ICALEO – Laser Microprocessing Conference

October 16-20, 2016 – San Diego (USA)

During ICALEO, the International Congress on Applications of Lasers & Electro-Optics, Camille HAIRAYE, doctoral student at IREPA LASER, will present her work regarding laser texturing  using a high power femtosecond fiber laser to create superhydrophobic surfaces.

About the event:

• Date: October 16-20, 2016
• Topics: material processing by laser, laser micro machining, nanofabrication
• Location: Sheraton San Diego / San Diego CA (USA)
• Attendees: academic researchers and industrials interested by laser technology

More information: www.lia.org/conferences/icaleo

Laser Microprocessing Conference – October,19

Microprocessing for Biological Applications Session

Abstract :

« Controlling the wettability of stainless steel by surface texturing using a high power femtosecond fiber laser »

The modification of metallic and non-metallic surfaces properties through laser texturing has been the subject of intense research during the last decade. Under laser irradiation, surface roughness is modified. The increase of roughness is accompanied by a change in the wettability of the surface with no additional coating. The role of different scales of roughness has been largely discussed in the literature. According to Wenzel relation, a surface having hydrophilic property will become more hydrophilic and a hydrophobic surface will exhibit an increase of its original property. However in practice, the situation is somewhat more complicated because wettability is the result of several parameters like surface tension and the exact chemical composition of the surface. The presence of oxygen and carbon atoms plays an essential role and is responsible for the evolution of the surface wettability during a period of about 20 days. The motivation for these studies stems from the interest of having self-cleaning surfaces, antibacterial surfaces for biomedical applications, or anti-icing or anti-corrosive surfaces for aeronautics.

In our study a high mean power diode-pumped Ytterbium fiber laser, integrated in micro-machining platform, has been used to texture stainless steel samples. It produces laser pulses of hundreds of femtoseconds in the near-infrared, with a repetition rate up to 2 MHz and a maximal energy of 150 µJ. Several authors have reported that superhydrophobic effect is obtained by the generation of self-organized micrometric structures. Nevertheless it is possible to improve the process rate by producing structures with designed geometries: the microstructures are thus generated by successive ablations of the material. With appropriate process parameters, it is easy to produce a superimposed self-organized nanostructures, which confers to the surface a dual-scale roughness, responsible for high hydrophobicity, with a contact angle as high as 160°.

By modeling the wetting behavior of a droplet on a microstructured surface by finite elements method, we illustrate the trend for the microstructure to enhance the initial wetting property of the surface. The evolution in time of the surface property after laser irradiation, related to surface chemistry, cannot be avoided but can be accelerated under certain conditions.

The production of a superhydrophobic behavior on non-flat surfaces at a reasonable rate, in conditions compatible with a production environment, remains a challenging issue. We will present a few hints toward such a goal.