Harnessing the Granularity of Micro-Electrode-Dot-Array Architectures for Optimizing Droplet Routing in Biochips

In this article, we consider the problem of droplet routing for Microelectrode-Dot-Array (MEDA) biochips. MEDA biochips today provide a host of useful features for droplet movement by making it possible to manoeuvre droplets at a much finer granularity and with significantly increased flexibility. More precisely, MEDA biochips support more degrees of freedom in navigation and volumetric manipulation such as diagonal movement, droplet reshaping, and fractional-level split-and-merge. This helps improve routing of droplets on microfluidic grids—in particular, when the space available on the grid is limited or blocked by obstacles. In this work, we discuss how these improved capabilities can be utilized in the realization of the desired routes on those biochips. To this end, we introduce a routing method that utilizes satisfiability solvers and guarantees the generation of optimal solutions, considering the set of MEDA operations we model. This significantly improves the state of the art, since previously proposed solutions either (1) relied on heuristics and, hence, were not able to guarantee the optimum or (2) only considered a subset of the MEDA features. The solution proposed in this work includes a formulation of all MEDA features, which, as illustrated by examples, allows for the determination of routing solutions with smaller completion times. Experimental evaluations confirm these findings.