A Model of Electrowetting, Reversed Electrowetting, and Contact Angle Saturation

made their great discovery of electromagnetic induction, there have been continuous developments in electrical power generation. Most people today get electricity from thermal, hydroelectric, or nuclear power generation systems, which use this electromagnetic induction phenomenon. Here we propose a new method for electrical power generation, without using electromagnetic induction, by mechanically modulating the electrical double layers at the interfacial areas of a water bridge between two conducting plates. We find that when the height of the water bridge is mechanically modulated, the electrical double layer capacitors formed on the two interfacial areas are continuously charged and discharged at different phases from each other, thus generating an AC electric current across the plates. We use a resistor-capacitor circuit model to explain the results of this experiment. This observation could be useful for constructing a micro-fluidic power generation system in the near future.

show abstract

“…In contrast to this, the contact area A T between the water and top plate changes appreciably during each oscillation period (Fig. 1b) 16,17 .…”

Section: Resultsmentioning

confidence: 87%

Electrical power generation by mechanically modulating electrical double layers

et al. 2013

View full text Add to dashboard Cite

show abstract

“…12,13 In this situation, a liquid droplet is placed on a dielectric-layer coated electrode, with the electrode and droplet essentially acting as the two plates of a capacitor.…”

Section: Introductionmentioning

confidence: 99%

“…5,12,14,15 The dynamics of electrowetting are rapid in this format, making it difficult to monitor the wetting dynamics. 16 Conductive surfaces, such as steel 17 and graphene/carbon nanotube films, 18 are being thus explored to lower the voltage and increase the timescale of electrowetting.…”

Section: Introductionmentioning

confidence: 99%

Low-Voltage Voltammetric Electrowetting of Graphite Surfaces by Ion Intercalation/Deintercalation

2016

View full text Add to dashboard Cite

We demonstrate low-voltage electrowetting at the surface of freshly cleaved highly oriented pyrolytic graphite (HOPG). Using cyclic voltammetry (CV), electrowetting of a droplet of sodium perchlorate solution is observed at moderately positive potentials on high-quality (low step edge coverage) HOPG, leading to significant changes in contact angle and relative contact diameter that is comparable to the widely studied electrowetting on dielectric (EWOD) system, but over a much lower voltage range. The electrowetting behavior is found to be reasonably fast, reversible and repeatable for at least 20 cyclic scans (maximum tested). In contrast to classical electrowetting, e.g. EWOD, the electrowetting of the droplet on HOPG occurs with the intercalation/de-intercalation of anions between the graphene layers of graphite, driven by the applied potential, observed in the CV response, and detected by X-ray photoelectron spectroscopy. The electrowetting behavior is strongly influenced by those factors that affect the extent of the intercalation/de-intercalation of ions on graphite, such as scan rate, potential polarity, quality of the HOPG substrate (step edge and step height), and type of anion in the solution. In addition to perchlorate, sulfate salts also promote electrowetting, but some other salts do not. Our findings suggest a new mechanism for electrowetting based on ion intercalation and the results are of importance to fundamental 2 electrochemistry, as well as diversifying the means by which electrowetting can be controlled and applied.3

show abstract

“…In EWOD microfluidics, microdroplets are placed on driving electrodes that are covered with hydrophobic (typically, Teflon or Cytop) and dielectric (typically, SiO 2 or parylene) layers [12,13], as depicted in the EWOD chip in Figure 1a. When a voltage is applied across the dielectric layer, the contact angle of the droplet is modified due to the change in the surface charge density [14], as depicted in the following Lippmann-Young equation:…”

Section: Theoretical Backgroundmentioning

confidence: 99%

Electrowetting-on-Dielectric by Wireless Powering

Byun

Cho

2013

Heat Transfer Engineering

View full text Add to dashboard Cite

Electrowetting-on-dielectric (EWOD), in which microdroplets are manipulated using electrical inputs, has drawn a great deal of attraction with applications of digital lab-on-a-chip and hot-spot cooling. In most EWOD actuations, the commonly used powering method is wired transmission, which may not be suitable for isolating and employing EWOD devices in hard-to-reach areas. In this study, we investigate wireless power transmission for EWOD utilizing inductive coupling. Since EWOD is typically operated by a high-input voltage although the current is minimal, wireless EWOD also requires a similarly high voltage at the receiver, unlike conventional inductive coupling. To meet this condition, the resonant inductive coupling method at a high resonant frequency is introduced and investigated. To optimize the transmission efficiency, we study the effects of many parameters, such as the frequency, inductance, and capacitance at the transmitter and receiver, the gap between the transmitter coil and receiver coil, and the droplet size, by measuring the voltage at the receiver and the contact angle of the droplet placed on a wirelessly operated EWOD chip. In addition, by applying amplitude modulation to the resonant inductive coupling, wireless AC-EWOD, which generates droplet oscillations and is a common mode for EWOD droplet handling, is also achieved. Finally, it is successfully demonstrated that a droplet is transported laterally by using an array of electrodes, which is also powered by an amplitude-modulated wireless signal.

show abstract

A Model of Electrowetting, Reversed Electrowetting, and Contact Angle Saturation

Cited by 83 publications

References 45 publications

Electrical power generation by mechanically modulating electrical double layers

Electrical power generation by mechanically modulating electrical double layers

Low-Voltage Voltammetric Electrowetting of Graphite Surfaces by Ion Intercalation/Deintercalation

Electrowetting-on-Dielectric by Wireless Powering

Contact Info

Product

Resources

About