image: The printable sensor is thin and flexible enough to wrap around a pencil, or adapt to the form of the human body or another substrate. Device performance is largely unaffected by bending. view more
Credit: 2015 Someya Laboratory
A University of Tokyo research group has developed a flexible, lightweight sensor that responds rapidly to tiny thermal changes in the range of human body temperature. This sensor is expected to find healthcare and welfare applications in devices for monitoring body temperature, for example of newborn infants or of patients in intensive care settings.
Flexible and wearable devices are increasingly being developed for healthcare and other applications where temperature and other sensors are integrated to provide feedback on patient health and wellbeing. Body temperature is a fundamental measurement and many low-cost flexible temperature sensors have been demonstrated, but devices developed to date require external circuitry to amplify the signal to allow accurate temperature measurement.
In their latest research, Professor Takao Someya and Dr. Tomoyuki Yokota's research group at the Graduate School of Engineering have developed a new printable, flexible, lightweight temperature sensor that shows a very high change in electrical resistance of up to 100,000 times over a range of just five degrees centigrade, allowing accurate temperature measurement without additional complicated display circuitry.
The key to the new sensor is the ability to precisely control the target temperature of the sensors. The sensor is composed of graphite and a semicrystalline acrylate polymer formed of two monomers, molecules that bond together to form a polymer chain. The target temperature range at which the sensor is most precise can be selected simply by altering the proportions of the two monomers. The research group achieved target temperatures between 25 and 50 degrees centigrade, a range which includes average human body temperature, and simultaneously realizing response times of less than 100 milliseconds and a temperature sensitivity of 0.02 degrees centigrade. The device was also stable even under physiological conditions, providing repeated readings up to 1,800 times.
The research group tested their new sensor by printing a flexible thermal monitoring device which was placed directly on the lung of a rat to measure lung temperature. The device successfully measured cyclic changes in lung temperature of just 0.1 degrees centigrade as the animal breathed, demonstrating its utility as a sensor for monitoring body vital signs in physiological (internal) settings.
"By printing an array of these sensors it is possible to measure surface temperature over a large area," says Professor Someya. He continues, "This sensor array can be attached to biological tissue such as the skin for precise monitoring in medical applications. Because the huge response of the sensor to temperature change allows us to simplify the circuitry, we could print our sensors onto adhesive plasters that could then monitor body temperature. For example, a plaster applied directly to a wound or after surgery could provide warning of infection by detecting local changes in temperature due to inflammation."
Other possible applications include wearable electronic apparel, where the sensor could be applied beneath fabric to measure temperature during sporting and other activities.
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This work was conducted in collaboration with the research group of Professor Walter Voit at the University of Texas at Dallas, USA.
Journal article/Conference paper
Tomoyuki Yokota*, Yusuke Inoue, Yuki Terakawa, Jonathan Reeder, Martin Kaltenbrunner, Taylor Ware, Kejia Yang, Kunihiko Mabuchi, Tomohiro Murakawa, Masaki Sekino, Walter Voit, Tsuyoshi Sekitani, and Takao Someya*, "Ultraflexible, large-area, physiological temperature sensors for multipoint measurements," Proceedings of the National Academy of Sciences of the United States of America, Online edition 2015/11/09
URL: https://dx.doi.org/10.1073/pnas.1515650112
DOI: 10.1073/pnas.1515650112
Collaborating institutions
University of Texas at Dallas, USA
Links
The University of Tokyo http://www.u-tokyo.ac.jp/en/
Graduate School of Engineering http://www.t.u-tokyo.ac.jp/etpage/
Someya Group Organic Transistor Lab http://www.ntech.t.u-tokyo.ac.jp/
ERATO Someya Bio-Harmonized Electronics Project http://www.jst.go.jp/erato/someya/en/
Research contact
Professor Takao Someya
Department of Electrical Engineering and Information Systems
Graduate School of Engineering
The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan
Email: someya@ee.t.u-tokyo.ac.jp
Tel: +81-3-5841-0411/6756
Fax: +81-3-5841-6709
Press officer contact
Graduate School of Engineering Public Relations Office
The University of Tokyo
The University of Tokyo, Hongo 7-3-1, Bunkyo-ku, Tokyo 113-8656, Japan
Tel: 03-5841-1790
Fax: 03-5841-0529
Email: kouhou@pr.t.u-tokyo.ac.jp
Funding
Japan Science and Technology Agency (JST) Exploratory Research for Advanced Technology (ERATO) Someya Bio-Harmonized Electronics Project
About the University of Tokyo
The University of Tokyo is Japan's leading university and one of the world's top research universities. The vast research output of some 6,000 researchers is published in the world's top journals across the arts and sciences. Our vibrant student body of around 15,000 undergraduate and 15,000 graduate students includes over 2,000 international students. Find out more at http://www.u-tokyo.ac.jp/en/ or follow us on Twitter at @UTokyo_News_en.
Journal
Proceedings of the National Academy of Sciences