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EMIL - Research project

Numerical study of the wettability of hierarchical relief surfaces treated by femtosecond laser


Femtosecond lasers are extremely versatile and promising for surface texturing since various structures can be produced ranging from laser-induced periodic surface structures (LIPSS) to much larger “grooves” and spikes [1]. By varying laser parameters, such as laser pulse energy, temporal and spatial pulse shape, polarization, repetition rate and scanning rate, it is possible to create a wide range of surface reliefs, including complex reliefs, hierarchical structures, and biomimetic surfaces providing possibilities of an efficient control over not only optical properties, but, importantly, of surface wettability. As a result, modern applications of such textured include self-cleaning surfaces, antibacterial treatment, and the increase of the integration and durability of dental and orthopedic implants. It should be noted, however, that the wettability of laser-textured surfaces experience changes with time caused by surface chemistry such as oxidation and/or molecular adsorption, the processes that are not yet enough studied. Moreover, most of the existing wetting models are oversimplified and account neither for droplet dynamics nor for surface chemistry. Therefore, there is a need for realistic numerical investigations of the processes taking place during liquid droplet deposition on laser-textured surfaces involving much more detailed treatment of the liquid-surface and gas-surface interfaces.
In this project, we start by proposing a detailed continuum-level modelling to study the wetting dynamics of a water droplet on several textured Ti6Al-4V alloy surfaces. The performed preliminary calculations have been firstly performed for a flat surface and several simplified reliefs (simple triangular reliefs and the one with two periods and heights). The obtained calculated evolutions of the droplet spreading parameter not only have provided a good agreement, but also explanations of several experimental underlining the perspectives of using more complex reliefs for efficient wettability control.

[1] Bonse, J. Kruger, S. H ̈ohm, A. Rosenfeld, Femtosecond laser-induced periodic surface structures, Journal of Laser Applications 24 (2012) 042006.
[2] Omeje, Ilemona S., and Tatiana E. Itina. “Numerical Study of the Wetting Dynamics of Droplet on Laser Textured Surfaces: Beyond Classical Wenzel and Cassie-Baxter Model.” arXiv preprint arXiv: 2111.08499 (2021).
[3] B.W.H. Van Beest, G.J. Kramer, and R.A. van Santen, “Force fields for silicas and aluminophosphates based on ab initio calculations”, Phys. Rev. Lett. 64, 1955 (1990).
[4] C. Rajappa, S.B. Sringeri, Y. Subramanian, and J. Gopalakrishnan, “Universal scaling in the aging of the strong glass former SiO2”, J. of Chem Phys. 140, 244512 (2014).
[5] S. Tsuneyuki, M. Tsukada, H. Aoki, and Y. Matsui, “First-Principles Interatomic Potential of Silica Applied to Molecular Dynamics”, Phys. Rev. Lett. 61, 869 (1988).
[6] A. Carre, J. Horbach, S. Ispas and W. Kob, “New fitting scheme to obtain effective potential from Car-Parrinello molecular-dynamics simulations: Application to silica”, EPL 82, 17001 (2008).

  • Omeje, I. S. and Itina, T., “Numerical Investigation of Laser Textured Surface Wettability,” the 7th Venice International School on Lasers in Materials Science (SLIMS), San Servolo Island, Venice, Italy, July 3-9, 2022. Oral Presentation
  • Omeje, I. S. and Itina, T., “Multiscale Simulation of Laser-Textured Surface Wettability: Toward Understanding the Role of Surface Oxidation and Molecular Adsorption” Multiscale Materials Modeling (MMM10) in Baltimore, USA, 2nd - 7th, October, 2022. Oral Presentation
  • Omeje, I. S. and Itina, "Numerical Study of Early Oxidation Effect on Wettability of Laser-treated Surface" 9th Nanotech & Nanomaterials Research Conference, June 12-14, 2023, Rome, Italy. Poster presentation