Inertial sensors

Carbon nanotube giant piezoresistive strain sensors

© Fraunhofer ENAS
Scheme of the fabricated CNT sensor on top of a MEMS membrane and typical sensor response curve.
© Fraunhofer ENAS
A calculated sensitivity map at different operation regimes.

The scalable fabrication of electronics and sensors in the context of Industry 4.0, the Internet of Things and for flexible/wearable electronics requires innovative approaches for the integration of new materials. One of these approaches is the integration of functional nanomaterials such as single-walled carbon nanotubes (SWCNTs). The intrinsic properties of SWCNTs, such as a high Young’s modulus, ultimate mechanical strength and the intrinsic giant piezoresistivity facilitate a new class of highly-miniaturized strain sensors standing out by versatile integration capabilities on different substrates or in complex systems. In recent years, Fraunhofer ENAS developed a technology platform for the scalable integration and characterization of CNTs on wafer level in cooperation with Chemnitz University of Technology. The superior performance of membrane-based carbon nanotube sensors characterized by gauge factors of up to β = 800 (β = ∆R R0-1 ε-1) exceeds the sensitivity of conventional silicon based strain sensors by half an order of magnitude. In continuing investigations, which combine technological and theoretical approaches, sensor operation regimes are explored where the intrinsic sensitivity is further enhanced to up to 150 percent. Different integration scenarios are available to integrate these miniaturized sensors onto a wide variety of substrates and materials. For example, efficient condition monitoring of safety-relevant applications is conceivable due to their low energy consumption and footprint.