State-of-the-Art Nanofluidics

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "A:Physics".

Deadline for manuscript submissions: closed (20 February 2022) | Viewed by 8268

Special Issue Editor

Department of Mechanical and Automotive Engineering, Kongju National University, Cheonan 31080, Republic of Korea
Interests: micro/nano fluidics; electrokinetics; desalination; ion exchange membrane; lab-on-a-chip
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Special Issue Information

Dear Colleagues,

Recently, nanofluidics has gained a tremendous amount of interest in high-performance microfluidic lab on a chip applications at the smallest scale level as well as conventional research fields. Basically, nanofluidics is the study of the behavior, manipulation, and control of fluids that are confined to structures of nanometer (typically 1–100 nm) characteristic dimensions (1 nm = 10−9 m). A significant growth of research in nanofluidics has been achieved, but there are still many challenges to understand new physical phenomena and underlying mechanism for nanofluidics. Based on those studies, a various applications for nanofluidics can be developed providing considerable opportunities. This special issue will highlight the progress that has been made in theory, fabrication, and application of recent micro/nano fluidics, as well as show readers new opportunities and insight of future nanofluidics.

Dr. Bumjoo Kim
Guest Editor

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Keywords

  • micro/nano fluidics
  • lab-on-a-chip
  • mass transport
  • electrokinetics
  • concentration polarization
  • fabrication of nanofluidic device
  • application of nanofluidics

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Published Papers (3 papers)

