Portable paper-based microfluidic device for rapid on-site screening of milk adulterants

Milk adulteration remains a significant public health concern in India, where conventional laboratory-based detection methods are often costly, time-consuming, and impractical for field use. This study introduces a novel paper-based microfluidic device designed for rapid, low-cost detection of multiple milk adulterants. The device comprises a 3D-printed strip holder and utilizes gravity-assisted capillary flow through porous paper, eliminating the need for hydrophobic barriers or external power sources. Its modular design allows for easy reuse of the holder while only replacing the paper strip for successive tests. The platform enables visual detection of common adulterants—including neutralizers, starch, hydrogen peroxide, urea, detergents, and boric acid—via reagent-specific colorimetric responses. The device meets the ASSURED criteria of World Health Organization for point-of-care diagnostics, offering a promising tool for decentralized milk quality monitoring and contributing to both consumer safety and improved supply chain transparency in the dairy industry. The device demonstrated a limit of detection (LOD) as low as 0.03% for urea and hydrogen peroxide, outperforming existing paper-based methods. The results were validated across five independent trials per condition, with high reproducibility and minimal cross-reactivity, confirming the diagnostic reliability of the platform.