Lys is the light sensor your circadian rhythm will thank you for wearing

We speak to Christina Blach Petersen about her bright light mission
Lys light sensor could shape your sleep

For the past 24 hours, I've been obsessed with how much light I'm getting. No coincidence that this is how much time has passed since I talked to Christina Blach Petersen, the Imperial College London graduate who wants us to rethink our entire relationship with light via Lys, her clip-on wearable sensor.

Lys – the Danish word for light – measures the intensity and spectral composition of the light we receive, as well as the timing and duration, and works best when worn close to the eyes, ideally on collars or necklaces.

Until now, this has been the job of photoreceptors in our eyes. The difference is that humans have no biological feedback mechanism. Our eyes send signals to the brain to regulate our internal environment but, unaware of the effects, we spend more and more of our waking hours hidden from the sun's energy.

"In the cafeteria downstairs [at Imperial], I found out it's 65 lux but outside on a cloudy day right now, it's probably 10,000 lux," Petersen tells me. I look down at the Lys iPhone app and it tells me it's only 39 lux where we're sitting in the foyer. "We are made to be in sync with nature's changing rhythm of intensity and colour throughout the day. But then we created these caves, these environments we live in and they have static light. In modern urban societies, we actually spend more time indoors than the real cave people did!"

Looking at light is more than simply another quantified self measurement – with Apple's Night Shift mode on the iPhone and software like f.lux for laptops, it's clear the industry is waking up to the effects of gadgets and their displays on our health.

The biggest impact could be on sleep. Petersen has built the app with a bright light goal, based on research from chronobiology professors such as Russell Foster. The aim is to get 30 minutes of light at 2,500 lux at the beginning of the day or as soon as possible. The second priority is to encourage people to quit any blue light, which reduces the production of the natural sleeping pill melatonin, in the two to three hours before bed.

In simple terms, these two lifestyle changes can help to regulate your circadian rhythm – the roughly 24 hour cycle we all have in our physiology – and lead to better sleep at night and more energy during the day.

Lys is the light sensor your circadian rhythm will thank you for wearing

I'm super excited about it becoming part of your skin

The benefits go much further than the obvious jetlag applications, though. Petersen cites studies that show people who regularly go for walks in daylight are healthier than those who work out in indoor gyms. Getting more bright light from the sun earlier could prevent us reaching for coffee or sugar, potentially preventing weight gain, and dealing with the problems caused by screens and reduced natural light could even help reduce the risk of cancer.

"When I first started to look at this concept, it was for a two week project with Intel during my Innovation Design Engineering course at Imperial and RCA," explained Petersen. "I made these wearable filters of LCD screens that I hacked; they could change colour throughout the day. It was mostly aimed at nurses working night shifts because some studies show they have 50% higher incidence of breast cancer according to their decreased melatonin production during the night."

Petersen is on the verge of sending 150 Lys prototypes out to testers for feedback and she aims to launch the product for around £99 in autumn 2017. She won't give me any details of the final design but stresses that the current unit is the quickest thing her small team of three (plus advisors and collaborators) could build.

Those collaborators include a psychology student at Surrey University, who will use the data to investigate the relationship between how much light we receive and our wellbeing.

Petersen has also talked to investment banks over concerns for the health of traders who spend all day at their desk then get the tube home, as well as a mental health home in Copenhagen that wants to combine her sensor with special circadian rhythm lights.


As for the future, the designer-entrepreneur predicts that within "a few years" we will see smart lights in homes and offices which react to our light needs based on our circadian rhythms and overall health. The Lys app will be able to show your rhythm next to nature's rhythm over the course of the year – particularly useful for anyone suffering from SAD in the winter. Circadian rhythm lights producing, for instance, warm, orange shades in bathrooms, have even been shown to lower the confusion levels of Alzheimer's patients in hospitals.

At this stage, Petersen is open to her technology being sold as an indie wearable or being used in existing accessories or smart clothing. "I'm super excited about it becoming part of your skin, things that aren't that visible, tech tattoos are so cool," she said. "Or in clothes, something you wear everyday. We have to start in a place like this. Fitbit's designs are not very new now, the next step will be really exciting."

What do you think?

Connect with Facebook, Twitter, or just enter your email to sign in and comment.