• Journal of Pharmaceutical Investigation
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• v.41 no.6
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• pp.337-345
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• 2011

The objective of this work is to investigate the effect of chemical enhancer and current on the flux of donepezil hydrochloride (DH) through skin. Ethanol and N-methyl pyrrolidone (NMP) were used as chemical enhancers in combination with iontophoresis. We also have studied the effect of pH on flux and evaluated the role of electroosmosis. In vitro flux study was performed at $33^{\circ}C$, using side-by-side diffusion cell and full thickness hairless mouse skin. Passive flux of DH without enhancer was very small. As the concentration of enhancer increased, passive flux increased. After current application, flux increased markedly and the time to reach maximum decreased. Without enhancer, maximum flux was about 50 fold larger than that obtained without current. These results indicate that electromigration is playing a major role for the transport. As the enhancer concentration increased, flux also increased. NMP and ethanol increased not only the passive delivery, but also the iontophoretic delivery. Flux results indicate that ethanol has better ability than NMP in enhancing the transport of DH. The magnitudes of increase in flux by these enhancers indicate that there is a large synergistic effect in flux enhancement. Flux results from pH study showed that electroosmotic flow is reversed at low pH and the flux is hindered. These results provided some information on the flux enhancing ability of ethanol and NMP in combination with iontophoresis. The data also provided some mechanistic insights into the role of electromigration and electroosmosis on flux through skin.

• Geotechnical Engineering
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• v.14 no.4
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• pp.77-90
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• 1998

To study the improvement of soft marine clay from southern coast of Korea under theelectroosmosis and electrophoresis conditions, several electrokinetic tests were carried out in electrokinetic(E/K) cell. In electroosmosis tests, various treatment times and current densities were used to investigate the strengthening effect under different conditions. From these tests results, it may be noted that electroosmotic strengthening of soft marine clay was effective in proportion to unit power consumption, current density and treatment time. However, electrophoresis method was not effective for thin soil.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.34 no.7
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• pp.715-720
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• 2010

We propose an electroosmosis-based air delivery scheme for polymer electrolyte fuel cells and experimentally investigate its feasibility. An electroosmotic pump under a low-frequency AC electric field is used to displace initially a volume of pump working liquids. This working liquid is then pumped into a space enclosed by a flexible membrane and the movement of the membrane delivers air to a fuel cell. We successfully demonstrated the operation of a forced-convection fuel cell using this technique. In this preliminary study, however, the power consumption of the pump exceeds the power generated by the fuel cell. We conclude this paper with a discussion of several ways to reduce the pump-to-fuel cell power ratio.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.09a
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• pp.215-218
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• 2004

The electrokinetically enhanced soil flushing had a great potential to improve the removal efficiency of polycyclic aromatic hydrocarbons (PAHs) from low permeable soils. A semi-pilot study of surfactant-enhanced electrokinetic process was investigated for the removal of phenanthrene from kaolinite. A nonionic surfactant, Tergitol 15-S-12 at 10 g/L was introduced as a flushing agent and 0.001M of sodium chloride was used as an electrolyte. When the constant voltage of 100 V was applied to the system for 25 days, only 0.66 kWh of electric power was consumed and the amount of electroosmotic flow was 6.9 L. The removal efficiency of phenanthrene was about 40 % and it can be improved by increasing the ion concentration of the flushing solution or the applied voltage.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.3
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• pp.327-333
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• 1999

Determination of chloride ion in concentrated NaOH solution by capillary electrophoresis has been studied. The analysis was performed by indirect UV absorption detection using chromate buffer at 254nm. The matrix effect of the sample has been observed so that the sensitivity in strong NaOH solutaion has decreased up to 10% of that in distilled water. The pH effect of the sample on the sensitivity of CE peaks has been investigated. The method for increasing the sensitivity have been investigated and the optimum pH and concentration of the buffer were 7.5 and 10mM, respectively. A cationic surfactant cetyltrimethylammonium bromide(CTAB), was added to a buffer solution in order to reverse the electroosmotic flow(EOF) in the capillary. This results in a short analysis time and better peak shapes. Using this optimum condition, the determination of chloride ion in real environmental sample has been performed, which is captured in strong NaOH absorbent prepared for absorbing gas from chimney. The standard addition method has been applied for the quantitative analysis, and it was obtained the good reproducibility.

