroplets confined within a microfluidic channel. Additionally, products generated at the anode and cathode can be isolated within descendant microdroplets. Specifically, ∼5 nL water-in-oil microdroplets are produced at a T-junction and then later split into two descendant droplets. During splitting, floor-patterned microelectrodes drive water electrolysis within the aqueous microdroplets to produce H+ and OH-. This results in a change in the pHs of the descendant droplets. The droplet pH can be regulated over a range of 5.9 to 7.7 by injecting controlled amounts of charge into the droplets. When the injected charge is between -6.3 and 54.5 nC nL-1, the measured pH of the resulting droplets is within ±0.1 pH units of that predicted based on the magnitude of the injected charge. This technique can likely be adapted to electrogeneration of other reagents within microdroplets.
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Affiliation(s)
- Logan M Wilder
- Department of Chemistry and the Texas Materials Institute, The University of Texas at Austin, 105 E. 24th Street, Stop A5300, Austin, Texas 78712-1224, USA.
| | - Jonathan R Thompson
- Department of Chemistry and the Texas Materials Institute, The University of Texas at Austin, 105 E. 24th Street, Stop A5300, Austin, Texas 78712-1224, USA.
| | - Richard M Crooks
- Department of Chemistry and the Texas Materials Institute, The University of Texas at Austin, 105 E. 24th Street, Stop A5300, Austin, Texas 78712-1224, USA.
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3
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Li W, Sun J, Gao Y, Zhang Y, Ouyang J, Na N. Monitoring of electrochemical reactions on different electrode configurations by ambient mass spectrometry. Trends Analyt Chem 2021. [DOI: 10.1016/j.trac.2021.116180] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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4
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Scida K, Eden A, Arroyo-Currás N, MacKenzie S, Satik Y, Meinhart CD, Eijkel JCT, Pennathur S. Fluorescence-Based Observation of Transient Electrochemical and Electrokinetic Effects at Nanoconfined Bipolar Electrodes. ACS APPLIED MATERIALS & INTERFACES 2019; 11:13777-13786. [PMID: 30880379 DOI: 10.1021/acsami.9b01339] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Bipolar electrodes (BPEs) are conductors that, when exposed to an electric field, polarize and promote the accumulation of counterionic charge near their poles. The rich physics of electrokinetic behavior near BPEs has not yet been rigorously studied, with our current understanding of such bipolar effects being restricted to steady-state conditions (under constant applied fields). Here, we reveal the dynamic electrokinetic and electrochemical phenomena that occur near nanoconfined BPEs throughout all stages of a reaction. Specifically, we demonstrate, both experimentally and through numerical modeling, that the removal of an electric field produces solution-phase charge imbalances in the vicinity of the BPE poles. These imbalances induce intense and short-lived nonequilibrium electric fields that drive the rapid transport of ions toward specific BPE locations. To determine the origin of these electrokinetic effects, we monitored the movement and fluorescent behavior (enhancement or quenching) of charged fluorophores within well-defined nanofluidic architectures via real-time optical detection. By systematically varying the nature of the fluorophore, the concentration of the electrolyte, the strength of the applied field, and oxide growth on the BPE surface, we dissect the ion transport events that occur in the aftermath of field-induced polarization. The results contained in this work provide new insights into transient bipolar electrokinetics that improve our understanding of current analytical platforms and can drive the development of new micro- and nanoelectrochemical systems.
