Infectious diseases and environmental pollution caused by toxic chemical agents such as heavy metals are significant concerns in the global world. For example, Mercury (Hg) and Arsenic (As) have been recognized as chemical threats for human health. It is difficult to achieve multiple detections of different types of targets in lateral flow strips because of the multiple reagent requirements, while microfluidic paper-based analytical devices (μ-PADS) can provide independent channels and testing areas for colorimetric analysis. Herein, our group develops a low-cost, multiplexing, instrument-free, and simple paper-based fluidics biosensor to quantitatively determine Hg and As amounts in a linear range of 0 ppm - 30 ppm with a detection limit of 1 ppm and 2 ppm, respectively. We will present an overview of the results obtained with our fabrication process, the design of the preliminary pattern and image analysis of the responses in the test area, and the specificity test and stability test results.