Mingkan Zhang

University of Wyoming, Ларами, Wyoming, United States

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Publications (13)58.91 Total impact

  • Zhenping Zeng · Li-Hsien Yeh · Mingkan Zhang · Shizhi Qian ·
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    ABSTRACT: Inspired by nature, functionalized nanopores with biomimetic structures have attracted growing interests in using them as novel platforms for applications of regulating ion and nanoparticle transport. To improve these emerging applications, we study theoretically for the first time the ion transport and selectivity in short nanopores functionalized with pH tunable, zwitterionic polyelectrolyte (PE) brushes. In addition to background salt ions, the study takes into account the presence of H(+) and OH(-) ions along with the chemistry reactions between functional groups on PE chains and protons. Due to ion concentration polarization, the charge density of PE layers is not homogeneously distributed and depends significantly on the background salt concentration, pH, grafting density of PE chains, and applied voltage bias, thereby resulting in many interesting and unexpected ion transport phenomena in the nanopore. For example, the ion selectivity of the biomimetic nanopore can be regulated from anion-selective (cation-selective) to cation-selective (anion-selective) by diminishing (raising) the solution pH when a sufficiently small grafting density of PE chains, large voltage bias, and low background salt concentration are applied.
    Nanoscale 09/2015; 7(40). DOI:10.1039/c5nr05828g · 7.39 Impact Factor
  • Mingkan Zhang · Ye Zhang ·
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    ABSTRACT: A laboratory-generated hierarchical, fully heterogeneous aquifer model (FHM) provides a reference for developing and testing an upscaling approach that integrates large-scale connectivity mapping with flow and transport modeling. Based on the FHM, three hydrostratigraphic models (HSMs) that capture lithological (static) connectivity at different resolutions are created, each corresponding to a sedimentary hierarchy. Under increasing system lnK variances (0.1, 1.0, 4.5), flow upscaling is first conducted to calculate equivalent hydraulic conductivity for individual connectivity (or unit) of the HSMs. Given the computed flow fields, an instantaneous, conservative tracer test is simulated by all models. For the HSMs, two upscaling formulations are tested based on the advection-dispersion equation (ADE), implementing space versus time-dependent macrodispersivity. Comparing flow and transport predictions of the HSMs against those of the reference model, HSMs capturing connectivity at increasing resolutions are more accurate, although upscaling errors increase with system variance. Results suggest: (1) by explicitly modeling connectivity, an enhanced degree of freedom in representing dispersion can improve the ADE-based upscaled models by capturing non-Fickian transport of the FHM; (2) when connectivity is sufficiently resolved, the type of data conditioning used to model transport becomes less critical. Data conditioning, however, is influenced by the prediction goal; (3) when aquifer is weakly-to-moderately heterogeneous, the upscaled models adequately capture the transport simulation of the FHM, despite the existence of hierarchical heterogeneity at smaller scales. When aquifer is strongly heterogeneous, the upscaled models become less accurate because lithological connectivity cannot adequately capture preferential flows; (4) three-dimensional transport connectivities of the hierarchical aquifer differ quantitatively from those analyzed for two-dimensional systems.
    02/2015; 51(3). DOI:10.1002/2014WR016202
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    Li-Hsien Yeh · Mingkan Zhang · Shizhi Qian ·
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    ABSTRACT: Fundamental understanding of ion transport phenomena in nanopores is crucial for designing the next-generation nanofluidic devices. Due to surface reactions of dissociable functional groups on the nanopore wall, its surface charge density highly depends upon the proton concentration on the nanopore wall, which in turn affects the electrokinetic transport of ions, fluid, and particles within the nanopore. Electrokinetic ion transport in a pH-regulated nanopore, taking into account both multiple ionic species and charge-regulation on the nanopore wall, is theoretically investigated for the first time. The model is verified by the experimental data of nanopore conductance available in the literature. Results demonstrate that the spatial distribution of the surface charge density at the nanopore wall and the resulting ion transport phenomena, such as ion concentration polarization (ICP), ion selectivity, and conductance, are significantly affected by the background solution properties like pH and salt concentration.
