Imaging Molecular Transport in Porous Membranes. Observation and Analysis of Electroosmotic Flow in Individual Pores Using the Scanning Electrochemical Microscope

1998 ◽  
Vol 70 (6) ◽  
pp. 1047-1058 ◽  
Author(s):  
Bradley D. Bath ◽  
Rachel D. Lee ◽  
Henry S. White ◽  
Erik R. Scott
Keyword(s):  
Electroosmotic Flow ◽  
Molecular Transport ◽  
Porous Membranes ◽  
Scanning Electrochemical Microscope

scholarly journals Quasi-Unidirectional Transport Bilayer Two-Dimensional Nanopores for Highly-Efficient Molecular Sieving

2021 ◽  
Vol 9 ◽  
Author(s):  
Chengzhen Sun ◽  
Cheng Liu ◽  
Kailin Luo ◽  
Bofeng Bai
Keyword(s):  
Hexagonal Boron Nitride ◽  
Single Layer ◽  
Molecular Transport ◽  
Single Layer Graphene ◽  
Porous Membranes ◽  
Two Dimensional ◽  
Gas Molecules ◽  
Dynamics Simulations ◽  
Two Sides ◽  
Molecular Sieving

Two-dimensional nanopores are very promising for high-permeance molecular sieving, but the molecular backflow from permeate-side to feed-side is not beneficial for improving molecular permeance. We study the quasi-unidirectional molecular transport through a graphene-hexagonal boron nitride bilayer nanopore, aiming to realize a high-permeance molecular sieving. Molecular dynamics simulations of CO2/CH4 separations show that the bilayer pore presents 3.7 times higher selectivity comparing to the single-layer graphene nanopore with the same size. The quasi-unidirectional molecular transport is attributed to the distinctive adsorption abilities of gas molecules on the two sides of bilayer nanopores and the inhibited molecular backflow from permeate-side to feed-side. This work provides a promising way to realize the ultra-permeable porous membranes with molecular permeance even higher than the single-layer atomic-thickness membranes.

Tools to Quantify Molecular Transport: Electroosmosis Dominates Electrophoresis of Fluoroquinolones Across the Outer Membrane Porin F (OmpF)

2019 ◽  
Author(s):  
Jayesh Arun Bafna ◽  
Sushil Pangeni ◽  
Mathias Winterhalter ◽  
M. Alphan Aksoyoglu
Keyword(s):  
Statistical Analysis ◽  
Diffusion Coefficients ◽  
Energy Barrier ◽  
Electroosmotic Flow ◽  
Channel Wall ◽  
Molecular Transport ◽  
Slowing Down ◽  
Outer Membrane Porin ◽  
Mobile Ions ◽  
Electroosmotic Velocity

We report that the dynamics of antibiotic capture and transport across a voltage-biased OmpF nanopore is dominated by the electroosmotic flow rather than the electrophoretic force. By reconstituting an OmpF porin in an artificial lipid bilayer and applying an electric field across, we are able to elucidate the permeation of molecules, and their mechanism of transport. This field gives rise to an electrophoretic force acting directly on a charged substrate, but also indirectly via coupling to all other mobile ions causing an electroosmotic flow. The directionality and magnitude of this flow depends on the selectivity of the channel. Modifying the charge state of three different substrates (Norfloxacin, Ciprofloxacin, and Enoxacin) by varying the pH between 6 and 9, while the charge and selectivity of OmpF is conserved, allows us to work under conditions where EOF and electrophoretic forces add or oppose. This configuration allows us to identify and distinguish the contributions of the electroosmotic flow and the electrophoretic force on translocation. Statistical analysis of the resolvable dwell-times reveals rich kinetic details regarding the direction and the stochastic movement of antibiotics inside the nanopore. We quantitatively describe the electroosmotic velocity component experienced by the substrates, and their diffusion coefficients inside the porin with an estimate of the energy barrier experienced by the molecules, caused by the interaction with the channel wall, slowing down the permeation by several orders of magnitude.

scholarly journals Transdermal electroosmotic flow generated by a porous microneedle array patch

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Shinya Kusama ◽  
Kaito Sato ◽  
Yuuya Matsui ◽  
Natsumi Kimura ◽  
Hiroya Abe ◽  
...  
Keyword(s):  
Electroosmotic Flow ◽  
Molecular Transport ◽  
Skin Barrier ◽  
External Pressure ◽  
Solid Polymer ◽  
Microneedle Array ◽  
Skin Sample ◽  
Assisted Delivery ◽  
Attractive Option ◽  
Model Drug

