Mechanically Robust, Superlubricating and Antifouling Bilayer Nanocoating for Micro-Bioimplants via a Dual-Function Metal Coordination Approach

Nanometer-thick ultrathin coatings with superior mechanical strength and desirable lubricating and antifouling performance are critical for the miniaturization of implantable medical devices. However, integrating these properties at the nanoscale remains challenging due to the inherent trade-off between mechanical strength and hydration as well as limitations in coating thickness. In this work, we address these challenges by employing dual-function metal coordination to construct a ∼25 nm thick bilayer structure. Contact mechanics and interfacial molecular force measurements confirm the dual role of vanadium (V^III) ions in forming this bilayer: V^III ions bridge the ligand sites to reinforce the protein bottom layer, and simultaneously anchor the end blocks of the designed ABA triblock hydrophilic polymers to form a hydrated, looping top layer. This V^III-enabled structure demonstrates remarkable load-bearing capacity and lubricating performance (i.e., friction coefficient μ on the order of 10^-3 over 100 cycles under ∼10 MPa), while it also exhibits excellent resistance to biofouling in complex biological fluids. This work presents a useful strategy for integrating seemingly incompatible properties into ultrathin coatings, offering the potential for customizing multifunctional surfaces for micro-devices/machines toward bioengineering applications.