In the simplest three-dimensional paper-based microfluidic devices, colorimetric signal is read from the entire area of a patterned zone that has been filled with a solution of analyte-containing sample and chemical reagents. Evaluation of low signal quantities by visual inspection or image analysis is often difficult because a small amount of color, which is distributed across the entire area of the readout zone, must be objectively distinguished from the color and texture of the paper background. As one potential solution to this problem, we have developed a new type of paper-based device where signal is generated at the interface of multiple converging liquid fronts. In our approach, each advancing front contains at least one component necessary for signal production and color is developed when these fronts meet. Because the position of these junctions can be controlled within the geometry of the device readout zone, signal generation is localized to a small, well-defined area. When directed to this space, colorimetric outputs from low concentrations of analyte are more intense than when distributed over a larger area, improving both the quantitative (i.e., sensitivity) and qualitative (i.e., ease of visual interpretation) capabilities of these devices. Additionally, reagents required for diagnostic assays cannot always be co-stored within paper-based devices, requiring additional channels or layers of material for mixing. In our devices, these excess channels and layers can be eliminated, as signal production occurs as soon as the advancing liquid fronts meet. This approach simplifies design requirements for three-dimensional paper-based microfluidic devices and enables sensitive detection of important biological analytes.<br/>

Generating signal at converging liquid fronts in three-dimensional paper-based microfluidic devices

256th National Meeting (2018)

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