    Analytical Chemistry 06/2013; 85(15). DOI:10.1021/ac401536g · 5.64 Impact Factor
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    Cetin Canpolat · Mingkan Zhang · William Rosen · Shizhi Qian · Ali Beskok ·
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    ABSTRACT: Induced-charge electroosmosis (ICEO) around multiple gold-coated stainless steel rods under different ac electric fields is analyzed using microparticle image velocimetry (micro-PIV) and numerical simulations. In the present investigation, the induced electric double layer (EDL) is in weakly nonlinear limit. The ICEO flow around multiple touching rods exhibits geometry dependent quadrupolar flow structures with four vortices. The velocity magnitude is proportional to the square of the electric field. The ICEO flow velocity also depends on the cylinder orientation. The velocity increases with increased radial distance from the rod's surface, attains a maximum, and then decays to zero. Experimental and numerical velocity distributions have the same trend beyond 0.2 mm of the rod's surface.
    Journal of Fluids Engineering 02/2013; 135(2-2). DOI:10.1115/1.4023452 · 0.93 Impact Factor
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    Li-Hsien Yeh · Mingkan Zhang · Sang W Joo · Shizhi Qian ·
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    ABSTRACT: In the next-generation nanopore-based DNA sequencing technique, the DNA nanoparticles are electrophoretically driven through a nanopore by an external electric field, and the ionic current through the nanopore is simultaneously altered and recorded during the DNA translocation process. The change in the ionic current through the nanopore as the DNA molecule passes through the nanopore represents a direct reading of the DNA sequence. Due to the large mismatch of the cross-sectional areas of the nanopore and the microfluidic reservoirs, the electric field inside the nanopore is significantly higher than that in the fluid reservoirs. This results in high-speed DNA translocation through the nanopore and consequently low read-out accuracy on the DNA sequences. Slowing down DNA translocation through the nanopore thus is one of the challenges in the nanopore-based DNA sequencing technique. Slowing down DNA translocation by lowering the fluid temperature is theoretically investigated for the first time using a continuum model, composed of the coupled Poisson-Nernst-Planck equations for the ionic mass transport and the Navier-Stokes equations for the hydrodynamic field. The results qualitatively agree with the existing experimental results. Lowering the fluid temperature from 25 to 0°C reduces the translocation speed by a magnitude of about 6.21 to 2.50 mm/sK (i.e. 49.82 to 49.71%) for the salt concentration at 200 and 2000 mM, respectively, improving the read-out accuracy considerably. As the fluid temperature decreases, the magnitude of the ionic current signal decreases (increases) when the salt concentration is high (sufficiently low).
    Electrophoresis 12/2012; 33(23). DOI:10.1002/elps.201200142 · 3.03 Impact Factor
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    Li-Hsien Yeh · Mingkan Zhang · Sang W Joo · Shizhi Qian · Jyh-Ping Hsu ·
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    ABSTRACT: A novel polyelectrolyte (PE)-modified nanopore, comprising a solid-state nanopore functionalized by a nonregulated PE brush layer connecting two large reservoirs, is proposed to regulate the electrokinetic translocation of a soft nanoparticle (NP), comprising a rigid core covered by a pH-regulated, zwitterionic, soft layer, through it. The type of NP considered mimics bionanoparticles such as proteins and biomolecules. We find that a significant enrichment of H(+) occurs near the inlet of a charged solid-state nanopore, appreciably reducing the charge density of the NP as it approaches there, thereby lowering the NP translocation velocity and making it harder to thread the nanopore. This difficulty can be resolved by the proposed PE-modified nanopore, which raises effectively both the capture rate and the capture velocity of the soft NP and simultaneously reduces its translocation velocity through the nanopore so that both the sensing efficiency and the resolution are enhanced. The results gathered provide a conceptual framework for the interpretation of relevant experimental data and for the design of nanopore-based devices used in single biomolecules sensing and DNA sequencing.
    Analytical Chemistry 10/2012; 84(21). DOI:10.1021/ac302429d · 5.64 Impact Factor
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    Li-Hsien Yeh · Mingkan Zhang · Ning Hu · Sang W Joo · Shizhi Qian · Jyh-Ping Hsu ·
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    ABSTRACT: Chemically functionalized nanopores in solid-state membranes have recently emerged as versatile tools for regulating ion transport and sensing single biomolecules. This study theoretically investigated the importance of the bulk salt concentration, the geometries of the nanopore, and both the thickness and the grafting density of the polyelectrolyte (PE) brushes on the electrokinetic ion and fluid transport in two types of PE brush functionalized nanopore: PE brushes are end-grafted to the entire membrane surface (system I), and to its inner surface only (nanopore wall) (system II). Due to a more significant ion concentration polarization (CP), the enhanced local electric field inside the nanopore, the conductance, and the electroosmotic flow (EOF) velocity in system II are remarkably smaller than those in system I. In addition to a significantly enhanced EOF inside the nanopore, the direction of the flow field near both nanopore openings in system I is opposite to that of EOF inside the nanopore. This feature can be applied to regulate the electrokinetic translocation of biomolecules through a nanopore in the nanopore-based DNA sequencing platform.
