Affordable Arsenic Detection Device Using Handmade Lokta Paper for Decentralized and Sustainable Manufacturing

The reliance on centralized manufacturing systems often shows vulnerability of global supply chains, as evidenced by disruptions during the COVID-19 pandemic and geopolitical conflicts. This study reports an affordable and portable paper strip sensor for arsenic detection in groundwater, developed using distributed manufacturing and sustainability principles. Handmade Lokta Paper (HLP), produced in the laboratory from bark of a native Lokta plant, Daphne, through eco-friendly methods, served as the sensor substrate. The HLP strip employed the Gutzeit reaction and integrated smartphone imaging for qualitative, semiquantitative, and quantitative arsenic analyses. The assay optimization was achieved with 1% (w/v) HgBr₂ impregnation, 5-min dipping time, 15-min arsine exposure, and imaging within 25 min. Testing of 21 groundwater samples from Nepal revealed strong agreement between the HLP strip and a commercial kit Econo-Quick (EQ) (Cohen's kappa = 0.811). The HLP strip demonstrated a lower limit of detection (18 vs. 20 µg/L) and limit of quantification (54 vs. 61 µg/L). Most water samples had arsenic concentrations below 10 µg/L, with few reaching Nepal's regulatory limit of 50 µg/L. In addition to robust analytical performance, the HLP strip exemplifies the scalability and cost-effectiveness of arsenic sensors, with a production cost of USD 0.37 per test-significantly lower than commercial alternatives. This innovation may foster local economic growth, minimize supply chain dependency, and reduce environmental impact through the sustainable utilization of Lokta paper. The study highlights the potential of integrating traditional materials with advanced analytical techniques to address global health and environmental challenges while promoting regional resilience and sustainability.