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India riding the photonics innovation wave

Low-cost spectroscopy, mobile phone-based imaging and laser-processed paper sensors are all examples of how photonics could help tackle India’s healthcare and environmental monitoring challenges.

Oliver Graydon

doi:10.1038/nindia.2019.46 Published online 11 April 2019

© PHOTONICS 2018

Could photonics be the answer to India’s need for portable, cost-effective cancer screening, greenhouse gas monitoring and water management? The innovation and ingenuity on display at a recent photonics conference in Delhi suggests the answer could be yes, if appropriate funding and support can be put in place.

The statistics are shocking. According to the World Health Organization, 14 out of the top 20 most polluted cities are in India. While much of the rest of the world had been cutting back on greenhouse gas emissions, India’s global share of greenhouse gas emissions grew 4.7 per cent to reach 7 per cent in 2016.

Furthermore, rates of diabetes, cancer and tuberculosis are raging across the country with much of the population not having access to the medical system, with only half a doctor for every 10,000 people. In India, each year around 220,000 people die from tuberculosis with the disease estimated to have cost the Indian economy US$340 billion between 2006 and 2014. It is a tragedy compounded by the rise of the antibiotic-resistant variant of the disease.

Cervical cancer causes around 73,000 female deaths a year and oral cancer is prevalent in men that chew tobacco, smoke or drink alcohol excessively. These sad statistics indicate that there is an opportunity and urgent need for cheap, easy-to-use sensors to address the country’s healthcare and environmental needs. The more encouraging news is that researchers across India are rising to the task and busy developing a wide variety of optical sensors to do just that and many impressive examples were showcased at PHOTONICS 2018.

© PHOTONICS 2018

Taking place between 12–15 December 2018 at the Indian Institute of Technology Delhi (IIT Delhi), PHOTONICS 2018 was India’s 14th biennial international conference on fiber optics and photonics. Featuring almost 500 posters, 7 parallel sessions and about 130 talks and an estimated 1,000 attendees PHOTONICS 2018 is not a small conference and was well attended by researchers from all over India, especially those working at various Indian Institutes of Technology (IITs) of which there are around 30 located at major cities throughout India. Many of these IITs have photonics research activities, each specializing in different areas and collectively they act as a powerhouse for innovation.

During the conference, Asima Pradhan’s group at IIT Kanpur had several posters and talks describing their activities in using fluorescence imaging to detect early-stage cervical and oral cancer. The hope is that a cost-effective system that is portable, cheap and easy to use could be employed to help promote remote screening, especially in rural communities by providing a clear visual indicator of precancerous or cancerous tissue.

In particular, the team has developed a handheld device for oral use that captures RGB images of fluorescence from the tissue inside the mouth. Oral tissue naturally contains the fluorophores porphyrin, nicotinamide adenine dinucleotide (NADH) and flavin adenine dinucleotide (FAD) that emit light at different wavelengths in the visible spectrum — NADH and FAD emit around 440 nm (blue) and 550 nm (green) while porphyrin emits at longer wavelengths in the red and near-infrared. Their analysis suggests that an increased porphyrin to FAD ratio — seen as increased red and less green fluorescence in the images — can be used as a diagnostic indicator of cancer, as the concentration of porphyrin increases and FAD decreases as the disease progresses.

© PHOTONICS 2018

Dalip Singh Mehta at IIT Delhi leads a collaboration that is also working hard on the topic and has developed a portable, low-cost system for detecting breast cancer. The system consists of a handheld device that uses a ring of blue LEDs to excite green fluorescence at around 525 nm from the dye fluorescein, an optical filter for selectively filtering the fluorescent signal and a mobile phone to take an image of the tissue.

The system is being used during surgical operations by Anurag Srivastava, Head of the Department of Surgery at the All India Institute of Medical Sciences (AIIMS) in New Delhi. Srivastava says that it is invaluable for providing a highly visual indicator of the presence of breast cancer.

“We simply inject fluorescein near the nipple and then shine blue light from an LED and look for green fluorescence,” he explained. Srivastava explains that bright green fluorescence is indicative of cancer because the fluorescein collects in much greater quantities in highly vascularised tissue associated with cancer that is undergoing angiogenesis.

Mehta is now actively developing related systems that offer spectroscopic functionality to provide richer diagnostic information and also devices that support micro-endoscope light delivery/collection in order to provide easier, more convenient access to deeper tissue.

