In biomedical applications, the surface hydrophobicity of devices holds significant importance as it plays a pivotal role in reducing the risk of biofilm formation and infection. By preventing the adhesion of blood, cells, and tissues, it can have far-reaching implications. Zinc oxide, endowed with biocompatibility and antibacterial properties, and the ease with which it can be structured at the nanoscale, makes it an apt material for surface hydrophobicity modification in the biomedical domain. This study aimed to address two primary objectives:​ firstly, the cultivation of zinc oxide nanorods on a stainless steel substrate with a focus on surface hydrophobicity modification, and secondly, the exploration of alterations in hydrophobicity and mechanical properties through the manipulation of zinc oxide nanorod orientation.

A meticulous procedure was followed to create a highly uniform zinc oxide seed layer on the substrate using atomic layer deposition. Various deposition temperatures ranging from 50 to 250 °C were employed to yield diverse crystal structures. To enhance surface crystallinity, an annealing process was conducted at 400 °C for 1 hour. Subsequently, zinc oxide nanorods were grown on the seed layer utilizing chemical bath deposition. The characterization of the seed layer’s crystal structure was executed through X-ray diffraction, while transmission electron microscopy allowed the observation of nanorod crystals. The morphology of the seed layer and nanorods was assessed via scanning electron microscopy. The assessment of hydrophobicity and measurement of mechanical properties were accomplished through contact angle measurement and nanoindentation, respectively.

The nanofabrication technique employed in this study reliably resulted in the growth of zinc oxide nanorods characterized by the well-known hexagonal wurtzite structure. Remarkably, the hydrophobic surface modification of the substrate was successfully achieved through the application of zinc oxide nanorods. A critical revelation of this research is the profound relationship between the crystal structure orientation of the seed layer and the growth direction of the nanorods. This observation led to the significant insight that nanorod arrangement could be controlled by manipulating the crystal structure of the seed layer, leveraging atomic layer deposition technology. Furthermore, it was established that nanorods aligned in a vertical orientation contributed to a weakening of surface hydrophobicity, although they exhibited enhanced mechanical properties.

The technology for controlling nanorod arrangment, as presented in this study, is not limited to application to specific biomedical devices, but can be promisingly utilized in overall biomedical devices depending on the specific nanorod array required. It demonstrates relevance to biosensors that perform optimally when zinc oxide nanorods are vertically aligned, while stents, requiring robust biofilm inhibition, exhibit superior performance when nanorods are randomly arranged. Furthermore, it is important to acknowledge that the ability to control nanorod arrangement also holds significance in broader industrial domains such as semiconductors and solar cells. The mechanism for controlling nanorod alignment through atomic layer deposition technology thus makes a valuable contribution to the body of knowledge in nanotechnology research.