A research team led by Professor Takayasu Sakurai and Professor Takao Someya at the University of Tokyo has succeeded in developing the world’s first flexible wireless completely organic sensor system. According to the report, the feasibility of this wireless system has been demonstrated by wirelessly supplying power and wirelessly transmitting data from a wet sensor. The sensor can be remotely powered, and data can be read from the sensor under optimal conditions.
The idea came from recent development of wireless sensors that are in wider use to measure a variety of physical information in the real world and the target of this measurement is gradually expanding from objects to humans. Therefore, in order to extract biological information from sensors that physically interact with the human body there is a need according to the researchers for functionality not required of conventional sensors, such as imperceptible softness and disposability from a hygienic perspective.
The result was carried out with a polymeric film and the team succeeded in developing a wirelessly powered flexible wet sensor sheet that transmits data wirelessly by implementing an organic integrated circuit (IC) on top. The key to this achievement was the introduction for the first time in the field of electromagnetic-resonance method a power transmission for the operation of an organic IC. This method enabled efficient wireless power and data transmission between the reader and the sensor over a distance.
The researchers structured the organic IC with three circuitry blocks. The first block receives power wirelessly by magnetic resonance at a rectifier circuit using organic diodes. The second block is placed on an organic ring oscillator with oscillating frequency that changes with resistance. The ring oscillator transmits the data of the resistance change caused by moisture or the presence of liquid. The third block is an electrostatic discharge (ESD) circuit comprising organic diodes protect the device from damage when touched by a charged human body (2-kV electrostatic discharge).The principle of this research could also be applied to sensors to detect humidity or pressure, other than moisture. This result will also find applications in a wide range of disposable sensors such as in sticking plasters and disposable diapers.
This research was carried out within the framework of the Strategic Basic Research Program of the Japan Science and Technology Agency (JST). And this achievement was presented at the 2014 IEEE International Solid-State Circuits Conference (ISSCC) in San Francisco, U.S.A, on February 12, 2014.
The University of Tokyo Research