Straightforward Patterning of Functional Polymers by Sequential Nanosecond Pulsed Laser Irradiation

Micropatterned functional interfaces on elastic substrates fabricated by fixing out of plane deformations

We report on the preparation of micropatterned functional surfaces produced by inducing an out-of-plane deformation on elastic substrates and fixing these by creating a rigid oxidized top layer. Specifically, the elastic substrate used was Polydimethylsiloxane (PDMS) and the rigid layer on top was created by ozonation of this material. We evidenced that the surface pattern formed is directly dependent on the pressure applied, the mechanical properties of the elastic substrate and on the dimensions and shape of the mask employed to define the exposed and non-exposed areas. In addition to the pattern formed, another interesting aspect is related to the ozone diffusion within the material. Softer PDMS enables more efficient diffusion and produced a thicker oxidized layer in comparison to rigid PDMS. Finally, a simulation was carried out using the distribution of Von Misses stresses of a solid plate to understand the conditions in which the applied force resulted in the rupture of the rigid oxidized layer under a permanent deformation.

High-Speed Erosion Behavior of Hydrophobic Micro/Nanostructured Titanium Surfaces

Ice accretion on aircrafts or their engines can cause serious problems and even accidents. Traditional anti-icing and de-icing systems reduce engine efficiency, which can be improved by the use of hydrophobic/icephobic coatings or surfaces that reduce the amount of bleed air or electric power needed. These hydrophobic/icephobic coatings or surfaces are eroded by high-speed air flow, water droplets, ice crystals, sand, and volcanic ash, resulting in the degradation, material loss, or deterioration of the coating's waterproof and anti-icing properties. Thus, the durability of hydrophobic micro/nanostructured surfaces is a major concern in aircraft applications. However, the mechanism responsible for material loss in hydrophobic micro/nanostructured surfaces resulting from high-speed erosion remains unclear. In this paper, hydrophobic titanium alloy surfaces with cubic pit arrays are fabricated by photoetching and tested using a high-speed sand erosion rig. Under the same impact conditions, the erosion rates of the micro/nanostructured titanium surfaces were similar to those of smooth titanium alloy, implying that the hydrophobic surface fabricated on the bulk material had erosion-resistant capabilities. The material loss mechanisms of the micro/nanostructures under different impact angles were compared, providing useful information for the future optimization of micro/nanostructures with the goal of improved erosion resistance.