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Kishimoto T, Doi K. Local Electric Field and Electrical Conductivity Analysis Using a Glass Microelectrode. ACS OMEGA 2022; 7:39437-39445. [PMID: 36340092 PMCID: PMC9631736 DOI: 10.1021/acsomega.2c05973] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/15/2022] [Accepted: 09/23/2022] [Indexed: 06/16/2023]
Abstract
Transport phenomena in microfluidic chips are induced by electric fields and electrolyte concentrations. Liquid flows are often affected by ionic currents driven by electric fields in narrow channels, which are applied in microelectromechanical systems, microreactors, lab-on-a-chip, and so forth. Even though numerical studies to evaluate those local fields have been reported, measurement methods seem to be under construction. To deeply understand the dynamics of ions at the microscale, measurement techniques are necessary to be developed. In this study, we propose a novel method to directly measure electrical potential differences in liquids, local electric fields, and electrical conductivities, using a glass microelectrode. Scanning an electrolyte solution, for example, KCl solutions, with a 1 μm tip under constant ionic current conditions, a potential difference in liquids is locally measured with a micrometer-scale resolution. The conductivity of KCl solutions ranging from 0.56 to 100 mM is evaluated from electric fields locally measured, and errors are within 5% compared with the reference values. It is found that the present method enables us to directly measure local electric fields under constant current and that the electrical conductivity is quantitatively evaluated. Furthermore, it is suggested that the present method is available for various electrical analyses without calibration procedures before measurements.
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Yamazaki H, Tsuji T, Doi K, Kawano S. Mathematical model of the auditory nerve response to stimulation by a micro-machined cochlea. INTERNATIONAL JOURNAL FOR NUMERICAL METHODS IN BIOMEDICAL ENGINEERING 2021; 37:e3430. [PMID: 33336933 DOI: 10.1002/cnm.3430] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/27/2019] [Revised: 11/20/2020] [Accepted: 12/13/2020] [Indexed: 06/12/2023]
Abstract
We report a novel mathematical model of an artificial auditory system consisting of a micro-machined cochlea and the auditory nerve response it evokes. The modeled micro-machined cochlea is one previously realized experimentally by mimicking functions of the cochlea [Shintaku et al, Sens. Actuat. 158 (2010) 183-192; Inaoka et al, Proc. Natl. Acad. Sci. USA 108 (2011) 18390-18395]. First, from the viewpoint of mechanical engineering, the frequency characteristics of a model device were experimentally investigated to develop an artificial basilar membrane based on a spring-mass-damper system. In addition, a nonlinear feedback controller mimicking the function of the outer hair cells was incorporated in this experimental system. That is, the developed device reproduces the proportional relationship between the oscillation amplitude of the basilar membrane and the cube root of the sound pressure observed in the mammalian auditory system, which is what enables it to have a wide dynamic range, and the characteristics of the control performance were evaluated numerically and experimentally. Furthermore, the stimulation of the auditory nerve by the micro-machined cochlea was investigated using the present mathematical model, and the simulation results were compared with our previous experimental results from animal testing [Shintaku et al, J. Biomech. Sci. Eng. 8 (2013) 198-208]. The simulation results were found to be in reasonably good agreement with those from the previous animal test; namely, there exists a threshold at which the excitation of the nerve starts and a saturation value for the firing rate under a large input. The proposed numerical model was able to qualitatively reproduce the results of the animal test with the micro-machined cochlea and is thus expected to guide the evaluation of micro-machined cochleae for future animal experiments.
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Affiliation(s)
- Hiroki Yamazaki
- Graduate School of Engineering Science, Osaka University, Osaka, Japan
| | - Tetsuro Tsuji
- Graduate School of Engineering Science, Osaka University, Osaka, Japan
| | - Kentaro Doi
- Graduate School of Engineering Science, Osaka University, Osaka, Japan
| | - Satoyuki Kawano
- Graduate School of Engineering Science, Osaka University, Osaka, Japan
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Doi K, Asano N, Kawano S. Development of glass micro-electrodes for local electric field, electrical conductivity, and pH measurements. Sci Rep 2020; 10:4110. [PMID: 32139704 PMCID: PMC7058011 DOI: 10.1038/s41598-020-60713-z] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2019] [Accepted: 02/14/2020] [Indexed: 01/25/2023] Open
Abstract
In micro- and nanofluidic devices, liquid flows are often influenced by ionic currents generated by electric fields in narrow channels, which is an electrokinetic phenomenon. Various technologies have been developed that are analogous to semiconductor devices, such as diodes and field effect transistors. On the other hand, measurement techniques for local electric fields in such narrow channels have not yet been established. In the present study, electric fields in liquids are locally measured using glass micro-electrodes with 1-μm diameter tips, which are constructed by pulling a glass tube. By scanning a liquid poured into a channel by glass micro-electrodes, the potential difference in a liquid can be determined with a spatial resolution of the size of the glass tip. As a result, the electrical conductivity of sample solutions can be quantitatively evaluated. Furthermore, combining two glass capillaries filled with buffer solutions of different concentrations, an ionic diode that rectifies the proton conduction direction is constructed, and the possibility of pH measurement is also demonstrated. Under constant-current conditions, pH values ranging from 1.68 to 9.18 can be determined more quickly and stably than with conventional methods that depend on the proton selectivity of glass electrodes under equilibrium conditions.
