Precise Droplet Dispensing in Digital Microfluidics with Dumbbell-Shaped Electrodes

Electro-wetting-on-dielectric (EWOD) enables the manipulation of droplets on a two-dimensional surface, which provides a versatile technique for digital microfluidics at a micro- or nano-scale. However, the deficiency of the dispensing precision has long limited its applications in micro total analysis systems (μ-TAS) where the accuracy of assays is largely determined by the volume control of the reagent dosing. This paper proposes optimum electrode designs and carries out characterization experiments to demonstrate the reproducibility of on-chip droplet generation with no extra external apparatus. The coefficient variation of the volumes of consecutively dispensed droplets from a non-refilling reservoir can be limited to below 0.3%, indicating the validity of the new electrode structure in practical applications.