Using air to make transparent pressure sensors

1 min read

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

The 3D sensor is said to detect wide pressure ranges, from human body weight to a finger touch, and to generate an electrical signal based on the sensed touch actions, while consuming far less electricity than conventional 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 hinders the development of highly-integrated pressure sensor arrays and transparent pressure sensors.

To create the sensors, the team decided to use highly conductive and transparent graphene transistors with air-dielectric layers.

"Using air as the dielectric layer in graphene FETs can significantly improve transistor performance due to the clean interface between graphene channel and air," says Jang-Ung Professor Park. "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 alters its thickness. The changes in the thickness are converted into an electrical signal and transmitted via metal nanowires and the graphene channel, expressing both the position and the intensity of the pressure.

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