Understanding the Optical Principles of UV-based Antifouling

Sammanfattning: In 2014 Salters et. al. introduced the concept of an UV-emitting wallpaper. By using UVC LEDs, a completely clean ship hull surface can be achieved without polluting the marine environment with biocides, normally associated with antifouling paints. A larger hull surface area could be illuminated by a single LED if the LED light is used efficiently. Exactly how the light exits the wallpaper material, is outcoupled, is not known. This must be understood for a more efficient product to be developed. Light outcoupling in the UV region is not well studied and the combination of light outcoupling and UV light’s antifouling effect has never been studied before. In this master’s thesis, we investigate what the antifouling causing light extraction mechanism is when UVC light, with a peak wavelength of 275 nm, is coupled into quartz. The following light extraction mechanisms, scattering, parallel rays, evanescent wave and Fresnel outcoupling, are all investigated by simulations and physical experiments. The results indicate that scattering is an important antifouling causing light extraction mechanism and the irradiance threshold value correlates with an irradiance of 1 · 10−8 W/mm2 that has been found in previous studies to be the threshold for an antifouling effect. The results also indicate an antifouling effect of parallel rays and Fresnel outcoupling. The antifouling effect of an evanescent wave remains undecided. It is concluded that none of the proposed antifouling causing light extraction mechanisms can definitely be ruled out.