Superomniphobic Surfaces for Military Applications: Nano- and Micro- Fabrication Methods: Year Two Report.

摘要

This report explains the work accomplished during the year 2 reporting period in four main areas. In the area of continued development of practical repellent coatings, a procedure was developed that results in improved durability under abrasion and water immersion while maintaining coating versatility. Additionally, a set of different layered superhydrophobic coatings has been proposed. In the area of understanding the relationship between surface wear and wetting characteristics for superhydrophobic surfaces, a methodology was devised using confocal scanning microscopy that permits collection of quantitative information for surface texture. This, combined with measuring the contact angles on superhydrophobic coatings that were worn systematically, was used to compare findings with the predictions based on the classical Cassie equation. The need to develop a new relationship was identified. In the area of theoretical work on developing fundamental knowledge about wetting of textured surfaces, a thermodynamic depiction of edge effect has been developed by free energy analysis. Results show good agreement with previous works. A universal wetting plot for describing the four wetting regions was obtained relating edge angle and intrinsic contact angle. The results have provided fundamental rules for designing robust superhydrophobic and superoleophobic surfaces. In the area of fabrication of textured surfaces by lithographic methods to achieve repellency for oily liquids and surfactant solutions, not only were the re-entrant structures proposed in the original proposal produced, but a new structured surface, called silicon grass, was produced that shows considerable promise for oleophobicity when compared to the re-entrant structures. The results of this work have been published in peer- reviewed publications and presented at international conferences.