Periodic Reporting for period 3 - SINTEC (Soft intelligence epidermal communication platform)
Reporting period: 2022-07-01 to 2023-06-30
SINTEC's aim is to provide a novel stretchable rigid-stretch PCB technology with stretchable substrate and liquid alloy, and its application in smart wireless patches for sport performance and clinical physiology and in a novel intra-body communication technology (Fat-IBC). The technology is based on digital printing, with the aim to provide personalized patches at a low premium and with a lower environmental footprint than State of the Art.
The project addresses four main objectives:
1. To demonstrate manufacturing of large area rigid-stretch PCB technology stretchable substrate and liquid alloy interconnects
2. To demonstrate and compare the advantages of compliant and stretchable multi-use smart patches for Fat-IBC and low-energy Bluetooth communication
3. To demonstrate the advantages of compliant and stretchable multi-use smart patches for electrophysiological sensing
4. To validate the large area rigid-stretch PCB integration technology in laboratory
The project addresses four main objectives:
1. To demonstrate manufacturing of large area rigid-stretch PCB technology stretchable substrate and liquid alloy interconnects
2. To demonstrate and compare the advantages of compliant and stretchable multi-use smart patches for Fat-IBC and low-energy Bluetooth communication
3. To demonstrate the advantages of compliant and stretchable multi-use smart patches for electrophysiological sensing
4. To validate the large area rigid-stretch PCB integration technology in laboratory
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.
• 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.
The progress beyond State of the Art (SoA) are here below summarized:
• Electronics hardware
In comparison with SoA, the sensor boards are very small and low power.
• PCB-technology
Compared to commercial SoA screen-printing of stretchable smart patches, the digital printing and hybrid integration of components of stretchable PCB and smart patches is novel and provides lower energy, materials and waste footprint in production. Compared to the production of commercial smart patches made by rigid multiuse modules and flexible disposables, life cycle analysis showed:
• 30% reduction of CO2 emissions due to decreased use of rigid printed circuit boards
• 30% energy savings due to decreased use of pressurized air and reflow ovens
• 15% reduction of production costs due to decreased use of printed circuit boards and the more efficient use of materials
• 30% increase of recyclability due to increased modularity and increased use of design for reusability and recyclability
• Comparison between Bluetooth and Fat-IBC
Compared to SoA, the phantoms are novel and much more precise for measuring inductive body communication. The skin-based 2.4 GHz bandwidth (the same as for BlueTooth) Fat-IBC provide much better signal strength than ordinary RF antennas on the body at the same transceiver power, e.g. with the RF BLE having –100 dB, the Fat-IBC will be at least 20 dB higher signal strength, with athletic bodies having typically –5dB lower signal strength than obese.
• Blood pressure retrieval algorithm
Compared to SoA, the AI algorithms show better results for signals acquired with SINTEC devices with its AI algorithm compared to Shimmer, with 3.29 and 5.32 for MAE, respectively. Subject-specific coefficients are obtained, which are used for continuous BP monitoring with an accuracy that complies with ANSI/AAMI/ISO 81060-2:2018, Universal Standard for the Validation of Blood Pressure Measuring Devices.
IoT gateway and platformAn 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.
• Electronics hardware
In comparison with SoA, the sensor boards are very small and low power.
• PCB-technology
Compared to commercial SoA screen-printing of stretchable smart patches, the digital printing and hybrid integration of components of stretchable PCB and smart patches is novel and provides lower energy, materials and waste footprint in production. Compared to the production of commercial smart patches made by rigid multiuse modules and flexible disposables, life cycle analysis showed:
• 30% reduction of CO2 emissions due to decreased use of rigid printed circuit boards
• 30% energy savings due to decreased use of pressurized air and reflow ovens
• 15% reduction of production costs due to decreased use of printed circuit boards and the more efficient use of materials
• 30% increase of recyclability due to increased modularity and increased use of design for reusability and recyclability
• Comparison between Bluetooth and Fat-IBC
Compared to SoA, the phantoms are novel and much more precise for measuring inductive body communication. The skin-based 2.4 GHz bandwidth (the same as for BlueTooth) Fat-IBC provide much better signal strength than ordinary RF antennas on the body at the same transceiver power, e.g. with the RF BLE having –100 dB, the Fat-IBC will be at least 20 dB higher signal strength, with athletic bodies having typically –5dB lower signal strength than obese.
• Blood pressure retrieval algorithm
Compared to SoA, the AI algorithms show better results for signals acquired with SINTEC devices with its AI algorithm compared to Shimmer, with 3.29 and 5.32 for MAE, respectively. Subject-specific coefficients are obtained, which are used for continuous BP monitoring with an accuracy that complies with ANSI/AAMI/ISO 81060-2:2018, Universal Standard for the Validation of Blood Pressure Measuring Devices.
IoT gateway and platformAn 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.