AbstractA microneedle array is an attractive option for a minimally invasive means to break through the skin barrier for efficient transdermal drug delivery. Here, we report the applications of solid polymer-based ion-conductive porous microneedles (PMN) containing interconnected micropores for improving iontophoresis, which is a technique of enhancing transdermal molecular transport by a direct current through the skin. The PMN modified with a charged hydrogel brings three innovative advantages in iontophoresis at once: (1) lowering the transdermal resistance by low-invasive puncture of the highly resistive stratum corneum, (2) transporting of larger molecules through the interconnected micropores, and (3) generating electroosmotic flow (EOF). In particular, the PMN-generated EOF greatly enhances the transdermal molecular penetration or extraction, similarly to the flow induced by external pressure. The enhanced efficiencies of the EOF-assisted delivery of a model drug (dextran) and of the extraction of glucose are demonstrated using a pig skin sample. Furthermore, the powering of the PMN-based transdermal EOF system by a built-in enzymatic biobattery (fructose / O2 battery) is also demonstrated as a possible totally organic iontophoresis patch.

scholarly journals Permeability of Epithelial/Endothelial Barriers in Transwells and Microfluidic Bilayer Devices

Micromachines ◽  
2019 ◽  
Vol 10 (8) ◽  
pp. 533 ◽  
Author(s):  
Timothy S. Frost ◽  
Linan Jiang ◽  
Ronald M. Lynch ◽  
Yitshak Zohar
Keyword(s):  
Shear Stress ◽  
Drug Development ◽  
Drug Absorption ◽  
Molecular Transport ◽  
Cell Junctions ◽  
Paracellular Transport ◽  
Porous Membranes ◽  
Transcellular Transport ◽  
Chip Technology ◽  
Bilayer Devices

Lung-on-a-chip (LoC) models hold the potential to rapidly change the landscape for pulmonary drug screening and therapy, giving patients more advanced and less invasive treatment options. Understanding the drug absorption in these microphysiological systems, modeling the lung-blood barrier is essential for increasing the role of the organ-on-a-chip technology in drug development. In this work, epithelial/endothelial barrier tissue interfaces were established in microfluidic bilayer devices and transwells, with porous membranes, for permeability characterization. The effect of shear stress on the molecular transport was assessed using known paracellular and transcellular biomarkers. The permeability of porous membranes without cells, in both models, is inversely proportional to the molecular size due to its diffusivity. Paracellular transport, between epithelial/endothelial cell junctions, of large molecules such as transferrin, as well as transcellular transport, through cell lacking required active transporters, of molecules such as dextrans, is negligible. When subjected to shear stress, paracellular transport of intermediate-size molecules such as dextran was enhanced in microfluidic devices when compared to transwells. Similarly, shear stress enhances paracellular transport of small molecules such as Lucifer yellow, but its effect on transcellular transport is not clear. The results highlight the important role that LoC can play in drug absorption studies to accelerate pulmonary drug development.

scholarly journals Tools to Quantify Molecular Transport: Electroosmosis Dominates Electrophoresis of Fluoroquinolones Across the Outer Membrane Porin F (OmpF)

2019 ◽  
Author(s):  
Jayesh Arun Bafna ◽  
Sushil Pangeni ◽  
Mathias Winterhalter ◽  
M. Alphan Aksoyoglu
Keyword(s):  
Statistical Analysis ◽  
Diffusion Coefficients ◽  
Energy Barrier ◽  
Electroosmotic Flow ◽  
Channel Wall ◽  
Molecular Transport ◽  
Slowing Down ◽  
Outer Membrane Porin ◽  
Mobile Ions ◽  
Electroosmotic Velocity

We report that the dynamics of antibiotic capture and transport across a voltage-biased OmpF nanopore is dominated by the electroosmotic flow rather than the electrophoretic force. By reconstituting an OmpF porin in an artificial lipid bilayer and applying an electric field across, we are able to elucidate the permeation of molecules, and their mechanism of transport. This field gives rise to an electrophoretic force acting directly on a charged substrate, but also indirectly via coupling to all other mobile ions causing an electroosmotic flow. The directionality and magnitude of this flow depends on the selectivity of the channel. Modifying the charge state of three different substrates (Norfloxacin, Ciprofloxacin, and Enoxacin) by varying the pH between 6 and 9, while the charge and selectivity of OmpF is conserved, allows us to work under conditions where EOF and electrophoretic forces add or oppose. This configuration allows us to identify and distinguish the contributions of the electroosmotic flow and the electrophoretic force on translocation. Statistical analysis of the resolvable dwell-times reveals rich kinetic details regarding the direction and the stochastic movement of antibiotics inside the nanopore. We quantitatively describe the electroosmotic velocity component experienced by the substrates, and their diffusion coefficients inside the porin with an estimate of the energy barrier experienced by the molecules, caused by the interaction with the channel wall, slowing down the permeation by several orders of magnitude.

