Food safety is a critical issue, and the detection of food pollutants is of paramount importance. The development of rapid, reliable, and effective tools for the identification of food contamination (i.e., pesticides) is crucial to meet the growing demand for safe high-quality food. This thesis presents the development of a colorimetric paper-based microfluidic biosensor for the detection of organophosphate pesticides (OPs) by measuring the quantity of the enzyme acetylcholine esterase (AChE). The biosensor uses a colorimetric assay to detect the presence of OPs in sample solutions based on the principle of enzyme inhibition. The AChE substrate chromogen indoxyl acetate (IDA) is used to identify these toxic substances.