Self-sanitizing Surfaces

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"What if hospitals (the equipment, furniture, floors, door handles, light switches and other surfaces) could disinfect themselves?  Well, that’s just what our latest invention does.  Self-sanitizing Surfaces is a technology that uses UV light to nearly eliminate microorganisms on medical devices and high-touch, near-patient surfaces.  The cleaning process is entirely automated; it can be carried out as frequently as desired with complete thoroughness.
Total Internal Reflection and the Evanescent Field Effect make this possible.  Have you ever seen those fluorescent menu boards in restaurants?  They use the much the same principle.  For example, we can position ultraviolet LED’s such that they illuminate the edges of a material thus sending light waves through it.  If the material has a high enough index of refraction compared to an adjacent medium (i.e. the air), the light waves can’t refract normally out of the material if they are at a critical angle.  This results in an optical phenomenon known as total internal reflection (TIR) when all of the waves are reflected within the original medium.  In other words, we’re trapping light within the medium.  As the frustrated light bounces around due to TIR, another phenomenon occurs where a surface wave forms at the boundary between the two mediums (i.e. the substrate and the air).  This phenomenon is known as the evanescent field effect.  It’s like a cloud or halo that is approximately one wavelength thick; mere nanometers.  When bacteria are in close proximity to the evanescent field, their higher index of refraction allows the trapped light energy to escape from within the material.  If the ultraviolet light is within the UVC wavelength band (280-100 nanometers) the exposure destroys the DNA of those pesky germs rendering them incapable of reproducing.  Even a small amount of ultraviolet energy for a short exposure period can be quite lethal to most common bacteria.   Since the relatively low energy ultraviolet light trapped within the material extends only about one wavelength from the material’s surface, it makes possible the design of germicidally effective event-triggered self-sanitizing surfaces that are safe for humans to touch and to look at without the need for personal protective equipment.