Multiple semi-quantitative colorimetric assays in compact embeddable microfluidic cloth-based analytical device (μCAD) for effective point-of-care diagnostic

Abstract

Cotton fabric is proposed as an alternative material for low-cost point-of-care devices. Cotton fabrics are vastly available, low cost and flexible. Simple wax patterning method was applied to create hydrophilic channels in cotton fabric. Three-dimensional (3D) colorimetric microfluidic device was made by folding 2D pattern along certain predefined lines. Three-dimensional devices show better mixing uniformity between reagents and analyte across the detection zones. On-chip colorimetric calibration is also proposed by putting predefined serially diluted samples next to the detection zones. Multiple assays can be integrated within a small surface area by stacking layers of individual assay device separated by a wax-impregnated fabric. We were able to detect glucose, nitrite and protein having concentration as low as 0.5 mM, 30 μM and 0.8 mg/mL, respectively, by bare eyes. Results of the assays from an unknown analyte sample and precalibrated serially diluted sample standards were displayed in a side-by-side configuration, and the interference of each analyte on the other reaction zones was investigated. These results are better than if the detection is merely taken from the calibration curve without integrated standard calibration. The mechanical durability, robustness and flexibility of 3D microfluidic cloth-based analytical device (μCAD) also make it easily embeddable to daily wearable product. We demonstrated multiple single-step qualitative assays using embedded 3D μCAD and propose a new concept of “point-of-sampling diagnostic”.