Biofilm inhibition on surfaces by ultraviolet light side-emitted from optical fibres

Bacterial biofilms are problematic wherever water contacts with surfaces. Although germicidal ultraviolet (UV)-C irradiation effectively inactivates microorganisms in flowing water, controlling surface biofilms is challenging due to light delivery limitations within enclosed and flowing water systems. Here, to overcome this, we developed a novel method using UV-C light-emitting diodes connected to side-emitting optical fibres (SEOFs) placed directly on metal surfaces. Targeting mixed-bacterial biofilms from the International Space Station where biofilms threaten critical water systems for astronauts, we successfully inhibited biofilm growth by delivering UV-C light at 265 or 275 nm with an irradiance of >10 µW cm−2 via SEOFs. In contrast, UV-A or UV-B at the same irradiance did not prevent biofilm growth. Energy-efficient intermittent UV-C duty-cycling experiments demonstrated that 10 min of irradiation followed by 50 min of dark time achieved equivalent results to continuous light exposure. Our research highlights the potential of SEOF technologies emitting UV-C light for effectively combating undesired biofilms in water systems. The combination of ultraviolet-C emitting diodes with side-emitting optical fibres can be used to effectively inhibit biofilm formation, as demonstrated within the water system of the International Space Station.