Synthesis of Smart Mesoporous Materials

2003 ◽  
Vol 775 ◽  
Author(s):  
G.V.Rama Rao ◽  
Qiang Fu ◽  
Linnea K. Ista ◽  
Huifang Xu ◽  
S. Balamurugan ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Mesoporous Materials ◽  
Fluorescent Dyes ◽  
Thermo Gravimetric Analysis ◽  
Molecular Transport ◽  
Solute Diffusion ◽  
Gravimetric Analysis ◽  
Stimuli Responsive ◽  
Porous Network ◽  
Hybrid Mesoporous Materials

AbstractThis study details development of hybrid mesoporous materials in which molecular transport through mesopores can be precisely controlled and reversibly modulated. Mesoporous silica materials formed by surfactant templating were modified by surface initiated atom transfer radical polymerization of poly(N-isopropyl acrylamide) (PNIPAAm) a stimuli responsive polymer (SRP) within the porous network. Thermo gravimetric analysis and FTIR spectroscopy were used to confirm the presence of PNIPAAm on the silica surface. Nitrogen porosimetry, transmission electron microscopy and X-ray diffraction analyses confirmed that polymerization occurred uniformly within the porous network. Uptake and release of fluorescent dyes from the particles was monitored by spectrofluorimetry and scanning laser confocal microscopy. Results suggest that the presence of PNIPAAm, a SRP, in the porous network can be used to modulate the transport of aqueous solutes. At low temperature, (e.g., room temperature) the PNIPAAm is hydrated and extended and inhibits transport of analytes; at higher temperatures (e.g., 50°C) it is hydrophobic and is collapsed within the pore network, thus allowing solute diffusion into or out of the mesoporous silica. The transition form hydrophilic to hydrophobic state on polymer grafted mesoporous membranes was determined by contact angle measurements. This work has implications for the development of materials for the selective control of transport of molecular solutes in a variety of applications.

Seeded Growth of Single-Crystal Two-Dimensional Covalent Organic Frameworks

2017 ◽  
Author(s):  
Austin M. Evans ◽  
Lucas R. Parent ◽  
Nathan C. Flanders ◽  
Ryan P. Bisbey ◽  
Edon Vitaku ◽  
...  
Keyword(s):  
Molecular Transport ◽  
Controlled Synthesis ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
Seeded Growth ◽  
Covalent Bonds ◽  
Crystalline Materials ◽  
Step Procedure ◽  
Structures And Properties ◽  
2D Polymer

<div> <div> <div> <p>Polymerizing monomers into periodic two-dimensional (2D) networks provides structurally precise, atomically thin macromolecular sheets linked by robust, covalent bonds. These materials exhibit desirable mechanical, optoelectrotronic, and molecular transport properties derived from their designed structure and permanent porosity. 2D covalent organic frameworks (COFs) offer broad monomer scope, but are generally isolated as polycrystalline, insoluble powders with limited processability. Here we overcome this limitation by controlling 2D COF formation using a two- step procedure. In the first step, 2D COF nanoparticle seeds are prepared with approximate diameters of 30 nm. Next, monomers are slowly added to suppress new nucleation while promoting epitaxial growth on the existing seeds to sizes of several microns. The resulting COF nanoparticles are of exceptional and unprecedented quality, isolated as single crystalline materials with micron-scale domain sizes. These findings advance the controlled synthesis of 2D layered COFs and will enable a broad exploration of synthetic 2D polymer structures and properties. </p> </div> </div> </div>

Seeded Growth of Single-Crystal Two-Dimensional Covalent Organic Frameworks

2017 ◽  
Author(s):  
Austin M. Evans ◽  
Lucas R. Parent ◽  
Nathan C. Flanders ◽  
Ryan P. Bisbey ◽  
Edon Vitaku ◽  
...  
Keyword(s):  
Molecular Transport ◽  
Controlled Synthesis ◽  
Two Dimensional ◽  
Covalent Organic Frameworks ◽  
Seeded Growth ◽  
Covalent Bonds ◽  
Crystalline Materials ◽  
Step Procedure ◽  
Structures And Properties ◽  
2D Polymer

<div> <div> <div> <p>Polymerizing monomers into periodic two-dimensional (2D) networks provides structurally precise, atomically thin macromolecular sheets linked by robust, covalent bonds. These materials exhibit desirable mechanical, optoelectrotronic, and molecular transport properties derived from their designed structure and permanent porosity. 2D covalent organic frameworks (COFs) offer broad monomer scope, but are generally isolated as polycrystalline, insoluble powders with limited processability. Here we overcome this limitation by controlling 2D COF formation using a two- step procedure. In the first step, 2D COF nanoparticle seeds are prepared with approximate diameters of 30 nm. Next, monomers are slowly added to suppress new nucleation while promoting epitaxial growth on the existing seeds to sizes of several microns. The resulting COF nanoparticles are of exceptional and unprecedented quality, isolated as single crystalline materials with micron-scale domain sizes. These findings advance the controlled synthesis of 2D layered COFs and will enable a broad exploration of synthetic 2D polymer structures and properties. </p> </div> </div> </div>

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