Revealing the Interaction Between the Structural Characteristics of Anodized Nanopores and Their Surface Wettability and Lubricity

Abstract Lithography-based techniques for cross-scale nanopore array fabrication are expensive, and the design of nanoporous structures relative to wettability or lubricity is intricate. This study presents a low-cost strategy integrating the anodization and pore-widening processes to successfully fabricate anodic aluminum oxide (AAO) nanoporous structures with pore diameters ranging from 40 to 330 nm and interpore distances ranging from 60 to 335 nm. This study reveals the synergistic regulation mechanism of pore characteristics on surface wettability and lubricity. Results showed that both pore diameter and interpore distance increase with applied voltage, and a minimum pore diameter of 40 nm achieves a low voltage (i.e., 40 V) and short anodization time. The pore-widening process significantly enhances pore uniformity. The AAO surface exhibits excellent lubricating properties with a minimum coefficient of friction of 0.05 after pore widening. In addition, the wettability of AAO can be precisely controlled by adjusting pore diameter and porosity. A small pore diameter of 40 nm exhibits hydrophobicity (contact angle of approximately 100°). The pore-widening process helps enhance the hydrophobicity of the AAO surface, where an appropriate pore diameter of 100 nm exhibits near superhydrophobicity (contact angle of approximately 141°). However, a large pore diameter of 330 nm exhibits superhydrophilicity (contact angle of approximately 4°). This study provides valuable insights into understanding the interaction between the structural characteristics and the surface properties of AAO, contributing to the development of high-performance nanopore array templates.