Phase separation during the spreading of human blood pool

The study of the spreading and evaporation of blood films is of crucial importance for biomedical and forensic applications. For the second application, we are interested in film (pool) spreading because it represents one of the most important evidence at a crime scene after a bloody event. By their interpretation, the investigator can make an opinion about what took place and at what time.

We will present our published results on phase separation, i.e., when the serum spreads outside the main blood pool. This latter occurs during the spreading of blood pools on a horizontal substrate, which was explained by the competition between coagulation and evaporation. 

To investigate the phase separation, blood pools with constant initial volumes on wooden floors that were either varnished or not were created at ambient temperatures of 21 °C, 29 °C, and 37 °C with a relative humidity varying from 20 to 90%. The same whole blood from the same donor was used for all experiments, and the pools were created directly. As a result, an increase in relative humidity was found to result in an increase in the final pool area. In addition, at the three different experimental temperatures, the serum spread outside the main pool at relative humidity levels above 50%.