Generation, characterization and modelling of bio-inspired asymmetric topographic structures via ps-pulsed direct laser interference patterning on metallic surfaces

This study presents a comprehensive approach for generating bioinspired asymmetric surface structures on copper alloys and tin-coated substrates using picosecond-pulsed Direct Laser Interference Patterning (ps-DLIP). By introducing controlled tilt angles during processing, sawtooth-like morphologies were fabricated and quantitatively characterized through confocal laser scanning microscopy and focused ion beam cross-sections. Three key surface parameters, i.e., profile depth, skewness, and kurtosis, were evaluated to assess structural asymmetry and functional potential. Results indicate that structured tin-coated substrates exhibit predominantly negative skewness, suggesting favorable tribological characteristics, whereas structured copper alloys enable pronounced asymmetry for friction anisotropy. To elucidate the structure-formation mechanisms, finite element modelling based on the two-temperature model was carried out for tin under 12 ps pulses. Simulations confirm melting as the dominant interaction mechanism, with evaporation and redeposition effects becoming relevant after multiple pulses. Heat accumulation between pulses was found negligible for the used frequencies, allowing independent treatment of successive shots. These findings provide a foundation for predictive structuring strategies and serve as a stepping stone for future research directions, including multi-pulse simulations and modelling of intermetallic phases. • Sawtooth structures were created on Cu alloy and Sn by tilting samples during DLIP. • The Cu alloy enables friction anisotropy, required for electrical connectors. • The first TTM application for Sn under visible laser light is provided. • Melting was identified as the primary interaction mechanism. • Structural asymmetry is driven by angle-dependent local absorption.