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Research

11 pages, 3049 KiB  
Article
Experimental Study on Ion Transport in Microfluidic Electrodialysis Using Partially Masked Ion Exchange Membranes
by Junsu Jang, Minsung Kim, Joonghan Shin, Daejong Yang, Minseok Kim and Bumjoo Kim
Micromachines 2022, 13(3), 356; https://doi.org/10.3390/mi13030356 - 24 Feb 2022
Cited by 8 | Viewed by 2366
Abstract
Electrodialysis using anion-exchange membranes (AEMs) and cation-exchange membranes (CEMs) has been widely used for water desalination and the management of various ionic species. During commercial electrodialysis, the available area of an ion-exchange membrane is reduced by a non-conductive spacer that is in contact [...] Read more.
Electrodialysis using anion-exchange membranes (AEMs) and cation-exchange membranes (CEMs) has been widely used for water desalination and the management of various ionic species. During commercial electrodialysis, the available area of an ion-exchange membrane is reduced by a non-conductive spacer that is in contact with the AEM/CEM. Although multiple reports have described the advantages or disadvantages of spacers, fewer studies have explored the effects of spacers on the mass transport effect of the reduced membrane area excluding the fluid flow change. In this paper, we present our experimental studies concerning mass transport in microfluidic electrodialysis systems with partially masked ion-exchange membranes. Six different types of masking membranes were prepared by the deposition of non-conductive films on parts of the membranes. The experimental results showed that the overlapped types (in which masking was vertically aligned in the AEM/CEM) exhibited a larger electrical conductance and better current/energy efficiency, compared with the non-overlapped types (in which masking was vertically dislocated in the AEM/CEM). We also observed that a reduction in the unit length of the unmasked ion-exchange membrane enhanced overall mass transport. Our results demonstrate the effects of patterned membranes on electrical resistance and desalination performance; they also identify appropriate arrangements for electromembrane systems. Full article
(This article belongs to the Special Issue State-of-the-Art Nanofluidics)
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12 pages, 4434 KiB  
Article
Simulation and Experimental Study of Ion Concentration Polarization Induced Electroconvective Vortex and Particle Movement
by Junghyo Yoon, Youngkyu Cho, Jaehoon Kim, Hyunho Kim, Kyuhwan Na, Jeong Hoon Lee and Seok Chung
Micromachines 2021, 12(8), 903; https://doi.org/10.3390/mi12080903 - 29 Jul 2021
Cited by 2 | Viewed by 3059
Abstract
Ion concentration polarization (ICP) has been widely applied in microfluidic systems in pre-concentration, particle separation, and desalination applications. General ICP microfluidic systems have three components (i.e., source, ion-exchange, and buffer), which allow selective ion transport. Recently developed trials to eliminate one of the [...] Read more.
Ion concentration polarization (ICP) has been widely applied in microfluidic systems in pre-concentration, particle separation, and desalination applications. General ICP microfluidic systems have three components (i.e., source, ion-exchange, and buffer), which allow selective ion transport. Recently developed trials to eliminate one of the three components to simplify the system have suffered from decreased performance by the accumulation of unwanted ions. In this paper, we presented a new ICP microfluidic system with only an ion-exchange membrane-coated channel. Numerical investigation on hydrodynamic flow and electric fields with a series of coupled governing equations enabled a strong correlation to experimental investigations on electroconvective vortices and the trajectory of charged particles. This study has significant implications for the development and optimization of ICP microfluidic and electrochemical systems for biomarker concentration and separation to improve sensing reliability and detection limits in analytic chemistry. Full article
(This article belongs to the Special Issue State-of-the-Art Nanofluidics)
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14 pages, 6918 KiB  
Article
Diffusivity Measurement by Single-Molecule Recycling in a Capillary Microchannel
by Bo Wang and Lloyd M. Davis
Micromachines 2021, 12(7), 800; https://doi.org/10.3390/mi12070800 - 6 Jul 2021
Viewed by 1989
Abstract
Microfluidic devices have been extensively investigated in recent years in fields including ligand-binding analysis, chromatographic separation, molecular dynamics, and DNA sequencing. To prolong the observation of a single molecule in aqueous buffer, the solution in a sub-micron scale channel is driven by a [...] Read more.
Microfluidic devices have been extensively investigated in recent years in fields including ligand-binding analysis, chromatographic separation, molecular dynamics, and DNA sequencing. To prolong the observation of a single molecule in aqueous buffer, the solution in a sub-micron scale channel is driven by a electric field and reversed after a fixed delay following each passage, so that the molecule passes back and forth through the laser focus and the time before irreversible photobleaching is extended. However, this practice requires complex chemical treatment to the inner surface of the channel to prevent unexpected sticking to the surface and the confined space renders features, such as a higher viscosity and lower dielectric constant, which slow the Brownian motion of the molecule compared to the bulk solution. Additionally, electron beam lithography used for the fabrication of the nanochannel substantially increases the cost, and the sub-micron dimensions make the molecule difficult to locate. In this paper, we propose a method of single-molecule recycling in a capillary microchannel. A commercial fused-silica capillary with an inner diameter of 2 microns is chopped into a 1-inch piece and is fixed onto a cover slip. Two o-rings on the sides used as reservoirs and an o-ring in the middle used as observation window are glued over the capillary. The inner surface of the capillary is chemically processed to reduce the non-specific sticking and to improve capillary effect. The device does not require high-precision fabrication and thus is less costly and easier to prepare than the nanochannel. 40 nm Fluospheres® in 50% methanol are used as working solution. The capillary is translated by a piezo stage to recycle the molecule, which diffuses freely through the capillary, and a confocal microscope is used for fluorescence collection. The passing times of the molecule through the laser focus are calculated by a real-time control system based on an FPGA, and the commands of translation are given to the piezo stage through a feedback algorithm. The larger dimensions of the capillary overcomes the strong sticking, the reduced diffusivity, and the difficulty of localizing the molecule. We have achieved a maximum number of recycles of more than 200 and developed a maximum-likelihood estimation of the diffusivity of the molecule, which attains results of the same magnitude as the previous report. This technique simplifies the overall procedure of the single-molecule recycling and could be useful for the ligand-binding studies in high-throughput screening. Full article
(This article belongs to the Special Issue State-of-the-Art Nanofluidics)
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