A low voltage driven digital-droplet-transporting-chip by electrostatic force

A low-voltage-driven digital-droplet-transporting chip with an open structure is designed, fabricated and characterized. The digital microfluidic chip is fabricated by the silicon planar process. Using only a single electrode panel, the droplet on the chip can be manipulated by electrostatic force under a dc driving voltage. The actuation principle is proposed and verified by the experiment. The experimental results show that the minimum driving voltage decreases as the thickness of the dielectric layer decreases. The driving voltage for a 3 μL deionized (DI) water droplet is reduced to 15 V in air and 13.5 V in oil by employing a thin dielectric layer of 600 nm with a high dielectric constant and a coating hydrophobic layer on the top. The DI water droplets are also demonstrated to be transported in two dimensions smoothly in a programmable manner, and the maximum transport speed reaches 96 mm/s. The droplets of normal saline, a solution of 0.9 wt% NaCl, are also successfully manipulated on the chip.