Evolution of Paper Microfluidics as an Alternate Diagnostic Platform

Since the inception of paper microfluidics, there has been a significant leap in developing microfluidic assays for wide range of applications, particularly in healthcare. Considering the average economic status of the population and epidemic outbreaks of diseases within territory of developing nations, it is indeed an essential demand to have an alternate diagnostic plat-form which is ideally expected to serve the purpose at faster and affordable means. In this context, introduction of the paper devices started with qualitative assays and thereafter it has subsequently evolved for semi-quantitative and quantitative platforms. Conventional diagnostic procedures involve time consuming multi step processes that are rather elaborate and expensive, necessitating the involvement of highly trained personnel for analysis. Paper based diagnostic procedures; on the other hand, normally deploy tiny amounts of physiological fluids and consumables, to achieve the same end objective at much reduced expenses and time. Towards this, colorimetric assays have shown significant promises, but are limited by the sensitivity of the diagnostic method. In an effort to improve the sensitivity of the detection, other approaches like fluorescent, electrochemical, luminescence have been progressively explored. In this Chapter, the discussion is systematically organized from fabrication of paper-based devices to their different applications in the diagnostic arena. Starting from the fabrication fundamentals and working principles, we delve deep on different colorimetric detection of bio-molecules, bacteria etc. We also focus on the critical aspect of plasma separation from the whole blood, which is a key for most colorimetric detections. Finally, we summarize the key findings about the advancements of these devices for practical use in resource-limited settings and bring out some new and unaddressed questions as well as challenges in the field.