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The Tuning of LIPSS Wettability during Laser Machining and through Post-Processing.
Michael J Wood1, Phillip Servio1, Anne-Marie Kietzig1
1Department of Chemical Engineering, McGill University, Montréal, QC H3A 0C5, Canada.
Nanomaterials (Basel, Switzerland)
|April 30, 2021
Summary
Post-processing treatments significantly alter the wettability of laser-induced periodic surface structures (LIPSS) on stainless steel. Controlling nanoparticle removal and atmospheric exposure is key to achieving desired hydrophilic or hydrophobic properties for robust surface engineering.
Area of Science:
- Materials Science
- Surface Engineering
- Nanotechnology
Background:
- Laser-induced periodic surface structures (LIPSS) offer tunable surface properties.
- Controlling wettability is crucial for various applications, including anti-fouling and self-cleaning surfaces.
- Stainless steel is a versatile material requiring surface modification for specific functionalities.
Purpose of the Study:
- To investigate the impact of post-processing treatments on the wettability of LIPSS-decorated stainless steel.
- To understand the role of atmospheric exposure and nanoparticle removal in determining surface hydrophilicity/hydrophobicity.
- To compare the reactivity of LIPSS surfaces with hierarchically rough surfaces.
Main Methods:
- Fabrication of LIPSS on stainless steel using laser micromachining.
- Post-processing treatments including exposure to CO2-rich atmosphere and boiling water baths.
- Removal or retention of non-sintered nanoparticles and agglomerates.
- Wettability measurements using water contact angle goniometry.
- Assessment of surface robustness and chemical reaction rates.
Main Results:
- Post-irradiation CO2 exposure enhances hydrophobicity, while boiling water treatment leads to hydrophilicity.
- Failure to remove nanoparticles results in a temporarily hydrophobic surface with a Cassie air-trapping layer (180° contact angle).
- Removal of nanoparticles reveals the underlying LIPSS, yielding a less hydrophobic surface (approx. 80° contact angle).
- LIPSS surfaces exhibit slower chemical reactions compared to hierarchically rough surfaces.
- Surface wettability degrades over time with repeated water contact, especially for treated surfaces.
Conclusions:
- Post-processing significantly influences the wettability and stability of LIPSS on stainless steel.
- Effective nanoparticle management is critical for achieving stable and predictable surface wettability.
- Hierarchical roughness enhances chemical reactivity compared to LIPSS alone.
- The long-term stability of engineered wettability requires careful consideration of environmental interactions and surface robustness.
