Nanostructure Based Wettability Modification of TiAl6V4 Alloy Surface for Anti-Biofilm—Superhydrophilic, Superhydrophobic and Slippery Surface

In the modern era, with the rapid development of nano-surface technology, basic scientific research on superhydrophilic surfaces with contact angles of less than 5° and superhydrophobic surfaces with contact angles of over 160° has begun to be applied to actual industries.<br/>On the other hand, unlike superhydrophobic/philic, studies on slippery surfaces are being studied in various fields recently. The slippery surface can be found in nature's pitcher plants. The slippery liquid-infused porous surfaces (SLIPS) surface proposed by Aizenberg group has a nano-porous surface structure and is water repellent, but the role of the structure is different from that of lotus leaves. The porous structure on the SLIPS surface serves to trap the slippery liquid such as lubricant, preventing other substances from sticking. Therefore, a lot of industrialization studies are being conducted on the slippery surface, such as self-healing and anti-biofilm.<br/>The anti-biofilm effect of this slippery surface can influence the recovery of the affected area in the human body, so it is a research topic of great interest in the medical community. Since studies in this field have not been conducted for a long time, many application studies using surfaces with various wetting properties have been investigated. However, ironically, such surface modification studies are rarely applied to TiAl6V4, the most representative metal inserted into the human body. TiAl6V4 material represents a metal for human insertion in the modern medical field with properties such as high strength, hardness, light weight, stable corrosion resistance, biocompatibility, and non-magnetic properties. Nevertheless, only a few superhydrophobic TiAl6V4 surface modification studies have been reported.<br/>In this study, we present various wettability modification methods including superhydrophilic/hydrophobic surfaces and SLIPS for TiAl6V4. In addition, the anti-biofilm performance of each fabricated surface was evaluated and compared. By modifying the TiAl6V4 surface to form micro/nanoscale roughness and changing the surface energy, a superhydrophilic surface and a superhydrophobic surface were presented, respectively. Furthermore, by lubricating the superhydrophobic surface, a SLIPS surface that mimics the surface of a pitcher plant was successfully fabricated. In this process, a parameter study was conducted to establish a uniform and highly complex micro/nano hierarchical structure fabrication method, using acid wet etching and hydrothermal oxidation. Since this method modifies the TiAl6V4 surface itself without attaching additional materials, there is no concern of delamination when inserted into the body as an implant. Each surface process was carefully analyzed physically and chemically.<br/>The TiAl6V4 surfaces we developed were subjected to evaluate the anti-biofouling effect for preventing surgical infection with bacteria. Tested bacteria include Pseudomonas aeruginosa and Staphylococcus aureus, which are reported in many clinical cases of periprosthetic infection. By using crystal violet staining of biofilm, we found that titanium plate obtains bio-film resistance upon bacteria when it has a micro-nano-structured hydrophobic surface or a nano-structured hydrophobic surface.