Mechanical behavior of vertically aligned carbon nanotubes under electrostatic tension

Due to their excellent physical properties and compatibility with micro-fabrication processes, vertically aligned carbon nanotubes (VA-CNTs) have been successfully integrated in various nano/micro-electromechanical system (NEMS/MEMS) devices, composites, and electronic circuits. Here, we investigate the behavior of VA-CNTs under electrostatic tension. Scanning electron microscopy revealed that electrostatic tension reorganizes the individual CNTs and increases their alignment, thereby increasing their stiffness, and resulting in a negative Poisson's ratio (NPR). High NPR values were obtained in the top portion of the VA-CNTs (the location of the greatest morphological change), while the other portions (a less significant morphological change) demonstrated smaller NPR values. Therefore, the electrostatic pressure induces an irreversible morphological change in the VA-CNTs, which, in turn, modifies their properties. This behavior makes VA-CNTs an attractive material for a wide range of micro- and nano-scale devices, wherein tunable mechanical properties and a versatile motion transformation are required. (C) 2019 Elsevier B.V. All rights reserved.