Use of Air in Electronics to make Pressure Sensors

Researchers from the Korean Ulsan National Institute of Science and Technology developed a method to make transistor-type active-matrix pressure sensors using foldable substrates and air-dielectric layers.

It is a 3D sensor and is said to detect wide pressure ranges, from a finger touch to human body weight, and to achieve an electrical signal based on the sensed touch actions. All of this while consuming far less electricity than traditional pressure sensors.

According to the researchers, most transistors are created with a silicon channel and silicon oxide-based dielectrics. However, these transistors have been found to be either lacking transparency or flexibility, which obstructs the development of highly-integrated pressure sensor host and transparent IC device pressure sensors.

The Institute team decided to use highly conductive and transparent IC device graphene transistors with air-dielectric layers to create the sensors. Jang-Ung Professor Park explains, "Using air as the dielectric layer in graphene FETs can significantly improve transistor performance due to the clean interface between graphene channel and air. The thickness of the air-dielectric layers is determined by the applied pressure. With that technology, it is possible to detect pressure changes far more effectively."

In this transistor, the force pressing the elastic body is transferred to the air-dielectric layer and changes its thickness. The development in the thickness are transformed into an electrical signal and transmitted via metal nanowires and the graphene channel, expressing both the position and the intensity of the pressure.

PhD student Sangyoon Ji explains, "This sensor is capable of simultaneously measuring anything from lower pressure, such as gentle tapping, to high pressure, such as human body weight. It can be applied to 3D touchscreen panels or smart running shoes."

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