Simultaneous multiple-droplet generation with meniscus filling on digital microfluidics chip

As digital microfluidics (DMF) becomes a popular approach to automating biochemical reactions for various fields, its applications requiring numerous droplets with high volume consistence in parallel analysis still present a great challenge. DMF conventionally utilizes the three-electrode method to split droplets one by one – it has low throughput and noticeable droplet volume variations. To address this challenge, a novel splitting method with a zigzag row-electrode design on electrowetting-based DMF chips is proposed. The liquid is first stretched on the row-electrode, then split by the electrode array. The row-electrode promotes the meniscus filling phenomena, providing larger overlapping areas, thereby stabilizing the volume of droplets generated. Twenty (20) droplets of 6–8 nL with the volumetric coefficient of variance (CV) at only 1.26% are simultaneously generated, excluding the droplets at both ends. Theoretical analysis is developed and validated by the experiments to realize the relationship of important geometrical parameters. This method can not only rapidly produce multiple daughter droplets with excellent droplet volume consistence, but also preserve the common DMF fabrication and actuation scheme without modification. It shows great promise for the DMF applications that require high-throughput downstream processes.