On the droplet velocity and electrode lifetime of digital microfluidics: voltage actuation techniques and comparison

Abstract

The distinct manageability of digital microfluidics (DMF) has rendered it a promising platform for building large-scale micro-reactors on a single chip for closed-loop automation. However, the limited velocity of the droplet transportation has hindered DMF from being utilized in high-throughput applications. This work investigates a control-engaged droplet actuation technique involving regular electronic hardware and computer-based software to simultaneously raise the velocity of the droplet transportation and elongate the electrode lifetime by lowering the root-mean-square value of the actuation voltage. The technique is based on a series of direct current (DC) pulses and multi-cycles of natural discharge coordinated with the droplet dynamic motions, facilitating real-time droplet position sensing. We found that the proposed technique was superior to both DC and AC in terms of the velocity. As to the electrode lifetime, all showed excellent performance under normal dielectric coating conditions, while AC (alternating current) performed the best under critical conditions. Altogether, this work exhibits a control-engaged electrode-driving scheme with a higher velocity and a longer lifetime compared with traditional DC actuation and for the first time provides a fundamental comparison among the techniques engaging different actuation signals.