Side-Emitting Optical Fibers for Delivery of UV-C Light to Disinfect Key Bacteria in Space Station Water and Storage and Conveyance Systems

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, orlimited 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). 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, UV-C 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 have developed a means of increasing the irradiation area of UV-C LEDs by >100x through the development of side-emitting optical fibers (SEOFs). This is achieved by coating the optical fiber in a novel way (patent-pending) that includes 1) tunable shape-, size-, and surface chemistry-modified silica nanoparticles (NP) that create photon and energy-scattering centers on the fiber surface and 2) a UV-C transparent polymer coating over the NPs that protects the SEOF while allowing light to enter the water.  Target applications for SEOF include potable water devices or tubing, biomedical devices or surface disinfection.  This Phase II STTR has the following technical objectives: Develop design specifications, drawings, bill of material costs and a techno-economic analysis for two portable LED-SEOF prototypes; Expand and further validate our proprietary Scattering Efficiency Model 1.0 developed in Phase I to include focusing lenses and  LED ray tracing to better predict light entrance into SEOFs; Investigate the potential to simplify specialty SEOF coating layer by modulating the inner glass surface interface of solarized glass optical fibers; Develop figures of merit for and fabricate SEOFs with uniform light emission along their length; Scale-up production of SEOFs and compare optical performance with lab-fabricated SEOFs; Improve percentage of light entering SEOF from LED that is side-emitted; Bundle and polish SEOFs to increase area that a single LED can irradiate; Evaluate mechanical integrity and chemical stability of fluorinated organic coatings on SEOFs; Identify and explore application of non-fluorinated UV-C transparent SEOF polymer coatings; Design and custom fabricate integrated LED-power supply modules that provide waterproof connection with SEOF modules; Demonstrate prototype biofilm mitigation in water storage containers and tubing systems. Deliverables: Final Report, two SEOF portable prototype devices

Microbial control in potable water systems; air/surface disinfection applications Biofilm control in major home appliances/water appliances; biomedical devices; legionella control; air/surface disinfection applications

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