used in a completely hand-drawn paper microfluidic device for point-of-care cancer screening. This solvent-free technique allows the potential to create improvised paper-based µTAS. However, pencil-on-paper can also lead to a non-uniform deposition of graphite, limiting the performance of these hand-drawn circuits. Another prominent physical integration method is screen printing, where ink is transferred onto areas of the paper-based microfluidic channels that are not blocked by a stencil. Dungchai et al. screen-printed carbon ink for the working and counter electrodes and silver/silver chloride ink as the reference electrode at the end of the microfluidic channel. Screen-printed electrodes on paper-based microfluidic devices have been used not only to develop biosensors for metabolites, but also to detect bacteria and heavy metals in food and water. Other physical integration methods (spray/spin coating, blending, and vacuum filtration) have been developed for paper electronics, but have yet to be implemented in paper-based microfluidic devices. One extra interesting physical integration method is combining paper-based devices with a portable lightbox to create uniform and repeatable lighting environments. The lightbox can be controlled either manually or remotely by a cellphone. Chemical Integration Chemical integration uses reactions to functionalize paper devices and create electrical nanostructures. Chemical integration techniques can be classified into two groups: in situ seed growth and polymerization. In situ seed growth (i.e., growing an interconnected nanoparticle layer) is an effective method for generating electrodes on paper microfluidic devices since the analyst can control its architecture and size. In situ growth of gold and silver nanoparticles is the most ubiquitous method for chemical integration of electrical components on paper microfluidic devices due to their signal amplification and conductivity. The metal seed solution is prepared via a reduction reaction of the metal salt and some combination of reductants like sodium borohydride, trisodium citrate, ascorbic acid, and/or hydroxylamine hydrochloride. Then, nanoparticles are grown embedded into the fibers of the microfluidic device by dispersing the seed solution on the hydrophilic area of the paper, which has been soaked in the reductant. Once the nanoparticles have grown, the device can be dried and characterized. The promise of in situ seed growth is that the nanoparticles are uniformly embedded on the platform and the embedded metal nanoparticles can also be further functionalized with substituents to increase the sensitivity of the microfluidic platform. For example, a paper-based microfluidic device was developed for both colorimetric and electrochemiluminescence sensing of lead by functionalizing palladium/gold nanoparticles with