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Rapid Particle Patterning in Surface Deposited Micro-Droplets of Low Ionic Content via Low-Voltage Electrochemistry and Electrokinetics.

Sidelman N, Cohen M, Kolbe A, Zalevsky Z, Herrman A, Richter S - Sci Rep (2015)

Bottom Line: However, the use of DC-induced electrokinetics in miniaturized devices is highly limited.We show that this is made possible in low ion content dispersions, which enable low-voltage electrokinetics and an anomalous bubble-free water electrolysis.This phenomenon can serve as a powerful tool in both microflow devices and digital microfluidics for rapid pre-concentration and particle patterning.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering Faculty of Engineering &University Center for Nano Science and Nanotechnology Tel Aviv University, Tel-Aviv, 69978, Israel.

ABSTRACT
Electrokinetic phenomena are a powerful tool used in various scientific and technological applications for the manipulation of aqueous solutions and the chemical entities within them. However, the use of DC-induced electrokinetics in miniaturized devices is highly limited. This is mainly due to unavoidable electrochemical reactions at the electrodes, which hinder successful manipulation. Here we present experimental evidence that on-chip DC manipulation of particles between closely positioned electrodes inside micro-droplets can be successfully achieved, and at low voltages. We show that such manipulation, which is considered practically impossible, can be used to rapidly concentrate and pattern particles in 2D shapes in inter-electrode locations. We show that this is made possible in low ion content dispersions, which enable low-voltage electrokinetics and an anomalous bubble-free water electrolysis. This phenomenon can serve as a powerful tool in both microflow devices and digital microfluidics for rapid pre-concentration and particle patterning.

No MeSH data available.


(a) Image comprised of 8 superimposed video frames showing electrokinetic particle trajectories between the positive pole (right) and negative pole (left), recorded at 1.5 V. (b) The simulated 2D potential map at an arbitrary voltage of 1.5 V in vacuum. The direction of electric field norm is indicated by the arrows. (c) Image comprised of 8 superimposed video frames showing the beginning of particle patterning (indicated by the arrow) in the inter-electrode region. (d,e) The stabilized patterns at applied voltages of 1.5 V and 2.0 V respectively. (f) Eectrochemical gold stripping and Cl2 gas bubbles observed in a dispersion droplet containing NaCl, at an applied voltage of 2.3 V. (See text for details).
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f2: (a) Image comprised of 8 superimposed video frames showing electrokinetic particle trajectories between the positive pole (right) and negative pole (left), recorded at 1.5 V. (b) The simulated 2D potential map at an arbitrary voltage of 1.5 V in vacuum. The direction of electric field norm is indicated by the arrows. (c) Image comprised of 8 superimposed video frames showing the beginning of particle patterning (indicated by the arrow) in the inter-electrode region. (d,e) The stabilized patterns at applied voltages of 1.5 V and 2.0 V respectively. (f) Eectrochemical gold stripping and Cl2 gas bubbles observed in a dispersion droplet containing NaCl, at an applied voltage of 2.3 V. (See text for details).

Mentions: A 30 μl aliquot of the dispersion was deposited on the device and DC voltage was applied. At a threshold voltage of 1.5 V (in the case of the TiO2 dispersion), a discernible continuous movement of the particles, from the positive pole to the negative pole, was recorded. Figure 2a is an image comprised of eight superimposed video frames, demonstrating particles trajectories. The first frame in the stack was acquired the moment 1.5 V were applied, and the time-gap between the first and last frames in the stack is 5.3 s. Figure 2b is the simulated 2D potential map and field direction at the substrate’s plane, in vacuum, at an arbitrary voltage of 1.5 V. It was obtained by solving Poisson’s equation for the device’s geometry using suitable boundary conditions. As can be seen, the recorded particle trajectories are consistent with the shape of the electric field.


Rapid Particle Patterning in Surface Deposited Micro-Droplets of Low Ionic Content via Low-Voltage Electrochemistry and Electrokinetics.

Sidelman N, Cohen M, Kolbe A, Zalevsky Z, Herrman A, Richter S - Sci Rep (2015)

(a) Image comprised of 8 superimposed video frames showing electrokinetic particle trajectories between the positive pole (right) and negative pole (left), recorded at 1.5 V. (b) The simulated 2D potential map at an arbitrary voltage of 1.5 V in vacuum. The direction of electric field norm is indicated by the arrows. (c) Image comprised of 8 superimposed video frames showing the beginning of particle patterning (indicated by the arrow) in the inter-electrode region. (d,e) The stabilized patterns at applied voltages of 1.5 V and 2.0 V respectively. (f) Eectrochemical gold stripping and Cl2 gas bubbles observed in a dispersion droplet containing NaCl, at an applied voltage of 2.3 V. (See text for details).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4543935&req=5

f2: (a) Image comprised of 8 superimposed video frames showing electrokinetic particle trajectories between the positive pole (right) and negative pole (left), recorded at 1.5 V. (b) The simulated 2D potential map at an arbitrary voltage of 1.5 V in vacuum. The direction of electric field norm is indicated by the arrows. (c) Image comprised of 8 superimposed video frames showing the beginning of particle patterning (indicated by the arrow) in the inter-electrode region. (d,e) The stabilized patterns at applied voltages of 1.5 V and 2.0 V respectively. (f) Eectrochemical gold stripping and Cl2 gas bubbles observed in a dispersion droplet containing NaCl, at an applied voltage of 2.3 V. (See text for details).
Mentions: A 30 μl aliquot of the dispersion was deposited on the device and DC voltage was applied. At a threshold voltage of 1.5 V (in the case of the TiO2 dispersion), a discernible continuous movement of the particles, from the positive pole to the negative pole, was recorded. Figure 2a is an image comprised of eight superimposed video frames, demonstrating particles trajectories. The first frame in the stack was acquired the moment 1.5 V were applied, and the time-gap between the first and last frames in the stack is 5.3 s. Figure 2b is the simulated 2D potential map and field direction at the substrate’s plane, in vacuum, at an arbitrary voltage of 1.5 V. It was obtained by solving Poisson’s equation for the device’s geometry using suitable boundary conditions. As can be seen, the recorded particle trajectories are consistent with the shape of the electric field.

Bottom Line: However, the use of DC-induced electrokinetics in miniaturized devices is highly limited.We show that this is made possible in low ion content dispersions, which enable low-voltage electrokinetics and an anomalous bubble-free water electrolysis.This phenomenon can serve as a powerful tool in both microflow devices and digital microfluidics for rapid pre-concentration and particle patterning.

View Article: PubMed Central - PubMed

Affiliation: Department of Materials Science and Engineering Faculty of Engineering &University Center for Nano Science and Nanotechnology Tel Aviv University, Tel-Aviv, 69978, Israel.

ABSTRACT
Electrokinetic phenomena are a powerful tool used in various scientific and technological applications for the manipulation of aqueous solutions and the chemical entities within them. However, the use of DC-induced electrokinetics in miniaturized devices is highly limited. This is mainly due to unavoidable electrochemical reactions at the electrodes, which hinder successful manipulation. Here we present experimental evidence that on-chip DC manipulation of particles between closely positioned electrodes inside micro-droplets can be successfully achieved, and at low voltages. We show that such manipulation, which is considered practically impossible, can be used to rapidly concentrate and pattern particles in 2D shapes in inter-electrode locations. We show that this is made possible in low ion content dispersions, which enable low-voltage electrokinetics and an anomalous bubble-free water electrolysis. This phenomenon can serve as a powerful tool in both microflow devices and digital microfluidics for rapid pre-concentration and particle patterning.

No MeSH data available.