Abstract
Ultra-short pulsed laser ablation enables a defined generation of micro-holes. A parameter study on the ablation characteristics of copper clearly reveals a benefit for green wavelength with lower threshold fluence, simultaneously increasing the Rayleigh length. The use of a circular drilling method allows a defined manufacturing of micro boreholes and micro through-holes with 35 μm diameter of up to 165 μm and 300 μm length. Introducing high-resolution micro-computed X-ray tomography studying the micro-hole evolution and adjacent geometrical transformations reveals micrometer resolution and high usability. The conical geometry evolving up to an aspect ratio of 5:1 fits well to established models known for percussion drilling. However, increasing the number of pulses leads to non-conical geometry evolution, and this resulting geometry is studied for the first time. Henceforth, the exact geometrical evolution from conical to cylindrical shape upon laser drilling can be resolved revealing the impact of multiple reflections at the generated steep flanks.
Highlights
In recent years, ultra-short pulsed laser (USP) machining is becoming a viable technology for industrial application [1]
1 inspire AG, Technoparkstrasse 1, Zurich, Switzerland 2 Department of Mechanical Engineering, IWF, ETH Zurich, Leonhardstrasse 21, Zurich, Switzerland focused spot being several tens of square micrometers allows texturing the surface in the micrometer range, and the interaction of linear-polarized light with the matter leads to hierarchical structures in the nanometer size known as laser-induced periodic surface structures (LIPSS)
It has been confirmed that micro-holes and micro-bores, drilled by an USP laser, can function as micro-reactors for CO2 reduction reactions in electrocatalysis. Due to their size and geometry, a proton gradient is formed after connection to an electrical source, in which carbon dioxide is converted into hydrocarbons [28]
Summary
Ultra-short pulsed laser (USP) machining is becoming a viable technology for industrial application [1]. Changing the focus in a continuous or stepwise manner directs the laser spot following a downward helical trajectory, called helical drilling With these processes, it is only possible to drill micro-holes, which are conical, whereby the taper angle is positive. An optimal flow of fuel or cooling air is the subject of many developments, whereby laser drilling offers new approaches This allows the bore geometry to be improved, production optimized, and damage to materials reduced [19, 20]. It has been confirmed that micro-holes and micro-bores, drilled by an USP laser, can function as micro-reactors for CO2 reduction reactions in electrocatalysis Due to their size and geometry, a proton gradient is formed after connection to an electrical source, in which carbon dioxide is converted into hydrocarbons [28]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
