A Numerical Study of Droplet Splitting using Different Spacers in EWOD Device
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Original Article
A Numerical Study of Droplet Splitting using Different Spacers in EWOD Device Zhaolong Wang, Xiongheng Bian & Liguo Chen
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Received: 8 January, 2020 / Accepted: 13 May, 2020 / Published online: 19 August, 2020 ⒸThe Korean BioChip Society and Springer 2020
Abstract In this paper, we investigated the droplet splitting using different spacers in the air. The droplets were manipulated by the EWOD force and the level set method was used for our numerical implementation. The results show that the property of spacer has the effect on the droplet splitting. Specifically, we showed that the re-merging occurred when split daughter droplets pass the sub-channels for the short spacer and unequal droplet splitting can be achieved for the off-centered obstacle. In the study of the thickness, the thicker spacer made the splitting process unstable. Furthermore, we found that the triangle spacer was optical for the separation from the consideration of pressure. Our task can provide some help for the design of the spacer size in the future. Keywords: Electrowetting-on-dielectric, Digital microfluidics, EWOD spacer, Droplet splitting, Level set method
Introduction
trowetting-on-dieletric6 and optoelectrowetting7. Among these, electrowetting-on-dieletric (EWOD) was applied widely by virtue of its unique structure and simple fabrication. And, the droplets can be manipulated simply by firing the electrodes on and off. The EWOD involves four basic operations, namely, transporting, splitting, merging and dispensing. In this paper, our focus is on the droplet splitting. Traditional droplet splitting involves three electrodes, with high wettability on the outer electrodes and low wettability on the middle, the mother droplet will be eventually split into two daughter droplets8, as shown in Figure 1. However, it has been reported that this conventional splitting has many disadvantages, including poor volume variation9, specific requirements for the electrode length, channel height10, and so on. Many improvement measures were proposed for this splitting in recent years, which primarily included the use of feedback control system11, crescent electrodes12 and “Y” shape electrodes13. Recently, the research of Dong et al has aroused our interest, they
As a platform for droplet operation, digital microfluidic has been widely used in biological science1, environmental monitoring2 and so on. In date several researchers have been devoted to the study of droplet manipulation. In these studies, numerous actuation methods have been reported, including dielectrophoresis3, magnetic force4, surface acoustic wave5, elecRobotics & Microsystem Center & Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University Suzhou 215123, China *Correspondence and requests for materials should be addressed to L. Chen ( [email protected])
Figure 1. Traditional droplet splitting process.
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BioChip J.
tion ∅. The zero level set was changed constantly with the continuous evolution of the level set function. Finall
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