Modelling and Validation of Microstructure Replication on Aluminum Foils from Laser-Patterned Stamps

Aluminum foils are commonly used in food and pharmaceutical packaging due to their outstanding combination of malleability, low cost, oxygen barrier and light reflectivity. Extra functionalities, like hydrophobicity or structural coloration, can be added to them by engineering topographical surfaces microstructures. In this work, cold embossing method is used to replicate microstructures from pre-structured stamps onto aluminum foils. The Direct Laser Interference Patterning (DLIP) method is used to structure periodic line-like textures on stainless steel plates. The produced stamps are employed to imprint the Al foils under different controlled pressures. A good transfer of the microtextures to the Al based material was observed, with a 6-40% relative difference in the structure depths between master and replica depending on pressure and aspect ratio of the structures on the steel mold. Although a complete replication of the stamp textures is not obtained due to incomplete stamp cavities filling and elastic recovery, the achieved structural coloring demonstrates a uniform microtexture on the foils. A model based on the finite element method is developed and validated by comparing the simulation results with the microstructured aluminum foils, yielding relative differences in the simulated and experimental structures depths below 20%