The influence of coagulation on the drying dynamics of blood pools.

Little is currently known about the importance of clotting during the drying of blood pools. While this is of little moment for droplets where drying occurs faster than contact-phase-induced clotting, clotting may significantly influence blood pools drying as it transform a liquid into a gel. To investigate this influence, we compare the drying of citrated and unmodified blood pools at constant haematocrit, showing large morphological differences during drying, both in the surface appearance, in the colour lightness, as well as in the generation and location of cracks. Further, we designed a clotting-reactivation protocol which allowed recovering the morphological evolution of pure blood drying while using citrate-sampled blood. This result opens the way to the use of citrated blood in blood pools investigations.

Drying colloidal systems: Laboratory models for a wide range of applications.

The drying of complex fluids provides a powerful insight into phenomena that take place on time and length scales not normally accessible. An important feature of complex fluids, colloidal dispersions and polymer solutions is their high sensitivity to weak external actions. Thus, the drying of complex fluids involves a large number of physical and chemical processes. The scope of this review is the capacity to tune such systems to reproduce and explore specific properties in a physics laboratory. A wide variety of systems are presented, ranging from functional coatings, food science, cosmetology, medical diagnostics and forensics to geophysics and art.

Morphology of drying blood pools.

Often blood pools are found on crime scenes which may provide information concerning the events that took place on the scene. However, there is a lack of knowledge concerning the drying dynamics of blood pools. This study focuses on the drying process of blood pools to determine what relevant information can be obtained for the forensic application. We recorded the drying process of blood pools with a camera while measuring the mass. We found that the drying process can be separated into five different stages: coagulation, gelation, rim desiccation, centre desiccation, and final desiccation. Moreover, by normalizing the mass and drying time we show that the mass of the blood pools diminish similarly and in a reproducible way for blood pools created under various conditions. In addition, we verify that the size of the blood pools is directly related to its volume and the wettability of the surface. Our study clearly shows that blood pools dry in a reproducible fashion. This preliminary work highlights the difficult task that represents blood pool analysis in forensic investigations, and how internal and external parameters influence its dynamics. We conclude that understanding the drying process dynamics would be advancement in time line reconstitution of events.