ICFO researchers design new health monitors that are flexible, transparent and based on graphene

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A flexible UV patch prototype capable of wirelessly transferring power and data and operating battery-free to sense the environmental UV-index, developed by a team of researchers at the ICFO

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A flexible and transparent device that can provide continuous and accurate measurements of multiple vital signs, developed by the ICFO

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A graphene patch that integrates onto the screen of a mobile phone and instantly measures and displays vital signs in real time when a user places a finger on the screen

Researchers at the Institute of Photonic Sciences (ICFO) have developed a new class of flexible, transparent and low-power wearables based on graphene to monitor multiple vital signs, such as heart rate, respiratory rate, blood pulse oxygenation and exposure to UV radiation. The study has been recently published in the Science Advances journal.

Oct 30, 2019

New technological devices are prioritising non-invasive tracking of vital signs not only for fitness monitoring, but also to prevent common health problems such as heart failure, hypertension and stress-related complications, among others. Wearable technology—wearables, to keep it short—based on optical detection mechanisms are proving an invaluable approach for reporting on our bodies inner workings and have experienced a large penetration into the consumer market. Current wearable technology, based on non-flexible components, does not deliver the desired accuracy and can only monitor a limited number of vital signs. To tackle this problem, conformable non-invasive optical-based sensors that can measure a broader set of vital signs are at the top of the end-users’ wish list.

In a recent study published in Science Advances, ICFO researchers—a research institute affiliated to the Universitat Politècnica de Catalunya · BarcelonaTech (UPC)—have proved the viability of a new class of flexible and transparent devices that are conformable to the skin and can provide continuous and accurate measurements of multiple vital signs, such as heart rate, respiratory rate, blood pulse oxygenation and exposure to UV radiation. While the device measures those parameters, the read-out is displayed and stored on a mobile phone connected to the device via Bluetooth. In addition, the device can operate battery-free since it is charged wirelessly through the telephone.

Wearables to monitor vital signs
It was very important for us to demonstrate the wide range of potential applications for our advanced light sensing technology by creating various prototypes, including the flexible and transparent bracelet, the health patch that can be integrated onto mobile phones and the UV monitoring patch for sun exposure. They have proved to be versatile and efficient due to these unique features”, explains the researcher Emre Ozan Polat, the first author of this publication.

The bracelet was manufactured to adapt to the skin surface and provide continuous measurements during activity. It incorporates a light sensor that records the change in volume of blood vessels due to the cardiac cycle and then extracts several vital signs such as heart rate, respiratory rate and blood pulse oxygenation.

The researchers have also developed a graphene patch that integrates onto the screen of mobile phones and instantly measures and displays vital signs in real time when a user places a finger on the screen. A unique feature of this prototype is that it uses ambient light to operate, thus promoting low-power consumption in these integrated wearables and allowing a continuous monitoring of health markers over long periods of time.

New technology based on graphene
ICFO’s advanced light sensing technology uses two types of nanomaterials: graphene, a highly flexible and transparent material made of one-atom thick layer of carbon atoms, and a light absorbing layer made of quantum dots. This technology brings new forms and design freedom to the wearables field, which makes it a powerful platform for product developers. The researcher Antonios Oikonomou, a business developer at the ICFO, emphasised the latter: “The booming wearables industry is eagerly looking to increase the fidelity and functionality of its products. Our graphene-based technology platform responds to this challenge with a unique proposition: a scalable, low-power system capable of measuring multiple parameters while allowing the integration of new form factors into products”.

Researcher Stijn Goossens, the co-supervisor of the study, added: “We have made a breakthrough by showing a flexible and wearable sensing system based on graphene light sensing components. The key was to pick the best of rigid and flexible materials. We used the unique benefits of flexible components for vital sign sensing and combined them with the high performance and miniaturisation of conventional rigid electronic components”.

Finally, the researchers were able to demonstrate a broad wavelength detection range with this technology, which extends the functionality of the prototypes beyond the visible range. Using the same core technology, they manufactured a flexible UV patch prototype capable of wirelessly transferring power and data and operating battery-free to sense the environmental UV-index. The patch features low power consumption and has a highly efficient UV detection system that can be attached to clothing or skin, and used to monitor radiation intake from the sun and alert the user of any possible overexposure.

We are excited about the prospects for this technology, which points to a scalable integration of graphene quantum dots into fully flexible circuits to enhance form, feel, durability and performance”, remarks the researcher Frank Koppens, the leader of the Quantum Nano-Optoelectronics group at the ICFO. “These results show that this flexible wearable platform is compatible with scalable manufacturing processes, which suggests that mass production of low-cost devices is within reach in the near future”, Koppens added.

This work was funded by the Cellex Foundation, the European Research Council’s Proof of Concept grant for the GRAPHEALTH project and the Graphene Flagship.