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Di Muccio G, Morozzo della Rocca B, Chinappi M. Geometrically Induced Selectivity and Unidirectional Electroosmosis in Uncharged Nanopores. ACS NANO 2022; 16:8716-8728. [PMID: 35587777 PMCID: PMC9245180 DOI: 10.1021/acsnano.1c03017] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Selectivity toward positive and negative ions in nanopores is often associated with electroosmotic flow, the control of which is pivotal in several micro-nanofluidic technologies. Selectivity is traditionally understood to be a consequence of surface charges that alter the ion distribution in the pore lumen. Here we present a purely geometrical mechanism to induce ionic selectivity and electroosmotic flow in uncharged nanopores, and we tested it via molecular dynamics simulations. Our approach exploits the accumulation of charges, driven by an external electric field, in a coaxial cavity that decorates the membrane close to the pore entrance. The selectivity was shown to depend on the applied voltage and becomes completely inverted when reversing the voltage. The simultaneous inversion of ionic selectivity and electric field direction causes a unidirectional electroosmotic flow. We developed a quantitatively accurate theoretical model for designing pore geometry to achieve the desired electroosmotic velocity. Finally, we show that unidirectional electroosmosis also occurs in much more complex scenarios, such as a biological pore whose structure presents a coaxial cavity surrounding the pore constriction as well as a complex surface charge pattern. The capability to induce ion selectivity without altering the pore lumen shape or the surface charge may be useful for a more flexible design of selective membranes.
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Affiliation(s)
- Giovanni Di Muccio
- Dipartimento
di Ingegneria Industriale, Università
di Roma Tor Vergata, Via del Politecnico 1, 00133, Rome, Italy
| | - Blasco Morozzo della Rocca
- Dipartimento
di Biologia, Università di Roma Tor
Vergata, Via della Ricerca Scientifica 1, 00133, Rome, Italy
| | - Mauro Chinappi
- Dipartimento
di Ingegneria Industriale, Università
di Roma Tor Vergata, Via del Politecnico 1, 00133, Rome, Italy
- E-mail:
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Leong IW, Tsutsui M, Yokota K, Taniguchi M. Salt Gradient Control of Translocation Dynamics in a Solid-State Nanopore. Anal Chem 2021; 93:16700-16708. [PMID: 34860500 DOI: 10.1021/acs.analchem.1c04342] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Tuning capture rates and translocation time of analytes in solid-state nanopores are one of the major challenges for their use in detecting and analyzing individual nanoscale objects via ionic current measurements. Here, we report on the use of salt gradient for the fine control of capture-to-translocation dynamics in 300 nm sized SiNx nanopores. We demonstrated a decrease up to a factor of 3 in the electrophoretic speed of nanoparticles at the pore exit along with an over 3-fold increase in particle detection efficiency by subjecting a 5-fold ion concentration difference across the dielectric membrane. The improvement in the sensor performance was elucidated to be a result of the salt-gradient-mediated electric field and electroosmotic flow asymmetry at nanochannel orifices. The present findings can be used to enhance nanopore sensing capability for detecting biomolecules such as amyloids and proteins.
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Affiliation(s)
- Iat Wai Leong
- The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Makusu Tsutsui
- The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Kazumichi Yokota
- National Institute of Advanced Industrial Science and Technology, Takamatsu, Kagawa 761-0395, Japan
| | - Masateru Taniguchi
- The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
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Hsu C, Lin CY, Alizadeh A, Daiguji H, Hsu WL. Investigation of entrance effects on particle electrophoretic behavior near a nanopore for resistive pulse sensing. Electrophoresis 2021; 42:2206-2214. [PMID: 34472124 DOI: 10.1002/elps.202100162] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2021] [Revised: 08/20/2021] [Accepted: 08/25/2021] [Indexed: 11/10/2022]
Abstract
Resistive pulse sensing using solid-state nanopores provides a unique platform for detecting the structure and concentration of molecules of different types of analytes in an electrolyte solution. The capture of an entity into a nanopore is subject not only to the electrostatic force but also the effect of electroosmotic flow originating from the charged nanopore surface. In this study, we theoretically analyze spherical particle electrophoretic behavior near the entrance of a charged nanopore. By investigating the effects of pore size, particle-pore distance, and salt concentration on particle velocity, we summarize dominant mechanisms governing particle behavior for a range of conditions. In the literature, the Helmholtz-Smoluchowski equation is often adopted to evaluate particle translocation by considering the zeta potential difference between the particle and nanopore surfaces. We point out that, due to the difference of the electric field inside and outside the nanopore and the influence from the existence of the particle itself, the zeta potential of the particle, however, needs to be at least 30% higher than that of the nanopore to allow the particle to enter into the nanopore when its velocity is close to zero. Accordingly, we summarize the effective salt concentrations that enable successful particle capture and detection for different pore sizes, offering direct guidance for nanopore applications.
