Dynamics of Droplet Motion Induced by Electrowetting

Abstract

Electrowetting has drawn significant interests due to the potential applications in electronic displays, lab-on-a-chip devices and electro-optical switches, etc. Current understanding of electrowetting-induced droplet dynamics is hindered by the inadequacy of available numerical and theoretical models in properly handling the dynamic contact angle at the moving contact line. A combined numerical and experimental approach was employed in this work to study the spatiotemporal responses of a droplet subject to EW with both direct current and alternating current actuating signals. The time evolution of the droplet shape was measured using high-speed photography. Computational fluid dynamics models were developed by using the Volume of Fluid-Continuous Surface Force method in conjunction with a selected dynamic contact angle model. It was found that the numerical models were able to accurately predict the key parameters of the electrowetting-induced droplet dynamics.

Axisymmetric and Nonaxisymmetric Oscillations of Sessile Compound Droplets in an Open Digital Microfluidic Platform

“…These images clearly depict that at the first axisymmetric oscillation mode 2 (i.e., at 25 Hz), the height of the compound droplet increased as the contact angle of the oil shell decreased. This observed phase relationship between the compound droplet height and contact angle is in contradiction with the case of a single-phase sessile droplet, 3,49 where for the first mode, as height increases, the contact angle also increases. This apparent contradiction is however easily explained by taking into consideration the fact that the oil contact line remains stationary while the core interface moves.…”

Electrowetting Using a Microfluidic Kelvin Water Dropper

“…The animation of the whole simulation can be find in Supplemental Video S1 . Because the applied voltage for electrowetting was obtained from the MWKD, a time-dependent voltage function was adapted in the simulation, unlike other research that used constant voltage values [ 25 ]. It can be seen that the simulation results closely match the experimental observations.…”

“…The simulation results were compared to the experimental observation side by side, so as to validate the model. Figure 2 illustrates the model adopted in the simulation, in which an axisymmetric configuration was used, assuming that the shape of the droplet is a perfect hemisphere [ 25 ]. The initial diameter of the water droplet in the model was set at 2.44 mm, in alignment with the actual size used in the experiment for comparison.…”

Thermal Load Simulation and Structure Improvement of High Speed Diesel Engine Piston

“…The g p and g T can be obtained using indicator diagram. According to classical Eichelberg formula(1), the instantaneous heat transfer coefficient of gas was calculated [2]:…”