Laser-Induced Changes in Surface Wettability: From Modeling to Applications

I.S. Omeje, T.E. Itina
One of the important advantages of femtosecond lasers resides in a possibility to form a set of hierarchical micro and nanostructures on solid surfaces thus allowing an efficient control over various surface properties. Among these properties, wettability is particularly affected and plays a crucial role in the development of numerous application not only in automobile or textile industry, but also in the biomedical field. Recently, several studies have already evidenced a pronounced effect of
more » ... ettability, among other factors, on the behavior of cells, bacteria and even of viruses on laser-textured surfaces. In particular, changing surface relief and controlling wetting properties have a potential to better guide cell repulsion or attraction to the surfaces. For instance, these processes are known to play a role in both osseointegration and mechanotransduction, which are known to be key process in dental and orthopedic implant integration, as well as in a bioengineering in general. Despite a large number of promising experimental results, it is still unclear how to predict and explain the wettability of laser textured surfaces. The classical models, such as the Wenzel and Cassie-Baxter, contain adjustable parameters and provide only rough explanations. The development of more realistic models remain challenging because of the lack of understanding of the effects of both surface and liquid properties on the behavior of a liquid droplet on the surface. In particular, the difficulty arises from the change in surface wettability with time after laser treatment, but also due to annealing, sterilization, ultra-sound or cold plasma treatment. The reasons for these changes are not yet well understood. To better understand this process, we use a continuum-level modeling [1] to study the wetting dynamics of liquid droplet on plane and laser-textured Ti, Ti alloys, as well as on several other surfaces. The role of various surface reliefs and chemical composition are examined. The calculated evolutions of the contact angle with time for both structured and non-structured surfaces provide explanations of a set of experiments. In particular, the performed simulations confirm the role of surface energy, indicate how capillary forces change as a function of surface relief and composition, allow us to examine the role of liquid viscosity, of droplet shape, etc. Our results clearly demonstrate that such simulations are helpful and suitable for the better understanding of the process involved in the wettability changes of lasertextured materials [1] S.F Kisler, Hydrodynamics of wetting" JC Berg (Ed.) Wettability, New York, 1993. 47
doi:10.24412/cl-35039-2021-21-47-47 fatcat:hdfk6fel7nbq3f2wuyrdem434e