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Ionic liquid flow along the carbon nanotube with DC electric field.

Shin JH, Kim GH, Kim I, Jeon H, An T, Lim G - Sci Rep (2015)

Bottom Line: For biological applications, a better understanding of the ionic solution pumping mechanism is required.The resulting electro-osmotic flow was attributed to the movement of an electric double layer near the electrode, and the flow rates along the CWEs were on the order of picoliters per minute.We classified into three pumping zones, according to the initiating voltage and faradaic reaction.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San31, Hyoja-dong, Pohang, Gyungbuk, 790-784, Republic of Korea.

ABSTRACT
Liquid pumping can occur along the outer surface of an electrode under a DC electric field. For biological applications, a better understanding of the ionic solution pumping mechanism is required. Here, we fabricated CNT wire electrodes (CWEs) and tungsten wire electrodes (TWEs) of various diameters to assess an ionic solution pumping. A DC electric field created by a bias of several volts pumped the ionic solution in the direction of the negatively biased electrode. The resulting electro-osmotic flow was attributed to the movement of an electric double layer near the electrode, and the flow rates along the CWEs were on the order of picoliters per minute. According to electric field analysis, the z-directional electric field around the meniscus of the small electrode was more concentrated than that of the larger electrode. Thus, the pumping effect increased as the electrode diameter decreased. Interestingly in CWEs, the initiating voltage for liquid pumping did not change with increasing diameter, up to 20 μm. We classified into three pumping zones, according to the initiating voltage and faradaic reaction. Liquid pumping using the CWEs could provide a new method for biological studies with adoptable flow rates and a larger 'Recommended pumping zone'.

No MeSH data available.


Related in: MedlinePlus

Flow rates of liquid pumped along the CWEs.(a) The flow rates increased with the applied voltage, with the exception of an applied voltage of 3.5 V condition (50 mM KCl; droplet volume: 2 μL).(b) The flow rates decreased with increasing distance between the two electrodes (applied voltage: 2.5 V; 50 mM KCl). Values were analyzed by paired t-test, mean ± standard error, n = 10, *p < 0.05, **p < 0.01.
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f7: Flow rates of liquid pumped along the CWEs.(a) The flow rates increased with the applied voltage, with the exception of an applied voltage of 3.5 V condition (50 mM KCl; droplet volume: 2 μL).(b) The flow rates decreased with increasing distance between the two electrodes (applied voltage: 2.5 V; 50 mM KCl). Values were analyzed by paired t-test, mean ± standard error, n = 10, *p < 0.05, **p < 0.01.

Mentions: For the first condition, the applied voltage was varied from 1.5 V to 3.5 V, while the other conditions remained fixed (Fig. 7a). The Helmholtz-Smoluchowski slip velocity (~εξE/η) describes the EOF, in which ε is the dielectric constant, ξ is the zeta potential, E is the applied electric field, and η is the solution viscosity. According to this equation, the flow rate of transported liquid is linearly proportional to the applied voltage, and inversely proportional to the distance between the two electrodes. In our results, the flow rates of the pumped liquid along the CWE increased with increasing applied voltage, with the exception of the 3.5 V bias. At 3.5 V, the liquid was pumped along the CWE, and small beads were expelled from the mother droplet. This phenomenon is caused by the repulsive force in the ionic solution close to the electrode34. These flying beads from the transported liquid were induced by the electric field and reduced the amount of transported liquid along the CWE. For this reason, the flow rate under a 3.5 V bias decreased, compared with that for a 3 V bias. For a bias of 1.3 to 3 V, the flow rates were linearly proportional to the applied voltages (R2 = 0.97).


Ionic liquid flow along the carbon nanotube with DC electric field.

Shin JH, Kim GH, Kim I, Jeon H, An T, Lim G - Sci Rep (2015)

Flow rates of liquid pumped along the CWEs.(a) The flow rates increased with the applied voltage, with the exception of an applied voltage of 3.5 V condition (50 mM KCl; droplet volume: 2 μL).(b) The flow rates decreased with increasing distance between the two electrodes (applied voltage: 2.5 V; 50 mM KCl). Values were analyzed by paired t-test, mean ± standard error, n = 10, *p < 0.05, **p < 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4488867&req=5

f7: Flow rates of liquid pumped along the CWEs.(a) The flow rates increased with the applied voltage, with the exception of an applied voltage of 3.5 V condition (50 mM KCl; droplet volume: 2 μL).(b) The flow rates decreased with increasing distance between the two electrodes (applied voltage: 2.5 V; 50 mM KCl). Values were analyzed by paired t-test, mean ± standard error, n = 10, *p < 0.05, **p < 0.01.
Mentions: For the first condition, the applied voltage was varied from 1.5 V to 3.5 V, while the other conditions remained fixed (Fig. 7a). The Helmholtz-Smoluchowski slip velocity (~εξE/η) describes the EOF, in which ε is the dielectric constant, ξ is the zeta potential, E is the applied electric field, and η is the solution viscosity. According to this equation, the flow rate of transported liquid is linearly proportional to the applied voltage, and inversely proportional to the distance between the two electrodes. In our results, the flow rates of the pumped liquid along the CWE increased with increasing applied voltage, with the exception of the 3.5 V bias. At 3.5 V, the liquid was pumped along the CWE, and small beads were expelled from the mother droplet. This phenomenon is caused by the repulsive force in the ionic solution close to the electrode34. These flying beads from the transported liquid were induced by the electric field and reduced the amount of transported liquid along the CWE. For this reason, the flow rate under a 3.5 V bias decreased, compared with that for a 3 V bias. For a bias of 1.3 to 3 V, the flow rates were linearly proportional to the applied voltages (R2 = 0.97).

Bottom Line: For biological applications, a better understanding of the ionic solution pumping mechanism is required.The resulting electro-osmotic flow was attributed to the movement of an electric double layer near the electrode, and the flow rates along the CWEs were on the order of picoliters per minute.We classified into three pumping zones, according to the initiating voltage and faradaic reaction.

View Article: PubMed Central - PubMed

Affiliation: Department of Mechanical Engineering, Pohang University of Science and Technology (POSTECH), San31, Hyoja-dong, Pohang, Gyungbuk, 790-784, Republic of Korea.

ABSTRACT
Liquid pumping can occur along the outer surface of an electrode under a DC electric field. For biological applications, a better understanding of the ionic solution pumping mechanism is required. Here, we fabricated CNT wire electrodes (CWEs) and tungsten wire electrodes (TWEs) of various diameters to assess an ionic solution pumping. A DC electric field created by a bias of several volts pumped the ionic solution in the direction of the negatively biased electrode. The resulting electro-osmotic flow was attributed to the movement of an electric double layer near the electrode, and the flow rates along the CWEs were on the order of picoliters per minute. According to electric field analysis, the z-directional electric field around the meniscus of the small electrode was more concentrated than that of the larger electrode. Thus, the pumping effect increased as the electrode diameter decreased. Interestingly in CWEs, the initiating voltage for liquid pumping did not change with increasing diameter, up to 20 μm. We classified into three pumping zones, according to the initiating voltage and faradaic reaction. Liquid pumping using the CWEs could provide a new method for biological studies with adoptable flow rates and a larger 'Recommended pumping zone'.

No MeSH data available.


Related in: MedlinePlus