Chemical and biomolecular analysis form an integral part of food contamination testing and healthcare diagnostics.The majority of the currently established detection methods are expensive, sophisticated and time consuming.Microfluidic-based lab-on-a-chip systems offer a promising alternative in this regard by enabling the development of simpler and relatively cost-effective platforms for analytical applications. In this work, we report the fabrication of a portable sensor platform using selective wax impregnation of cellulosic paper. The application of the fabricated paper-based lab-on-achip device is demonstrated for the qualitative and quantitative detection of starch contamination in milk using colorimetry. Integration of a detection procedure with smartphone imaging allows for on-the-spot data collection, thus overcoming thechallenges of sample storage, handling and transportation to lab facilities. This approach offers a versatile method for diagnostic and sensing applications in resource-limited areas, especially in developing and underdeveloped countries.