An Approach to Improve Energy Efficiency during Antimicrobial Blue Light Inactivation: Application of Pulse-Width Modulation Dimming to Balance Irradiance and Irradiation Time

Abstract

Antimicrobial blue light (aBL) is an effective non-destructive inactivation technique and has received increasing attention. Despite its significance, the existing research has not thoroughly delved into the impacts of irradiance and irradiation time on enhancing energy efficiency during aBL inactivation and the explanation of the enhancement effect of pulse exposure. In this paper, a series of Escherichia coli inactivation experiments with different duty cycles, pulse frequencies, and irradiation times were conducted, and the relative concentrations of reactive oxygen species (ROS) were measured under corresponding conditions. A two-dimensional (2-D) Hom model was proposed to evaluate the effect of irradiance and irradiation time. The results show that, compared to continuous exposure, pulsed aBL (duty cycle = 25%) can save ~37% of the energy to achieve the same inactivation effect and generate a 1.95 times higher ROS concentration. The 2-D Hom model obtains the optimal combination of average irradiance and time according to the desired reduction and shows that the irradiation time has a higher weight than the irradiance (1.677 and 1.083, respectively). Therefore, using pulse exposure with a lower average irradiance for a longer period of time can achieve a better inactivation effect when consuming equivalent energy. The proposed pulse-width modulation dimming approach helps promote the application of the aBL technique.

Enhanced antimicrobial efficacy and energy efficiency of low irradiance 405-nm light for bacterial decontamination

“…5 and 7 demonstrate that the enhancement in inactivation efficacy observed for lower irradiance exposures is apparent for various S. aureus and P. aeruginosa populations in suspension. These findings support those of Zhang et al ( 2023 ), who, whilst investigating the energy efficiency of pulsed 405-nm light for inactivation of E. coli suspensions, demonstrated that exposure time has greater influence over inactivation than that of irradiance, thus suggesting that greater reductions could be achieved when lower irradiances are employed over extended time periods, compared to higher irradiances over shorter time periods. By contrast, however, results for S. aureus exposed at an initial population density of 10 9 CFUmL −1 deviate from the overall findings of this study for reasons that are not yet fully understood.…”