Carbon Nanotubes for Mechanical Sensor Applications

Abstract

Herein, the evolution of carbon nanotubes (CNTs) as functional material in nano‐ and microelectromechanical systems (N/MEMS) is featured. Introducing material morphologies for the CNTs in a homologue series (single CNTs—bundles, fibers, yarns—networks and thin films), different concepts for mechanical sensors based on the intrinsic and extrinsic properties of the CNT materials are introduced (piezoresistive effect, strain‐induced band bending, charge tunneling). In a rigorous theoretical treatment, the limits of the achievable sensor performance (i.e., gauge factor) are derived and discussed in the context of applications. A careful literature survey shows that highest sensitivity is reached for devices exploiting the intrinsic transport properties of single CNTs. For reliability tests of such sensor systems made from nanomaterials and classical MEMS, the specimen‐centered approach (SCA) is introduced to give viable insights into the structure property relationships and failure modes of CNT mechanical sensors. CNT actuation occurs on the macro‐, micro‐, and nanoscales via atomic force microscopy, electrostatic gating, integration in N/MEMS systems, or through substrate bending.

Giant Piezoresistive Effect of CdS@C Hybrid Nanobelts for Volatile Real-Time Sensor and Erasable Nonvolatile Memory to Stress

“…It can be expected that a strong interface coupling effect can take place between two nanostructures owing to the existence of affluent surface states. , In addition, QDs can form effective trap centers, and the filling of trap level is tunable. Therefore, some novel properties are likely to appear. , For carbon materials, they can generally show superior conductive properties, and furthermore, they can show a PZR effect as well. − Therefore, it is more suitable as a matrix of a hybrid composite structure to build high-performance GPZR materials. For the nanostructure with one-dimension (1D), in addition, it is extremely beneficial to build a single nanostructure-based two-terminal device, and thus, it is very easy for the actual physical mechanism to be well-identified by the simple configuration in comparison with nanostructure assemblies. − Accordingly, it is more appropriate for an individual 1D nanostructure to serve as a building block to directly construct a nanodevice.…”

Directional Response of Randomly Dispersed Carbon Nanotube Strain Sensors

“…When blended with epoxy resin, even the cure temperature was found to have an influence on the gauge factor, but the diameters of the nanotubes and their conductivity play more dominant roles, together with the nature of the polymer matrix. In this regard, Wagner et al [6] also reviewed the parameters influencing the Gauge Factor (GF).…”

“…The electrical resistivity of a randomly dispersed CNT-polymer composite can be attributed to two main factors, as sketched in Figure 1 (taken from reference [6]): the intrinsic electrical resistance of the nanotubes, and the contact resistance among adjacent nanotubes. Since the gap between CNT contact points is filled with polymers, the contact resistance or tunneling resistance is several orders of magnitude higher than the inherent carbon nanotube resistance.…”

“…The distance among contact points increases by tensile strains, thereby increasing the tunneling resistance. [6], with CC permission).…”

Sensoric Micro and Nano Systems

“…The research topics of the contributions span from the simulation and modeling of strain‐sensing nano devices based on carbon nanotubes (CNTs) via the fundamentals of the heterogeneous integration of nano materials into MEMS test stages to miniaturized optical sensing devices . More generally, contributions touch the analysis of the nanomaterials and their interfaces to microscopic elements with advanced spectroscopy methods, novel smart‐systems integration of fludic devices based on nanomembranes and rolled‐up structures, structure formation of magnetic nanoparticles in fluids and the monolithical realization of a silicon‐based strain sensor .…”