Lotus LADM Based Self-Decontaminating Surfaces   [open pdf - 1MB]

"Recent events have lead to new concerns about biowarfare, bioterrorism, chemical warfare and chemical terrorism. Because of the potential range of agents that could be used, a non-specific decontamination system is desirable. Of particular interest are materials whose surfaces have been modified to be self-decontaminating and self-regenerating. Other beneficial attributes are that the surfaces be self-cleaning and very light weight. We have developed superhydrophobic coating materials. We have also developed Light Activated Decontamination Materials, LADM, that produce singlet oxygen. In addition novel sporicidal compounds were synthesized having thiolate functionality. Our approach simultaneously addresses surface modification, self-cleaning, and sporicide. To form our LADM coatings, a scaffold polymer was bonded to the surface of fibers. Then photo-active agents were grafted to this scaffold polymer. This increased the available photo-active agents 1000 fold. These photo-active agents absorb visible light and transfer the energy to oxygen in the air to generate singlet oxygen, which has been shown to destroy chemical and biological agents. Singlet oxygen was also expected to destroy spores. Self-cleaning surfaces rely on the Lotus effect in which water is suspended upon a hydrophobic surface with air gaps between different segments of the hydrophobic material. The droplet is supported on the raised portions with air gaps below large portions of the droplet. To render the surface superhydrophobic, or self-cleaning, we bonded short fibers to the surface through flocking. By controlling the flocking process, we could control the fiber height and spacing. These two factors have been shown to be important to generating the Lotus effect. This was not be sufficient to render the surface superhydrophobic. However, by modifying the surface further with fluorochemical or long chain alkanes, we were able to convert the surface from hydrophobic to superhydrophobic."

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