Numerical and experimental analysis of a novel passive feedback valve for variable fluid volume metering in centrifugal microfluidic platforms

• A novel passive valve named Feedback Valve was designed for metering fluids in centrifugal microfluidic platforms. • The valve enables metering of various fluid volumes using a single fixed geometry. • A new mechanism for unpriming the siphon allows reusing the Feedback Valve unit in sequential processes. • The valve operates based on generating a negative gauge pressure inside the initial fluid loading chamber. • Unlike conventional units, this valve is reusable and capable of metering any desired volume on demand. In lab-on-a-disc systems, operations that involve repeated reagent handling demand the integration of repeatable valves and a suitable metering unit operation. This study introduces and designs a novel operating unit called the feedback valve and investigates its performance through network simulation. This passive, integrated, and reusable unit, facilitates accurate fluid metering and enables reusable volume measurements. One of the key features of this unit is its ability to create an adjustable measurement range by varying the disk rotation speed. This capability, along with its repeatability, permits the measurement of different fluid volumes using only one specific geometry. This unit holds significant potential for laboratory applications such as ELISA and PCR, which involve multiple sequential washing steps. Experimental results show that at different radial positions of the siphon outlet (ranging from 25 to 40 mm), the volume of measured fluid can be adjusted between 60 and 270 μ L by varying the disk rotation speed. The measured volumes showed a maximum standard error of the mean (SEM) of 5 μ L (n = 5). This passive, repeatable, and adjustable valve enables precise fluid metering, though it is currently limited to fully sealed or ventless inlet chambers.