    Nanoscale 07/2012; 4(16):5169-77. DOI:10.1039/c2nr31069d · 7.39 Impact Factor
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    Li-Hsien Yeh · Mingkan Zhang · Shizhi Qian · Jyh-Ping Hsu · Shiojenn Tseng ·
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    ABSTRACT: Nanopores functionalized with synthetic or biological polyelectrolyte (PE) brushes have significant potentials to rectify ionic current and probe single biomacromolecules. In this work, electric-field-induced ion transport and the resulting conductance in a PE-modified nanopore are theoretically studied using a continuum-based model, composed of coupled Poisson–Nernst–Planck (PNP) equations for the ionic mass transport, and Stokes and Brinkman equations for the hydrodynamic fields in the exterior and interior of the PE layer, respectively. Because of the competition between the transport of counterions and co-ions in the nanopore, two distinct types of ion concentration polarization (CP) occur at either opening of the PE-modified nanopore. These distinct CP behaviors, which significantly affect the nanopore conductance, can be easily manipulated by adjusting the bulk salt concentration and the imposed potential bias. The induced CP in the PE-modified nanopore is more appreciable than that in the corresponding bare solid-state nanopore.
    The Journal of Physical Chemistry C 04/2012; 116(15):8672–8677. DOI:10.1021/jp301957j · 4.77 Impact Factor
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    Li-Hsien Yeh · Mingkan Zhang · Shizhi Qian · Jyh-Ping Hsu ·
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    ABSTRACT: Nanopores have emerged as promising next-generation devices for DNA sequencing technology. The two major challenges in such devices are: (i) find an efficient way to raise the DNA capture rate prior to funnelling a nanopore, and (ii) reduce the translocation velocity inside it so that single base resolution can be attained efficiently. To achieve these, a novel soft nanopore comprising a solid-state nanopore and a functionalized soft layer is proposed to regulate the DNA electrokinetic translocation. We show that, in addition to the presence of an electroosmotic flow (EOF), which reduces the DNA translocation velocity, counterion concentration polarization (CP) occurs near the entrance of the nanopore. The latter establishes an enrichment of the counterion concentration field, thereby electrostatically enhancing the capture rate. The dependence of the ionic current on the bulk salt concentration, the soft layer properties, and the length of the nanopore are investigated. We show that if the salt concentration is low, the ionic current depends largely upon the length of the nanopore, and the density of the fixed charge of the soft layer, but not upon its degree of softness. On the other hand, if it is high, ionic current blockade always occurs, regardless of the levels of the other parameters. The proposed soft nanopore is capable of enhancing the performance of DNA translocation while maintaining its basic signature of the ionic current at high salt concentration. The results gathered provide the necessary information for designing devices used in DNA sequencing.
    Nanoscale 03/2012; 4(8):2685-93. DOI:10.1039/c2nr30102d · 7.39 Impact Factor
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    Mingkan Zhang · Li-Hsien Yeh · Shizhi Qian · Jyh-Ping Hsu · Sang W. Joo ·
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    ABSTRACT: The effect of the local liquid permittivity surrounding the DNA nanoparticle, referred to as the local permittivity environment (LPE) effect, on its electrokinetic translocation through a nanopore is investigated for the first time using a continuum-based model, composed of the coupled Poisson–Nernst–Planck (PNP) equations for the ionic mass transport and the Stokes and Brinkman equations for the hydrodynamic fields in the region outside of the DNA and within the ion-penetrable layer of the DNA nanoparticle, respectively. The nanoparticle translocation velocity and the resulting current deviation are systematically investigated for both uniform and spatially varying permittivities surrounding the DNA nanoparticle under various conditions. The LPE effect in general reduces the particle translocation velocity. The LPE effect on the current deviation is insignificant when the imposed electric field is relatively high. However, when the electric field and the bulk electrolyte concentration are relatively low, both current blockade and enhancement are predicted with the LPE effect incorporated, while only current blockade is predicted with the assumption of constant liquid permittivity. It is thereby shown that regardless of the electric field imposed the predictions on ionic current with considering the LPE effect are in good qualitative agreement with the experimental observations obtained in the literature.
