The Key highlights and achievements are here below summarized:
• Electronics hardware
Two electronic modules dedicated to SINTEC were realized and tested in the first trials, leading to further improvements in fixing bugs and in the optimization of the tools used to collect the data coming from the device. The first electronic module was within 10 mm diameter and hold low power intelligence and communication with PPG, 3 DOE accelerometer and temperature sensor. The second and final module had in addition sensing for bioimpedance and ECG, and logging of data. With the logging, the module was larger. In addition, changing firmware for the commercially available HI and SensorTile has broadened the capabilities of the SINTEC platform, since each hardware provides different sensor configurations.
• PCB-technology
A fabrication protocol was established for rigid-stretch PCB based sensor nodes with wireless electrophysiological readouts (ECG monitoring). The protocol consists of assembling components, digital patterning of liquid alloy circuitry, dielectric encapsulant and soft skin adhesive on a soft stretchable substrate. A novel implementation is the use of sports tapes in the form of skin adhesive patches ensuring the reliable adherence of reusable electronic modules to the skin even during intense sports performance. The PCB-technology was demonstrated on a large-scale A4 format. The KPI was met as manufacturing was made of an A4-sized stretchable foil with two-layers of conductors with line width of 0.1 mm, 0.2 mm via interconnects, and a pitch of 0.5 mm.
In the final review, printing with jet dispensing showed a ten times higher throughput than capillary printing.
• Comparison between Bluetooth and Fat-IBC
Fat-IBC technology in wearable sensor networks could offer channel signal losses of around 0.6-1.0 dB/cm, high data rates and support various modulation schemes. The wireless propagation is dependent on the body composition but also on the type of antenna. Our work shows that optimizing antennas in relation to the body tissues improves the system performance with respect to systems with antennas not considering that, such as, for instance, typical commercial Bluetooth antennas. These findings are consistent with previous works and could compete with the current State-of-the-Art, including, for instance, other body-centric wireless communication modalities not studied in the project, such as galvanic and capacitive coupling. For the evaluation, we developed advanced physical phantom models of the human torso as test platforms and studied the technologies on these platforms and human volunteer models. Our sequence of studies allowed us to validate epidermal Fat-IBC technology in the lab.
• Blood pressure retrieval algorithm
After establishing signal quality indices to evaluate the SINTEC electrophysiological signals, assessing the best signal processing techniques and the best sensor positioning on the body, a protocol was established to record ECG and PPG signals useful for continuous BP monitoring. The developed algorithm extracts HR and PTT features from the ECG and PPG. These features are then used to calibrate the algorithm through machine learning techniques using values recorded with a reference device.
• IoT gateway and platform
An IoT platform was deployed to facilitate the storage and representation of the signals generated by the sensors. For this purpose, a wireless gateway was created to receive, in a star configuration, the streaming data from the sensors. The gateway forwards the data to a FIWARE-based IoT platform that stores the data in HLT7/FHIR format. The platform is compatible with any client capable of reading FHIR entities through the FHIR API. The project has also developed a responsive front-end for sensor data management.
