Modeling of spatial–temporal distribution of the components in the drying sessile droplet of biological fluid

Using lubrication theory, drying processes of sessile droplets of blood serum (i.e. colloids with the salt admixture) on a solid hydrophilic horizontal substrate are studied. The concentration of the solute is supposed to be high enough to ensure good adhesion and strong anchoring (pinning) of the triple line, thereby a drop is desiccating with constant base. The simulation of spatial distribution of the components in the droplet of biological fluid drying on a substrate is performed using advection–diffusion equation. The proposed model explains the redistribution of components in a sessile drop of biological fluid when it dries. Competition between advection and diffusion leads to large particles (protein) accumulating at the edge of the drop (well-known coffee-ring effect), while solutes (salts) are distributed more uniformly across the diameter of the sample.