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In recent years, measuring and monitoring analyte concentrations continuously, frequently, and periodically has been a vital necessity for certain individuals. We developed a cotton-based millifluidic fabric-based electrochemical device (mFED) to monitor glucose continuously and evaluate the effects of mechanical deformation on the device’s electrochemical performance. The mFED was fabricated using stencil printing (thick film method) for patterning the electrodes and wax-patterning to make the reaction zone. The analytical performance of the device was carried out using the chronoamperometry method at a detection potential of −0.2 V. The mFED has a linear working range of 0–20 mM of glucose, with LOD and LOQ of 0.98 mM and 3.26 mM. The 3D mFED shows the potential to be integrated as a wearable sensor that can continuously measure glucose under mechanical deformation.

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”.

Time-based microfluidic absorption sampling was proposed using cotton fiber-based device made in swab stick. The assay was optimized and compared with conventional pipetted drop sampling using the same device. Reagents were integrated into cotton fiber device for assessing concentration of analytes by the colorimetric detection method through time-based absorption sampling microfluidic system. All assay parameters were first optimized using conventional pipette-based drop sampling. The color intensity is linear in the relevant concentration range of the analytes. The LOD are 0.189 mM for glucose and 6.56 μM for nitrite, respectively. These values are better than conventional drop sampling. The fiber-containing swab itself functions as sampling, assay and calibration device. Microfluidic cotton fiber-based assay device was fabricated and can determine analyte concentration in artificial salivary samples, colorimetrically, by time-based absorption sampling without the need of complex equipments.