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.
