SBIR-STTR Award

Bacteria and biofilms pose health and operational challenges in human support systems. Germicidal UV-C disinfection using mercury-based lamps is a widely used technology that has numerous safety and reactor configuration disadvantages. Light emitting diodes (LEDs) are mercury-free alternative and other advantages are making them competitive and a lower cost alternative for disinfection (e.g. lack of warm up time, tunable radiation, long life of use). However, a crucial technology barrier of LED disinfection is the small surface area that emits irradiation, which necessitates arrays of many LEDs within even the smallest reactor, and thus has been a major limitation to their adoption. We propose a means of increasing the irradiation area of LEDs by >100x through the development of side-emitting optical fibers (SEOF), essentially creating UV-C germicidal flexible glowsticks which can be bundled together with tens of optical fibers delivering light from a single LED. Currently only visible light SEOFs are commercially available. To overcome this wavelength dependent barrier, we recently discovered a nanotechnology-based solution to achieve side-emission from optical fibers in the UV-C range. This is achieved by coating an optical fiber in a new and novel way using shape-, size-, and surface chemistry modified silica nanoparticles that create light-scattering centers on the surface of the fiber. The coated fiber is then overlaid with a UV-C transparent polymer that protects the fiber and prevents nanoparticle release into water and allows germicidal light to enter the water. This STTR proposal outlines a detailed work plan to develop this nanotechnology solution from the proof-of-concept phase to pre-design phase. Potential NASA Applications (Limit 1500 characters, approximately 150 words) Disinfection of tanks and piping systems to mitigate biofilm growth and support system dormancy using only UV-C light Potential Non-NASA Applications (Limit 1500 characters, approximately 150 words) Disinfection applications (using only UV-C light, no chemicals) for large or irregular shaped commercial or industrial or spaces, water, food, air filters, medical applications, and consumer products

Bacteria in water and surface-attached biofilms pose health and operational challenges in human support systems. Current biofilm control technologies (i.e., hydrophobic surfaces, biocide-impregnated plastic coatings, chemical biocides, mercury-based lamps or light emitting diodes (LEDs)) either work for a very short duration, lead to residual chemical by-products of concern, have impractical physical designs, or limited light irradiation capacity. We propose a means of increasing the irradiation area of a UV-C LED by >100x by launching its light into side-emitting optical fibers (SEOFs), essentially creating germicidal flexible glowsticks. Currently only visible light SEOFs are commercially available. However, we discovered a technology (patent-pending) using silica nanoparticles (NPs) permanently attached to optical fibers that achieve side-emission of UV-C light along the entire optical fiber length. This is achieved using our dual-layer SEOF that includes 1) tunable shape-, size-, and surface chemistry-modified silica NPs that create photon and energy-scattering centers on the fiber surface and 2) UV-C transparent polymer coating over the NPs that protects the SEOF while allowing light to enter the water. Flexible individual or bundled SEOFs can deliver light from UV-C LED(s) to large surface areas. Our SEOF technology targets biofilm control in water or air, including narrow channels in potable water devices or tubing, biomedical devices or surface disinfection. Research performed during the Phase I STTR successfully 1) optimized the SEOF NP coating, 2) advanced development of desirable light profiles along SEOF, 3) developed a proprietary first-principle optical fiber light scattering mathematical model to engineer the SEOF and 4) demonstrated bacterial inactivation in water or on surfaces. This Phase II STTR proposal advances research initiated in Phase I and develops prototype devices for technology demonstration (TRL 5). Potential NASA Applications (Limit 1500 characters, approximately 150 words) Microbial control in potable water systems; air/surface disinfection applications Potential Non-NASA Applications (Limit 1500 characters, approximately 150 words) Biofilm control in major home appliances/water appliances; biomedical devices; legionella control; air/surface disinfection applications