Recent Research and Emerging Challenges in the System-Level Design of Digital Microfluidic Biochips

Microfluidic biochips are replacing the conventional biochemical analyzers, and are able to integrate on-chip all the basic functions for biochemical analysis. The "digital" biochips are manipulating liquids not as a continuous flow, but as discrete droplets on a two-dimensional array of electrodes. Basic microfluidic operations, such as mixing and dilution, are performed on the array, by routing the corresponding droplets on a series of electrodes. The challenges facing biochips are similar to those faced by microelectronics some decades ago. Computer-Aided Design tools for microfluidics are in their infancy, and designers are currently using manual, bottom-up design approaches to implement such biochips. Considering their architecture and the design tasks that have to be performed, the design of digital biochips has similarities to the high-level synthesis of integrated circuits. Motivated by this similarity, a few researchers have recently started to propose approaches for the top-down design of biochips. So far, they have assumed that operations are executing on virtual modules of rectangular shape, formed by grouping adjacent electrodes, and which have a fixed placement on the array. However, operations can actually execute by routing the droplets on any sequence of electrodes on the biochip. In this paper, we outline the original module-based synthesis problem, and then we present recent work which eliminates the concept of virtual modules and allows droplets to move on the chip on any route during operation execution. We discuss the advantages of such an approach, and identify the challenges and opportunities of system-level design of digital microfluidic biochips.