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Affiliation(s)
- Chien Hsu
- Department of Mechanical Engineering, The University of Tokyo, Tokyo, Japan
| | - Chih-Yuan Lin
- Department of Chemical Engineering, National Taiwan University, Taipei, Taiwan
| | - Amer Alizadeh
- Department of Mechanical Engineering, The University of Tokyo, Tokyo, Japan.,Department of Chemical and Petroleum Engineering, University of Calgary, Calgary, Canada
| | - Hirofumi Daiguji
- Department of Mechanical Engineering, The University of Tokyo, Tokyo, Japan
| | - Wei-Lun Hsu
- Department of Mechanical Engineering, The University of Tokyo, Tokyo, Japan
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Alizadeh A, Hsu WL, Wang M, Daiguji H. Electroosmotic flow: From microfluidics to nanofluidics. Electrophoresis 2021; 42:834-868. [PMID: 33382088 PMCID: PMC8247933 DOI: 10.1002/elps.202000313] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2020] [Revised: 12/16/2020] [Accepted: 12/19/2020] [Indexed: 01/06/2023]
Abstract
Electroosmotic flow (EOF), a consequence of an imposed electric field onto an electrolyte solution in the tangential direction of a charged surface, has emerged as an important phenomenon in electrokinetic transport at the micro/nanoscale. Because of their ability to efficiently pump liquids in miniaturized systems without incorporating any mechanical parts, electroosmotic methods for fluid pumping have been adopted in versatile applications—from biotechnology to environmental science. To understand the electrokinetic pumping mechanism, it is crucial to identify the role of an ionically polarized layer, the so‐called electrical double layer (EDL), which forms in the vicinity of a charged solid–liquid interface, as well as the characteristic length scale of the conducting media. Therefore, in this tutorial review, we summarize the development of electrical double layer models from a historical point of view to elucidate the interplay and configuration of water molecules and ions in the vicinity of a solid–liquid interface. Moreover, we discuss the physicochemical phenomena owing to the interaction of electrical double layer when the characteristic length of the conducting media is decreased from the microscale to the nanoscale. Finally, we highlight the pioneering studies and the most recent works on electro osmotic flow devoted to both theoretical and experimental aspects.
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Affiliation(s)
- Amer Alizadeh
- Department of Mechanical Engineering, The University of Tokyo, Tokyo, Japan
| | - Wei-Lun Hsu
- Department of Mechanical Engineering, The University of Tokyo, Tokyo, Japan
| | - Moran Wang
- Department of Engineering Mechanics, Tsinghua University, Beijing, P. R. China
| | - Hirofumi Daiguji
- Department of Mechanical Engineering, The University of Tokyo, Tokyo, Japan
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Wang Z, Hsu WL, Tsuchiya S, Paul S, Alizadeh A, Daiguji H. Joule Heating Effects on Transport-Induced-Charge Phenomena in an Ultrathin Nanopore. MICROMACHINES 2020; 11:E1041. [PMID: 33256113 PMCID: PMC7761093 DOI: 10.3390/mi11121041] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2020] [Revised: 11/21/2020] [Accepted: 11/24/2020] [Indexed: 01/14/2023]
Abstract
Transport-induced-charge (TIC) phenomena, in which the concentration imbalance between cations and anions occurs when more than two chemical potential gradients coexist within an ultrathin dimension, entail numerous nanofluidic systems. Evidence has indicated that the presence of TIC produces a nonlinear response of electroosmotic flow to the applied voltage, resulting in complex fluid behavior. In this study, we theoretically investigate thermal effects due to Joule heating on TIC phenomena in an ultrathin nanopore by computational fluid dynamics simulation. Our modeling results show that the rise of local temperature inside the nanopore significantly enhances TIC effects and thus has a significant influence on electroosmotic behavior. A local maximum of the solution conductivity occurs near the entrance of the nanopore at the high salt concentration end, resulting in a reversal of TIC across the nanopore. The Joule heating effects increase the reversal of TIC with the synergy of the negatively charged nanopore, and they also enhance the electroosmotic flow regardless of whether the nanopore is charged. These theoretical observations will improve our knowledge of nonclassical electrokinetic phenomena for flow control in nanopore systems.
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Affiliation(s)
| | - Wei-Lun Hsu
- Department of Mechanical Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan; (Z.W.); (S.T.); (S.P.); (A.A.)
| | | | | | | | - Hirofumi Daiguji
- Department of Mechanical Engineering, The University of Tokyo, Bunkyo-ku, Tokyo 113-8656, Japan; (Z.W.); (S.T.); (S.P.); (A.A.)
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Leong IW, Tsutsui M, Murayama S, He Y, Taniguchi M. Electroosmosis-Driven Nanofluidic Diodes. J Phys Chem B 2020; 124:7086-7092. [PMID: 32701281 DOI: 10.1021/acs.jpcb.0c04677] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Fundamental understanding of ion transport in a fluidic channel is of critical importance for realizing iontronics. Here we report on asymmetric ion transport in a low thickness-to-diameter aspect ratio nanopore. Under uniform salt concentration conditions, the cross-pore ionic current showed ohmic characteristics with no bias polarity dependence. In stark contrast, despite the weak ion selectivity expected for the relatively large nanopores employed, we observed diode-like behavior when a salt gradient was imposed across the thin membrane. This unexpected result was attributed to the electroosmotic flow that served to modulate the access resistance through dragging the condensed ions into or out of the nanopore orifices. The simple mechanism was also revealed to be effective in fluidic channels of various size from micro- to nanoscale enabling rectification of the property engineering by the pore geometries. The present findings allow for novel designs of artificial ion channel building blocks.
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Affiliation(s)
- Iat Wai Leong
- The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Makusu Tsutsui
- The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Sanae Murayama
- The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
| | - Yuhui He
- Wuhan National Laboratory for Optoelectronics, School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, P. R. China
| | - Masateru Taniguchi
- The Institute of Scientific and Industrial Research, Osaka University, Ibaraki, Osaka 567-0047, Japan
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