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Affiliation(s)
- Karen Scida
- Department of Mechanical Engineering , University of California Santa Barbara , Santa Barbara , California 93106 , United States
| | - Alexander Eden
- Department of Mechanical Engineering , University of California Santa Barbara , Santa Barbara , California 93106 , United States
| | - Netzahualcóyotl Arroyo-Currás
- Department of Pharmacology and Molecular Sciences , Johns Hopkins University School of Medicine , Baltimore , Maryland 21205 , United States
| | - Sean MacKenzie
- Department of Mechanical Engineering , University of California Santa Barbara , Santa Barbara , California 93106 , United States
| | - Yesil Satik
- Department of Mechanical Engineering , University of California Santa Barbara , Santa Barbara , California 93106 , United States
| | - Carl D Meinhart
- Department of Mechanical Engineering , University of California Santa Barbara , Santa Barbara , California 93106 , United States
| | - Jan C T Eijkel
- Department of Electrical Engineering, Mathematics and Computer Science , University of Twente , Enschede , Overijssel 7522 , The Netherlands
| | - Sumita Pennathur
- Department of Mechanical Engineering , University of California Santa Barbara , Santa Barbara , California 93106 , United States
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5
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A Diffusion-Based pH Regulator in Laminar Flows with Smartphone-Based Colorimetric Analysis. MICROMACHINES 2018; 9:mi9120616. [PMID: 30477093 PMCID: PMC6315573 DOI: 10.3390/mi9120616] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2018] [Revised: 11/07/2018] [Accepted: 11/19/2018] [Indexed: 01/10/2023]
Abstract
A strategy for an on-chip pH regulator is demonstrated computationally and experimentally, based on the diffusion characteristics of aqueous ionic solutions. Micro-flows with specific pH values are formed based on the diffusion behaviors of hydrogen and hydroxide ions in laminar flows. The final achieved pH value and its gradient in the channel can be regulated by the amount of ions transported between laminar flows, and the experimental results can be further generalized based on the normalized Nernst-Planck equation. A smartphone was applied as an image capture and analysis instrument to quantify pH values of liquids in a colorimetric detection process, with monotonic response range of ~1⁻13.
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Fu K, Han D, Ma C, Bohn PW. Ion selective redox cycling in zero-dimensional nanopore electrode arrays at low ionic strength. NANOSCALE 2017; 9:5164-5171. [PMID: 28393950 DOI: 10.1039/c7nr00206h] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Surface charge characteristics and the electrical double layer (EDL) effect govern the transport of ions into and out of nanopores, producing a permselective concentration polarization, which dominates the electrochemical response of nanoelectrodes in solutions of low ionic strength. In this study, highly ordered, zero-dimensional nanopore electrode arrays (NEAs), with each nanopore presenting a pair of recessed electrodes, were fabricated to couple EDL effects with redox cycling, thereby achieving electrochemical detection with improved sensitivity and selectivity. These NEAs exhibit current amplification as high as 55-fold due to the redox cycling effect, which can be further increased by ∼500-fold upon the removal of the supporting electrolyte. The effect of nanopore geometry, which is a key factor determining the magnitude of the EDL effect, is fully characterized, as is the effect of the magnitude and sign of the charge of the redox-active species. The observed changes in limiting current with the concentration of the supporting electrolyte confirm the accumulation of cations and repulsion of anions in NEAs presenting negative surface charge. Exploiting this principle, dopamine was selectively determined in the presence of a 3000-fold excess of ascorbic acid within the NEA.
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Affiliation(s)
- Kaiyu Fu
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA.
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Fanavoll EV, Harrington DA, Sunde S, Singh G, Seland F. A microfluidic electrochemical cell with integrated PdH reference electrode for high current experiments. Electrochim Acta 2017. [DOI: 10.1016/j.electacta.2016.11.147] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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8
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Read TL, Joseph MB, Macpherson JV. Manipulation and measurement of pH sensitive metal–ligand binding using electrochemical proton generation and metal detection. Chem Commun (Camb) 2016; 52:1863-6. [DOI: 10.1039/c5cc09326k] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
Boron doped diamond generator-detector electrodes can both change and monitor the binding state of the pH sensitive metal–ligand complex [Cu2+:TETA] by locally varying pH and measuring the free metal concentration.
