Precise dispensing technology for point-of-care diagnosis with micro-volume blood

Precise dispensing of droplets is a crucial step for acquiring reliable diagnostic results. When a source sample volume is limited, the need for precise dispensing of submicroliter and nanoliter quantities is especially important. In this work, we developed a positive-displacement high-precision dispensing technique using a nickel electroformed tube with an inner diameter accuracy of 5 μm or less. When a dispensing variation of 100 nL was evaluated using a photometric method, the most stable coefficients of variation (CV) were observed for a tube thickness of 50 μm with hydrophobic treatment, where the average CV value was 1.3%. Furthermore, the glucose concentration in 200 nL of animal-based control serum was colorimetrically measured using enzymatic reactions without drying and mixing reagents. The CV value of the analysis was approximately 3%, suggesting that several biochemical panels can be precisely measured even from one drop of blood. The present positive-displacement dispenser ensures zero contamination and almost-zero dead volume and therefore would be useful for multi-panel clinical diagnosis.