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Overview from TED

It's an increasingly common sight in hospitals around the world: a nurse measures our height, weight, blood pressure, and attaches a glowing plastic clip to our finger. Suddenly, a digital screen reads out the oxygen level in our bloodstream. How did that happen?

Sajan Saini shows how pairing light with integrated photonics is leading to new medical technologies and less invasive diagnostic tools.

"Future labs-on-a-chip may easily, rapidly, and non-invasively detect a host of illnesses."

White Brick Wall
Sajan Saini


TED-Ed Original lessons feature the words and ideas of educators brought to life by professional animators.



If, like me, you were left utterly flabbergasted by President Trump’s light-bulb moment – a stony-faced suggestion to ingest household bleach to cure Coronavirus – then you may appreciate details of some genuine scientific innovation.

In June 2019, Sajan Saini – a former lecturer at Princeton University and current Education Director at AIM Photonics Academy, MIT - released a TED-Ed lesson entitled “How light technology is changing medicine.” And, unlike Trump, he knows what he’s talking about!

Whilst a lot of TED content centres around real-life presentations – with a speaker, an audience and some snazzy slides - this lesson utilises a series of short animations to convey key points... much like my own iluli videos!

I’m clearly a fan of this style of content, and for good reason. If a picture is worth a thousand words, then a video must be worth a great deal more! Animations offer an engaging way of breaking down oft-complex topics into easily digestible pieces. Topics that may at first have felt daunting, instead become understandable and accessible to all. This is one such topic.

Saini’s lesson begins with a current example of light being used in medicine:

"It’s an increasingly common sight in hospitals around the world: a nurse measures our height, weight, blood pressure, and attaches a glowing plastic clip to our finger. Suddenly, a digital screen reads out the oxygen level in our bloodstream. How did that happen? How can a plastic clip learn something about our blood… without a blood sample?"

Thankfully, it’s been a long time since I’ve paid a visit to a hospital. In fact, the last doctor I encountered was played by Jodie Whittaker(!) I am therefore yet to experience the above-mentioned “glowing” finger clip, but I’m wholly intrigued nonetheless. What does it do? How does it work? We’re about to find out…


For starters, it’s called a Pulse Oximeter – a non-invasive, electronic device designed to measure the saturation of oxygen carried in red blood cells.  Using a tiny red LED light on one side of the finger clip and a light detector on the other, it measures the ratio of oxygenated vs oxygen-free haemoglobin molecules (what your lungs transfer oxygen to when you inhale). Oxygen-free haemoglobin absorbs more red light than its oxygenated counterpart, impacting the amount of light that makes it through to the other side.

But light technology isn’t restricted to LEDs.

In December 2013, the UN General Assembly 68th Session proclaimed 2015 as the International Year of Light and Light-based Technologies (IYL). According to the IYL website:

"With the invention of the laser just over 50 years ago, the role of light in medical procedures has grown immensely. Lasers are especially crucial in dermatology (skin), ophthalmology (eyes), and dentistry due to their precision and high power density.

"More recently, light applications - specifically lasers - have been used in medical diagnosis due to their non-invasive properties. Routine diagnostics such as tissue oxygenation, early detection of tumours by fluorescence, and early detection of dental cavities are all performed by laser-based medical apparatus."

Clearly lasers play a big part too, but light has been making waves in the medical sector a long time before their invention. Way back in 1903, Danish physician – and founder of modern phototherapy - Niels Ryberg Finsen, won the Nobel Prize in Medicine for the application of light in the treatment of skin diseases. 

According to Britannica:

"In 1893 Finsen found that lengthy exposure of smallpox sufferers to the red light formed by exclusion of the violet end of the spectrum prevents the suppuration of the pustules, or formation of characteristic pockmarks. Aware of the bacteria-destroying effects of sunlight, he developed an ultraviolet treatment for lupus vulgaris, a form of skin tuberculosis, which met with great success."

Finsen’s Medical Light Institute was founded in Copenhagen in 1896.

A letter to the editor of The Journal of the American Medical Association (dated 30th December, 1901) offers an incredible insight into how light therapy was employed at the turn of the 20th century.

Entitled “A Visit to Finsen’s Institute” the author A. K. Warner, M.D. relates:

"In the ampitheater, which consists of one large square room, you are at once enveloped in an intense red glare coming from the electric globes. There are six 22,000 candle power arc-lights, shaded with red paper. They remind you very much of piano lamps. About each lamp six patients recline, each upon an elevated couch, with a nurse standing by his or her side.

"The light is so glaring that both patients and nurses have to wear dark glasses. Each patient requires a separate nurse, for it is necessary to hold continually a disc firmly pressed against the face, through which the light is projected."

He continues:

"The tubes that direct the light upon the affected surface look very much like telescopes. There is one tube for each patient. The purpose of the telescopic arrangement is that all the heat rays shall be eliminated, and only the chemical, consisting of blue, violet and ultra-violet, allowed to pass on. For it appears they alone possess the bactericidal power. The exclusion of the yellow and red rays is effected by an ingenious combination of lenses together with the assistance of water. The treatment consumes one hour.

"…The power to furnish the arc-lights is in the basement immediately beneath the operating room. It was necessary to have their own plant in order to generate the extreme amount of electricity required."

Wow. I thought the “future” of medicine was a fascinating subject. Little did I realise that the accounts of yesteryear could be just as engrossing.

The “one nurse per patient” policy is particularly eye-opening. It’s truly saddening that - after years of austerity in the UK -  dedicated one-to-one care just doesn’t exist anymore. Not unless you’re seriously wealthy, anyway…


Back in the present day and Saini’s Ted-Ed lesson is teaching me a thing or two about 21st century treatments:

"Today, an emerging medical sensor industry is exploring all-new degrees of precision chemical fingerprinting, using tiny light-manipulating devices no larger than a tenth of a millimeter. This microscopic technology, called integrated photonics, is made from wires of silicon that guide light— like water in a pipe— to redirect, reshape, even temporarily trap it."

One such silicon wire – circular in shape - forms a ring resonator device. Traditionally used in fibre optic communication networks, ring resonators are designed to efficiently route different wavelengths of light. According to Saini:

"Someday this kind of data traffic routing may be adapted for miniature chemical fingerprinting labs, on chips the size of a penny. These future labs-on-a-chip may easily, rapidly, and non-invasively detect a host of illnesses, by analysing human saliva or sweat in a doctor’s office or the convenience of our homes."

The proposed labs-on-a-chip could detect illnesses ranging from cancer to infectious diseases by measuring wavelengths, aided by a tiny on-chip computer library of different chemical fingerprints. Sounds complicated, doesn’t it? But the results could be incredible!

For more than a century, scientists have endeavoured to repurpose light to carry and extract information – with varying degrees of success. Given time, exciting breakthroughs such as labs-on-a-chip could radically transform medicine as we know it. But, thankfully, not in the way President Trump envisages…

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