Ultrafast Laser Processing
Dr. Emmanuel Stratakis
Bioinspired Surface Processing
The Ultrafast Laser Micro- and Nano- processing (ULMNP) laboratory, Savvas Georgiou, of IESL research is focused on the development of novel ultrafast pulsed laser processing schemes for controlled structuring at micro- and nano- scales of a variety of solid materials. By applying ultrashort UV, VIS and IR laser pulses novel surface structures with sub-micron sized features are produced while the physical properties of semiconductor, dielectric and metallic surfaces are significantly modified. Developed methods include laser micro/nano surface structuring performed in different media, direct laser writing with variable laser polarization states and combination of those. Further control over the surface topology is achieved by proper functionalization of the 3D structures obtained with well-defined nanostructures.
The artificial surfaces developed by processing under ambient or controlled gaseous environments exhibit controlled dual-scale roughness, that mimics the complexity of hierarchical morphology of natural surfaces with exciting properties (i.e. the Lotus leaf, the shark skin, the butterfly wings), comprising micro-conical structures decorated with nanometre sized protrusions. The biomimetic morphology attained gives rise to notable multifunctional properties when combined with methods of tailoring the surface chemistry.
Research results indicate that appropriate combination of topography and chemistry can lead to artificial surfaces that are: (a) of extremely low surface energy, thus water repellent and self-cleaned, (b) smart, i.e show the ability to change their surface properties in response to different external stimuli, (c) colorized i.e light diffraction under certain irradiation conditions, (d) reducing friction on lubricant conditions and (e) functional in the sense that exhibit remarkable physical properties compared to the bulk. Additionally laser-produced biomimetic surfaces realize the ability to tailor the morphology non-chemically which is an important advantage for the use of such structures as models to study the dependence of growth, division and differentiation of cells on the surface energy of the culture substrate and as scaffolds for tissue regeneration.
Figure 1: Biomimetic surface functionalization of metallic, dielectric and semiconductor solid surfaces.
 E. Skoulas, A. Manousaki, C. Fotakis, and E. Stratakis, “Biomimetic surface structuring using cylindrical vector femtosecond laser beams,” Sci. Rep., vol. 7, no. November 2016, p. 45114, 2017.
 G. D. Tsibidis, E. Skoulas, and E. Stratakis, “Ripple formation on nickel irradiated with radially polarized femtosecond beams,” Opt. Lett., vol. 40, no. 22, p. 5172, 2015.
 V. Zorba et al., “Biomimetic artificial surfaces quantitatively reproduce the water repellency of a lotus leaf,” Adv. Mater., vol. 20, no. 21, pp. 4049–4054, Nov. 2008.
 E. I. Stratakis and V. Zorba, Biomimetic Artificial Nanostructured Surfaces, vol. 7. 2012.
 A. Papadopoulos, E. Skoulas, G. D. Tsibidis, and E. Stratakis, “Formation of periodic surface structures on dielectrics after irradiation with laser beams of spatially variant polarisation: a comparative study,” Appl. Phys. A Mater. Sci. Process., vol. 124, no. 2, p. 146, 2018.
 G. D. Tsibidis, C. Fotakis, and E. Stratakis, “From ripples to spikes: A hydrodynamical mechanism to interpret femtosecond laser-induced self-assembled structures,” Phys. Rev. B – Condens. Matter Mater. Phys., vol. 92, no. 4, pp. 1–6, 2015.
 G. D. Tsibidis, M. Barberoglou, P. A. Loukakos, E. Stratakis, and C. Fotakis, “Dynamics of ripple formation on silicon surfaces by ultrashort laser pulses in subablation conditions,” Phys. Rev. B – Condens. Matter Mater. Phys., vol. 86, no. 11, p. 115316, 2012.
 G. D. Tsibidis, E. Skoulas, A. Papadopoulos, and E. Stratakis, “Convection roll-driven generation of supra-wavelength periodic surface structures on dielectrics upon irradiation with femtosecond pulsed lasers,” Phys. Rev. B, vol. 94, no. 8, 2016.
Mr. Evangelos Skoulas
Mr. Alexandros Mimidis
Mr. Andreas Lemonis
Mrs. Christina Lanara
Mr. Nikolaos Livakas