A scheduling and routing algorithm for digital microfluidic ring layouts with bus-phase addressing

Digital microfluidic systems (DMFS) are a new class of lab-on-a-chip systems for biochemical analysis. A DMFS uses electro wetting to manipulate discrete droplets on a planar array of electrodes. The chemical analysis is performed by repeatedly moving, mixing, and splitting droplets on the electrodes. Recently, there has been a lot of interest in developing algorithms and computational tools for the design, simulation, and performance evaluation of DMFS. In this paper, we present an algorithm for coordinating droplet movement in batch mode operations on ring layouts with bus-phase addressing. In bus- phase systems, each electrode is not individually addressable, instead a set of electrodes are all controlled by the same signal. Though this hardware design simplifies chip fabrication, it increases the complexity of routing droplets. The presented algorithm allows multiple independent reactions, each with two reactants and one product, and chain reactions with multiple stages, where each stage produces reactants for the next stage, to take place simultaneously on the chip. This algorithm is scalable to different number of reactions within a limit which depends on the size of the layout, placement of sources and number of phases used. It also addresses any sensor constraints under which droplets need to visit sensor locations for specified amounts of time. We present simulation results using our algorithm to coordinate droplet movements for example analyses on a ring layout.