In order to better care for patients, infants, and the elderly, research teams worldwide are investigating novel ways to continuously monitor people's health by tracking key life signs such as heart rate and body temperature. Such applications require sensors that are flexible and wireless for maximum comfort, self-powered to avoid replacement of batteries, and cheap enough to permit disposable use to ensure proper hygiene.
A new wearable electronic device that is the brainchild of scientists at the University of Tokyo might fit those criteria. It’s an armband that combines a temperature sensor to measure body heat under the arm, a piezoelectric speaker to provide audible feedback, amorphous silicon solar cells for power, and circuits made of organic ink printed onto a plastic film. The same researchers previously developed flexible electronic skins with an eye toward covering prosthetic limbs and humanoid robots.
The team said the medical armband contains the first organic circuit able to produce sound, and is first device to incorporate an organic power supply circuit. These organic circuits increase the range of illumination at which the armband can operate by 7.3 times; this allows it to be used indoors.
The armband can emit an audible buzz when the body temperature it detects exceeds a preset limit. That temperature can be anywhere between 36.5 and 38.5 degrees Celsius. The scientists do not plan on incorporating a video display onto the armband. “We think sending information wirelessly is more important," said the study’s lead author, Hiroshi Fuketa.
The researchers noted the armband could incorporate other sensors to monitor heart rate, blood pressure, or moisture, as well as a flexible battery to store energy from the solar cells so the device can continue working after dark. The scientists will present the armband at the 2015 IEEE International Solid State Circuits Conference (ISSCC) in San Francisco on 24 February.
Photo: Sakurai Lab/Someya Lab
Charles Q. Choi is a science reporter who contributes regularly to IEEE Spectrum. He has written for Scientific American, The New York Times, Wired, and Science, among others.