Mechanically Robust,\nSuperlubricating and Antifouling\nBilayer Nanocoating for Micro-Bioimplants via a Dual-Function Metal\nCoordination Approach

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