Interfacial Assembly Reprograms Defect-Mediated Bending Mechanics in Rigid Biogenic Nanofibrils

silk fibroin on the nanofibril surface progressively suppresses kink expression, smooths contour curvature, and shifts the bending mode from kink-dominated segmented reorientation toward distributed bending. Selective removal of the assembled interfacial layer partially restores the original high-curvature features and defect-mediated bending state, demonstrating that the effect is largely reversible and arises from contour statistical redistribution rather than permanent modification of the rigid backbone. Our results establish interfacial assembly as a route to reprogram defect expression in rigid biogenic nanofibrils and thereby tune single-fibril bending mechanics. This framework may provide broader insight into interface-controlled mechanics in other high-aspect ratio biogenic fibrillar systems.