Fabrication techniques for microfluidic paper-based analytical devices and their applications for biological testing: A review

Paper is increasingly recognized as a user-friendly and ubiquitous substrate for construction of microfluidic devices. Microfluidic paper-based analytical devices (μPADs) provide an alternative technology for development of affordable, portable, disposable and low-cost diagnostic tools for improving point of care testing (POCT) and disease screening in the developing world, especially in those countries with no- or low-infrastructure and limited trained medical and health professionals. We in this review present fabrication techniques for microfluidic devices and their respective applications for biological detection as reported to date. These include: (i) fabrication techniques: examples of devices fabricated by using two-dimensional (2D) and three-dimensional (3D) methods; (ii) detection application: biochemical, immunological and molecular detection by incorporating efficient detection methods such as, colorimetric detection, electrochemical detection, fluorescence detection, chemiluminescence (CL) detection, electrochemiluninescence (ECL) detection, photoelectrochemi (PEC) detection and so on. In addition, main advantages, disadvantages and future trends for the devices are also discussed in this review.