Thiru Kanagasabapathi and Ashok Sridhar from TNO@Holst Centre showcase their new wearable health patch for Io(M)T applications in the OPE Journal of May 2021.
Digital health technologies are changing the way healthcare is delivered, shifting the focus away from treating patients towards ensuring the well-being of a person, and in taking preventive measures for vulnerable groups of people. Patient care is transitioning to de-centralised care settings with real-time monitoring. This helps healthcare practitioners to deliver care outside of the traditional hospital environment. This has a positive impact on the patient's experience and well-being, resulting in greater human-centricity in healthcare. Wearable devices play a key role in facilitating this transition in care delivery, and this is expected to gain momentum with increasing access to 5G technology.
Wearable health patches for human-centric healthcare
Wearable devices for health applications come in various shapes and sizes. Wrist-worn devices, smart clothing, health patch devices and EEG headsets are some examples. Of these, wearable health patches are probably the most versatile, offering the possibility to include a variety of sensors for collecting multiple electrophysiological and optical signals. Apart from sensors, a typical wearable health patch consists of an energy source and a data processing module with storage and (wireless) communication capabilities. The readout electronics are reusable and the battery is rechargeable. The rest of the patch needs to be replaced typically after a week's use.
Parameters that can be measured by wearable health patches include, but are not limited to, heart rate, heart rate variation (HRV), respiration rate, respiration depth, temperature, oxygen saturation and blood pressure. With the advancement of sensing technologies and miniaturisation of sensors, even more parameters can be measured, giving a holistic picture of the wearer's physiological status. For instance, biochemical sensors that can analyse sweat, saliva, blood, tears, etc., can be used to probe biomarkers, thereby giving the health care practitioner a detailed insight into a person's health.
Key challenges in wearable health patch development
There are certain key challenges that need to be addressed while developing a wearable health patch device. To start with, there is no 'one-type-fits-all' wearable device that can fulfil the application needs of different target groups. A wide range of factors influence the configuration, applicability and the accuracy of a health patch. The interaction between the different layers of a wearable health patch is key in delivering an optimised device suitable for real world applications. It is critically important to select suitable materials. Skin contact layers of the patch such as the electrodes for good quality signal acquisition, adhesives to ensure long-term reliable adhesion and the substrates that can provide sufficient stretchability, conformability and breathability, are crucial elements of the patch, both individually, and in combination with other layers. This complex interaction requires innovative materials, the selection of which requires specialised knowledge of printed electronics. Traditional electronics can yield flexible circuitry (e.g., polyimide-copper flex PCB), but not stretchable circuitry, especially for a multi-layered circuit structure. In the case of a health patch device worn across, e.g., the chest, it is essential that the device is stretchable. Printed electronics offers the possibility to additively print the circuit structures using special stretchable inks or pastes on stretchable substrates, resulting in a device that can expand by 20% or more, over hundreds of thousands of cycles.
Shaping the next generation of wearable health patch devices
TNO@Holst Centre specialises in developing electronic devices that are flexible, stretchable, wearable, washable and conformable. A key development is the "wearable health patch platform", which was developed together with 2M Engineering from Valkenswaard in the Netherlands. This platform addresses some of the key challenges highlighted in the previous section, and offers the possibility to customise the health patch device based on the application needs.
As an independent R&D innovation centre, TNO@Holst Centre aims to support companies that want to develop and commercialise wearable devices for IoMT applications, based on its wearable health patch platform. To this end, TNO@Holst Centre is performing clinical trials to validate the health patch platform for different use cases including COPD, IBD and sleep monitoring. This will help both companies that might want to co-develop a wearable health patch with TNO@Holst Centre by considerably shortening the development and validation process, as well as hospitals and pharmaceutical companies that might want to use this health patch platform for their own clinical studies.