Dec. 17, 2020
Inactivation effect (99.99%) of Nichia’s deep UV LEDs on the novel coronavirus (SARS-CoV-2)
Nichia Corporation (Headquarters: Anan City, Tokushima; President: Hiroyoshi Ogawa; hereinafter “Nichia”) announces confirmation through experimentation of the inactivation effect (99.99%) of NICHIA’s 280 nm deep UV LEDs on the novel coronavirus SARS-CoV-2.
1. Outline of the experimental results
This experiment was carried out by Professor Masako Nomaguchi and Assistant Professor Takaaki Koma of Tokushima University Graduate School of Biomedical Sciences.
They confirmed that irradiating SARS-CoV-2 with UV for 30 seconds at 51mJ/cm2exhibited 99.99% inactivation (Table 1).
The Efficacy Assessment of Disinfecting Substances Alternative to Alcohol for Use Against Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) (Ministry of Economy, Trade and Industry) has judged virucidal efficacy of disinfecting substances against SARS-CoV-2 on the basis of the criterion set at a 99.99% or more reduction in viral titer.
The virucidal effect of handwashing and hand sanitizers, recommended as measures to control infectious diseases, is reported to be
• about 99% when washing hands with running water for 15 seconds1) and
• 99.99% when using commonly-available alcohol-based hand sanitizer (containing 77–81% ethanol) for 30 seconds2).
However, to obtain a higher virucidal effect by handwashing with running water, you have to wash your hands thoroughly by rubbing them together and, when you use alcohol solution for disinfection, surfaces should be sufficiently wetted with it. These measures require time and effort.
We found that deep UV LEDs may have a high virucidal effect while saving time and effort.
|Irradiation time||Inactivation effect|
Table 1. Inactivation effect by irradiation time (reference values)
Picture 1. Experimental environment (reconstruction)
Irradiation conditions: irradiation distance 50 mm, irradiance 1.7 (mW/cm2)
（SARS-CoV-2/Hu/DP/Kng/19-020, Genbank: LC528232）was provided by Kanagawa Prefectural Institute of Public Health.）
2. Virucidal power
Sterilization by deep UV LEDs involves the following two factors:
• Wavelength: The difference in the virucidal effect according to wavelength3) shows that a wavelength of 260 nm exhibits the highest virucidal effect (100%) (Figure 2).
• Optical output power: Higher optical output power (radiant flux) of LEDs (Figure 3) is favorable.
Virucidal power is obtained by multiplying the virucidal effect according to wavelength by optical output power. (Figure 4)
While the life span of the 265 nm LED is expected to be approximately 2,000 hours, that of the 280 nm LED is expected to be approximately 20,000 hours, or roughly 10 times as long as that of the 265 nm LED.
The shorter the wavelength of light emitted from UV LEDs meanslower performance, such as output and lifespan.Therefore, the power conversion efficiency (i.e. wall-plug efficiency or WPE) of the UV LED also declines sharply. Conversely, 280 nm LEDs can present higher output and longer lifespans
On the basis of the virucidal power described above and lifespans of LEDs, NICHIA decided to propose a wavelength of 280 nm in the inactivation experiment
Figure 2. Difference in the virucidal effect according to wavelength
Figure 3. Optical output power
Figure 4. Virucidal power
3. Contribution of pilot products
NICHIA has contributed additional prototype hand-held UV irradiation devices that were made for the inactivation experiment to Tokushima Prefecture (20 units) and Tokushima University (30 units). This rechargeable, portable device can be easily used for sanitizing common spaces and surfaces where alcohol-based solution cannot be used.
This device is equipped with 12 deep UV LEDs at intervals of 25 mm These LEDs offer the industry’s highest radiant flux, 70 mW (typical value), and WPE, 3.6%, at the peak wavelength of 280 nm (typical value) (according to Nichia research).
Nichia continues to be committed to developing deep UV LEDs with higher output and higher virucidal effects, and hopes that various products equipped with our deep UV LEDs that can prevail against the new coronavirus to help people lead better lives.
1) The Journal of the Japanese Association for Infectious Diseases, 80:496-500, 2006.
2) J. Antibact. Antifung. Agents, Vol.48, No.9, pp.477-480 (2020).
3) JIS Z8811-1968
Public Relations, Nichia Corporation