Biomimetic surface structuring using cylindrical vector femtosecond laser beams

We report on a new, single-step and scalable method to fabricate highly ordered, multi-directional and complex surface structures that mimic the unique morphological features of certain species found in nature. Biomimetic surface structuring was realized by exploiting the unique and versatile angular profile and the electric field symmetry of cylindrical vector (CV) femtosecond (fs) laser beams. It is shown that, highly controllable, periodic structures exhibiting sizes at nano-, micro- and dual-scale micro and nano scales can be directly written on Ni upon line and large area scanning with radial and azimuthal polarization beams. Depending on the irradiation conditions, new complex multi-directional nanostructures, inspired by the Shark skin morphology, as well as superhydrophobic dual-scale structures mimicking the Lotus leaf water repellent properties can be attained. It is concluded that the versatility and features variations of structures formed upon scanning with CV beams is by far superior to those obtained via laser processing with linearly polarized beams. More important, by exploiting the capabilities offered by fs CV optical fields, the present technique can be further extended to fabricate even more complex and unconventional structures. We believe that our approach provides a new concept in laser processing of materials, which can be further exploited for expanding the breadth and novelty of potential applications.