Manipulation of multiple droplets on N×M grid by cross-reference EWOD driving scheme and pressure-contact packaging

This paper reports two recent breakthroughs in our development of EWOD-based (ElectroWetting On Dielectric) digital (droplet) microfluidic circuits: a driving scheme and a packaging scheme, both of which greatly simplify fabrication and make large-array chips a reality. This paper will explain (1) the concept of cross-reference driving, which allows single-layer electrode fabrication, including the techniques to allow simultaneous driving of multiple droplets and (2) pressure-contact connection, which greatly simplifies packaging and assembly for high-density EWOD devices. The efficacy of the driving concept is demonstrated by transporting four droplets simultaneously, each along its own path, on a 9×9 grid and performing essential fluidic functions such as creation, cutting, merging, and mixing of droplets.