14. Nanomechanical Application of CNT

Carbon nanotubes (CNT) are appropriate for nanoscale mechanical system such as nano-switches and nanomechanical resonators for mass sensor application because of their lightweight, high aspect ratio, and extraordinary mechanical properties. The resonator miniaturization is crucial in bringing highly sensitive force and mass detection into practice, so that the CNTs are appropriate for the force and mass sensing. Here, we focus on highly sensitive mass and force detections using CNT mechanical resonators as nanomechanical application of CNTs. Loss factors of the multiwall-CNT resonators, which determine the sensitivity of the resonator, are strongly correlated to the CNT diameter due to the van der Waals interaction between layers. Down-mixing method for detecting the resonance frequencies of CNT mechanical resonators is one of key techniques to achieve the extremely high sensitivity. The doubly clamped CNT resonators consisting of single-wall CNTs achieved the sensitivity with ∼10 zN Hz^-1/2 at 1.2 K in ultrahigh vacuum. For the ambient condition, which is preferable for the biological samples, optical detection using opt-mechanical heterodyne technique was proposed and achieved high mass sensitivity with ∼100 zg under the atmospheric conditions. We believe that this extraordinarily high sensitivity offers new possibilities for the investigation of a wide range of materials, especially nanoscale materials.