Nanometer-thick lateral polyelectrolyte micropatterns induce macrosopic electro-osmotic chaotic fluid instabilities

Weßling, Matthias; Morcillo, L. Garrigós; Abdu, Said

doi:10.1038/srep04294

Cited by 48 publications

(20 citation statements)

References 23 publications

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“…Balster et al experimentally proved that chemical heterogeneity as well as micrometer‐sized geometrical embossed undulations, indeed, may impact on the evolution of electroconvection resulting in a decreased plateau length. Nanometer‐thick micrometer‐sized polyelectrolyte patterns transferred through microcontact printing on top of a membrane have the same effect on the emergence of electroosmotic induced fluid instabilities . Other works have shown that also hydrophobic surfaces lead to an intensified evolution of electroconvective vortices mixing the diffusion boundary layer .…”

Section: Introductionmentioning

confidence: 97%

2D Patterned Ion‐Exchange Membranes Induce Electroconvection

Roghmans

Evdochenko

Stockmeier

et al. 2018

Adv Materials Inter

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Concentration polarization is a diffusion‐limited phenomenon for ion transport in electrodialysis based desalination processes. Once a so‐called limiting current is reached, the resistance of the system rises notably manifested as a plateau region in the current–voltage curves. For long it is hypothesized that altering the surface properties of the membrane can overcome the diffusional transport limitation by the induction of electroconvective vortices mixing the laminar boundary layer. To systematically investigate the influence of geometrical and chemical membrane surface topology on the evolution of electroconvection, circular patterns of polystyrene, poly(2‐vinylpyridine) (P2VP), and P2VP microgels are inkjet printed on cation‐exchange membranes. All types of patterns cause an insignificant increase in membrane resistance but they reduce the plateau lengths indicating the desired accelerated onset of electroconvection. In case of polystyrene (PS) patterns, the drop in plateau length results in a small reduction in transport resistance for overlimiting currents. However, membranes modified with linear P2VP and P2VP microgel patterns do exhibit a significantly decreased resistance in this region at a simultaneous increase of the limiting current density. Direct numerical simulations support the interpretation that the surface charge of the printed patterns influences the direction of the vortices being advantageous during ion transport toward the membrane.

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Section: Introductionmentioning

confidence: 97%

2D Patterned Ion‐Exchange Membranes Induce Electroconvection

Roghmans

Evdochenko

Stockmeier

et al. 2018

Adv Materials Inter

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“…In the electrochemical behavior of heterogeneous ion-exchange membranes, the electrical inhomogeneity of their surface, consisting ofthe presence of the regions with high (ion-exchanger phase) and low (polyethylene phase) conductivity, plays an important role. In [1][2][3][4][5][6][7][8][9][10], the possibility of mass transfer intensification in an electromembrane system by improving the morphology of the surface of ion-exchange membranes was demonstrated. The use of membranes with optimized surface morphology in the process of electrodialysis for desalting and deionization of natural waters and technological solutions creates the prerequisites for a significant increase in the efficiency of these processes in the limiting and overlimiting current modes.…”

Section: Introductionmentioning

confidence: 99%

A Study of Ralex Membrane Morphology by SEM

et al. 2019

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A comparative analysis of the effect of the manufacturing technology of heterogeneousion-exchange membranes Ralex CM Pes manufactured by MEGA a.s. (Czech Republic) on the structural properties of their surface and cross section by SEM was carried out. The CM Pes membrane is a composite of a sulfonated ion-exchanger with inert binder of polyethylene and reinforcing polyester fiber. In the manufacture of membranes Ralex the influence of two factors was investigated. First, the time of ion-exchange grain millingvaried at a constant resin/polyethylene ratio. Second, the ratio of the cation-exchanger and the inert binder of polyethylene varied. It has been found that the membrane surface becomes more electrically homogeneous with the growth of the ion-exchanger loading and a decrease in its particle size. With an increase in the milling time of resin grainsfrom 5 to 80 min a more than 1.5-fold decrease in their radius and in the distance between them was revealed.Besides, there is a 1.5-fold decrease in the fraction, as well as in the size of pores and structure defects. The fraction of the ion-exchange phase on the membrane surface decreases by 7%. With an increase in the resin loading from 45 to 70 wt %, the growth of the fraction of conducting regions on the surface is almost twofold, while their sizes remain practically unchanged. More significant changes in the surface structure of the studied membranes are established in comparison with the cross section. An increase in the resin content in the membranes from 45 to 70 wt % corresponds to a 43% increment of its fraction on the cross-section.The increase in the ion-exchanger content of Ralex membranes is accompanied by the growth of the fraction of macropores and structure defects on the membrane surface by 70% and a twofold decrease in the distance between conducting zones.

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“…Standard heterogeneous membranes display local limiting and overlimiting currents several times the average of homogeneous membranes, but with lower surface-averaged current densities 10 . However, recently, nanometer thick polyectrolyte layers deposited in micropatterns on ion exchange membranes were found to significantly shorten the limiting plateau length in the IV curve and increase OLC 11 . Thus, understanding the interactions between these two modes of electroconvection provides a promising avenue for designing surfaces that enhance OLC.…”

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confidence: 99%

On the Dynamical Regimes of Pattern-Accelerated Electroconvection

Davidson

Weßling

Mani

2016

Sci Rep

137

124

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Recent research has established that electroconvection can enhance ion transport at polarized surfaces such as membranes and electrodes where it would otherwise be limited by diffusion. The onset of such overlimiting transport can be influenced by the surface topology of the ion selective membranes as well as inhomogeneities in their electrochemical properties. However, there is little knowledge regarding the mechanisms through which these surface variations promote transport. We use high-resolution direct numerical simulations to develop a comprehensive analysis of electroconvective flows generated by geometric patterns of impermeable stripes and investigate their potential to regularize electrokinetic instabilities. Counterintuitively, we find that reducing the permeable area of an ion exchange membrane, with appropriate patterning, increases the overall ion transport rate by up to 80%. In addition, we present analysis of nonpatterned membranes, and find a novel regime of electroconvection where a multivalued current is possible due to the coexistence of multiple convective states.

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Nanometer-thick lateral polyelectrolyte micropatterns induce macrosopic electro-osmotic chaotic fluid instabilities

Cited by 48 publications

References 23 publications

2D Patterned Ion‐Exchange Membranes Induce Electroconvection

2D Patterned Ion‐Exchange Membranes Induce Electroconvection

A Study of Ralex Membrane Morphology by SEM

On the Dynamical Regimes of Pattern-Accelerated Electroconvection

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