(230e) Low Frictional Mesoporous Titanium Dioxide Film by Geometrical Roughness-Induced Heterogeneous Nanostructure From Titanate

It is of great importance to construct a low frictional heterogeneous titanium dioxide (TiO₂) surface by physical strategy. Native dense TiO₂ layers prefer to forming on bulk titanium (Ti) substrates. However, the poor frictional TiO₂ on Ti surface is not favorable to fluid flow, resulting in harmful effects including but not limited to thrombus, nonspecific adsorption of proteins and cells, osteoarthritis. Thus surface modification with chemical functional groups was utilized to provide a heterogeneous stable and bacteria-resistant TiO₂ surface. But the inducing poor biocompatibility is of great concern and the functional groups are susceptible to oxidation, hydrolysis or thermal degradation.

An approach to low surface friction by constructing geometrical roughness-induced nano-patterned heterogeneous surfaces could confer adsorbates resistance and maintain the surface biocompatibility. Atomic force microscopy (AFM), with a nanoscale sensitivity, offers an unprecedented opportunity to explore the molecular-level factors that govern friction on various surfaces.

Herein, we reported a simple physical strategy based on titanate by constructing a roughness-induced nano-patterned heterogeneous mesoporous TiO₂ film to induce long-range hydrophobic interactions to further low friction. With AFM measurement, the friction coefficient (0.0026, measured in open system: air environment, at 25°C, relative humidity: ~50%) of mesoporous TiO₂ film is lower than 1/25 of dense one (0.067). Due to the existence of TiO₂(B) (59.7% in weight), mesoporous TiO₂ film keeps the structure thermal stability, further leading to the secondary nano-patterned pores (<15nm). By AFM adhesion analysis, the distribution of adhesion with Si₃N₄ tip on mesoporous TiO₂ surface shows heterogeneous property with a bimodal peak (3nN, 12nN) caused by the presence of the aforesaid secondary nano-patterned pores and TiO₂ particles. While the adhesion distributions on dense TiO₂ surface is single(12nN), showing homogeneous, attributing to TiO₂ particles. In AFM phase results, the secondary nano-patterned pores on mesoporous TiO₂ film induce long-range hydrophobic interactions, leading to a relatively hydrophobic boundary region around each hydrophobic pore patch. The boundary length extension can effectively increase the coverage of the hydrophobic phase (nano-patterned pores) to further reduce friction. The strategy to low mesoporous TiO₂ film friction by geometrical roughness-induced heterogeneous nanostructure from titanate benefits the fluid flow to further block the propensity of various adsorbates to avidly stay on the interfaces and it can maintain TiO₂ native biocompatibility.