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Sensor detects diaper wetness

Posted: 17 Feb 2014 ?? ?Print Version ?Bookmark and Share

Keywords:sensor? organic? wireless?

A team of researchers from the University of Tokyo has engineered what they claim is the first flexible wireless organic sensor system in the world. The sensor can be inserted inside a diaper, and wirelessly sends an alert once it detects a need for changing. The feasibility behind this system has been successfully demonstrated by wirelessly supplying power and wirelessly transmitting data from a wet sensor.

Led by professors Takayasu Sakurai and Takao Someya, the team explains that they implemented an organic IC on top of a polymeric film, enabling a flexible wet sensor sheet to transmit data wirelessly.

Sensor detects diaper wetness

It further reveals that introducing an electromagnetic-resonance method in power transmission to operate an organic IC was the key to their achievement. This method facilitated the effective wireless transmission of power and data between the reader and the sensor, which are distanced from each other.

The 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) circuit comprising organic diodes that function to protect the device from damage when touched by a human body charged with 2kV 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 recent 2014 IEEE International Solid-State Circuits Conference (ISSCC) in San Francisco.

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