Applications of thread-based microfluidics: Approaches and options for detection

Affordable and accessible diagnostic tools in resource-limited settings remains an urgent need to improve global public health. Due to the low-cost, accessibility, simplicity and portability, paper- and thread-based microfluidics have gained significant attention in the development of diagnostic devices over the past few years. Compared to paper, microfluidic thread-based analytical devices (μTADs) are superior in many aspects, such as greater mechanical strength, better flexibility, and superior practicability for modification under wet conditions. This review is focused on driving forces (wicking action, gravitational force and electrophoretic force) for fluid transport on threads, detection techniques (colourimetric detection, electrochemical detection, electrochemiluminescence detection, fluorescence detection, spectrometry-based detection, etc.) and applications (biological diagnostics, immunoassays, wearable devices, health monitoring, food and environmental safety, etc.) in μTADs. The fabrication techniques, readout equipment, advantages, drawbacks, and applications of each detection method are summarized. The most important challenges and perspectives are discussed for further advances and improvements of μTADs.