Nanoscale Patterning of metallic surfaces with laser patterned tools using a nanoimprinting approach09.12.2022
Want do learn how to pattern a surface with micro- and sub-micro-scale features without changing the surface chemistry? Have a look at the joint publication of TU Wien, TU Darmstadt and Uni Saarland. They demonstrate that a laser pattern with both micro- and nano-scale features can be precisely transferred from a tool to a metal substrate during a room temperature nanoimprinting process. In this process, the typical chemical modifications of the laser process are avoided.
By the way, the interplay of topography and chemistry on wetting properties of laser-patterned was demonstrated in this article
In this study, the researchers demonstrate that metallic substrates with a nanocrystalline grain size can be structured down to the micro- and nanometer range during a room temperature nanoimprinting process. WC-Co hard metal dies are patterned by Direct Laser Interference Patterning (DLIP), generating an array of separated asperities with a height of 4.7 µm and a spacing of 11.3 µm. Additionally, Laser Induced Periodic Surface Structures (LIPSS) with a spacing of 500 nm are formed as a hierarchical substructure. The patterned dies can be used to deform metallic substrates due to their high hardness. For structure replication, the WC-Co tool is pressed onto a nanocrystalline CuZn30 model alloy at room temperature.
The pattern transfer process from the hard metallic tool to the nanocrystalline alloy is discussed in detail: At low contact pressures, the asperities on the tools act as single contact points, leading to the formation of separated dimples with a depth of up to 0.8 µm in the nanocrystalline alloy. At high contact pressures, the tool pattern, including the LIPSS is almost completely transferred to the substrate. The formed asperities protrude out of the surface, with a height to width aspect ratio of 0.4. It is thereby demonstrated, that plastic flow processes during the imprinting of nanocrystalline alloys allow for the replication of the DLIP tool pattern, even down to nano-scaled LIPSS. The imprinted array of surface asperities exhibits hydrophobic properties, due to a combined topographical and chemical influence on the wetting behaviour.
Paul Braun, Philipp Grützmacher, Leonie Frohnapfel, Frank Mücklich, Karsten Durst, Applied Surface Science, 2022, 155786, https://doi.org/10.1016/j.apsusc.2022.155786