• BioChip Journal
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• v.12 no.4
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• pp.317-325
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• 2018

This paper investigated the effects of ionic strength in the medium on a preconcentrator for a protein sample with low concentration. The preconcentration chip was designed and fabricated using a polydimethylsiloxane replica through standard lithophotography. A glass substrate is silanized prior to functionalizing the nanoparticles for self-assembly at a designed region. Due to the overlap of electrical double layers in a nanofluidic channel, a concentration polarization effect can be achieved using an electric field. A nonlinear electrokinetic flow is induced, resulting in the fast accumulation of proteins in front of the induced ionic depletion zone, so called exclusion-enrichment effect. Thus, the protein sample can be driven by electroosmotic flow and accumulated at a specific location. The chip is used to collect fluorescein isothiocyanate-labeled bovine serum albumin (FITC-BSA) diluted in phosphate-buffered saline (PBS) buffer solution. Different concentrations of the buffer media were studied herein. Fluorescence intensity images show that the buffer concentration of 4 mM is more appropriate than all the other ones. The sample of FITC-BSA with an initial concentration of $10{\mu}M$ in the 4 mM PBS solution increases its concentration at the desired region by up to 50 times within 30 min, demonstrating the results in this investigation.

• Journal of Environmental Science International
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• v.13 no.2
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• pp.149-159
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• 2004

In the removal of heavy metals from the mine deposit using electrokinetic processes, the effects of operation under both constant current and constant potential conditions were estimated. The results of soil pH distributions for DDW-20 V and DDW-100 mA cases after the electrokinetic remediation tests were observed. In the former case, soil pH was not much changed and kept to almost constant value just little higher than initial soil pH of 3.52, except near the cathode, which was about pH 5. While in the latter case, soil pHs of anode and the cathode regions were less than pH 3 and about 6, respectively. The electroosmotic flow to the cathode increased rapidly till 10 hrs and decreased steadily and then maintained to constant rate until the end of operation at constant current condition. Electric potential gradient was continuously increased to as much as 34.375 V/cm. At the steady state, values of the apparent electric conductivity for DDW-20 V and DDW-100 mA were around 40 ${\mu}\textrm{s}$/cm and 30 ${\mu}\textrm{s}$/cm, respectively. In the DDW-100mA test, Cu, Cd, and Zn except Pb showed the tendency of moving toward the cathode. While in the DDW-20 V case, it was observed that Cu, Zn, and Pb except Cd were not moved to any directions. The results of the tests demonstrated that the electrokinetic soil remediation process could be operated better under constant current condition than constant electric potential condition.

• Journal of Pharmaceutical Investigation
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• v.40 no.1
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• pp.23-31
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• 2010

In our previous work on levodopa delivery at pH 2.5 using iontophoresis, we found that cathodal delivery showed higher permeation than anodal delivery and electroosmosis plays more dominant role than electrorepulsion. In this work, we studied the transdermal transport of levodopa at very low pH (pH=1.0) where all levodopa molecules are cations, and evaluated some factors which affect the transdermal transport. The transport study at pH 2.5 was also conducted for comparison. The contribution of electrorepulsion and electroosmosis on flux was also evaluated. Using stable aqueous solution, the effect of electrode polarity, current density, current type and drug concentration on transport through skin were studied and the results were compared. We also investigated the iontophoretic flux from hydroxypropyl cellulose (HPC) hydrogel containing levodopa. In vitro flux study was performed at $33^{\circ}C$, using side-by-side diffusion cell. Full thickness hairless mouse skin were used. Current densities applied were 0.2, 0.4 or $0.6\;mA/cm^2$. Contrary to the pH 2.5 result, anodal delivery showed higher flux, indicating that electrorepulsion is the dominant force for the transport, overcoming the electroosmotic flow which is acting against the direction of electrorepulsion. Cumulative amount of levodopa transported was increased as the current density or drug concentration was increased. When amount of current dose was constant, continuous current was more beneficial than pulsed current in promoting levodopa permeation. Similar transport results were obtained when hydrogel was used as the donor phase. These results indicate that iontophoretic delivery of zwitterion such as levodopa is much complicated than that can be expected from small ionic molecules. The results also indicate that, only at very low pH like pH 1.0, electrorepulsion can be the dominant force over the electroosmosis in the levodopa transport.

