They can sense 'almost anything'

When you take a photo with a simple digital camera, the camera sets a few parameters depending on the amount of light in the environment.

But how does it get to know the ‘amount of light?’ Behind the scenes, there is a device that can ‘sense’ the intensity of light. Similarly, there are devices that can sense different things — temperature, pressure, motion etc.

It’s not an exaggeration to say that sensors are one of the most fundamental units of an increasingly connected world in which we thrive.

“If you have a fibre Bragg grating, you can sense almost anything,” says Sundarrajan Asokan, professor at the Department of Instrumentation and Applied Physics in Indian Institute of Science, Bengaluru.

In the last decade, his work on, what are called, the fibre Brag gratings has resulted in remarkably sensitive sensors for a wide variety of applications. When he says, “one can ‘sense almost anything’ with a fibre Bragg grating,” he means it.

The sensors created by him can measure your pulse pressure, can sense if an elephant is approaching or moving away, can reliably catch onto a specific biomolecule in blood, and can even detect if a tsunami is developing beneath the vast Indian Ocean.

Some of the sensors, specially developed for the Aeronautical Development Agency under the Development Initiative for Smart Aircraft Structure programme, can replace long electrical cables in the wings of the aircraft and can constantly monitor the structural health of the wings.

He, along with researchers from the Department of Civil Engineering, has developed sensors that monitor the structural integrity of bridges. Recently, his lab has also come up with sensors to detect harmful gases like carbon dioxide and nitrogen dioxide.

The fibre Bragg grating is the dark horse of Sundarrajan’s work. Called the FBG, in short, the fibre Bragg grating is a highly skilled makeover of an optical fibre that delivers high speed internet to our houses and offices.

The interesting property they exhibit is that they reflect one wavelength, like a mirror, and allow other wavelengths to pass through, like a piece of transparent glass. Optical fibres are mainly used in electronic communication, and Sundarrajan’s is one of the few labs in the country that study them for sensing purposes.

Sundarrajan has also successfully combined futuristic materials like graphene with the FBG to create ultrasensitive biosensors. He and his collaborator, Prof Ajay Sood, removed the outer layer of the optical fibre and put a single layer of reduced graphene oxide to form the ‘etched fibre Bragg grating’.

Using this configuration, the team developed a sensor to detect ‘C-reactive protein’, a protein which is produced in excess during infections. An above normal C-reactive protein level is a reliable biomarker for inflammations and cardiovascular diseases. Sundarrajan and Ajay are working to develop this technology into a full-fledged, yet handy, medical diagnostic kits.

Health applications
With more than six crore diabetics, India has the second highest number of people affected by diabetes. Looking at the current trend, the number may reach 10 crores by 2030. More alarmingly, more than 40 lakh Indians, aged between 20 and 79, are not even aware that they are diabetic.

One of the key interventions that can help manage this situation is the development of cheap, reliable and handy diagnostic tools.

Sundarrajan and Ajay have developed a highly sensitive sensor that can accurately measure glucose concentration in healthy blood. This tool, once fully developed, can potentially replace complex, time consuming chemical methods that are used in hospitals today.

Over a period of time, the sensors developed by Sundarrajan have the potential to take state of the art medical diagnostics to peoples’ doorsteps. If realised, this could be a transformation of the highest kind because poor villagers with no access to reliable medical facilities should travel all the way to the nearest town or city even for a simple blood test.

Not only are such trips expensive, but also force them to lose a day’s labour. Sundarrajan’s work has the potential to flip this situation around, and take world class diagnostics to individual households in villages.

With no dearth of ideas to sense different things, and a dedicated team of students, Sundarrajan’s lab is all set to play a fundamental role in the technological advancement of the country — a role that is akin to the role of a sensor in this hyper-connected world.

(The author is with Gubbi Labs, a Bengaluru-based research collective)