PCB-based digital microfluidic platform for droplet mixing on an open surface

This paper presents a digital microfluidic (DMF) platform based on a printed circuit board (PCB) for droplet mixing. Mixing droplets without a top cover plate is important for bio-chemical analysis. For this reason, a more efficient mixing method is required especially for mixing a viscous liquid droplet in an open surface. Here, to improve the performance of droplet mixing, we propose the integration of an acoustically oscillating bubble to an electrowetting-on-dielectric (EWOD) chip, which can generate microstreaming inside the droplet. Firstly, an EWOD chip integrated with through-holes for bubble trapping was designed and fabricated through PCB fabrication. This PCB manufacturing technology helps to place more electrodes in the limited chip size. Secondly, we developed the custom-made circuit and interface to individually control multiple actuators (including EWOD actuation and acoustic excitation). Finally, an operation test was conducted to evaluate the capability of not only droplet transportation but also mixing on an open surface. The proposed PCB-based DMF platform for bubble-induced droplet mixing was experimentally verified and expected to make DMF chips more efficient when used for clinical point-of-care diagnostic applications.