A gravity-driven microfluidic metering system for automation of multiplexed bioassays

Automatic and precise fluid manipulation is essential in microfluidic applications. Microfluidic metering, in particular, plays a critical role in achieving the multiplexity of assays, reaction consistency, quantitative analysis, and the scalability of microfluidic operations. However, existing fluid metering techniques often face limitations, such as high complexity, high cost, reliance on external accessories, and lack of precision, which have restricted their use in multiplexed and quantitative analysis, especially in portable applications. In this study, we present a novel portable gravity-driven metering system designed for automated multiplexed fluid metering, multistep fluid control, and multi-chamber signal readout. Our metering chip utilizes gravitational force to dispense sample liquids, allowing for versatile and precise metering. Guided by a series of numerical simulations, we optimized the design of our metering chip to achieve rapid and accurate liquid metering. Furthermore, thermal control valves were employed to facilitate automated and programmable fluid transfer, eliminating the need for external equipment. To enhance user experience, we developed a smartphone-assisted readout pod for seamless integration with the metering chip. We validated the efficacy of our platform through a proof-of-concept multiplexed analysis of urinary biomarkers, demonstrating high sensitivity, specificity, and absolute quantification capabilities. Our gravity-driven metering system shows significant potential for applications in multiplexed diagnostics, drug screening, and material synthesis, effectively addressing critical needs in fluid manipulation and analysis.