Implementation and characterisation of a sterilisation module consisting of novel 265 nm UVC LED packages

To efficiently fight against the COVID-19 pandemic, a sterilisation module using 265 nm UVC LED packages was developed. In this paper, the performance of the sterilisation module in terms of irradiance uniformity, junction temperature increase and sterilisation efficiency were characterised. The irradiance uniformity fluctuation across the four corners and the centre point in a 130 mm × 130 mm area was below 10%, exhibiting good uniformity. Uniform irradiance was important to achieve consistent sterilisation, which was the primary difference between the UVC LED package developed and commercial UVC LED packages. Key to achieving uniform irradiance was the structure, consisting of a stacked silicon reflector and a secondary optical lens designed by ray tracing simulation. The junction temperature increase of the 265 nm UVC LED package driving at 200 mA was only 28°C, sufficiently low to exhibit better reliability and performance. A 99.99% sterilisation efficiency on E. coli bacteria was achieved within one minute with UV dosage of 2.7 mJ/cm2 at 200 mA driving current. From the results, the novel 265 nm UVC LED package was a time-efficient solution for disinfection purposes. © 2021 The Hong Kong Institution of Engineers.

222-Nanometer Far-UVC Exposure Results in DNA Damage and Transcriptional Changes to Mammalian Cells.

Ultraviolet (UV) germicidal tools have recently gained attention as a disinfection strategy against the COVID-19 pandemic, but the safety profile arising from their exposure has been controversial and impeded larger-scale implementation. We compare the emerging 222-nanometer far UVC and 277-nanometer UVC LED disinfection modules with the traditional UVC mercury lamp emitting at 254 nm to understand their effects on human retinal cell line ARPE-19 and HEK-A keratinocytes. Cells illuminated with 222-nanometer far UVC survived, while those treated with 254-nanometer and 277-nanometer wavelengths underwent apoptosis via the JNK/ATF2 pathway. However, cells exposed to 222-nanometer far UVC presented the highest degree of DNA damage as evidenced by yH2AX staining. Globally, these cells displayed transcriptional changes in cell-cycle and senescence pathways. Thus, the introduction of 222-nanometer far UVC lamps for disinfection purposes should be carefully considered and designed with the inherent dangers involved.

Analysis and design of SARS-CoV-2 disinfection chambers based on UVC LEDs

With this work we propose a guideline for the development of efficient and effective UVC surface disinfection systems for SARS-CoV-2 based on LED technology. The work analyzes the optical and electrical characteristics of state of the art UVC LEDs. From the most recent scientific literature, optical simulations, and laboratory experiments we propose guidelines for the design of high efficiency LED based antiviral system for the treatment of contaminated surfaces. To validate the guidelines two different UVC-LED irradiation systems, for spherical and flat surfaces, have been designed, manufactured and tested. Results indicate a log-4 inactivation of SARS-CoV-2 in few minutes. © COPYRIGHT SPIE. Downloading of the is permitted for personal use only.

A Study on the Effect of Integrated Ozone and UVC-LED Approaches on the Reduction of Salmonella typhimurium Bacteria in Droplets

In the wake of the SARS-CoV-2 pandemic, inactivating bioaerosols became a pivotal issue which helps to prevent the transmittance of SARS-CoV-2. Thus, the current study was conducted to investigate a potential inactivating method using both ozone (O-3) and ultraviolet C (UVC). Individual and integrated effects of O-3 and UVC were compared. A solution containing approximately 4 similar to 7.3 x 10(6) CFU/mL of Salmonella typhimurium bacteria was used to produce bacteria droplets. These droplets were exposed to O-3 and UVC to determine the reduction rate of bacteria. The exposure times were set as 1 and 30 minutes. Ozone concentrations were 100 and 200 ppmv. UVC-LEDs were used as a UVC source. Peak wavelength of the UVC-LED was 275 nm and the irradiation dose was 0.77 mW/cm(2). In terms of O-3 and UVC-LED interaction, 194 ppmv styrene was used as a target compound to be removed. Considering the O-3 and UVC-LED interaction, the presence of O-3 could reduce the performance of the UVC-LED, and UVC-LED could also reduce significant amount of O-3. The sequence of O-3 and UVC-LED treatment was as follows: O-3 was exposed at first, then UVC-LED, and this order showed the best reduction ratio ( > 99.9%). Therefore, if O-3 and UVC-LED is used to disinfect Salmonella typhimurium bacteria contained in droplets, bacteria should be separately exposed to O-3 and UVC-LED in order to improve the inactivation efficiency.