Chapter 8: Low-cost Microfluidic Paper-based Analytical Devices (μPADs): Fabrication Methods, Flow Control, and Applications

This chapter covers microfluidic paper-based analytical devices (µPADs), including their origin, characteristics, fabrication methods, the control of liquid imbibition within µPADs, and applications of µPADs in various analytical fields. µPADs (made from paper) are inherently thin, and inexpensive, and function without external pumps due to the porous structure of the paper. These attributes, along with their other advantages, make µPADs suitable candidates for meeting the ASSURED criteria of the World Health Organization (WHO) for diagnostics in the developing world. Since their invention circa 2007, numerous µPADs have been developed for a wide range of applications, limited only by imagination. These devices are produced using a wide variety of techniques, ranging from those traditionally employed for paper substrates and microfluidics to advanced technologies such as 3D printing. µPADs are designed to detect a broad spectrum of signals, ranging from chemical to biological in origin, using either simple one-layer forms or more complex 3D networks of interconnected channels.