Researchers at the University of Navarra in Pamplona, Spain, and photonics innovation hub ACTPHAST 4R have developed an optical air sensor to detect volatile organic compounds (VOCs) in industrial settings in real time.
VOCs can be extremely dangerous to health, with some causing long-term respiratory ailments and even death, and are highly explosive. Current detectors use metal oxide electronic sensors, which show a change in electrical conductivity when exposed to VOCs, and must be heated above 150˚C, making them unsuitable for areas where electricity is unsafe. Results may need to be processed by a laboratory, and to now, no technology has been developed that can perform real-time, automatic checks in chemical or fuel tanks. When tanks are emptied, staff may have to enter them to ensure no trace of vapour or liquid remains, putting them at risk through inhaling the compounds, or through generating static and causing an explosion.
The new demonstration device, developed by a team led by Dr César Elosúa Aguado from Navarra’s Electrical, Electronic Engineering and Communications Department, uses optical fibres, and has no electrical or flammable components, avoiding many of the problems of conventional devices. It looks at the interaction between the cladding modes and the sensitive coating. Elosúa explains that the sensor surface is coated with zinc oxides, which react when VOCs are present. The system can then detect changes in the refractive index of the zinc oxide sensing material, rather than changes in electrical conductivity. Sensors can be tuned to react only to a specific substance, based on the molecular properties of the VOC.
‘Cladding modes are a part of the optical signal that is ‘forced’ to travel by a Bragg reflector, not through the core but around the cladding, enabling an interaction with the surrounding media,’ says Elosúa, adding: ‘The reaction mechanism between the metallic oxide and the VOC is a reversible redox chemical reaction. The selectivity of these materials is low, so they react to a wide range of solvents with different sensitivities. Therefore, sensors with different responses combine to form a specific pattern for each VOC. The sensor response will be used to train an artificial intelligence system capable of identifying the different VOC samples.’
Essential to the development of the technology was the innovation support from ACTPHAST 4R, which provided the cutting-edge photonics expertise necessary to develop and test it, and substantially funded the innovation work.
‘ACTPHAST 4R provided us with open access to expert coaching in the accelerated development and deployment of photonics, as well as hands-on training in the facilities of one of Europe’s top competence centres for our application and complementary business coaching on our future plans towards commercialisation of our technology,’ says Elosúa. ‘The application process via the ACTPHAST 4R website was quick and easy too. We would recommend working with ACTPHAST 4R to any researchers looking to innovate with photonics.’
The pre-prototype demonstrator requires further testing before being made commercially available through licensing or a university spinout company, but Elosúa says that it is a ‘major scientific breakthrough concept’.