Fat content and hematocrit: How do the constituents of milk and blood influence their final deposition patterns?

A sessile droplet containing particulates leaves a ring-like formation when it is dried. Particle size, shape, and volume fraction can affect the final deposition pattern and the crack density by manipulating the contact line dynamics and the internal flow. When there is more than one type of particle suspended in a droplet, the combination results in more complex dynamics and patterns. Here we explore two different biofluids, blood and milk, that can be thought of as a mixture of particulates with different sizes, densities, and stiffness to study how the concentration of different particles affects the final drying pattern. Various types of milk ranging from skim milk to cream diluted in water are used, and the results are compared to blood with different hematocrit, focusing on the ring width and the crack pattern.