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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.


Top: the temporal-spatial evolution (left to right) of two pH zones in a Uind solution at 2.0 V due to a bubble free electrolysis (top).A basic, green region forms near the negative electrode and an acidic zone near the positive electrode can be seen). Bottom: temporal-spatial evolution (left to right) of stable pH zones, and particle patterning on the border of the pH zones. The border between the zones, where patterning occurs, is indicated by white arrows.
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f4: Top: the temporal-spatial evolution (left to right) of two pH zones in a Uind solution at 2.0 V due to a bubble free electrolysis (top).A basic, green region forms near the negative electrode and an acidic zone near the positive electrode can be seen). Bottom: temporal-spatial evolution (left to right) of stable pH zones, and particle patterning on the border of the pH zones. The border between the zones, where patterning occurs, is indicated by white arrows.

Mentions: A significant factor, responsible for patterning, is that although bubble-free electrolysis takes place and bubbles do not evolve, pH changes at the electrodes still occur. The pH changes are the reason why particles slow down and pattern. The experimental evidence of the occurrence of pH changes is shown in Fig. 4 top. A 30 μl droplet of a universal pH indicator34 (Uind), which exhibits a broad color spectrum over a large pH range, was deposited on a device. The conductivity of the Uind solution was measured to be only 37.3 μS/cm, indicating that its ion content is low. Indeed, when 2.0 V were applied, bubble-free electrolysis was observed. The temporal-spatial evolution of the pH zones was monitored, and is demonstrated in Fig. 4 top (a comprehensive evolution of the pH zones is shown in supplementary Figure 3).


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)

Top: the temporal-spatial evolution (left to right) of two pH zones in a Uind solution at 2.0 V due to a bubble free electrolysis (top).A basic, green region forms near the negative electrode and an acidic zone near the positive electrode can be seen). Bottom: temporal-spatial evolution (left to right) of stable pH zones, and particle patterning on the border of the pH zones. The border between the zones, where patterning occurs, is indicated by white arrows.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

f4: Top: the temporal-spatial evolution (left to right) of two pH zones in a Uind solution at 2.0 V due to a bubble free electrolysis (top).A basic, green region forms near the negative electrode and an acidic zone near the positive electrode can be seen). Bottom: temporal-spatial evolution (left to right) of stable pH zones, and particle patterning on the border of the pH zones. The border between the zones, where patterning occurs, is indicated by white arrows.
Mentions: A significant factor, responsible for patterning, is that although bubble-free electrolysis takes place and bubbles do not evolve, pH changes at the electrodes still occur. The pH changes are the reason why particles slow down and pattern. The experimental evidence of the occurrence of pH changes is shown in Fig. 4 top. A 30 μl droplet of a universal pH indicator34 (Uind), which exhibits a broad color spectrum over a large pH range, was deposited on a device. The conductivity of the Uind solution was measured to be only 37.3 μS/cm, indicating that its ion content is low. Indeed, when 2.0 V were applied, bubble-free electrolysis was observed. The temporal-spatial evolution of the pH zones was monitored, and is demonstrated in Fig. 4 top (a comprehensive evolution of the pH zones is shown in supplementary Figure 3).

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.