Smart wearables that never need battery recharging
Smart watches and fitness trackers are already widely available, but developing other wearable devices that need to use real-time data and can communicate wirelessly, for example in healthcare and sports, could be limited by battery life. “The energy supply to wearable devices is probably the most serious challenge among the technological bottlenecks,” explains Smart2Go project coordinator Matthias Fahland, department head at the Fraunhofer Institute for Organic Electronics, Electron Beam and Plasma Technology in Dresden, Germany. An autonomous energy-supply platform eliminates the need for recharging. “The project developed an energy storage unit – essentially a lithium-ion battery – as a bendable, lightweight, ultrathin strip that can adapt to the shape and requirements of the wearable product,” he says. It is connected to an energy-harvesting device and energy-storing supercapacitors via special interfaces, connectors and sensors such as piezo sensors which measure changes in pressure, acceleration and temperature, or light sensors and technologies. “It also includes a communication unit, allowing a customer to monitor not only the energy flow, but also any data connected to the application,” he adds.
Applications tested
The platform was tested with two different products being developed by consortium partners. They include a pressure-sensitive smart ski which registers ski curvature and ski deflection as it moves across the snow, using sensors and other ways of measuring changes. This provided information on performance and quality of turns and has potential for real-time feedback on fitting and injury analysis. It was also tested on a smart safety jacket that integrates lighting and other technologies for use in extreme environments including extreme cold, snow and rain; and a smart backpack for carrying electronic equipment which integrates solar cells on top and wiring within the backpack. Other potential applications include smart medical devices such as those developed under the EU-funded WEARPLEX and SocketSense projects, lifetime tracking of wild animals, smart labels for packaging, and active machine parts to detect malfunctions in real time.
Flexible but standardised platform for different applications
A special feature is the standardisation of the interfaces so that the platform can be adapted to different uses and products, Fahland explains. It was deliberately conceived so that some elements could be easily replaced to serve niche products or new approaches in development which have limited market volume but need a sustainable and effective energy supply from a mobile source. But this was also a major challenge. “The amount of engineering work to get this adaptive battery to new, completely different applications was not easy,” explains Fahland. He points out that the strip battery not only has to adapt to any shape and different wiring, connectors and layouts, but must also be thoroughly tested in each application to ensure reliability.
Energy harvester technologies
The type of energy harvester or battery power source can also be changed, further increasing the variability of the platform, he notes. The project used an advanced organic photovoltaic (OPV) energy harvester from a consortium member that was already an established producer and was able to improve the efficiency of solar cells during the project as well as produce various cell shapes. A second energy source, at an earlier stage of development, was a thermoelectric harvester that uses body heat to power low-voltage devices such as sensors and temperature monitors incorporated in clothing and equipment. “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,” Fahland says.
Keywords
Smart2Go, fitness trackers, wearables, energy, battery, battery life, energy harvester, ski, WEARPLEX, OPV, photovoltaic, energy, solar cells, piezo sensors