    The Journal of Physical Chemistry C 02/2012; 116(7). DOI:10.1021/jp211798x · 4.77 Impact Factor
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    Mingkan Zhang · Ye Ai · Ashutosh Sharma · Sang W Joo · Dong-Soo Kim · Shizhi Qian ·
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    ABSTRACT: Electrokinetic particle translocation through a nanopore containing a floating electrode is investigated by solving a continuum model, composed of the coupled Poisson-Nernst-Planck (PNP) equations for the ionic mass transport and the modified Stokes equations for the flow field. Two effects due to the presence of the floating electrode, the induced-charge electroosmosis (ICEO) and the particle-floating electrode electrostatic interaction, could significantly affect the electrokinetic mobility of DNA nanoparticles. When the electrical double layers (EDLs) of the DNA nanoparticle and the floating electrode are not overlapped, the particle-floating electrode electrostatic interaction becomes negligible. As a result, the DNA nanoparticle could be trapped near the floating electrode arising from the induced-charge electroosmosis when the applied electric field is relatively high. The presence of the floating electrode attracts more ions inside the nanopore resulting in an increase in the ionic current flowing through the nanopore; however, it has a limited effect on the deviation of the current from its base current when the particle is far from the pore.
    Electrophoresis 07/2011; 32(14):1864-74. DOI:10.1002/elps.201100050 · 3.03 Impact Factor
  • Mingkan Zhang · Ye Ai · Dong-Soo Kim · Jun-Ho Jeong · Sang W Joo · Shizhi Qian ·
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    ABSTRACT: Many biocolloids, biological cells and micro-organisms are soft particles, consisted with a rigid inner core covered by an ion-permeable porous membrane layer. The electrophoretic motion of a soft spherical nanoparticle in a nanopore filled with an electrolyte solution has been investigated using a continuum mathematical model. The model includes the Poisson-Nernst-Planck (PNP) equations for the ionic mass transport and the modified Stokes and Brinkman equations for the hydrodynamic fields outside and inside the porous membrane layer, respectively. The effects of the "softness" of the nanoparticle on its electrophoretic velocity along the axis of a nanopore are examined with changes in the ratio of the radius of the rigid core to the double layer thickness, the ratio of the thickness of the porous membrane layer to the radius of the rigid core, the friction coefficient of the porous membrane layer, the fixed charge inside the porous membrane layer of the particle and the ratio of the radius of the nanopore to that of the rigid core. The presence of the soft membrane layer significantly affects the particle electrophoretic mobility.
    Colloids and surfaces B: Biointerfaces 06/2011; 88(1):165-74. DOI:10.1016/j.colsurfb.2011.06.027 · 4.15 Impact Factor
  • Ye Ai · Mingkan Zhang · Sang W. Joo · Marcos A. Cheney · Shizhi Qian ·
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    ABSTRACT: The effects of electroosmotic flow (EOF) oil the ionic current rectification (ICR) phenomenon in conical nanopores,ire studied comprehensively With use of a continuum model, composed of Nernst-Planck equations for the ionic concentrations, the Poisson equation for the electric potential, and Navier-Stokes equations for the flow field. It is found that the preferential Current direction of a negatively charged nanopore is toward the base (tip) under a relatively high (low) kappa R(1), the ratio of the tip radius size to the Debye length. The direction also changes with the charge polarity of the nanopore. The EOF effect on the ionic Current rectification ratio in a conical nanopore becomes noticeable at an intermediate kappa R(1) and Surface charge density of the nanopore, meanwhile increasing significantly with the applied voltage.
    The Journal of Physical Chemistry C 03/2010; 114(9-9):3883-3890. DOI:10.1021/jp911773m · 4.77 Impact Factor

Publication Stats

252 Citations
58.91 Total Impact Points


  • 2013-2015
    • University of Wyoming
      • Department of Geology and Geophysics
      Ларами, Wyoming, United States
  • 2010-2013
    • Old Dominion University
      • • Institute of Micro and Nanotechnology
      • • Department of Mechanical and Aerospace Engineering
      Norfolk, Virginia, United States