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EETE MAR 2015

FLEXIBLE ELECTRONICS Flexible organic circuit makes fever alarm By Peter Clarke Researchers from the University of Tokyo have developed a fever alarm armband, a flexible, selfpowered wearable device that includes a temperature sensor and sounds an alarm in case of high body temperature. The armband, developed by research groups lead by Professor Takayasu Sakurai at the Institute of Industrial Science and Professor Takao Someya at the Graduate School of Engineering, combines a flexible amorphous silicon solar panel, a piezoelectric speaker, temperature sensor, and a power supply circuit created with organic components in a single flexible, wearable package. The organics circuits are based on CMOS FETs that operate at 12V. The armband is for the monitoring of health indicators, such as heart rate and body temperature, in infants and the elderly and in patient care. Such sensors need to be light, flexible and wireless for patient comfort and low-cost so they can be disposable for reasons of hygiene. Conventional sensors on rigid printed circuit boards do not meet those objectives the researchers said. The University of Tokyo’s flexible solution incorporates organic components that can be inkjet printed on a polymer film. The fever alarm armband includes the first organic circuit able to produce an audible output, and the first to incorporate an organic power supply circuit, the researchers claim. The thermal sensor detects when the temperature reaches a pre-set value in the range 36.5 to 38.5 degrees C. “Our fever alarm armband demonstrates that it is possible to produce flexible, disposable devices that can greatly enhance the amount of information available to carers in healthcare settings,” says Professor Someya. “We have demonstrated the technology with a temperature sensor and fever alarm, but the system could also be adapted to provide audible feedback on body temperature, or combined with other sensors to register wetness, pressure or heart rate.” The armband is 30 cm long and 18 cm wide, and can be worn either directly on the skin or on top of clothing. The device is designed so that the thermal sensor is located between the arm and the body. The organic power supply circuit is located under the piezo film speaker to reduce surface area. Source: 2015 Sakurai Lab/Someya Lab. Printed OLEDs make large advertising more communicative TBy Julien Happich he VTT Technical Research Centre of Finland is now able to print large Organic Light-Emitting Diodes (OLEDs) to create patterned and flexible light-emitting surfaces on advertising displays, info signs and lighting fixtures, using conventional screen printing techniques. Placed between two electrodes, one of which is transparent, the organic lightemitting semiconductor produces light as electric current is conducted through the component. The 0.2mm thin stack of electrodes and polymer layers can now be printed not only onto glass or steel surfaces but also onto flexible plastic films, enabling significantly larger light surfaces and expanding the usage possibilities of the technology. This type of light-emitting plastic film and processing in ambient atmosphere had not been created before on this scale, according to the research center. Production of such electroluminescent surfaces could now be done in facilities such as traditional printing houses. The luminosity of OLED (lm/W) amounts up to around one third of an LED’s luminosity, but is has one advantage: OLED emits light throughout its entire surface, whereas LED is a spotlight technology. Today, VTT’s plastic OLED film will only emit light for around a year, since light-emitting polymer materials are susceptible to oxygen and moisture. In the future, the film’s lifespan is expected to increase as better screen protectors and oxygen barriers are developed. “The plastic film is optimally suited to advertising campaigns, in which large light-emitting surfaces can be used to draw significantly more attention than can be gained through mere printed graphics or e-ink-type black-and-white displays that do not emit light,” said Head of Research Area Raimo Korhonen from VTT. A large-surface light-emitting plastic film developed by VTT is based on OLED technology. (Photo: Juha Sarkkinen). The OLED light could not only be used for advertising or signalling, it could also be operated as a wireless communication link, subrepticely pushing data to IoT applications on top of its visible message. 42 Electronic Engineering Times Europe March 2015 www.electronics-eetimes.com


EETE MAR 2015
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