Piezo-gated flexible transistors: A path to energy-efficient multi-functional piezotronic devices

Developing smart sensors and advanced electronics for the need of the internet of things prevails yet under the constraint of energy efficiency. Therefore, the development of multi-functional devices toward low power is the research spotlight. Due to the low energy consumption, semiconductor-based piezo-gated devices hold great promises. Herein, a flexible multi-dimensional strain sensor by growing two ZnO thin film-based terminals on both sides of a mica substrate is developed. This Multidimensional Piezo-Gated Flexible Transistor (M-PGFT) device successfully detects the positive (upward) bending, negative (downward) bending, and compressive load. Where the gauge factor (GF) of the Top/Bottom terminals under positive and negative bending strains are -3.44/ +9.78 and +5.44/-4.03, respectively, and +94.93/+74.70 for compressive load is obtained. Notably, the GF of both ZnO terminals is asymmetric under two bending types of loads, whereas symmetric under compressive load. This unique behavior made this smart multi-dimensional strain sensor to distinguish between different types of strains. Furthermore, the same device can be implemented as a piezo-gated three-valued logic device, demonstrating standard ternary inversion and standard ternary NAND operations. This study presents a unique and simple design to fabricate flexible multi-functional piezo-gated devices for multi-dimensional strain sensing and three-valued logic operation at low power.