Have you ever basked in the beauty of an early morning sunrise or sunset? Well, there’s more to the kaleidoscope of feel-good, Bob Ross-esque colors than meets the eye: This relaxing sight is actually intended to orient our biological clocks. Sunlight regularly evolves, changing colors from reddish-white in the morning to bluish-white during the day and back to reddish in the evening. These shifts cue the body to produce different hormones, like the sleep hormone melatonin, to coax you to bed at night or perform other necessary bodily functions.
Because we humans stay indoors quite often (hello pandemic!), it’s crucial to ensure our 24-hour sleep-wake patterns — or circadian rhythms — stay on point. That’s why researchers are embracing smart lighting: This technology typically uses LEDs that alternate between different light wavelengths. Such adjustments aim to help regulate our circadian rhythms in a similar manner to the sun. Now, scientists have dipped their toes in the quantum realm to bring the great outdoors into your home.
According to a recent paper published in the journal Nature Communications, researchers at Cambridge University have developed a technology that ups the efficiency and color saturation of a standard LED using quantum dots, or synthetic nano-sized crystals that can transport electrons. Unlike your standard LED that produces white light through three primary colors — red, green, and blue — QD-LEDs broaden that limited palette to produce a more dynamic smart lighting system that more closely resembles daylight’s ever-changing color temperatures. With a bit more tinkering, this sort of innovation may be helpful to keep our circadian rhythms in check when we’re stuck indoors.
“This is a world-first: a fully optimized, high-performance quantum-dot-based smart white lighting system,” Jong Min Kim, the new paper’s co-author and professor of electrical engineering at Cambridge University, said in a press release. “This is the first milestone toward the full exploitation of quantum-dot-based smart white lighting for daily applications.”
What they did — Quantum dots — which are essentially semiconductors that only consist of a sprinkle of atoms — have been in development for the last 40 years and are typically used to create LCD displays with a relatively brighter and more precise range of colors compared to standalone LED technology. They work like this: When a quantum dot receives a hit of energy — whether from a laser beam, electric, or magnetic field — its electrons eat up this energy and emit light. The ultimate color you get is determined by how small the dot is, as well as the material it’s made of.
Kim and his team took quantum dots between 3 and 30 nanometers in diameter and used machine learning to determine the optimal layout that would render the best spectrum and color temperatures. To test out their smart lighting system, the team devised a device with a color temperature range of 2243 kelvins (mimicking the red hues of early morning) to 9207 kelvins (about the color you’d feel from a midday sun). This QD-LED device vastly outshined the standard LED, which on average is only able to muster a 2200 to 6500 kelvin range.
Why it matters — Light, and the absence of it, drives our circadian rhythms, says Mariana Figueiro, director of Mount Sinai’s Center for Light and Health Research in New York City who studies light’s impact on human health.
Figueiro explains that our biological clocks typically keep ticking regardless of our environment and run on intervals that last a bit longer than 24 hours. But “what you need is that daily light/dark exposure that will reset your clock and maintain you in sync with that 24-hour cycle.”
To convey that information, the body relies on a specialized group of neurons called intrinsically sensitive retinal ganglion cells (ipRGCs). These cells contain melanopsin, a photopigment whose activity depends on how much light it’s exposed to.
When light enters your eyeball and hits the retina, where the ipRGCs chill out, a switch is flipped and tells your brain — and your biological clock — whether it’s day or night. (In blind individuals where the retina is intact, their brains still receive information about light changes but they may be totally unaware these changes are even happening.)
Because many hormones in the body are released on a tight schedule, any disturbances in our circadian rhythms effectively mess up a hormone’s ETA, harming both physical and mental health. Melatonin is one prime example many might be familiar with, but Figueiro says hormones like cortisol (the stress hormone), ghrelin (the hunger hormone), and leptin (a hormone that regulates fat storage and energy levels), are all driven by circadian rhythms to varying extents.
If these hormones are dysfunctional for too long, people can develop chronic inflammation leading to conditions like obesity, cardiovascular disease, neurodegenerative diseases, and even cancer.
On top of that, light’s precise color has a significant impact. Wavelengths resulting in blue light are beneficial during the day because they help with wakefulness, memory, cognition, and boosting mood. But at night, studies have found blue light exposure may slash melatonin levels (which are stimulated by nighttime red light), leading to late-night screen users not getting enough sleep.
Digging into the details — While the QD-LED technology does seem intriguing, Figueiro says, one important quality for human health is missing in the study’s equation: light intensity.
Artificial lights, Figueiro explains, can’t compete with the level of brightness we experience outside on a sunny day, which has a luminous intensity (or lux) of 50,000 to 100,000 compared to 300 to 500 lux indoors.
“Everybody talks about mimicking the spectrum of daylight — nothing will mimic or match the amount of light you get outdoors,” she says. “People get hung up on the spectrum because they can manipulate the spectrum and change it.” But unless you change the intensity of light in tandem, don’t expect any miraculous benefits.
In addition to the right color and intensity, the direction from which light hits our eyes also matters for circadian biology, says Constantin-Cosmin Ticleanu, a light researcher at the University College London’s Bartlett School of Environment, Energy and Resources.
“The ipRGCs in the retina are not equally distributed across the retina,” he explains to Inverse. “They are more concentrated in the lower part of the retina, which is not surprising because if you think about the natural conditions of light in the sky… [it’s typical] to look up horizontally in front of us.”
Studies have shown that light directed toward our eyes vertically, not horizontally, at about 250 lux is recommended during the daytime. Since the QD-LEDs are still a proof-of-concept, it’s hard to judge the directionality aspect just yet. Hopefully, that factor is incorporated into future lighting devices as the technology continues to evolve.
What’s next — “The ability to better reproduce daylight through its varying color spectrum dynamically in a single light is what we aimed for,” Gehan Amaratunga, a professor of engineering at Cambridge University who also co-led the research, said in a press release. “We achieved it in a new way through using quantum dots. This research opens the way for a wide variety of new human responsive lighting environments.”
QD-LEDs have a long way to go before they can fulfill that bright promise, but here’s to an illuminating first of many steps yet to come.