In the Optical Sensors and Metrology session, Tapanendu Kundu from IIT Bombay gave a talk entitled ‘Photonics sensors: applications to socially relevant issues’. The main focus of Kundu’s talk was on the research taking place at IIT Bombay to safeguard water. He and his co-workers are developing low-cost sensors for detecting contamination and pathogens in water and also sensors for monitoring the moisture content of soil to help farmers optimize their irrigation practices and thus save water by eliminating unnecessary over-watering of crops.

“Research shouldn’t be about just publishing a paper, we want to make an impact in a socially relevant issue,” Kundu told delegates. “We have to go from the lab to the land.”

The team has developed a variety of water-contamination sensors based on the absorption of the evanescent light field in functionalized optical fibres. The idea is that a section of an optical fibre is bent into a U-shape and its surface functionalized to bind a specific pathogen such as Escherichia coli, for example. When the U-shaped part of the fibre comes into contact with contaminated water, the binding on the surface of the fibre changes the absorption of the evanescent light field, allowing remote, optical detection of the pathogen.

The team has also developed a non-contact, diffuse reflectance spectroscopy system for monitoring the moisture content and nitrogen, phosphorus and potassium levels in soil, which are all vital for healthy crop growth. The system works by interpreting changes in the visible–near-infrared spectra of soil. It is self-powered by solar cells and a battery and is also Internet-enabled so that it can send results to an app on a remote user’s phone so that the farmer can optimize the watering and use of fertilizer. The team has now applied for a patent for the design and it is being commercialized. “India is facing the worst water crisis in a generation. Over 70 per cent of water used in irrigation is wasted in India,” commented Kundu. “Using our system over a period of 21 days, 4,000 litres of water was saved in strawberry fields.”

© PHOTONICS 2018

Turning from the land to the air, several posters at the conference described photonic-based systems for greenhouse gas monitoring, in particular CO2. Anirban Roy and co-workers from IIT Gandhinagar in Gujarat had a poster showing the design and results of a portable mid-infrared tunable diode laser spectroscopy system for measuring atmospheric CO2 levels. The team makes use of a quantum cascade laser operating at around 4 μm to interrogate the CO2 absorption at 4.139 μm. During field tests at the Mount Abu field station in Rajasthan the team measured background CO2 levels of between 365 and 419 ppm, while in the urban environments of Ahmedabad and Gandhinagar much higher levels of up to 740 ppm were measured. The team is now working to try to reduce the size and weight of the system, which is currently rack mounted.

In an unrelated study, Ramya Selvaraj and co-workers from IIT Madras described their work on CO2 gas sensing from the exhaust of vehicles using a supercontinuum laser and photoacoustic spectroscopy. “We want to show that a broadband, low-energy source in the near-infrared region can be used for photoacoustic spectroscopy,” explained Selvaraj. “In the future, we would like to have a fibre-coupled online monitoring system using near-infrared LEDs”.

A talk from Collin Sones from the University of Southampton, UK on the topic of laser-processed paper-based microfluidic sensors caused quite a stir at the conference. He described how laser-induced photopolymerization (commonly known as direct laser writing) can be used to write wall-like structures in paper treated with a liquid photopolymer. As a result, it’s possible to form microfluidic channels and microfluidic wells on a paper substrate by simply scanning a laser beam, resulting in paper ‘lab on a chip’ sensors for low-cost, point-of-care medical diagnostics. Sones says that the approach is attractive because it offers an easy route to create multiplexed sensors and could be ideal for testing for antibiotic resistance for diseases such as tuberculosis, which is a chronic problem in India.

“Point-of-care diagnostics need to be low cost, sensitive, specific, user-friendly and robust,” commented Sones. “Paper is an ideal platform as it’s biocompatible, low cost and disposable. It also has this beautiful property of capillary action for transporting liquids so doesn’t need an external fluid pump”. Sones says that a simple laser pointer with less than 1 mW output power is sufficient to write the patterned structures and that a writing speed of 1 m/s is possible, making the process amenable to mass production.

Be it fundamental science or more applied research, the message at PHOTONICS 2018 was clear. Photonics is alive and kicking in India and the level of ingenuity of the research is impressive. Going forward, the opportunity exists for photonics to bring life-changing transformations to healthcare and environmental sensing in the country, but for this to have maximum impact and realize its true potential greater support and funding will need to be put in place.

This article first appeared in Nature Photonics.