Recognizing that current wearable health monitors based on nonflexible components do not deliver the desired accuracy and can only monitor a limited number of vital signs, a team of researchers at The Institute of Photonic Sciences (ICFO; Barcelona, Spain) has demonstrated a class of flexible and transparent wearable devices that are conformable to the skin and can provide continuous and accurate measurements of multiple human vital signs. These devices can measure heart rate, respiration rate, and blood pulse oxygenation, as well as exposure to UV radiation from the sun. While the device measures the different parameters, the readout is visualized and stored on a mobile phone interface connected to the wearable via Bluetooth. In addition, the device can operate battery-free since it is charged wirelessly through the phone.
"It was very important for us to demonstrate the wide range of potential applications for our advanced light sensing technology through the creation of various prototypes, including the flexible and transparent bracelet, the health patch integrated on a mobile phone, and the UV monitoring patch for sun exposure," reports Dr. Emre Ozan Polat, first author of the paper that describes the work.The bracelet was fabricated in such a way that it adapts to the skin surface and provides continuous measurement during activity. The bracelet incorporates a flexible light sensor that can optically record the change in volume of blood vessels, due to the cardiac cycle, and then extract different vital signs such as heart rate, respiration rate, and blood pulse oxygenatiion.
The researchers also integrated a graphene health patch onto a mobile phone screen, which instantly measures and displays vital signs in real time when a user places one finger on the screen. The prototype device uses ambient light to operate, promoting low-power-consumption in these integrated wearables and allowing continuous monitoring of health markers over long periods of time.ICFO's advanced light sensing technology implements two types of nanomaterials: graphene, a highly flexible and transparent material made of one-atom thick layer of carbon atoms, together with a light-absorbing layer made of quantum dots. The demonstrated technology brings a new form factor and design freedom to the wearables' field, making graphene-quantum-dots-based devices a strong platform for product developers.
Finally, the researchers demonstrated a broad wavelength detection range with the technology, extending the functionality of the prototypes beyond the visible range. By using the same core technology, they have fabricated a flexible UV patch prototype capable of wirelessly transferring both power and data, and operating battery-free to sense the environmental UV index. The patch operates with a low power consumption and has a highly efficient UV detection system that can be attached to clothing or skin, and used for monitoring radiation intake from the sun, alerting the wearer of any possible overexposure.
Full details of the work appear in the journal Science Advances.