Enhanced Frictional Anisotropy and Wear Resistance via Bioinspired Hybrid Graphene Oxide - Titania Nanopatterned Surfaces

In this study, the development of a snake-skin-inspired hybrid surface has been demonstrated using tilted titania nanorods fabricated by the glancing angle deposition (GLAD) technique and subsequently coated with graphene oxide (GO) sheets. The nanotribological properties of both the hybrid and uncoated surfaces have been characterized using lateral force microscopy (LFM). Direction-dependent friction anisotropy is observed in both cases. The friction force along and opposite to the tilt direction of the nanorods is higher than the friction measured after rotating the surface by 90 °. The friction anisotropy is more pronounced on the hybrid surface. The surface also exhibits significantly enhanced wear resistance compared to the uncoated textured surface due to the stress-shielding effect of the GO layer. Interestingly, the lateral force maps reveal a significant interaction between the scanning tip and individual nanorods, even when they are buried beneath the GO layer. Furthermore, the Peak Force Quantitative Nano mechanics (PFQNM) is performed to quantify nanomechanical properties, which contribute to understanding the nanoscale tribological properties of the textured surface. The experimental findings are interpreted with the Hertzian contact theory applied to a thin film on a compliant foundation. Altogether, the realization of the wear-resistant hybrid surface, its direction-dependent frictional response, and the quantitative interpretation of the results presented here define a robust methodology for controlling friction for engineering applications.