Electroosmotic flow in nanoporous membranes in the region of electric double layer overlap

Leese, Hannah S.; Mattia, Davide

doi:10.1007/s10404-013-1255-0

Cited by 11 publications

(14 citation statements)

References 37 publications

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“…(b) Electro-osmotic experiments EOF measurements in the CNT membranes were conducted using a custom-made rig and membrane holder described by Leese & Mattia [6]. The membranes were sandwiched between two platinum mesh electrodes (99.99%, 52 mesh per inch) and placed across two flanges using soft rubber to ensure seal.…”

Section: Materials and Methods (A) Carbon Nanotube Membrane Fabricationmentioning

confidence: 99%

Electro-osmotic flow enhancement in carbon nanotube membranes

Mattia

Leese

Calabrò

2016

Phil. Trans. R. Soc. A.

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In this work, experimental evidence of the presence of electro-osmotic flow (EOF) in carbon nanotube membranes with diameters close to or in the region of electrical double layer overlap is presented for two different electrolytes for the first time. No EOF in this region should be present according to the simplified theoretical framework commonly used for EOF in micrometre-sized channels. The simplifying assumptions concern primarily the electrolyte charge density structure, based on the Poisson-Boltzmann (P-B) equation. Here, a numerical analysis of the solutions for the simplified case and for the nonlinear and the linearized P-B equations is compared with experimental data. Results show that the simplified solution produces a significant deviation from experimental data, whereas the linearized solution of the P-B equation can be adopted with little error compared with the full P-B case. This work opens the way to using electro-osmotic pumping in a wide range of applications, from membrane-based ultrafiltration and nanofiltration (as a more efficient alternative to mechanical pumping at the nanoscale) to further miniaturization of lab-on-a-chip devices at the nanoscale for in vivo implantation.

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Section: Materials and Methods (A) Carbon Nanotube Membrane Fabricationmentioning

confidence: 99%

Electro-osmotic flow enhancement in carbon nanotube membranes

Mattia

Leese

Calabrò

2016

Phil. Trans. R. Soc. A.

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“…Given the sodium ion molar conductivity as

{normalΛ}_{+} = 5 \times 10^{- 3} S m^{2} / mol

, the effective molar conductivity of buffer ions other than sodium was estimated as

{normalΛ}_{-} = 2.7 \times 10^{- 3} S m^{2} / mol

. For this buffer concentration, the ζ ‐potential value for the AOO's membrane surface has been reported as –60 mV .…”

Section: Methodsmentioning

confidence: 99%

“…Given the sodium ion molar conductivity as ⌳ + = 5 × 10 −3 Sm 2 /mol, the effective molar conductivity of buffer ions other than sodium was estimated as ⌳ − = 2.7 × 10 −3 Sm 2 /mol [42]. For this buffer concentration, the -potential value for the AOO's membrane surface has been reported as -60 mV [43,44]. The total electric current passing through an EO pump, with defined conductivity and pressure gradient, is related to the potential difference across the membrane, V eff /L, Eq.…”

Section: Electrical Current In Electroosmotic Flowmentioning

confidence: 99%

Maximizing fluid delivered by bubble‐free electroosmotic pump with optimum pulse voltage waveform

Tawfik

Díez

2016

Electrophoresis

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In generating high electroosmotic (EO) flows for use in microfluidic pumps, a limiting factor is faradaic reactions that are more pronounced at high electric fields. These reactions lead to bubble generation at the electrodes and pump efficiency reduction. The onset of gas generation for high current density EO pumping depends on many parameters including applied voltage, working fluid, and pulse duration. The onset of gas generation can be delayed and optimized for maximum volume pumped in the minimum time possible. This has been achieved through the use of a novel numerical model that predicts the onset of gas generation during EO pumping using an optimized pulse voltage waveform. This method allows applying current densities higher than previously reported. Optimal pulse voltage waveforms are calculated based on the previous theories for different current densities and electrolyte molarity. The electroosmotic pump performance is investigated by experimentally measuring the fluid volume displaced and flow rate.

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“…A simple electrochemical method capable of tracking the passage of an electrolytic solution through the barrier layer as the pore opens can be used to precisely control this process. 7,8 The result is the formation of freestanding structures, which have become popular as model membrane systems that can be used to study the effects of nanoscale confinement on fluid flow, [8][9][10][11] wetting behaviour, 12,13 surface friction, 14,15 or for nanoparticle synthesis. 16,17 In this configuration, they are usually defined as anodic alumina membranes (AAMs).…”

Section: Introductionmentioning

confidence: 99%

Controlled hydrothermal pore reduction in anodic alumina membranes

Mattia

Leese

2014

Nanoscale

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Porous anodic aluminium oxide nanostructures are popular templates for the fabrication of a wide range of nanomaterials. When open at both ends, they are now being used as model membranes, called anodic alumina membranes (AAM). In both cases, their appeal resides in the possibility of accurately controlling pore size via the anodization voltage, with a narrow size distribution. This characteristic, though, is maintained only in specific pore size ranges, reflecting specific ordering regimes in the material. Outside these domains, less ordered structures are obtained. Furthermore, the smallest pores currently achieved by anodization are about ∼10 nm in diameter, using sulphuric acid, which yields very thin and fragile nanostructured membranes. In this work we address these limitations by decoupling the control of pore size from the anodization stage. We achieve this by subjecting AAMs produced under a high order regime (40 V, 0.3 M oxalic acid) to a post-anodization hydrothermal treatment using steam. With this process we were able to decrease the pore size by 80% down to ∼10 nm. The membranes retain their integrity and are more robust than AAMs with the same pore structure produced via anodization in sulphuric acid.

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Electroosmotic flow in nanoporous membranes in the region of electric double layer overlap

Cited by 11 publications

References 37 publications

Electro-osmotic flow enhancement in carbon nanotube membranes

Electro-osmotic flow enhancement in carbon nanotube membranes

Maximizing fluid delivered by bubble‐free electroosmotic pump with optimum pulse voltage waveform

Controlled hydrothermal pore reduction in anodic alumina membranes

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