Sustainable cotton fabric-based microfluidic platform for smartphone-assisted flow characterization and colorimetric iron detection

Increasing need of low-cost and portable analytical devices have motivated search for inexpensive materials as substrates for performing chemical assays. In this study, fabric-based microfluidic platform was developed using cotton substrate through a facile patterned cutting-based fabrication method for smartphone assisted colorimetric detection of iron in water. Both the spot-test and flow-test device configurations were designed without relying on sophisticated instruments. Physicochemical characterization using SEM and FTIR, confirmed the porous cellulose structure that allows capillary action of fluids. Flow studies were conducted in straight and dual-inlet channel configurations and fitted into the mathematical model. Flow behavior on cotton substrate follows the Lucas-Washburn equation with coefficients of determination 0.985 and 0.986 respectively, validating the capillary induced fluid transport within the fabric matrix. Formation of the ferric thiocyanate complex formed the basis of detection of iron which was quantified using digital image analysis. The empirical results followed a logarithmic response over the entire concentration range of 5-1000 ppm (R² = 0.9227) and a linear response in the low concentration range of 5-100 ppm (R² = 0.9536). The proposed method showed a repeatability of 2.09%, intermediate precision below 2% and spike recoveries in the range of 94.8% and 104.7% for real water samples. Overall Analytical GREEnness (AGREE) of 0.83 and life cycle assessment (LCA) climate change impact of 0.00409 kg CO 2 -Eq, demonstrated the advantages of renewable substrate, low reagent consumption and simple fabrication process with miniscule carbon footprints. The developed fabric-based microfluidic platform provides an environmentally sustainable platform for water quality monitoring with significant potential for point-of-use applications.