Flexible Droplet Routing in Active Matrix–Based Digital Microfluidic Biochips

Abstract

The active matrix (AM)-based architecture offers many advantages over conventional digital electrowetting-on-dielectric (EWOD) microfluidic biochips, such as the capability of handling variable-size droplets, more flexible droplet movement, and precise control over droplet navigation. However, a major challenge in choosing the routing paths is to decide when the droplets are to be reshaped depending on the congestion of the intended path, or split- and route sub droplets,and merging them at their respective destinations. As the number of microelectrodes in AM-EWOD chips is large, the path selection problem becomes further complicated. In this article, we propose a negotiation-guided flow based on routing of subdroplets that obviates the explicit need for deciding when the droplets are to be manipulated, yet fully utilizing the power of droplet reshaping, splitting, and merging them to facilitate their journey. The proposed algorithm reduces routing cost and provides more freedom in deadlock avoidance in the presence of multiple routing tasks by assigning certain congestion penalty for sibling subdroplets and fluidic penalty for heterogeneous droplets. Compared to existing techniques, it reduces latest arrival time by an average of 29% for several benchmark and random test suites. Furthermore, our method is observed to provide 100% routability of nets for all test cases, whereas existing and baseline routers fail to produce feasible solutions in many instances. We also propose a reliable mode droplet routing strategy where the number of unreliable splitting operations can be reduced by paying a small penalty on latest arrival time.