Integrated Droplet Driving and Sensing Circuit for Enhanced Position Feedback in AM-DMF System

With the increasing throughput of droplet manipulation and the decreasing droplet size in the active-matrix digital microfluidics (AM-DMF) system, achieving a precise and stable control of small droplets has become an urgent issue. This paper proposes a hydrogenated amorphous silicon thin film transistor (a-Si: H TFT)-based capacitive droplet position sensing circuit. This circuit integrates droplet driving and sensing functions effectively. The variance of sensing outputs for different droplet samples and load-driving ability are enhanced by introducing an inverter serving as the inverting amplifier. Simulation results show that this circuit can stably provide driving voltages over 46 V and achieve a sensing output variance of 25 V between deionized (DI) water and silicone oil. Tests of the other two samples have also been conducted. The applicability of this circuit in high-throughput arrays has also been verified. In a 12 W 10 array filled with oil-surrounded DI water, the sensing output variance remains over 22 V. This circuit demonstrates the potential of driving droplets and supplying effective droplet position feedback for the high-throughput AM-DMF system, enabling the closed-loop droplet control.