## 1 Introduction  
Generating periodical sub-wavelength structures on material surfaces by interaction with pulsed laser beams has been known for some time [1; 2; 3; 4]. The structures in the form of parallel ripples--laser-induced periodic surface structures (LIPSS)--have been reported on various materials, including dielectric materials, metals, semiconductors, and graphene [5; 6; 7]. Being in the nanometer scale, and with the occurrence due to the laser-surface interaction, they are a frequent subject of investigation in nano-optics (nanophotonics).  
The causes of LIPSS generation and shaping are seen most probably in the emergence of the surface plasmon polariton (SPP), as well as in the hydrodynamic features [8; 9; 10]. If compared to single layer metal films, more regular LIPSS are generated with low-fluence femtosecond (fs) laser beam interaction with multilayer thin metal films, since the existence of the metal sublayer influences the quality and stability of LIPSS [11].  
Changing the wetting and tribological properties of the material by LIPSS formation opens new fields of application in nano/microfluidics, optofluidics, fluid microreactors, biomedicine, biochemical sensors, and thermal management [12; 13]. The control of wetting properties and achieving super-hydrophobic surfaces by laser interaction have been reported for various materials: stainless steel, TiAl alloy, Si and materials coated with hydrophobic materials, such as chloroalkylsilane and fluoroalkylsilane [14; 15; 16]. In all mentioned cases super-hydrophobicity is achieved by the chemical modification of the surface or micro-structuring.  
Laser interaction can induce the change in chemical composition of the surface, forming ultra-thin oxide layers, which contribute to the wetting. Wetting is initially enhanced, but as time passes, it is ultimately reversed by surface chemistry phenomena that take place on the irradiated surfaces--i.e., hydrophobicity is increased [17; 16].  
Van der Waals and electrostatic forces play an important role in adsorption, adhesion and wetting phenomena [18]. The Casimir force shows application potential in the field of micro- and nano-electromechanical systems--engineered devices, where controlling forces between microscopic bodies or surfaces are crucial for a variety of applications [19; 20]. The influence of submicron surface corrugations on Lifshitz-van der Waals forces have been calculated for polyethylene, where surface nano-patterning is responsible for changing the forces from attractive to repulsive [21; 22]. For metal surface nano-structuring at scales below the plasma wavelength, the Casimir interaction decreases faster than usual for large inter-surface separation, while at short separations an equivalent pressure is larger [23]. The motivation of our study is to experimentally reveal the link between wetting and nano-corrugation [21; 22] and to extend the potential application of nanostructures. Surface nanostructures affect the optical characteristics via refractive index on the one hand, while on the other, they influence the wetting characteristics. Patterning the surface of the lamellar material changes the characteristics of the interface, as well as the characteristic of the bulk to some extent. The nanometer level of the patterns increases the importance of their control and places it in the field of nano-optics/nano-photonics.  
The morphology of surface micro/nanostructures obtained by fs laser is evaluated with the aim of determining the influence of morphology on their wetting. By interaction with fs laser beam, we generated LIPSS on the surfaces of several metallic multilayer materials. We estimated the contact angle (CA) difference for different materials and also for materials before and after LIPSS forming, thus examining the change in hydrophobicity.