How photonics is dramatically changing the medical world

The medical field is on the verge of a revolution, all thanks to... light. Medical devices will soon become so small and inexpensive that they will become part of everyday equipment. The driving force behind this technological revolution is photonics. ‘It is the fastest growing ‘‘enabling” technology we know’, says Roel Baets, head of the Photonics Research Group.

Suppose you have diabetes. Together with some 500,000 other Flemish people, you suffer from this lifelong incurable disease. It is one that, with good monitoring, will not have a significant impact on your quality of life. However, this monitoring requires a certain amount of effort, as you need to keep a constant eye on your blood sugar levels. Today, this is done through a small finger prick, sometimes up to four times a day.

This got professor Roel Baets and his team thinking. For years, they have been working together on one simple question: ‘How could you monitor blood sugar levels without needing to constantly prick your finger?’. The answer is through light. ‘We have developed a small device that can be implanted under the skin for a period of one to two years which measures blood glucose levels every five minutes based on light absorption. Glucose absorbs more or less light depending on its wavelength. By radiating light through the blood or through tissue, it is possible to detect glucose’. This technological discovery is a world first and a medical application of photonics. Spin-off company Indigo Diabetes is now pushing ahead with this idea.

What is photonics?

Photonics refers to the term photon, meaning light particle. It is a collective term for the study of light and the broad range of possible techniques and applications that make use of it.

Everyday and possible future applications of photonics include the fibre-optic cables you use to surf the internet, the solar panels on your roof, the little clip that is slid over your finger to measure your blood oxygen saturation levels in hospital, the latest LED spots in your home, automated car driving systems and laser eye surgery procedures.

The technology is still quite nascent, with most major photonics innovations dating back to the last 25 years. However, in this quarter of a century, things have been developing at a fast pace. The big boxes used for watching television have not long disappeared from our living rooms. Now we are able to watch series ‘on demand’ from anywhere in the world via our smartphone.

Ghent University at the forefront

Photonics is both big science and big business. At Ghent University, this is very much the case. ‘In the past, top researchers had to go to the United States to stay at the forefront of photonics research. Now, our alumni are finding exciting roles within Ghent itself. This is great to see’, says Roel. ‘The Tech Lane Ghent Science Park campus in Zwijnaarde has become a real hub, where researchers from all disciplines connected to photonics and entrepreneurs are able to interact with one another. Innovative, international companies are even opening offices next to the campus to attract researchers to work for them.’

Ghent University has therefore become one of the world leaders in the field of photonics. This is primarily due to silicon, a semiconductor that is mainly used in electronics, for example to produce the chips inside your laptop or smartphone. Over the last 60 years, these chips have become increasingly small, faster and cheaper as they are produced on such a large scale.

It is therefore not difficult to see why the Ghent University team saw an opportunity in this area. ‘We were among the first in Europe to explore the idea of using silicon in photonics. At first, that seemed like an exotic idea, perhaps even somewhat ‘academic’. However, today, silicon-based photonics is a burgeoning sector’. Just as chips are used in electronics to transmit electrical signals, silicon photonics uses chips to transmit light or optical signals. Not only is this faster, but, with light, you can also send a lot more data, all while consuming less energy.

The bottom line is that using silicon together with photonics allows us to design the devices built around it as very small, efficient and cheap to produce.

Not just for the chosen few

Roel's research group deliberately strives for applications that are affordable for the general public, especially within the medical field. ‘We could focus our efforts on the expensive devices found in hospitals, such as MRI and CT scanners. Although these are very valuable, we want to create devices for everyone, not just for the “chosen few.”

‘Given that these chips can be produced on such a large scale, their price can be reduced significantly. In the past, a device might have cost a thousand, ten thousand or even a hundred thousand euro to produce. Nowadays, devices for home use can be produced for just a few euro.’

Roel uses the example of CO2 meters. He explains that ‘such devices rely on light, as CO2 itself absorbs light of specific wavelengths. To measure the concentration of CO2 in the air, the device emits light. By measuring the degree to which that light signal is weakened, we can calculate how much CO2 is present. Such devices previously cost hundreds of euro. Today, they are available for just under fifty.'

Detecting heart disease

If it were up to Roel, you would soon not only be able to measure CO2 levels at home, but you would also be able to examine your own heart condition. ‘Doctors told me that, in addition to blood pressure, you need one other indicator to assess people's cardiovascular health. Pulse wave velocity, the speed at which a wave of blood pressure travels through the arteries following every heartbeat, for instance, provides very useful additional information.’

Based on this indicator, it is possible to measure the aortic wall’s level of stiffness, which in turn provides an indication as to a person's overall cardiovascular health. ‘In young and healthy individuals, this velocity is usually about five metres per second. This means that the artery wall is very elastic and therefore not hardened. However, as people get older or become affected by certain diseases, the arterial wall tends to stiffen, forming a rigid tube. In such cases, the waves travel at a much higher velocity, up to between ten and fifteen metres per second. If the speed is higher than average for a person’s age and condition, it may be indicative of a particular health problem.’

Currently, there is no device that can measure pulse wave velocity in a straightforward manner. ‘This is what we are currently trying to create’, says Roel. ‘To date, together with experts at the Biomedical Engineering department of Ghent University, we have been able to develop a prototype using silicon photonics. A preliminary clinical study showed that there is still work to be done, so we are not yet ready to bring the device to the market. That being said, we are certainly on the right track.’

The ultimate goal? ‘To develop a small and handy device, which we hope to make as cheap as possible, meaning that not only would the university hospitals of this world be able to acquire one, but also general practitioners and perhaps, in time, even the average citizen. That is the only way to speed up the detection of heart disease.’

Endless possibilities

Photonics research has significant potential when it comes to practical applications. For example, research into diabetes monitoring has led to the establishment of spin-off Indigo Diabetes. This Ghent-based company managed to raise 38 million euro over the last year and hopes to bring a working sensor to the market by 2023.

Besides Indigo Diabetes, eight other spin-off companies working with photonics have been established at Ghent University over the past 15 years. These go beyond medical applications. ‘For example, we have one spin-off that monitors infrastructure reliability, including wind turbines or the stability of bridges. Before being able to visually detect large cracks, we are able to use photonics to detect whether something is going wrong at an early stage’. Once again, although the technology has been around for many years, the spin-off's researchers are developing smaller and cheaper devices than those currently on the market.

The possibilities are endless. ‘Although the future is difficult to predict, we are certain photonics is one of the fastest growing “enabling technologies” around’. According to Roel, ‘photonic chips are much more diverse than their electronic counterparts. With electronics, it is all about transistors, which serve to either switch or amplify signals. However, this is as far as that technology goes. Although a lot can be done with electronics, it is fairly limited compared to the optical field, where it is possible to produce a whole range of colours, features, materials and therefore applications. Today, almost everything around you has something to do with photonics. In the future, this is only set to increase.’

 Roel Baets Roel is a full professor at the Faculty of Engineering and Architecture. His favourite spot is the Belvedere at the Boekentoren. ‘During my PhD, we took a powerful two-metre-long green laser up there and drew shapes on the clouds at night. It was winter and then it started to snow. It was magical and spectacular.’