Implementing AC Signal Driving in Digital Microfluidic Chips with Active-Matrix Thin-Film Transistors

In this work, we propose a novel method for implementing AC signal driven droplets on electrowetting-on-dielectric (EWOD) chips. The electrode arrays of the EWOD chips are manufactured using active-matrix thin-film transistor (AM-TFT) technology. The AC signal used to drive droplets is achieved through a combination of five TFTs in one pixel. The metal oxide indium gallium zinc oxide (IGZO) as active layer is used to fabricate the TFTs. Results show that the IGZO TFTs have excellent electrical characteristics, with a field-effect mobility of 8.2 cm²/V·s, a threshold voltage of 0.5 V, a subthreshold swing of 0.31 V/decade, and an on/off current ratio of greater than 10⁷. The simulation and experimental results indicate that the combination of five TFTs in one pixel can output stable AC signal. The droplets driven by AC signal on the EWOD chips can implement the basic manipulation such as generation, movement, splitting, and merging. This technology improves the flexibility and configurability of droplet manipulation on AM-TFT-based EWOD chips, which is of great significance for the rapid mixing of droplets, anti-adsorption of biological macromolecules, and prevention of cross contamination.