Segregation in the Desiccated Sessile Drops of the Biological Fluids∗

The priority in the investigation of the dehydration self-organization phenomenon in biological fluids belongs to Prof. E. G. Rapis. While seeming simple, the effect turned out to be extremely complicated and to involve a number of interrelated processes of different nature. The biological fluids are complex colloidal systems. Even the slightest variation in the composition of a liquid leads to total changes in the dynamics of phase transitions during drop drying. Despite the application of the effect to practical medical diagnostics, and the drastic improvement of our understanding of pattern formation, complex non-linear dynamics of pattern formation in drops of biological fluids is mostly unclear. Nevertheless, the performed analysis allows to draw the conclusion that the main effects observed in the dehydration of biological fluids are typical for colloidal solutions in general and can be described in the framework of conventional approaches. The dried droplet of the biological fluid is structurally complex. In particularly, there are protein ring at the periphery and dendritic crystalls in the central area of the sample (Fig. 1). The visual appearance of a sample is used for diagnosing a wide range of diseases. Rather clear relationships of the ’pattern — pathological processes’ type have been revealed.