Investigation and optimisation of pulsed 405nm LEDs and their use in a blended environmental decontamination system

  • Jonathan Bernard Gillespie

Student thesis: Doctoral Thesis


With the rise in strains of antibiotic resistant bacteria, and with that, the rising rates of hospital infection, there is a drive for new antimicrobial infection control technologies. One such technology is the use of narrow spectrum light with a central wavelength in the region of 405 nm - henceforth referred to as '405 nm light' - which has been developed for continuous environmental decontamination applications. This study investigates the use of this pulsed 405 nm light, to evaluate potential operational advantages that this delivery method may provide when compared with continuous 405 nm light.;The initial part of the study investigates the fundamental effects of pulsed operation of light emitting diodes (LEDs), by altering a range of parameters including the frequency of the pulsing, the peak irradiance, the duty cycle and the exposure time, and the resulting effects on the antimicrobial action. Results using pulsed 405 nm light demonstrated more efficient bacterial inactivation, yielding a higher electrical energy efficiency and optical efficiency, suggesting beneficial results in using pulsed 405 nm light over continuous 405 nm light.;The study then investigates, more specifically, the application of pulsed 405 nm light to the area of continuous environmental decontamination. The study documents the design, build and testing of a prototype blended pulsed antimicrobial white light based on pulsed 405 nm LEDs - supplemented by red, green and yellow/amber wavelengths to produce the blended white light. The pulsed blended white light prototype demonstrated an improved colour quality with the supplementary colours when compared with the 405 nm light alone whilst demonstrating effective antimicrobial action.;Overall, this study provides the first evidence of the use of pulsed 405 nm LEDs and the operational advantages over continuously run 405 nm LEDs in terms of antimicrobial action. The study then utilises this pulsed delivery system to develop a pulsed blended white light prototype system, a possible viable future design option for continuous environmental decontamination systems.
Date of Award30 Jul 2020
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SponsorsEPSRC (Engineering and Physical Sciences Research Council)
SupervisorMichelle Maclean (Supervisor) & Martin Given (Supervisor)

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