Microfluidic cloth-based analytical devices: Emerging technologies and applications

Cloth (or fabric) is an omnipresent material that has various applications in everyday life, and has become one of the things people are most familiar with. It has some attractive properties such as low cost, ability to transport fluid by capillary force, high tensile strength and durability, good wet strength, and great biocompatibility and biodegradability. Hence, cloth is an ideal material for the development of economical and user-friendly diagnostic devices for many applications including food detection, environmental monitoring, disease diagnosis and public health. Microfluidic cloth-based analytical devices (mu CADs) (or microfluidic fabric-based analytical devices (mu FADs)) first emerged in 2011 as a low-cost alternative to conventional laboratory testing, with the goal of improving point of care testing and disease screening in the developing world. In this review, we examine the advances in the development of mu CADs from 2011 to 2020, especially highlighting emerging technologies and applications related to the mu CADs. First, different fabrication methods for mu CADs are introduced and compared. Second, a series of cloth-based microfluidic functional components are discussed, including microvalves, fluid velocity control elements, micromixers, and microfilters. Then, electroanalytical mu CADs are described, especially focusing on the use of cloth-based electrodes. Next, various detection methods for mu CADs, together with their corresponding applications, are compared and categorized. In addition, the current development of wearable mu CADs is also demonstrated. Finally, the future outlook and trends in this field are discussed.