Dual-Mode Undistorted Visual Fluorescent Sensing Strategy through Manipulating the Coffee-Ring Effect on Microfluidic Paper-Based Chip

To overcome the insufficient sensitivity due to distortionof thefluorescent images by mobile devices, we first developed a novel dual-modestrategy for undistorted visual fluorescent sensing on & mu;PADby technically manipulating the coffee-ring effect of the fluid sample.Based on the manipulating coffee-ring effect, we divided the horizontaldirection of the resulting fluorescence image into 600 pixels andobtained more accurate quantitative information to avoid image distortion.The bovine serum albumin-stabilized gold nanoclusters-copperion complex was used as the fluorescent probe, combined with a smallimaging box and a smartphone, to achieve a rapid testing of histidinein human urine. The output image was analyzed in dual mode: RGB numericalanalysis in pixel units and the direct measurement of the fluorescentstrips length (limit of detection (LOD) is 0.021 and 0.5 mM, respectively),and improved antidistortion for visual fluorescent sensing. This strategycan overcome the distortion of a smartphone-visualized fluorescentimage and shows great potential for rapid and convenient analysis.