From Flat to Folded: An instrument-free solution for chemical and biological paper-based sensing using A-PAP pen technology

Having economical, flexible, disposable and readily manufacturable devices for everyday sensing applications is of paramount importance. We report a novel and cost-effective technique for fabricating paper-based devices using an Advanced PAP (A-PAP) pen, which is capable of withstanding typical aqueous solutions and organic solvents. The quick fabrication process does not require any sophisticated instrumentation or a heating step, making it a promising technology for resource-limited settings. Using an A-PAP pen, we have fabricated two-dimensional (2D) paper-based devices for chemical detection of heavy metal and nitrite. We have also demonstrated the versatility of fabrication technique for biological sensing using 2D lateral flow paper-based devices for the detection of dopamine. Furthermore, the technique is also validated for fabricating complex three-dimensional (3D) paper-based devices using a paper origami technique for heavy metals sensing. The ready-to-use devices can be fabricated in seconds, making them convenient for on-the-spot testing. Overall, this technique provides a valuable tool for creating affordable, efficient, and accessible chemical and biological testing solutions.