Drying of pendant drops of blood

The analysis of patterns in dried blood droplets has made it possible to generate strategies to detect health problems in patients and to address problems in forensic sciences. Therefore, studying various forms of droplet drying could enhance the efficiency of pathology diagnosis and the comprehension of crime scenes. In this paper, we report the study of the pattern formation generated by drying pendant blood droplets with different initial volumes (V = 3–24 μ L ). We find two distinct groups of deposits: dried drops with radial symmetry (Group I) and dried drops with lateral deposition of blood serum (Group II). Lateral deposition arises from drop collapse induced by hematocrit agglomeration at the drop apex. Our findings reveal that the collapse process consistently takes place at an angle 11 degrees below the initial contact angle, irrespective of the initial droplet volume. Finally, we provide evidence that the mass contained in a droplet promotes the occurrence of the unstable drying mode.