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Affiliation(s)
- Tania L. Read
- Department of Chemistry
- University of Warwick
- Coventry
- UK
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10
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Xu W, Foster E, Ma C, Bohn PW. On-demand in situ generation of oxygen in a nanofluidic embedded planar microband electrochemical reactor. MICROFLUIDICS AND NANOFLUIDICS 2015; 19:1181-1189. [PMID: 30319319 PMCID: PMC6178959 DOI: 10.1007/s10404-015-1636-7] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2015] [Accepted: 08/25/2015] [Indexed: 06/07/2023]
Abstract
In situ generation of reagents and their subsequent use downstream presents new opportunities to amplify the utility of nanofluidic devices by exploiting the confined geometry to address mass transport limitations on reaction kinetics and efficiency. Oxygen, an inherently valuable reactant, can be produced from electrolysis of water, a process that can be conveniently integrated within a nanofluidic system. Here, we construct and characterize a nanofluidic device consisting of a planar microband electrode embedded within a nanochannel for in situ electrochemical generation and optical monitoring of O2. Fluorescein, a dye with a pH-sensitive emission intensity, was used to monitor the spatiotemporal characteristics of the oxidation of H2O, using the co-produced H+. Application of anodic potentials at the nanochannel-embedded electrode results in a decrease in fluorescence intensity, which reflects the decreasing solution pH. A combination of fluorescence intensity and chronoamperometric response was used to quantitatively determine proton generation, and the H+/O2 stoichiometry was then used to determine the concentration of the O2 in the channel. Comparison of the experimental results to finite element simulations validates the use of fluorescein emission intensity to spectroscopically determine the local oxygen concentration in the nanochannel. By varying the applied potential, spatially averaged O2 concentrations ranging from 0.13 to 0.41 mM were generated. The results demonstrate a convenient route to in situ modulation of the dissolved O2 level in a nanofluidic device and the use of an optical probe to monitor its spatial and temporal distribution under flow conditions.
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Affiliation(s)
- Wei Xu
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Erick Foster
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Chaoxiong Ma
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
| | - Paul W Bohn
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN 46556, USA
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
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12
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Ma C, Zaino Iii LP, Bohn PW. Self-induced redox cycling coupled luminescence on nanopore recessed disk-multiscale bipolar electrodes. Chem Sci 2015; 6:3173-3179. [PMID: 28706689 PMCID: PMC5490416 DOI: 10.1039/c5sc00433k] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 03/19/2015] [Indexed: 11/21/2022] Open
Abstract
We present a new configuration for coupling fluorescence microscopy and voltammetry using self-induced redox cycling for ultrasensitive electrochemical measurements. An array of nanopores, each supporting a recessed disk electrode separated by 100 nm in depth from a planar multiscale bipolar top electrode, was fabricated using multilayer deposition, nanosphere lithography, and reactive-ion etching. Self-induced redox cycling was induced on the disk electrode producing ∼30× current amplification, which was independently confirmed by measuring induced electrogenerated chemiluminescence from Ru(bpy)32/3+/tri-n-propylamine on the floating bipolar electrode. In this design, redox cycling occurs between the recessed disk and the top planar portion of a macroscopic thin film bipolar electrode in each nanopore. Electron transfer also occurs on a remote (mm-distance) portion of the planar bipolar electrode to maintain electroneutrality. This couples the electrochemical reactions of the target redox pair in the nanopore array with a reporter, such as a potential-switchable fluorescent indicator, in the cell at the distal end of the bipolar electrode. Oxidation or reduction of reversible analytes on the disk electrodes were accompanied by reduction or oxidation, respectively, on the nanopore portion of the bipolar electrode and then monitored by the accompanying oxidation of dihydroresorufin or reduction of resorufin at the remote end of the bipolar electrode, respectively. In both cases, changes in fluorescence intensity were triggered by the reaction of the target couple on the disk electrode, while recovery was largely governed by diffusion of the fluorescent indicator. Reduction of 1 nM of Ru(NH3)63+ on the nanoelectrode array was detected by monitoring the fluorescence intensity of resorufin, demonstrating high sensitivity fluorescence-mediated electrochemical sensing coupled to self-induced redox cycling.
