Thread-based microfluidics for blood typing: A perspective on evolution, mechanistic insights, and translational future

Blood typing testing is a life-determining prerequisite for safe transfusion, emergency care, and maternal health. However, conventional methods—such as tube and gel column agglutination—remain dependent on centralized laboratories, skilled personnel, refrigerated centrifuges, and relatively large blood volumes, which severely limits their deployment in resource-limited or point-of-care settings. Microfluidic platforms emerge as a promising alternative by miniaturizing assays, reducing sample/reagent consumption, and enabling pump-free capillary transport. Notably, thread-based microfluidic devices offer ultra-low cost, ubiquity, flexibility, and a natural fibrous architecture that mechanically traps agglutinated red blood cells while failing to immobilize free ones, making them uniquely attractive for point-of-care blood typing. Recently, thread-based blood typing has achieved two major transformations, namely, structural evolution from 2D chromatographic separation to 3D single-thread architectures and detection upgrade from naked-eye observation to smartphone-based identification. In this review, we provide a discussion on the recent advances in thread-based microfluidics for blood typing. We shed light on the design principles and detection mechanisms of various thread-based microfluidic blood typing methods, highlighting their capabilities for simple, economical, rapid, and precise point-of-care testing. Finally, we outline several promising directions for the further development of these thread-based blood typing methods, providing our perspectives on their path toward practical applications.