Anisotropic strain-field-induced change of the electronic conductivity of graphene sheets and carbon nanotubes

Since the discovery of carbon nanotubes (CNTs), there have been many efforts to develop various electronic devices and sensors. The authors have also validated the possibility of a highly sensitive strain sensor using popular resin in which multi-walled CNTs (MWNTs) were dispersed uniformly. It is, however, indispensable for clarifying how to change the electronic state of a deformed CNT for assuring the stable performance of the sensor because the reported sensitivity has ranged widely. In this study, the relationship between the deformation characteristic of a CNT under strain and its electronic conductivity was analyzed quantitatively. The analysis result obtained from density functional theory (DFT) calculation showed that the orbital hybridization was occured when the local curvature exceeded about 0.3 Å^-1, inducing the decrease in the band gap. Based on the analytical results, a twodimensional strain sensor was developed by applying buckling deformation-induced conductivity change of MWNTs by using MEMS technology.