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Affiliation(s)
- Chaoxiong Ma
- Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN 46556 , USA .
| | - Lawrence P Zaino Iii
- Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN 46556 , USA .
| | - Paul W Bohn
- Department of Chemistry and Biochemistry , University of Notre Dame , Notre Dame , IN 46556 , USA .
- Department of Chemical and Biomolecular Engineering , University of Notre Dame , Notre Dame , IN 46556 , USA
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13
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Haywood DG, Saha-Shah A, Baker LA, Jacobson SC. Fundamental studies of nanofluidics: nanopores, nanochannels, and nanopipets. Anal Chem 2014; 87:172-87. [PMID: 25405581 PMCID: PMC4287834 DOI: 10.1021/ac504180h] [Citation(s) in RCA: 157] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Affiliation(s)
- Daniel G Haywood
- Department of Chemistry, Indiana University , Bloomington, Indiana 47405-7102, United States
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14
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Morikawa K, Tsukahara T. Investigation of Unique Protonic and Hydrodynamic Behavior of Aqueous Solutions Confined in Extended Nanospaces. Isr J Chem 2014. [DOI: 10.1002/ijch.201400095] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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15
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Zaino LP, Contento NM, Branagan SP, Bohn PW. Coupled Electrokinetic Transport and Electron Transfer at Annular Nanoband Electrodes Embedded in Cylindrical Nanopores. ChemElectroChem 2014. [DOI: 10.1002/celc.201402111] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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16
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Contento NM, Bohn PW. Tunable electrochemical pH modulation in a microchannel monitored via the proton-coupled electro-oxidation of hydroquinone. BIOMICROFLUIDICS 2014; 8:044120. [PMID: 25379105 PMCID: PMC4189302 DOI: 10.1063/1.4894275] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2014] [Accepted: 08/19/2014] [Indexed: 05/30/2023]
Abstract
Electrochemistry is a promising tool for microfluidic systems because it is relatively inexpensive, structures are simple to fabricate, and it is straight-forward to interface electronically. While most widely used in microfluidics for chemical detection or as the transduction mechanism for molecular probes, electrochemical methods can also be used to efficiently alter the chemical composition of small (typically <100 nl) microfluidic volumes in a manner that improves or enables subsequent measurements and sample processing steps. Here, solvent (H2O) electrolysis is performed quantitatively at a microchannel Pt band electrode to increase microchannel pH. The change in microchannel pH is simultaneously tracked at a downstream electrode by monitoring changes in the i-V characteristics of the proton-coupled electro-oxidation of hydroquinone, thus providing real-time measurement of the protonated forms of hydroquinone from which the pH can be determined in a straightforward manner. Relative peak heights for protonated and deprotonated hydroquinone forms are in good agreement with expected pH changes by measured electrolysis rates, demonstrating that solvent electrolysis can be used to provide tunable, quantitative pH control within a microchannel.
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Affiliation(s)
- Nicholas M Contento
- Department of Chemical and Biomolecular Engineering, University of Notre Dame , Notre Dame, Indiana 46556, USA
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17
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Zhou H, Li G, Yao S. A droplet-based pH regulator in microfluidics. LAB ON A CHIP 2014; 14:1917-1922. [PMID: 24745036 DOI: 10.1039/c3lc51442k] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
In this paper, we develop a strategy to form on-demand droplets with specific pH values. The pH control is based on electrolysis of water in microfluidics, and the produced hydrogen and hydroxyl ions are separated and confined in individual containers during the droplet generation, triggered by a pressure pulse. By tuning the applied voltages and pressure pulses, we can control on demand the pH value in a droplet.
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Affiliation(s)
- Hongbo Zhou
- Department of Mechanical and Aerospace Engineering, Hong Kong University of Science and Technology, Hong Kong, China.
