Biomimetic surface structuring using cylindrical vector femtosecond laser beams

Abstract

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- micro/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’s 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 is by far superior to those obtained via laser processing with linearly polarized beams. More important, by exploiting the capabilities offered by fs CV 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 materials processing, which can be further exploited for expanding the breadth and novelty of applications.

Ripple formation on silver after irradiation with radially polarised ultrashort-pulsed lasers

“…only related with the pronounced enhanced ripple periodicity or depth due to the dissimilar spatial profile of the deposited energy but also with a different orientation of the produced profile. More specifically, the ripple formation induced by RP (see Fig.10 for NP=2) are concentric periodic structures that have also been observed experimentally in previous works 17,33,35,40,41 . Indeed, a simulated two-dimensional pattern that is illustrated in Fig.10a shows the surface profile while the height distribution is shown in Fig.10b.…”

“…It was shown that the spatial form of the RP does not only lead to structures of different periodicity compared to those induced if LP beams are used ( Fig.9) but also produce structures of (spatially) variable height ( Fig.7-8) and spatial distribution (Fig.10b). This is a significant prediction (which was verified experimentally for Ni in a previous work 33,35 or semiconductors 40,41 ) as it demonstrates the capability of controlling characteristics of morphological features with the use of different polarization states. It should be mentioned, though, that a systematic experimental validation of the numerical results is required to confirm the accuracy of the proposed model for irradiation of noble metals with small electron-phonon coupling constant.…”

“…Hence, the rippled profile is repeated for NP>2. Regarding the significance of the periodic structures produced by RP beams, it has been shown that dynamic surface processing with this polarisation gives rise to formation of biomimetic structures 33 . This is achieved by exploiting the unique and versatile angular profile of femtosecond RP beams.…”

Formation of periodic surface structures on dielectrics after irradiation with laser beams of spatially variant polarisation: a comparative study

“…More specifically, laser beams with cylindrical states, namely radial and azimuthal polarization, have gained considerable attention in the past two decades, as the symmetry of the polarization enables new processing strategies [17] with applications in various fields including microscopy, lithography [18], electron acceleration [19], material processing [17,20,21] and optical trapping [22]. The so-called cylindrical vector beams (CVB) have been the topic of numerous theoretical and experimental investigations [20,[23][24][25][26][27][28][29]. A recent work on nickel irradiation with femtosecond pulses revealed morphological changes for LPB and CVB for various fluences and number of pulses [30].…”

Generation of micro- and nano-morphologies on a stainless steel surface irradiated with 257 nm femtosecond laser pulses

“…Femtosecond lasers made it possible to structure the surface of various materials such as metals, 1 ceramics, 2,3 dielectrics 4,5 and semiconductors. 6 These modications are attributed to be linked to both laser induced structures and chemical surface composition changes during the irradiation. Laser induced structures, such as periodical formations like grooves and spikes, are reported to induce remarkable modications of surface wetting, 7-10 tribological, 11 and optical properties.…”