Use of AutoPAD to design a single layer device that splits a sample into three test zones. The left column displays a section of code used to create the design, where the command to be modified is highlighted in yellow. The middle column displays the AutoPAD output (as a PNG file) of the full device design. The right column is an image of a paper-based device fabricated from the AutoPAD design with red dye added into the channels. The top and bottom rows illustrate original and modified designs. Adapted from Martinez et al.1.