A Multiscale Mechanistic Framework for Polydopamine Dyeing in Ultrablack Wool Textiles

Polydopamine (PDA)-dyed wool textiles offer a potentially scalable route to ultrablack materials that combine wide-angle reflectance suppression, flexibility, breathability, and biocompatibility. Their development, however, has remained largely empirical, lacking structural and mechanistic foundations for PDA dyeing, and prior ultrablack wool systems have been restricted to merino-based single-jersey fabrics. Here, we establish a multimodal structural and mechanistic framework for PDA dyeing by integrating dopamine polymerization chemistry, fiber surface chemistry and ultrastructure, as well as macroscopic fabric architecture. These factors collectively govern dye uptake and optical response. Dye formulation optimization reduces the dyeing time to 15-30 min across merino and generic wool fibers spanning diverse fabric architectures. Notably, fabric architecture emerges as a dominant design variable for controlling wide-angle optical response, a previously underappreciated lever for engineering photonic textiles. Mechanistic analysis of dopamine polymerization reveals PDA formation in wool as an absorption-driven dyeing process rather than a purely surface-coating process, whose uptake and interactions within the porous fibrous matrix contribute to near-zero reflectance when plasma-treated. Together, these findings provide a material design blueprint for scalable ultrablack wool textiles and offer broader principles for flexible photonic devices.