Dynamics of droplet motion induced by Electrowetting

Lu, Yi; Sur, Aritra; Pascente, Carmen; Annapragada, S. Ravi; Ruchhoeft, Paul; Liu, Dong

doi:10.1016/j.ijheatmasstransfer.2016.10.040

Cited by 60 publications

(32 citation statements)

References 56 publications

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“…The layer thickness was varied from 50 to 300 nm to provide several different capacitance values of the SiO 2 layer. It is worth to note that the resonance frequencies for droplet oscillation are not affected by the capacitance of a dielectric layer used [ 41 ]. Thus, the oscillation performance on the SiO 2 layers was characterized at the same resonance frequencies as the ones of the ion gel.…”

Section: Resultsmentioning

confidence: 99%

Capacitance Effects of a Hydrophobic-Coated Ion Gel Dielectric on AC Electrowetting

Lee

Park

2021

Micromachines

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We present experimental studies of alternating current (AC) electrowetting dominantly influenced by several unique characteristics of an ion gel dielectric in its capacitance. At a high-frequency region above 1 kHz, the droplet undergoes the contact angle modification. Due to its high-capacitance characteristic, the ion gel allows the contact angle change as large as Δθ = 26.4°, more than 2-fold improvement, compared to conventional dielectrics when f = 1 kHz. At the frequency range from 1 to 15 kHz, the capacitive response of the gel layer dominates and results in a nominal variation in the angle change as θ ≈ 90.9°. Above 15 kHz, such a capacitive response of the gel layer sharply decreases and leads to the drastic increase in the contact angle. At a low-frequency region below a few hundred Hz, the droplet’s oscillation relying on the AC frequency applied was mainly observed and oscillation performance was maximized at corresponding resonance frequencies. With the high-capacitance feature, the ion gel significantly enlarges the oscillation performance by 73.8% at the 1st resonance mode. The study herein on the ion gel dielectric will help for various AC electrowetting applications with the benefits of mixing enhancement, large contact angle modification, and frequency-independent control.

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Section: Resultsmentioning

confidence: 99%

Capacitance Effects of a Hydrophobic-Coated Ion Gel Dielectric on AC Electrowetting

Lee

Park

2021

Micromachines

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“…The driving waveform consists of a driving voltage sequence, which plays a key role in oil shrinking for a stable gray scale display. However, due to the presence of oil splitting, oil oscillation, and charges trapping in EWDs, they lead to a reduction of aperture ratio and display stability [16][17][18]. In studies of suppressing oil splitting, a method that was used to effectively reduce oil splitting by adding a voltage rising gradient was proposed [19].…”

Section: Introductionmentioning

confidence: 99%

Toward Suppressing Oil Backflow Based on a Combined Driving Waveform for Electrowetting Displays

Long

Zhang

et al. 2022

Micromachines

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Electrowetting display (EWD) is a new type of paper-like reflective display based on colored oil, which has gradually become one of the most potential electronic papers with low power consumption, fast response, and full color. However, oil backflow can occur in EWDs, which makes it difficult to maintain a stable aperture ratio. In order to improve the stability of the aperture ratio of EWDs, a new driving waveform was proposed based on analyzing the phenomenon of oil backflow. The driving waveform was composed of a shrinking stage and a driving stage. Firstly, a threshold voltage of oil splitting was calculated by analyzing the luminance curve of EWDs, which were driven by different direct current (DC) voltages. Then, an exponential function waveform, which increased from the threshold voltage, was applied to suppress oil splitting. Finally, a periodic signal combined with a reset signal with a DC signal was applied during the driving stage to maintain a stable aperture ratio display. Experimental results showed that the charge trapping effect could be effectively prevented by the proposed driving waveform. Compared with an exponential function waveform, the average luminance value was increased by 28.29%, and the grayscale stability was increased by 13.76%. Compared to a linear function waveform, the aperture ratio was increased by 10.44% and the response time was reduced by 20.27%.

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“…The earliest driving waveform of EWDs is a pulse width modulated (PWM) square wave [24]. However, some defects are caused by this driving waveform, such as gray scale distortion which is caused by contact angle hysteresis [25][26][27][28]; maximum aperture ratio is reduced due to oil splitting [29][30][31]; oil backflow caused by charge trapping in the hydrophobic insulator [32][33][34][35][36]. The movement of oil is directly controlled by the driving waveform, the optimization of driving waveform can affect the display effect of EWDs.…”

Section: Introductionmentioning

confidence: 99%

Review of Driving Waveform for Electrowetting Displays

Zhang

Zeng

et al. 2021

Front. Phys.

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Electrowetting display (EWD) is the most potential technology among new electronic paper technologies. It not only has the advantages of electrophoretic display (EPD) technology but also can realize color video playback. Therefore, this technology has been widely studied in recent years. Driving waveform is a voltage sequence which can drive pixels to display gray scales in EWDs. As one of the key technologies, it directly affects the display effect of pixels. In this paper, we give a review of the display principle of EWDs and the research status of driving waveforms. At the same time, the contact angle hysteresis, charge trapping, and oil splitting are also reviewed, which can provide a reference value for designing driving waveforms.

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Dynamics of droplet motion induced by Electrowetting

Cited by 60 publications

References 56 publications

Capacitance Effects of a Hydrophobic-Coated Ion Gel Dielectric on AC Electrowetting

Capacitance Effects of a Hydrophobic-Coated Ion Gel Dielectric on AC Electrowetting

Toward Suppressing Oil Backflow Based on a Combined Driving Waveform for Electrowetting Displays

Review of Driving Waveform for Electrowetting Displays

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