LEDs being used in health-related applications

Article By : Yoelit Hiebert

Here are a few examples of LEDs being used as part of new developments in health-related applications.

LEDs are continuing to be part of new developments in health-related applications. Here are a few examples of the broad range of fields in which they are being used to improve human health and well-being.

Circadian entrainment

Circadian entrainment refers to the synchronization of our internal biological clock based upon external environmental indicators like the sun’s motion across the sky. There has been great interest in LED-based lighting products that can promote entrainment to help us sleep better at night, feel more alert during the day, and even improve overall health. Exposure to lighting with appropriate blue wavelength content is especially important during daylight hours to impede melatonin production, which helps us feel more awake and energetic.

But blue light is also associated with retinal damage, as described in IEC/EN 62471 Photobiological Safety of Lamps and Lamp Systems. This standard provides guidance for exposure limits and measurement procedures for all electrically-powered, incoherent broadband optical radiation sources, including LEDs. The standard defines a blue light hazard sensitivity curve that peaks at 435-440 nm and decreases to negligible values at 550 nm.

Blue LEDs are typically composed of a mixture of both blue-violet (415-455 nm) and blue-turquoise (456-490 nm) in approximately equal proportions. Altering the proportions to favor blue-turquoise could be advantageous for maximizing circadian entrainment, while minimizing blue light hazard. At least one manufacturer is now offering an LED package with selectable ratios of blue-violet to blue-turquoise, depending upon the desired CCT.

Treatment of ovarian cancer

An application being developed by Animated Dynamics in association with Purdue University uses IR LEDs to help determine if a specific chemotherapy treatment would be effective, sparing the patient unnecessary exposure to toxic side-effects.

The technique involves comparison of the light scatter resulting from shining an IR LED source on a biopsy sample both before and after application of chemotherapy compounds to the biopsied tissue. The absence of apoptosis (death of tissue cells), as indicated by comparison of the light scatter, would signal that a given chemotherapy treatment would most likely not be effective in treating the actual tumor. Initial trials focused on patients with ovarian cancer, and the goal is to use the data to determine which treatments have the best chance of arresting the disease.

Bacterial deactivation

With the advent of COVID-19, interest in germicidal disinfection has exploded and manufacturers of LED packages have responded. The preponderance of offerings emit UVC, which poses a potential exposure risk, but Nichia has just released a package characterized as a dual-purpose LED that is not harmful to humans. This package provides both white light for general illumination and violet light at 405 nm for deactivation of bacterium like Pseudomonas aeruginosa, Staphylococcus aureus (staph), and Escherichia coli (E. coli). The graph below shows the difference between emission spectra of a “conventional” white light emitter and the new Nichia package across the visible spectrum. The peak at 405 nm is about four times more intense than the typical blue peak associated with a phosphor-converted white LED, but in a region to which the human eye is not as sensitive.

graph of Nichia LED emission spectrumThis graph compares the emission spectrum of the Nichia NF2W585AR-P8 LED package to a conventional phosphor-converted white LED. Source: Nichia

Independent testing commissioned by Nichia indicated that the dual-purpose package deactivates up to 98.9% of Pseudomonas aeruginosa within five hours of continuous illumination of a surface 40 cm away at 1000 lux output. Because the light is within the visible range, there are no harmful impacts to the human eye due to continuous exposure. One impediment to wide-spread adoption of this technology may be the requirement for the light source to operate for lengthy durations to achieve maximum efficacy. And while this technology may prove effective against bacteria, it is not adequate for deactivation of viruses, including SARS-CoV-2.

Medicinal cannabis

And, finally, no discussion of how LEDs are used in health applications would be complete without touching upon medicinal cannabis, an industry that has absolutely exploded thanks in no small part to the use of LED lighting.

Fluence by Osram recently released results from a two-year study conducted in partnership with Wageningen University and Research and Texas Original Compassionate Cultivation to determine the impact of supplemental LED lighting in a greenhouse environment on plant characteristics, such as yield and concentrations of metabolites like cannabinoid and terpene. Even small improvements in yield or potency can far outweigh the implementation cost of an optimized lighting system, so research in this area is quite robust. This study, involving three different cannabis cultivars, concluded that high intensity, broad spectrum (i.e., 400 – 700 nm) supplemental light can maximize both yield and metabolites and lower intensity, broad spectrum lighting will not have as great an impact on yield, while still improving metabolite levels.

This article was originally published on EDN.

Yoelit Hiebert has worked in the field of LED lighting for over 10 years and has experience in both the manufacturing and end-user sides of the industry.

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