Yes, we agree with that and try our best in the BEWELL project to achieve this. But the challenges are quite significant to transform a powerful, conventional electronics stack into “stretchy electronics”.
The LOPEC conference for printed electronics featured our presence during the business conference part, in which we will present “Opportunities and challenges of printed electronics” from the perspective of a jewelry manufacturer.
“Even Austrian jewelry manufacturer Swarovski adds functionality to their crystals through printed electronics.” During the presentation we will showcase how we do this for wearable electronics in the Horizon project “BEWELL”.
An early technology demonstration was shown in the Prinse 20 seminar end of January at VTT in Oulu Finland. There the Imec Museic evaluation board was connected with printed electrodes in the targeted patch form factor to measure ECG in wrist. The result is shown in Figure 1.
Figure 1: ECG sensing demonstration using printed electrodes and the Imec Museic evaluation board.
The next version of technology demonstrations for skin patches will utilize several functional layers integrated as a vertical stack structure as schematically illustrated in Figure 2.
Figure 2: Skin patch layer structure under development.
Printing multi-layered electronics on stretchable or flexible substrates needs a solution to fabricate electrically conducting vias from one layer to another through the substrates. VTT has developed a reliable via printing process on stretchable TPU substrate. Scientific manuscript is under preparation.
In order to create fully independent product without need for any external charger and external connectors, the battery is connected with a state-of-the-art perovskite module which has enough output voltage for charging the battery outside and also at indoor light conditions. The perovskite module is built onto flexible PET substrate and has round shape in order to be compatible for integrated with all other elements of the final product. In picture below, the processing steps, top and cross-section views and electrical performance are demonstrated of flexible PSC module created for BEWELL project at IMEC.
LIB were developed based on the BASMATI layout FP7, Contract No. 646159.
LIB Test cell in BASMASTI format
The big advantage of the research in BEWELL is a new quasi solid electrolyte, based on the PEO/LiTFSI system. This electrolyte warranties high mechanical stability and good cycle-ability. The EIS diagram of the cell is shown below
EIS diagram of the printed LIB cell
Also, a good cycle-ability could be shown.
Cycling diagram of the LIB test cell
This result is very encouraging. In the course of the project the electrolyte will be improved in terms of internal resistance and printability.
Generation 0 was used to measure electrocardiogram (ECG) signal and compared to standard lab equipment. Following a period of rest, the heart rate was raised through exercise on a stationary bike and once again brought to rest.
These are promising results which will be further improved in next generation designs where the electrode spacing is increased and the electrode configuration is optimized.
Skin patch for monitoring emotional stress to control its negative effects on well-being and skin condition.
Physiological parameters continuously tracked by the skin patch to derive stress and wellbeing:
Electro-cardiogram (ECG): Cardiovascular activity, indicator for stress and body exertion
Electro-dermal activity (EDA): Sweat-gland activity, main indicator for stress
Acceleration sensor: Activity level/sleep
Other biosignals: e.g. temperature
Printed secondary battery
Flexible haptics module
Two-part design: Durable and removable part enabled by special adhesives
Prototype of the Functional Decorative Layer for the Swarovski Wellbeing Patch
Energy harvesting has been shown and validated under real light conditions at Swarovski (see sun exposure in the picture above)
The Smart Patch can interact with users through a Functional Crystal interface, which allows to display defined symbols by color change through the underlying LED matrix printed on a flexible PET substrate.
For the POLAR use case a design was defined, consisting of different modules in a bracelet which are connected and work together as a monitor. Beside different modules the outer sides show Solar Cells (SC) and a display (MLCD) while the inner sides show Haptic elements (HAP1/2) for communication by vibration and PPG measurement interfaces (OHR). All electronics (including MCU, memory, RF transceiver and battery) are assembled on Flexible Printed Circuit. Other technologies are possible to use also like printed electronics or textile wires for interconnections.
A smart wrist-band demonstrator has been implemented. Figure 1 shows the demonstrator structure. The demonstrator has two locations for PPG hear rate measurement and acceleration sensing. Figure 2 shows the manufactured demonstrator in hand and a mobile app to collect data. Figure 3 shows an FFT spectrogram of one channel of the PPG data. The heart rate signal can be detected among the motion artefacts.