Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 16Citation - Scopus: 16Slip Effects on Ionic Current of Viscoelectric Electroviscous Flows Through Different Length Nanofluidic Channels(American Chemical Society, 2020) Şen, Tümcan; Şen, Tümcan; Barışık, Murat; Barışık, Murat; 01. Izmir Institute of Technology; 03.10. Department of Mechanical Engineering; 03. Faculty of EngineeringThe pressure driven slip flow of an electrolyte solution is studied through different nanofluidic channel lengths at varying salt concentrations. The viscous-thickening due to the electrostatic interactions within the electric double layer and the reverse ionic transport due to the streaming potential are developed. The influence of the Navier slip boundary condition is described under both electroviscous and viscoelectric effects with a surface charge regulation (CR) model while the observed behavior is compared and validated with molecular dynamic (MD) calculations from multiple studies. Results show that electroviscous and viscoelectric effects decrease transport. Earlier studies at the no slip boundary presented an increase of ionic current by increasing salt concentration and decreasing channel length. In contrast, our study found that the ionic current occurred almost independent of both salt concentration and channel length, except for very short channels and very low salt concentrations, when electroviscous and viscoelectric effects were considered. In the case of the constant slip length condition, ionic conduction was enhanced, but velocity slip developing on surfaces showed significant variation based on the salt concentration and channel length. This is due to the natural CR behavior enhancing the surface charge and consequential near surface electrohydrodynamics as a result of increase in salt concentration and/or decrease of channel length. Considering that the electroviscous effect alone creates up to 70% lower velocity slips than Poiseuille flow predictions, while further including the viscoelectric effect, results in an almost no-slip condition at high salt concentrations and/or short channels. As a result, the ionic current of a viscoelectric electroviscous slip flow is found to be equal to 1/3 of an electroviscous slip flow and to decrease with a decrease in the channel length.Article Citation - WoS: 32Citation - Scopus: 34Pore Size and Porosity Dependent Zeta Potentials of Mesoporous Silica Nanoparticles(American Chemical Society, 2020) Yakın, Fetiye Esin; Şen, Tümcan; Barışık, Murat; Barışık, Murat; Şen, Tümcan; 01. Izmir Institute of Technology; 03.10. Department of Mechanical Engineering; 03. Faculty of EngineeringMesoporous silica nanoparticles (MSNPs) are synthesized in the various forms of porous structures according to an application's needs, while their zeta potentials play a major role in their function. We show that variation in pore size and/or porosity yields a substantial decrease in MSNP zeta potential up to 25% lower than the theoretical zeta potential predictions for a flat surface at the corresponding ionic conditions in moderate pH range. By considering surface chemistry as a function of local ionic conditions (charge regulation), we calculated local zeta potentials around the MSNP which showed variation between pore openings and solid surfaces. Through a systematic study, we evaluated an average three-dimensional zeta potential for MSNPs with various conditions, based on the ratio of the area covered by pore openings to the rest of the MSNP surface area as a function of three-dimensional porosity and pore size. Results show that the high overlap of ionic layers inside the pores creates electric potentials close to zeta potential of the remaining surface, but large pore size and/or high ionic salt concentration yields divergence. We characterized the variation of MSNP zeta potential in terms of porosity (epsilon(3D)), pore size (D-pore), and ionic condition quantified by Debye length (lambda) and obtained unified behavior as a function of the nondimensional group of epsilon(3D)(D-pore/lambda). For epsilon(3D)(D-pore/lambda) < 0.01, MSNP zeta potential remains similar to flat plate predictions, but it decreases by increasing epsilon(3D)(D-pore/lambda) value. The influence of pore entrances on surface zeta potential increases nonlinearly by the increase of porosity and/or decrease of EDL overlap, similar to a change of area to volume ratio. The current findings are important for the understanding and further control of mesoporous particle transport in various promising and groundbreaking applications such as targeted drug delivery.