A high-precision nanoliter droplet dispensing system based on optoelectrowetting with tunable droplet volume

The capacity to generate high-precision droplets within Lab-on-a-Chip (LOC) devices is essential for numerous biochemical applications, such as DNA sequencing and drug delivery. In this study, we introduce an optoelectrowetting (OEW)-based droplet manipulation system that utilizes a novel droplet dispensing strategy, enabling precise nanoliter droplet dispensing with tunable droplet volume. The system comprises an OEW microchip, a liquid crystal display (LCD) projector connected to a laptop for generating customized light patterns, and a microscope equipped with a charge-coupled device (CCD) camera mounted above the OEW microchip for real-time observation. Simulations and experiments were conducted to investigate the optimal conditions for high-precision droplet dispensing. The system demonstrated exceptional stability in generating uniform droplets, with a minimum relative error (RE) of 0.45% and coefficient of variation (CV) of 2.49% for dispensing droplets of a volume of 36.52 nL. An experiment was conducted to dispense droplets of varying sizes, demonstrating the system's exceptional capability to generate droplets across a broad size range. The system was further validated through its application in polymerase chain reaction (PCR) amplification, confirming its performance in small-scale biochemical reactions. The results indicate that the proposed OEW droplet dispensing system is highly proficient in generating high-precision small-scale droplets with tunable volume. It also demonstrates its capability for biochemical processing and superior performance in sub-200 nL droplet dispensing compared to conventional pipetting techniques. This advancement holds significant potential for enhancing the performance and efficiency of LOC devices in biochemical research and clinical applications.