The world’s first flexible wireless organic sensor system - Disposable sensors that can electrically functionalize a Band-Aid or diapers -




Within the framework of the Strategic Basic Research Program of the Japan Science and Technology Agency (JST), a research team led by Professor Takayasu Sakurai and Professor Takao Someya at The University of Tokyo has succeeded in developing the first flexible wireless organic sensor system in the world. The feasibility of this wireless system has been demonstrated by wirelessly supplying power and wirelessly transmitting data from a wet sensor.
Because of the recent significant progress of wireless sensors, they are expected to be widely in use to measure various physical information in a real space. Recently, the measurement targets of sensors are expanding swiftly from objects to humans. In order to extract biological information from sensors that physically interact with the human body, we are facing issues that have not been required of conventional sensors, such as imperceptible softness and disposability from a hygienic perspective. 
The team has succeeded in developing a wirelessly powered flexible wet sensor sheet that transmits data wirelessly by implementing an organic integrated circuit (IC) on top of a polymeric film. Introducing an electromagnetic-resonance method in power transmission for the operation of an organic IC for the first time in the field was key to this achievement. This method enabled them to effectively transmit power and data wirelessly between the reader and the sensor, which are far apart. This organic IC is structured with three circuitry blocks. The first block receives a wireless power supply with the magnetic-resonance method at a rectifier circuit using organic diodes. The second block is placed on an organic ring oscillator with oscillating frequencies that change with the resistance. The ring oscillator transmits the data of the resistance changes caused by moisture or the presence of liquid. The third block is an electrostatic discharge (ESD) circuitcomprising organic diodes that enable to protect the device from damage when touched by a charged human body (2-kV electrostatic discharge).
The principle of this research could be applied to sensors to detect humidity or pressure, other than moisture. This result will be applied to disposable sensors such as sticking-plaster-type sensors. 
This achievement was presented at the 2014 IEEE International Solid-State Circuits Conference (ISSCC) in San Francisco, U.S.A, on February 12, 2014.


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