Polarity-Dependent Nonclassical Blood Wetting Behavior

At the surfaces of blood-contacting implantable medical devices, blood wetting behavior initiates the interfacial process that influences hemocompatible performance. Understanding this process beyond simple-liquid wetting is therefore critical for connecting surface properties to biological interfacial responses and for guiding the rational design of hemocompatible materials. However, conventional wetting theories often do not clearly distinguish the wetting mechanisms of multicomponent biological fluids such as blood. Here, we report a systematic investigation into the wetting behavior of whole blood and its underlying interfacial mechanisms on a range of solid substrates with different surface free energy components. This investigation revealed that blood wettability is governed primarily by the polar component of solid surface free energy. Remarkably, the blood contact angle decreases with increasing surface polarity up to a critical threshold, above which it anomalously increases before declining again. Comparative analyses of plasma and simulated body fluid further suggest that the observed wetting behavior is consistent with protein adsorption and protein-mediated interfacial restructuring. These findings provide a new physical perspective for the rational design of hemocompatible materials and deepen the fundamental understanding of wetting behavior and mechanisms in complex fluids.