NASA Langley Research Center researchers are experts at producing carbon nanotube (CNT)-based sensors for structural health monitoring (SHM). The sensors can be embedded in structures of all geometries to monitor conditions both inside and at the surface of the structure to continuously sense changes. Having accumulated a body of knowledge on how to deposit and align CNTs, NASA is adept at manipulating the CNTs into specific orientations to create small, powerful, and flexible sensors. One of the sensors created by NASA is a highly flexible sensor for crack growth detection and strain field mapping that features a very dense and highly ordered array of single-walled CNTs. NASA is seeking companies that are interested in licensing technology or engaging NASA in joint research in the area of CNT sensors.
Global, real-time structural health monitoring systems for air and space vehicles require new strategies for the development of extremely small and lightweight sensors that are embeddable and scalable to arrays. Geometries with very thin regions (e.g., leading edges), sharp changes (e.g., wing/fuselage junctions), or areas of extremely high curvature are often impossible to instrument. NASA solves this issue with a flexible CNT-based structural health monitoring sensor for measuring the induced strain, pressure, and temperature both within and at the surface of a structure — an attractive candidate for smart skin technologies.
NASA’s process for the deposition and alignment of CNTs onto metallic electrodes uses chemically functionalized lithographic patterns. This method consistently produces aligned CNTs in the defined locations. Using photo- and electron-beam lithography, NASA patterns simple Cr/Au thin film circuits on oxidized silicon substrates. The samples are then re-patterned with a CNT-attracting, self-assembled monolayer of 3- aminopropyltriethoxysilane (APTES) to delineate the desired CNT locations between electrodes. The application of an electric field to the metallic contacts during the deposition of the solutionsuspended, single-wall carbon nanotubes causes alignment of the CNTs along the field direction.
The sensors can be mass produced, are inexpensive, and can be packaged in small sizes (0.5 μm2). They require less power and produce less waste heat per square centimeter than electronic or piezoelectric transducers.
This technology can be used in CNT sensors embedded in bridges, roads, tunnels, and other structures to monitor strain, wear, and tear; in turbines to monitor crack growth; and in aerospace structures for smart skin to monitor strain, pressure, and temperature conditions. It can monitor fatigue and exposure both inside and at the surface of the aircraft skin.