doi: 10.3850/978-981-11-0749-8_667
Influence of the Pulse Repetition Rate on the Hierarchical Features of Micro-Channels Fabricated by ns Lasers in Different Materials
R. Jagdheesh, A. Tur and J.L. Ocaña
Centro Láser UPM, Universidad Politécnica de Madrid, Ctra. de Valencia, km, 7.3, 28031, Madrid, Spain
Abstract
Laser micromachining/microstructuring is a promising technique to create micro-patterns on material surface with very low distortion to peripheral area and high precision. Thin sheets of stainless steel, aluminum and silicon were micromachined with ultraviolet laser pulses of around 30 ns full width half maximum (FWHM) in order to create micron scale features, namely micro-channels. Laser pulses with different pulse periodicities ranging from 5-40 µs time spacing with the same pulse energy, fluence and number of pulses per unit area were applied to study the impact of the pulse repetition rate on the achieved micro features. The micro-channels fabricated with different pulse periodicities on stainless steel (SS), aluminum (Al) and silicon (Si) with ns laser exhibited significant variations in terms of depth and cleanliness of the surface (i.e. considering the aggregation of molten material). Stainless steel and aluminum showed an enhancement of 30% in the depth of the generation micro-channels when comparing long time spacing to high pulse repetition rates, while Si has recorded an increase of 100%. The experimental results show that the pulse period/time interval between successive pulses is significant in determining the geometry and surface cleanliness of the laser machined micro channels, a fact that, however, has also revealed a technologically relevant way for the generation of surface micro/nanostructures with modified wettability.
Keywords: Laser, Micromachining, Surface Microstructuration, Hierarchical Structure, Hydrophobicity.
