Fig. 6.

How particle immunoagglutination affects the flow distance and velocity profiles. (A) The flow distances at 30 s are longer with the positive samples (orange boxes) than the negative samples (blue boxes). (B) With no virus present, the singlet Ab-particles (green) quickly diffuse to the wetting front, lowering the surface tension and the flow velocity. Nitrocellulose fibers are colored in light orange and saliva proteins in dark orange. (C) With virus present (blue), immunoagglutination occurs, creating larger and heavier particle clusters, leaving very few singlet Ab-particles diffusing to the wetting front. (D) The Ab-particles on the negative sample are mostly in the singlet form and take more time to reach constant velocity (top), while fewer singlet Ab-particles on the positive sample are able to reach the flow interface due to immunoagglutination, so it takes less time to reach constant velocity (bottom).