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Affiliation(s)
- Kentaro Doi
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan.
| | - Naoki Asano
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan
| | - Satoyuki Kawano
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka, 560-8531, Japan.
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Doi K, Nito F, Kawano S. Cation-induced electrohydrodynamic flow in aqueous solutions. J Chem Phys 2018; 148:204512. [PMID: 29865816 DOI: 10.1063/1.5006309] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Recently, single-molecule manipulation techniques in micro- and nanofluidic channels have attracted significant attention. To precisely control the transport velocity, the dynamics of the surrounding liquid must be understood in addition to the behavior of the target particles. Some unknowns about interactions between electrolyte ions and solvents remain to be clarified from a microscopic viewpoint. Herein, we propose a technique to generate a liquid flow driven by ion transport phenomena, the so-called electrohydrodynamic (EHD) flow, where electrolyte ions are dialyzed using a cation-exchange membrane. With this method, it is possible to apply an electric body force in liquids, which is different from electroosmotic flows that are limited to ion transport in electric double layers, and is expected to be a good candidate for detailed control of liquid flows in micro- and nanofluidic channels. To collect basic design data based on the knowledge of microscopic fluid dynamics of the present technique, a mathematical model of an EHD flow dragged by electrical carriers in an ionic current is developed and results are compared with experimental data. In our experiments, EHD flows are efficiently driven by applied electric fields in a cation dominant current. To induce such an EHD flow, the externally applied electric potential can be drastically reduced to 2.0 V in comparison with previous methods because we do not need an excessively high voltage to inject electrical charges into liquids. This method enables us to induce EHD flows in aqueous solutions and is expected to open the door to low-voltage driven liquid flow control.
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Affiliation(s)
- Kentaro Doi
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Fumika Nito
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
| | - Satoyuki Kawano
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University, Toyonaka, Osaka 560-8531, Japan
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Carlier T, Chambrier MH, Ferri A, Estradé S, Blach JF, Martín G, Meziane B, Peiró F, Roussel P, Ponchel F, Rèmiens D, Cornet A, Desfeux R. Lead-Free α-La₂WO₆ Ferroelectric Thin Films. ACS APPLIED MATERIALS & INTERFACES 2015; 7:24409-24418. [PMID: 26477357 DOI: 10.1021/acsami.5b01776] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
(001)-Epitaxial La2WO6 (LWO) thin films are grown by pulsed laser deposition on (001)-oriented SrTiO3 (STO) substrates. The α-phase (high-temperature phase in bulk) is successfully stabilized with an orthorhombic structure (a = 16.585(1) Å, b = 5.717(2) Å, c = 8.865(5) Å). X-ray-diffraction pole-figure measurements suggest that crystallographic relationships between the film and substrate are [100]LWO ∥ [110]STO, [010]LWO ∥ [11̅0]STO and [001]LWO ∥ [001]STO. From optical properties, investigated by spectroscopic ellipsometry, we extract a refractive-index value around 2 (at 500 nm) along with the presence of two absorption bands situated, respectively at 3.07 and 6.32 eV. Ferroelectricity is evidenced as well on macroscale (standard polarization measurements) as on nanoscale, calling for experiments based on piezo-response force-microscopy, and confirmed with in situ scanning-and-tunneling measurements performed with a transmission electron microscope. This work highlights the ferroelectric behavior, at room temperature, in high-temperature LWO phase when stabilized in thin film and opens the way to new functional oxide thin films dedicated to advanced electronic devices.
