Nanomechanical characterization and modeling of anodized porous aluminum oxide thin films with photografted anti-biofouling polymer brushes on their pore walls

Nanocomposites are known for their unique properties with many potential applications. In the present work, porous anodic aluminum oxide (AAO) thin films were processed on glass substrates and subsequently photo-grafted with a zwitterionic anti-biofouling polymer. This allows to fabricate scratch-resistant, transparent anti-biofouling films. The microstructure and how it is affected by nanomechanical testing are investigated by scanning electron microscopy and atomic force microscopy. It is shown that the polymer forms a thin layer on the pore walls and in deionized water, the pore diameter changes due to swelling of the polymer. The nanomechanical and scratch resistance properties are studied using a nanoindenter testing system. The experimental results are validated via numerical calculations. The values of the elastic modulus and hardness are shown to be in good agreement with the numerical ones, and under dry conditions, higher values were obtained in comparison to wet films. There is also a large agreement between modeling and microscopic deformation behavior of the films. Finally, the critical loads in dry and wet conditions for the non-coated AAO samples are approximately the same, while for the coated samples, the critical load is reached rapidly in wet condition in comparison to the dry one.