Numerical study of the microdroplet actuation switching frequency in digital microfluidic biochips

Abstract

In this article, an electrohydrodynamic approach is used to study the microdroplet actuation in contemporary digital microfluidic biochips. The model is employed to analyze the microdroplet motion, and investigate the effects of the key parameters on the devices performance. The modeling results are compared to the experimental observations, and it is shown that the model provides an accurate representation of digital microfluidic transport. An extensive parametric variation is used to derive the maximum actuation switching frequency for ranges of the microdroplet size, gap spacing between the top and bottom plates and electrode pitch size. As a result, scalability of the devices is investigated, and it is shown that the microdroplet transfer rates change inversely with the system size, and microdroplet average velocity is nearly the same for different system scales. As a result of this study, an adjustable force-based actuation switching frequency implementation is proposed, and it is shown that faster microdroplet motion is obtained by in situ adjusting of the switching frequency. Finally, it has been observed that fastest microdroplet motion, despite similar studies conducted in the literature, is not achieved via actuating the next electrode as soon as the microdroplet touches it. Indeed, the switching frequency spectrum is dependent on the physical and geometrical properties of the system.