Multifunctional PDA@Fe nanoparticles enable a synergistic-adhesive and supportive lubricating film underwater

The mussel-inspired adhesion of polydopamine (PDA) provides a possibility for the formation of transferring lubrication films underwater. However, the inherent softness of PDA film limits its application in heavy-load lubrication situation. Therefore, a series of PDA@Fe core–shell nanoparticles were synthesized and their wettability and lubrication performance were evaluated. Compared to bare 304 stainless steel, the water contact angle of the PDA@Fe nanoparticle-coated surface is reduced from 86° to 48°. Tribological tests on steel–steel friction pairs show that, compared with deionized water, the PDA@Fe suspension reduces the friction coefficient and wear rate by up to 28.5 % and 56.6 %, respectively. Furthermore, EDS analysis reveals that PDA@Fe nanoparticles adhere to the worn surface and form a synergistic-adhesive and supportive lubricating film, in which Fe nanoparticles provide mechanical support and enhance PDA adhesion through ionic chelation. PDA, in turn, contributes hydration lubrication. This synergy results in highly efficient friction and wear reduction, suggesting that the multifunctional PDA@Fe nanoparticles offer an eco-friendly and durable solution for water-lubricated systems.