Investigating the used of pulsed RYGB LEDs to create a blended white light for antimicrobial applications

With the growing problem of antibiotic-resistant strains of bacteria, the drive for alternative methods of disinfection is increasing. Optical disinfection is currently a topic of interest, with UV-light traditionally used for this application; but 405-nm violet-blue light also has exploitable antimicrobial properties, with recent studies demonstrating its application for continuous environmental decontamination. This study investigates using pulsed 405-nm LEDs, in conjunction with pulsed red, yellow and green LEDs, to create a blended white light with antimicrobial properties. Despite 405-nm light being effective in terms of microbial inactivation, 405-nm light alone would be uncomfortable to work under, given the narrow-band wavelength and thus low Colour Rendering Index (CRI). Therefore, if a blended white light could be produced whilst containing enough 405-nm light content, it would be more comfortable to work under, and could possibly be used as standard room lighting, with the added benefit of environmental decontamination.
To do this, Pulse Width Modulation (PWM) was employed to control the apparent intensities of each of the 4 LED colours, in order to create a blended light. The LEDs were specifically controlled using a microcontroller programmed to output PWM signals to each LED, to create the required combination of wavelengths and intensities for white light. The output of the prototype was then captured and assessed using a spectrometer and compared with the output of standard fluorescent lighting to assess the success of the blending. Finally, the prototype underwent antimicrobial testing using the bacterium Staphylococcus aureus, a common cause of hospital-acquired infection. These results demonstrate the potential to create a blended, pulsed-light system with antimicrobial properties, which could have practical decontamination applications.