Hyphenating paper-based biosensors with smartphones

Paper-based biosensors are small, lightweight, inexpensive diagnostic devices made from paper. These characteristics enable these devices to be popular candidates for point-of-care testing in resource poor settings. They are a versatile platform that has a variety of uses, including clinical diagnostics, infectious disease monitoring, environmental sampling, and food safety screening. Paper-based biosensors are robust and reliable diagnostic methods; they have been in use for over 40 years and are constantly evolving to meet ever more complicated diagnostic criteria. Earlier iterations include the dipstick assay and the lateral flow assay. In the dipstick assay, chemical reactions cause the paper to change colour when wet; the lateral flow assay moves fluid across the paper by simple diffusion or capillary action to produce simple colorimetric biochemical reactions. More recently, microfluidic pads have incorporated lab-on-a-chip principles: printed flow channels, 3-dimensional folding, and even (paper-based) switches to allow more complicated chemical and biochemical reactions. This chapter will explore the different types of paper-based biosensor, their designs and uses. Further, it will explore smartphones as an adjunct device capable of enhancing the paper-based biosensors' capabilities, due to the smartphone's ubiquity, high-powered camera, onboard processing, and digital connectivity.