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Affiliation(s)
- Thomas Carlier
- Unité de Catalyse et de Chimie du Solide, UMR 8181 CNRS, Faculté des Sciences Jean Perrin, Université d'Artois , Rue Jean Souvraz, SP 18, F-62300 Lens, France
| | - Marie-Hélène Chambrier
- Unité de Catalyse et de Chimie du Solide, UMR 8181 CNRS, Faculté des Sciences Jean Perrin, Université d'Artois , Rue Jean Souvraz, SP 18, F-62300 Lens, France
| | - Anthony Ferri
- Unité de Catalyse et de Chimie du Solide, UMR 8181 CNRS, Faculté des Sciences Jean Perrin, Université d'Artois , Rue Jean Souvraz, SP 18, F-62300 Lens, France
| | - Sonia Estradé
- LENS, MIND-In2UB, Electronics Department, Universitat de Barcelona (UB) , Martí i Franquès 1, Barcelona 08028, Spain
| | - Jean-François Blach
- Unité de Catalyse et de Chimie du Solide, UMR 8181 CNRS, Faculté des Sciences Jean Perrin, Université d'Artois , Rue Jean Souvraz, SP 18, F-62300 Lens, France
| | - Gemma Martín
- LENS, MIND-In2UB, Electronics Department, Universitat de Barcelona (UB) , Martí i Franquès 1, Barcelona 08028, Spain
| | - Belkacem Meziane
- Unité de Catalyse et de Chimie du Solide, UMR 8181 CNRS, Faculté des Sciences Jean Perrin, Université d'Artois , Rue Jean Souvraz, SP 18, F-62300 Lens, France
| | - Francesca Peiró
- LENS, MIND-In2UB, Electronics Department, Universitat de Barcelona (UB) , Martí i Franquès 1, Barcelona 08028, Spain
| | - Pascal Roussel
- Unité de Catalyse et de Chimie du Solide, UMR 8181 CNRS, Ecole Nationale Supérieure Chimie Lille , Cité Scientifique, Bât C7, F-59652 Villeneuve d'Ascq, France
| | - Freddy Ponchel
- Institut d'Electronique, de Microélectronique et de Nanotechnologies, DOAE, UMR 8520 CNRS, Université de Valenciennes et du Hainaut-Cambrésis , F-59313 Valenciennes 9, France
| | - Denis Rèmiens
- Institut d'Electronique, de Microélectronique et de Nanotechnologies, DOAE, UMR 8520 CNRS, Université de Valenciennes et du Hainaut-Cambrésis , F-59313 Valenciennes 9, France
| | - Albert Cornet
- LENS, MIND-In2UB, Electronics Department, Universitat de Barcelona (UB) , Martí i Franquès 1, Barcelona 08028, Spain
| | - Rachel Desfeux
- Unité de Catalyse et de Chimie du Solide, UMR 8181 CNRS, Faculté des Sciences Jean Perrin, Université d'Artois , Rue Jean Souvraz, SP 18, F-62300 Lens, France
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Doi K, Yano A, Kawano S. Electrohydrodynamic flow through a 1 mm(2) cross-section pore placed in an ion-exchange membrane. J Phys Chem B 2015; 119:228-37. [PMID: 25412032 DOI: 10.1021/jp5071538] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In recent years, the control of ionic currents has come to be recognized as one of the most important issues related to the efficient transport of single molecules and microparticles in aqueous solutions. However, the complicated liquid flows that are usually induced by applying electric potentials have made it difficult to address a number of unsolved problems in this area. In particular, the nonequilibrium phenomena that occur in electrically non-neutral fields must be more thoroughly understood. Herein, we report on the development of a theoretical model of liquid flows resulting from ion interactions while focusing on the so-called electrohydrodynamic (EHD) flow. We also discuss the development of an experimental system to optically and electrically observe EHD flows using a 1 mm(2) cross-section pore placed in an ion-exchange membrane where cation and anion flows can be separated without the use of a charged environment. Although micro/nanosized flow channels are usually applied to induce electric double layer overlaps to utilize strong electroosmotic effects, our system does not require such laborious fabrication processes. Instead, we visualize EHD flows by using a millimeter size pore immersed in an alkaline aqueous solution. In this setup, liquid flows passing through the pore along the direction of ion flow, whose velocity reaches on the order of 1 mm/s, can be clearly observed by applying a few volts of electric potential. Furthermore, the transient phenomena associated with ionic responses are theoretically elucidated.
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Affiliation(s)
- Kentaro Doi
- Department of Mechanical Science and Bioengineering, Graduate School of Engineering Science, Osaka University , Toyonaka, Osaka 560-8531, Japan
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