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18
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Ma C, Contento NM, Gibson LR, Bohn PW. Recessed Ring–Disk Nanoelectrode Arrays Integrated in Nanofluidic Structures for Selective Electrochemical Detection. Anal Chem 2013; 85:9882-8. [DOI: 10.1021/ac402417w] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Affiliation(s)
- Chaoxiong Ma
- Department of Chemistry and Biochemistry, and ‡Department of Chemical and Biomolecular
Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Nicholas M. Contento
- Department of Chemistry and Biochemistry, and ‡Department of Chemical and Biomolecular
Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Larry R. Gibson
- Department of Chemistry and Biochemistry, and ‡Department of Chemical and Biomolecular
Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
| | - Paul W. Bohn
- Department of Chemistry and Biochemistry, and ‡Department of Chemical and Biomolecular
Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States
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Gibson LR, Branagan SP, Bohn PW. Convective delivery of electroactive species to annular nanoband electrodes embedded in nanocapillary-array membranes. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2013; 9:90-97. [PMID: 22907773 DOI: 10.1002/smll.201200237] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/31/2012] [Revised: 06/15/2012] [Indexed: 06/01/2023]
Abstract
Significant technological drivers motivate interest in the use of reaction sites embedded within nanometer-scale channels, and an important class of these structures is realized by an embedded annular nanoband electrode (EANE) in a cylindrical nanochannel. In this structure, the convective delivery of electroactive species to the nanoelectrode is tightly coupled to the electrochemical overpotential via electroosmotic flow. Simulation results indicate that EANE arrays significantly outperform comparable microband electrode/microchannel structures, producing higher conversion efficiencies at low Peclet number. The results of this in-depth analysis are useful in assessing possible implementation of the EANE geometry for a wide range of electrochemical targets within microscale total analysis systems.
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Affiliation(s)
- Larry R Gibson
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, IN 46556, USA
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20
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Halpern AR, Donavan KC, Penner RM, Corn RM. Wafer-Scale Fabrication of Nanofluidic Arrays and Networks Using Nanoimprint Lithography and Lithographically Patterned Nanowire Electrodeposition Gold Nanowire Masters. Anal Chem 2012; 84:5053-8. [DOI: 10.1021/ac3007285] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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21
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Branagan SP, Contento NM, Bohn PW. Enhanced mass transport of electroactive species to annular nanoband electrodes embedded in nanocapillary array membranes. J Am Chem Soc 2012; 134:8617-24. [PMID: 22506659 DOI: 10.1021/ja3017158] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Electroosmotic flow (EOF) is used to enhance the delivery of Fe(CN)(6)(4-)/Fe(CN)(6)(3-) to an annular nanoband electrode embedded in a nanocapillary array membrane, as a route to high efficiency electrochemical conversions. Multilayer Au/polymer/Au/polymer membranes are perforated with 10(2)-10(3) cylindrical nanochannels by focused ion beam (FIB) milling and subsequently sandwiched between two axially separated microchannels, producing a structure in which transport and electron transfer reactions are tightly coupled. The middle Au layer, which contacts the fluid only at the center of each nanochannel, serves as a working electrode to form an array of embedded annular nanoband electrodes (EANEs), at which sufficient overpotential drives highly efficient electrochemical processes. Simultaneously, the electric field established between the EANE and the QRE (>10(3) V cm(-1)) drives electro-osmotic flow (EOF) in the nanochannels, improving reagent delivery rate. EOF is found to enhance the steady-state current by >10× over a comparable structure without convective transport. Similarly, the conversion efficiency is improved by approximately 10-fold compared to a comparable microfluidic structure. Experimental data agree with finite element simulations, further illustrating the unique electrochemical and transport behavior of these nanoscale embedded electrode arrays. Optimizing the present structure may be useful for combinatorial processing of on-chip sample delivery with electrochemical conversion; a proof of concept experiment, involving the generation of dissolved hydrogen in situ via electrolysis, is described.
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Affiliation(s)
- Sean P Branagan
- Department of Chemical and Biomolecular Engineering, University of Notre Dame, Indiana 46556, United States
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