Researchers from NCKU University in Taiwan have developed the first “dual-mode” piezotronic force sensor. The new sensor will make it possible to develop extremely sensitive force sensors for use in industrial, structural engineering and HMI applications.

The rise of IoT and Industry 4.0 has made piezoelectrics, materials that generate electric charge when a strain is applied to them, increasingly important as remote low power force sensors.

Existing sensors utilise strain-induced “Schottky barrier height (SBH) modulation”. However, “piezo-gated” devices, an alternative approach, is less well explored or understood. This has limited the development of more advanced piezotronic sensors that can capture multidimensional effects for use in industrial and engineering applications.

The NCKU researchers have developed what the describe as the first dual-mode piezo-gated thin-film transistor, or PGTFT, along with an analytical model of its working mechanism.

The PGTFT exhibits what the researchers describe as “an unprecedented operation between two modes”, namely depletion and accumulation, and a record gauge factor (ratio of relative change in current to mechanical strain) of 2780, indicating its extreme sensitivity.

“PGTFTs relying solely on the piezo-gating effect are essential for developing advanced piezotronic devices. But, most PGTFTs reported so far show indistinct piezo-gating effect through SBH modulation induced by piezoelectric fields, and can detect only one-dimensional strain,” said Prof Chuan-Pu Liu, one of the study’s authors.

“These findings will pave the way for the development and application of multi-dimension strain-sensing PGTFTs,” said Prof Liu. This could lead to novel human-machine interfaces that are compact, cost-effective, and less power-hungry.”