Modification of Optical and Tribological Properties by Laser-Induced Periodic Surface Structures

Abstract
Femtosecond lasers are currently one of the best alternatives for fast large area nanotexturing due to their high intensity and extremely short interaction time, which allows for the creation of a wide variety of surface structures with excellent topography control and accuracy and negligible degradation of the bulk material. Moreover, this process is cost-effective, fast and simple, dismissing the need of vacuum technologies or the use of potentially harmful chemical compounds. Upon irradiation with femtosecond laser pulses with fluences near or slightly above the materials ablation threshold, parallel ripples known as Laser-Induced Periodic Surface Structures (LIPSS) form at the materials surface. These structures have a wide variety of potential applications since they affect surface properties such as wettability, light reflectivity and transmittance, osseointegration capability of implant materials, bacteria adhesion and biofilm formation, and the materials tribological behaviour. However, results found in literature regarding the influence of LIPSS on materials friction are often contradictory due to the complex nature of the interactions occurring, which makes the outcome difficult to predict. In this presentation, the influence of LIPSS on the friction behaviour of silicon in the Si/Sapphire and Si/PTFE tribosystems will be analysed by considering the interplay between the main contributions to the friction coefficient: adhesion, deformation and ploughing. In addition, some of the most prominent optical applicationsfor LIPSS and our current line of work will be covered.