Hierarchical Micro/Nanoscale Surface Texturing

Hierarchical micro/nanoscale surface texturing is the fabrication principle shared by the paper and the patents in this dossier: creating two scales of roughness — micro-scale features plus nano-scale features — on a metal surface. In this source the texture is produced by etching the interior of aluminum tubes, creating "micro- and nano-pits."

Feature scales reported in the dossier

The dossier supplies specific feature-scale numbers from the patents:

• US2019319152A1 / US2015136226A1 describe a metal or metal alloy with "hierarchical micro-scale and nano-scale structure shapes" that is super-hydrophobic and has a spectral reflectance of less than 30% for at least some wavelengths in the 0.1 μm to 10 μm range.
• US10876193B2 describes indentations with a micro-rough surface of features on the order of 0.5 to 100 microns and a nano-rough surface of features on the order of 1 to 500 nanometers, applicable to metals, glass, enamel, polymers, and semiconductors.

The paper abstract itself does not give feature dimensions; the dossier's numbers come from the patent abstracts.

Why two scales

The dossier does not explain the physical rationale for the two-scale structure in detail. The standard account — that hierarchical roughness traps air in a composite solid–air interface and thereby raises the apparent water contact angle — is not spelled out in the source material. The dossier presents the hierarchical structure as the defining feature of the patented surfaces and as the treatment applied to the tube interiors.

Related pages

• Superhydrophobicity — the property the texture produces.
• US2019319152A1 — Super-Hydrophobic Surfaces and Methods for Producing Super-Hydrophobic Surfaces and US10876193B2 — Methods for Making a Material Superwicking and/or Superwetting (Superhydrophilic) — the patents that specify the feature scales.
• chemistry — surface treatment and wetting chemistry.