Low temperature polysilicon pixel circuits for active-matrix digital microfluidic chips

Abstract

Emerging active-matrix digital microfluidic imposes stringent requirements on driving signals, yet conventional pixel circuits used in flat panel displays struggle to provide the necessary voltage. In this paper, we present three novel pixel circuits for active-matrix digital microfluidic chips: the 3T1C, Inverter, and SRAM designs. All proposed circuits are fabricated with low-temperature polysilicon technology, which is compatible with mainstream display backplane manufacturing processes. The characteristics and positive bias stability of the implemented thin-film transistors have been validated. Additionally, a comparative analysis is conducted against existing pixel designs. The circuits’ performance was evaluated under varying Gate pulse widths and driving voltages to determine the optimal driving strategy. With the appropriate driving voltage, the SRAM structure is capable of achieving an output exceeding 20 V. Moreover, the holding time, long-term operational stability, and illumination stability of the circuits were evaluated and compared. Experimental results demonstrate that the SRAM structure outperforms in both output performance and stability. An active-matrix digital microfluidic chip with a 640 × 280 array was fabricated using the SRAM pixel structure, which highlights its scalability. The simplified circuit structure, coupled with an output voltage exceeding 20 V, addresses the limitations of conventional pixel circuits for digital microfluidic applications. These novel designs offer innovative and reliable driving solutions for LTPS-based active-matrix digital microfluidics systems, further advancing the application of display technology in non-display fields.