• The Transactions of the Korean Institute of Electrical Engineers C
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• v.54 no.5
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• pp.227-231
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• 2005

We have developed a microsystem with a capillary electrophoresis (CE) and an electrochemical detector (ECD). The microfabricated CE-ECD systems are adequate for a disposable type and the characteristics are optimized for an application to the electrochemical detection. The system was realized with polydimethylsiloxane (PDMS)-glass chip and indium tin oxide electrode. The injection and separation channels (80 um wide$\ast$40 um deep) were produced by moulding a PDMS against a microfabricated master with relatively simple and inexpensive methods. A CE-ECD systems were fabricated on the same substrate with the same fabrication procedure. The surface of PDMS layer and ITO-coated glass layer was treated with UV-Ozone to improve bonding strength and to enhance the effect of electroosmotic flow. For comparing the performance of the ITO electrodes with the gold electrodes, gold electrode microchip was fabricated with the same dimension. The running buffer was prepared by 10 mM 2-(N-morpholino)ethanesulfonic acid (MES) titrated to PH 6.5 using 0.1 N NaOH. We measured olectropherograms for the testing analytes consisted of catechol and dopamine with the different concentrations of 1 mM and 0.1 mM, respectively. The measured current peaks of dopamine and catechol are proportional to their concentrations. For comparing the performance of the ITO electrodes with the gold electrodes, electropherograms was measured for CE-ECD device with gold electrodes under the same conditions. Except for the base current level, the performances including sensitivity, stability, and resolution of CE-ECD microchip with ITO electrode are almost the same compared with gold electrode CE-ECD device. The disposable CE/ECD system showed similar results with the previously reported expensive system in the limit of detection and peak skew. When we are using disposable microchips, it is possible to avoid polishing electrode and reconditioning.

• Korean Journal of Materials Research
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• v.23 no.1
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• pp.13-17
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• 2013

The alignments of polystyrene particles of $1{\mu}m$ and $5{\mu}m$ sizes in an aqueous colloidal system were observed by varying the electric field strength, the frequency and the water flow. Spherical mono-dispersed polystyrene particles dispersed in pure water were put into a perfusion chamber; an AC electric field was applied to the Au/Cr electrodes with a 4 mm gap on the glass substrate. The mixture of the $1{\mu}m$ and $5{\mu}m$ sized polystyrene particles at 0.5 vol% concentrations for each size was set in the dielectrophoresis conditions of 1 kHz and 150 V/cm. Large particles of $5{\mu}m$ size were aligned to form chains as the result of the dielectrophoresis force interaction. On the contrary, small particles of $1{\mu}m$ size did not form chains because the dielectrophoresis force was not sufficiently large. When the electric field increased to 250 V/cm, small particles were able to form chains. After the chains were formed from both large and small particles, they began to coalescence as time passed. Owing to the electroosmotic flow of water, wave patterns along the perpendicular direction of the applied electric field appeared at the conditions of 200 Hz and 50 V/cm, when the dielectrophoresis force was small. This wave pattern also appeared for small particles at 1 kHz and 150 V/cm conditions due to the flow of solvent when water was forced to circulate.