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Smart and Flexible Energy Supply Platform for Wearable Electronics

Periodic Reporting for period 2 - Smart2Go (Smart and Flexible Energy Supply Platform for Wearable Electronics)

Reporting period: 2020-10-01 to 2022-06-30

The widespread introduction of wearable devices is expected to be one of the major trends in the next one or two decades. Therefore, making devices thinner, safer, more flexible and easy to integrate are major goals of current development activities. Presently various obstacles still hinder the expected rapid development. The energy supply to wearable devices is probably the most serious challenge among these technological bottlenecks.
The Smart2Go project tackles exactly this topic. The aim of the Smart2Go project is the creation of an autonomous energy-supply platform. Based on the results of the project, it will be possible to use a wearable device without caring about recharging over its entire lifetime. This aim will be achieved by the combination of a powerful, thin and scalable battery with appropriate energy harvesting technologies. Each unit will be capable for a storage capacity of up to 110 mWh (10 cm² area). All the performances will be retained after bending. The project will also develop ultrathin and lightweight films that will provide protection against environmental and mechanical impacts, handling and radiation. A roll-to-roll manufacturing approach for the integration of all the components into the Smart2Go energy supply platform will ensure suitable production capacity with low manufacturing costs. All these parameters had been fixed as overall objectives. They were the basis for all particular aims in the work packages and deliverables.
The performance of the Smart2Go energy supply platform was demonstrated in two application cases: (1) sports equipment integrating Smart2Go platform and pressure sensitive array and (2) safety garment integrating Smart2Go platform and lighting technologies (OLEDs).
All technical solutions had been developed in the first phase of the project. Various improvements and innovations had to be settled in order to achieve this.
Several highlights can be found in the material development. A flexible and robust embedding approach has been developed. Extensive test cycles had been performed at various partner sites under the coordination of TRELIC.
In terms of the energy storage, single layer pouch prototype cells were developed. They have a nominal capacity of 60mAh. The cells showed in an excellent cycling behaviour. After 500 cycles a capacity retention of 83% was measured. The prototypes will be basis the key components of the Smart2Go energy supply platform. The work was done using semi-industrial equipment, thus ensuring a smooth way towards an effective manufacturing process and consequently the low cost level.
The batteries can be supported by supercapacitors of 5 mF capacitance. They had been developed and adapted to the platform by the University of Tampere.
The outstanding element of the platform is the integrated energy management system. The Smart2Go partners developed under the leadership of the Technical Research Centre of Finland (VTT) a standalone fully programmable testing device (1-layer printed circuit board on PET, overall size: 20 x 40 mm) comprising of Bluetooth communication platform, an energy harvesting circuitry, on-board printed antenna and an accelerometer component, which acts as an internal sensor for system wake-up and motion detection. In parallel, several electrically conductive adhesives (ECA) had been tested with the aim to identify the most reliable and user-friendly interconnection technologies, able to connect the various parts of the Smart2Go platform. All materials for the platform had been defined. Prototypes showed the necessary mechanical robustness. Tests over 1000 bending cycles showed no performance loss. All milestones related to the platform had been achieved.
The platform is open for both energy different harvesting technologies and different applications. During the project, two energy harvesting technologies had been connected to the platform. They are now ready for usage either in the applications tackled directly in the project or in new scenarios after it. One of them, the organic photovoltaic (OPV) is a matured technology. Various cell shapes can be provided. An efficiency beyond 5% was reached (exceeding the original aim of the project). This was achieved by testing new molecules as donors and acceptors. The geometrical fill factor (GFF) was increased to 88%. All this process studies were done on a specific coating line dedicate to OPV.
The thermoelectric modules are the second energy harvesting approach. This is a challenging way since the technical readiness level was lower at the beginning of the project. Nonetheless, the partner succeeded in connecting a fully flexible module with the platform. The areal size of one generator was 13 cm², the module delivered a power density of power 0.33 µW/cm² at 25 K temperature difference.
The partners ATOMIC and Joanneum Research lead the activities for one of the application cases. Lamination trials of fully printed piezo electric sensors to the skis were done at Joanneum Research and preliminary mechanical tests were done at Atomic. From the measurements, a model was developed to derive the bending response of the PyzoFlex® sensors in the ski application. The full integration of the Smart2Go Energy Supply Platform (ESP) into the demonstrator was done. The full functionality was demonstrated in field tests in both indoor and outdoor ski resorts.
First mockups of the integration of organic light emitting diodes (OLED) stripes and OPV modules into garment were devised by Helly Hansen and Fraunhofer FEP. This application is challenging since the everyday usage required to exceed the specific objective of the bending radius. The partners devised a folding strategy for OLED, resulting into concept for the realization of prototypes in the second part of the Smart2Go project.
The Smart2Go consortium presented an energy supply platform. It can integrate different technologies for applications in wearable technologies, as it was anticipated in the proposal.
The demonstration of functionality was done in real use cases. The results of the project are ready for further exploitation.
Apart from the particular aims of the project, the work done so far strengthens European competitiveness in various key sectors.
The big European player in battery manufacturing, VARTA, could improve its abilities in making new types of flexible batteries. Knowledge about material design and manufacturing steps had been widened. The same holds true for ASCA in terms of photovoltaics. Both sectors have a huge implication on the transfer process of the supply in European in the next decades.
The work done at University of Southampton (completely flexible thermoelectric module) shows that unique solutions can be devised. Even though it is in a lower technology readiness level at the moment, it can materialize itself into a unique selling point in the longer perspective.
The partners regarded the sustainability of the entire platform: Under the leadership of the Technical Research Centre of Finland (VTT), a detailed analysis was made based on the data provided by all partners. The document comprised an analysis of the global warming potential for all materials, the fossil resource use as well as the natural resource use. The results will be taken into account for all future application scenarios.
Micro battery thin
Energy supply platform
Micro battery size
TE module
Micro batteries
Micro battery bended
Fields of application and examples of product use cases for the Smart2Go energy supply platform.
Block diagram of a fictitious Smart2Go device.
ATO ski