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Prioritize UVC LED Output Over Lifetime in Healthcare Applications

Eoin Connolly

Eoin Connolly

President & CEO

The surge of innovation in infection prevention is fueled by reducing instances of healthcare-associated infections (HAIs) and combating the growing threat of superbugs. In the United States, the Centers for Disease Control and Prevention (CDC) has reported substantial improvements in controlling the incidents of HAIs while noting that there is still much work to do.

As a result, medical equipment providers are considering how UVC provides infection prevention and control in portable devices which could be used by healthcare professionals at the point-of-care or to disinfect high touch surfaces (e.g. personal electronics, medical carts, and diagnosis equipment). This focus on portability places a premium on technologies that are compact, lightweight, can be battery powered and withstand on-demand use.

Since low-pressure germicidal lamps fall short on many of these requirements, medical equipment design engineers see UVC LEDs as a natural fit for new and existing products. A challenge here is that adding UVC to portable medical equipment is a new endeavor for many OEMs, and the readily available studies online are based on visible LED characteristics—which generally recognize long lifetime as the primary value of this technology. But in these types of applications, there is a different priority: speed of disinfection.

As with visible LEDs, a UVC LED is, by its very nature, a constant current device. This means that when the forward current applied to the diode changes, the UVC output of the diode increases or decreases proportionally. Essentially, there is a trade-off between output power and lifetime—which Kevin Kahn from our Field Application Engineering team explains further in this article on UVC LED lifetime.

As outlined by Dr. Kahn, the L-value for a UVC LED is the point at which the UVC output has degraded to a percentage of its initial value. However, this value is dependent on the operating conditions (e.g. drive current) and thus is not an absolute figure.

The graph below shows that when the LED is operated at 700 mA, it has an L75 of 500 hours, meaning that the LED produced 75 percent (45 mW) of the initial UVC output (60 mW) at 500 hours. In contrast, when operated at 350 mA the LED has an L90 of 500 hours, meaning that the LED produced 90 percent (30 mW) of the initial output (33 mW) at 500 hours.

  • At 500 hours, the UVC output and percentage of original UVC output (L value) varies based on the drive current of the device.
    At 500 hours, the UVC output and percentage of original UVC output (L value) varies based on the drive current of the device.

Understanding this operating behavior for a set of UVC LEDs helps inform product design. For example, a chamber to deliver surface disinfection to a cell phone or stethoscope in a healthcare setting requires high pathogen reduction (6 log of E. coli) in under 30 seconds. If the chamber is operated 30 times a day, every day, an LED system would be used 92 hours per year and less than 500 hours in a typical five-year product lifetime. In this case, achieving a higher dosage with higher UV intensity in 30 seconds takes priority over achieving an inflated lifetime requirement. By understanding the cumulative operating time and comparing this with the LED characteristic, a design engineer could decide to operate the LED at 700 mA to provide 50 percent higher UVC output than if operated at 350 mA.

For medical equipment OEMs, it is important to understand how the relationship between UVC output and LED lifetime impacts the end product. In healthcare settings, delivering a high rate of disinfection in the least amount of time ensures that equipment and devices are being disinfected and put back in the rotation faster. This means higher productivity and a higher level of confidence in infection prevention—addressing some of the common concerns of stakeholders in healthcare.