Foldable 3-D Pressure Sensor Based On Graphene

Foldable 3-D Pressure Sensor Based On Graphene - Featured Graphene research Sensors Wearables


3-D active-matrix pressure developed with transistors with air-dielectric layers. Source: UNISTResearchers from South Korea’s Ulsan National Institute of Science and Technology (UNIST) have created an active-matrix 3D tactile pressure sensor using foldable substrates and air-dielectric layers. 

The device could potentially detect a wide range of pressures ranging from human body weight to the touch of a finger. It also has the ability to detect different types of touch, such as swiping or tapping. The sensor contains transparent features and has the ability to generate an electrical signal based on touch actions, all while using less electricity than conventional pressure sensors. 

From Electronics360,  “Transistors are generally created with a silicon channel and silicon oxide-based dielectrics but these transistors either lack transparency or are inflexible hindering its utility in fabricating pressure sensor arrays and transparent pressure sensors. UNIST in its pressure sensor development used transparent graphene transistors with air-dielectric layers in order to improve the performance of the transistors due to the clean interface between graphene channel and air.’The thickness of the air-dielectric layers is determined by the applied pressure,’ says Jang-Ung Park of Materials Science and Engineering at UNIST. ‘With that technology, it would be possible to detect pressure changes far more 3-D active-matrix pressure sensors developed with graphene transistors with air-dielectric layers effectively.'”

Foldable 3-D Pressure Sensor Based On Graphene - Featured Graphene research Sensors Wearables
(a,b) Schematic images of pressure-sensitive graphene FETs with air-dielectric layers before (a) and after (b) the folding, respectively. The air-dielectric layer is placed between the graphene channel and the gate electrode as illustrated in the schematic image (inset). (c,d) Optical microscopy image for graphene FETs with air-dielectric layer surrounded by p-PDMS supporting walls. Scale bars, 200??m. (c) Source, drain electrodes and graphene channel are shown. Black squares are the p-PDMS supporting walls that form the air-dielectric layer. (d) Top gate electrodes cover the air-dielectric holes by substrate folding. (e) Photograph of the fabricated pressure-sensitive graphene FETs, Scale bar, 1?cm.

The Process

“In order to create the 3-D pressure sensors, researchers placed a graphene channel, metal nanowire electrodes and an elastic body that traps air on one side of the foldable substrate and covered the other side of the substrate like a lid to keep in the air. As force is pressed, the elastic body is transferred to the air-dielectric layer and alters its thickness. The changes in the air-dielectric layer is converted into an electrical signal and transmitted via metal nanowires and the graphene channel, expressing the position and intensity of the pressure.”

Sending and receiving signals by flowing electricity becomes possible when pressure is generated. Researchers said that since most of the components are transparent, the sensors can be manufactured with invisible pressure sensors. This could result in a new way to successfully implement active-matrix pressure sensors that consume less power and have faster response times the passive-matrix sensors. 

“This study not only solves the limitations of conventional pressure sensors, but also suggests the possibility to apply them to various fields by combining pressure sensors with other devices such as display,” Park said.


Publication Journal: Park, Jang-ung et al., Integrated arrays of air-dielectric graphene transistors as transparent active-matrix pressure sensors for wide pressure ranges, Nature Communications 8, Article number: 14950 (2017), doi:10.1038/ncomms14950