Desiccation Patterns of Plasma Sessile Drops.

The renewed interest in plasma desiccation patterns focuses on the potential of these patterns to be developed into a platform of low-cost and facile diagnostic methods to interpret health conditions of donors. During desiccation, several physical mechanisms are simultaneously acting on the plasma sessile drop; these include material redistribution, buildup/release of local internal stresses, protein aggregation, and salt crystallization. After desiccation, cracking patterns and "superimposed" crystal-like patterns are formed. It has been reported that these characteristic patterns were influenced by changes in plasma compositions caused by diseases. Potential applications of these patterns in diagnosis are, however, limited by our understanding of formation mechanisms of cracking patterns and chemical compositions of crystal-like patterns. To address these limitations, this research studied morphologies of desiccated plasma patterns and the influence of sodium chloride to the pattern formation at both macroscopic and microscopic levels. Experimental results show that cracking patterns of plasma from healthy adults form throughout the desiccated deposit; propagation directions of cracks are found to have correlations to local dominant stresses, which are governed by the development of gelation. Crystal-like patterns are located in the drop center, which are caused by the heterogeneous distribution of macromolecular proteins and sodium chloride within the plasma sessile drop during desiccation; these patterns are influenced by the concentration of sodium chloride. With the increase of the concentration of sodium chloride, the distribution area of crystal-like patterns enlarges; whereas, the number of cracks decreases.