Abstract
Using a lotus leaf as our model, we fabricated an extremely low surface energy micro/nanostructured coating for textiles that repel oil, water, and chemical warfare agents (CWAs) using a simple process that is suitable for large scale production. This coating, called “OmniBlock”, consisted of approximately 200-nm silica nanoparticles, tetraethylorthosilicate, 3-glycidoxypropyl trimethoxysilane, and a perfluorooctanoic acid-free fluoropolymer (Fluorolink S10) that was cross-linked between Si-O-Si groups via a sol-gel process. The perfluorooctanoic acid-free fluoropolymer-coated silica nanoparticles were simply applied to the surface of a cotton fabric by a dip–dry–cure process, forming dense, continuous, and uniform layers of OmniBlock coating. OmniBlock modified the surface of the cotton fibers, creating a rough, high surface area uniform coating with many micro-crevasses. As a result, n-dodecane, water, and CWAs beaded up without wetting the surface, exhibiting large contact angles of 154° for water and 121° for n-dodecane, with a small shedding angle of 5° and contact angle hysteresis of 3.2° for water. The designed coating showed excellent liquid repellence properties against three types of CWAs: 129°, 72°, and 87° for sulfur mustard (HD), soman (GD), and VX nerve agents, respectively. Furthermore, OmniBlock coating shows good mechanical properties under tensile strength and wash tests. This remarkable ability to repel CWAs is likely to have potential military applications in personal protective equipment systems requiring self-cleaning functions.
Highlights
Liquid repellent surfaces with self-cleaning properties are of current research interest, which have been mainly inspired by lotus leaf, known as the Lotus effect [1,2,3]
We reported the average value of surface contact angles for at least five measurements after resting for 30 s, and the measurements were made on different areas of the coated sample
Images of the OmniBlock-coated cotton fabric in Figure 2c indicate that the perfluorooctanoic acid (PFOA)-free area of the fiber [61]
Summary
Liquid repellent surfaces with self-cleaning properties are of current research interest, which have been mainly inspired by lotus leaf, known as the Lotus effect [1,2,3]. The effect occurs due to the micro/nanostructures on the leaf that are covered with hydrophobic waxes, providing a low surface free energy [4]. This wax combined with the micro/nanostructures results in a hierarchical double structure in which air pockets form on the surface, repelling water by dramatically increasing the contact angle of water droplets [2]. Water droplets capture dust particles by rolling on the leaf, and in doing so, exhibit self-cleaning properties. Researchers have developed self-cleaning textile by combining low surface energy materials such as organic silanes [20,21], fluorinated silanes [22,23], alkyl amines [24], and creating surface
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