## 1 Introduction  
In recent decades, the study of super-hydrophobicity has become essential in many industrial sectors. From a fundamental point of view, the description of the phenomena of wettability is essentially based on the understanding of the nature of interactions that develop between the liquid and the wet surface. The chemical physics parameters of a surface play an essential role in the wettability properties. By controlling the chemical nature of the surface, we can obtain hydrophobic surfaces. Moreover, using factors which increase the actual contact surface, such as roughness or structure of surfaces can improve it and make it a superhydrophobic surface, which is often sought in the high-technology sectors where self-cleaning surfaces are required [1, 2].  
To illustrate this, take as example the lotus leaf, which has a natural superhydrophobic surface. Indeed, the surface of the lotus leaf is covered by micro and nano-structures and wax which make it superhydrophobic [3, 4, 5, 6, 7]. One of the techniques used for reproducing these structures is based on photolithography. However, lithography is expensive and unsuitable to non-planar system models. So how else can we prepare a super- hydrophobic surface?  
Cross-linked poly-dimethylsiloxane (PDMS) has an attractive combination of materials that has flexibility and hydrophobic surface properties [8]. Various approaches have been used to modify the surfaces of PDMS, including: chemical methods [9; 10; 11] and physical methods, such as ultraviolet ozone [12], and oxygen plasma [8; 13]. In this paper, we used molding in order to reach the required roughness. Then, we measured the contact angle to determine the degree of hydrophobicity of the hydrophobic film of PDMS. The surface texture of the mold is obtained by a combination of UV/Ozone irradiation and suitable elastic deformation; this process mimics the natural apparition of wrinkles on the human skin.  
Human skin is essentially composed of two primary layers: the epidermis, which provides waterproofing and serves as a barrier to infection; and the dermis, which cushions the body from stress and strain. The dermis, whose thickness is about a millimeter, consists of a set of proteins, like collagen fibers, which provide flexibility and elasticity to the skin (Young modulus E is around 0.2-3 MPa). The epidermis is essentially composed of keratinocytes and is much thinner than the dermis with a larger elastic modulus due to its lamellar composition [14]. This difference in elastic modulus, together with aging or compression, yields to wrinkles.  
Superhydrophobic surfaces created by elastic instability can contribute to the recent advances in microfluidics which allowed the development of rheometers on a chip [15; 16; 17], where microfluidics is a competitive platform for performing rheometry. Therefore, the control of wall adherence and degree of slipping become central topics for this sort of applications application of microfluidics [18; 19; 20]. In this sense, the application of superhydrophobic surfaces can potentially help to investigate and analyze the influence of patterned surfaces in microrheometry.  
Other potential applications of superhydrophobic surfaces is that they improve coalescence-induced micro-droplet jumping [21], and they can avoid the intensive usage of biocides in antibacterial materials by reducing the bacterial adhesion [22].