The system provides a platform for researchers and manufacturers to perform testing according to protocols developed by a National Institutes of Health (NIH)-NIST panel, which published a consensus framework for evaluating ultraviolet (UV) efficacy in 2021.
The researchers describe the new system in the SPIE Journal of Biomedical Optics, explaining that it consists of an LED array, an optical fiber assembly that can be scanned across a 2-inch (5-cm) Petri dish, precise power and temperature controls and the ability to house liquid or agar media.
The system's optical assembly contains a spectrometer to ensure that the wavelength and irradiance levels are correct, a digital camera to document bacterial colony density across the Petri dish, and a high-speed linear actuator that moves the fiber in a programmable pattern across the agar plate to create the desired exposure pattern.
The researchers measured the effectiveness of UV light (265 nanometers) for inactivation of methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli (E. coli), common causes of skin, soft tissue and urinary tract infections, as the agar plates move beneath the light to create a "kill curve" that reveals how quickly a certain dose of UV light kills MRSA and E. coli.
While this study focused on UV LEDs emitting light at a 265-nanometer wavelength, the system can be used to test other UV sources, such as mercury lamps or excimer lamps. With appropriate optical modifications, the measurement approach could be extended to longer or shorter wavelengths, including visible and infrared light.
The system's compact 11-by-9-by-5.5 inch (28-by-23-by-14-cm) benchtop design makes it suitable for various research, development and production environments.
NIST intends to make the ultraviolet (UV)-C LED irradiance metrology system available to researchers and standards development organizations for evaluations of UV light sources. The system also allows manufacturers to demonstrate the efficacy of UV-C LEDs and other lights.
The NIST system is one of several efforts the agency has developed to support effective use of UV light for germicidal technologies, including a UV radiometer calibration service, a UV LED spectroradiometer and several scientific publications.
