Thin-Film Transistor Digital Microfluidics Circuit Design with Capacitance-Based Droplet Sensing

Area of Science:

• Microfluidics
• Electrical Engineering
• Sensor Technology

Background:

• Digital microfluidics (DMF) systems face challenges in precise droplet control due to expanding pixel arrays.
• Existing droplet sensing circuits often suffer from droplet perturbation, affecting accuracy.

Purpose of the Study:

• To propose a novel capacitance-based droplet sensing system for thin-film transistor DMF.
• To enhance droplet driving and sensing precision in active matrix electrowetting-on-dielectric (AM-EWOD) chips.

Main Methods:

• Development of a capacitance-based sensing circuit with a unique inner and outer dual-pixel electrode structure.
• Integration of droplet driving and sensing functionalities within a single circuit.
• Utilizing a novel fan-shaped thin-film transistor structure.

Main Results:

• The proposed circuit achieves a 48 V pixel voltage for droplet driving.
• Demonstrated a sensing voltage difference exceeding 10 V between deionized water and silicone oil, indicating high sensing accuracy.
• Verified the stability of threshold voltage drift and temperature.

Conclusions:

• The novel dual-pixel electrode design effectively minimizes droplet perturbation during sensing.
• The system offers precise droplet driving and accurate sensing capabilities for DMF applications.
• The design is suitable for integration into AM-EWOD chips for closed-loop droplet control.