Ultrafine sensing using carbon nanotube arrays

Arrays of Carbon Nanotubes (CNTs) have shown the ability to react as foam-like structures and display local buckling within the bulk. The arrays, or turfs, are high aspect ratio CNT fibers that extend up to 1 mm in height. The material has great promise for engineering and sensing applications, though an understanding of the material response is still at infancy. Here, we perturb CNT array turfs by uniform compressive contact and measure the electrical resistance change in two directions, normal and transverse to the tubes. Resistance changes as a function of strain exhibit a sensitivity increase of 7 times in the transverse versus normal directions. The increase is hypothesized to be to the localized buckling induced reorganization of the individual CNTs at the surface, which results in tube densification. Characterization of the buckling region by nanoindentation has shown an increase in the contact stiffness. Micro-Raman spectroscopy corroborates the results where a measured increase in tube interactions provides a denser fiber network. The results give fundamental insight into the resistivity of the CNT arrays and their application as high-resolution contact sensors, microscale electrical contacts, and chemical sensors.