Investigation of aligned carbon nanotube architectures to understand the actuation mechanism

Abstract

The various excellent properties of carbon nanotubes (CNTs) are in the focus of researchers since years. Moreover architectures, built of CNTs, show active behavior in terms of deflections. There-fore they have to be set up like a capacitor within an electric field and covered by a matrix of free movable ions. The mechanism behind this phenomenon is still discussed obsessively rather to be an quantum-mechanical elongation of the C-bonds or to be caused by electrostatic repulsion of charged agglomerated CNTs. Formally investigated paper-like architectures, known as Bucky-papers, consist of randomly oriented CNTs. This paper presents several experimental approaches and results documenting doubts about the ability to clarify the active mechanism by investigating the electromechanical properties of those paper-like architectures. In contrast a novel test set-up for analyzing specimen, providing highly vertically aligned CNTs, is presented. This high resolution test set-up is designed to analyze CNT-specimen in thickness-direction optically. The vertically aligned CNT-architectures, also called CNTarrays, consist of multi-walled CNTs (MWCNTs). The MWCNT-arrays are highly hydrophobic and can only be moistened by polar liquids like ionic liquids (ILs). The latest results of the electro-mechanical system as well as further challenges dealing with ILs and different kinds of CNT-arrays are presented. The presented measurement method allows an even more precise investigation of the electro-mechanical behavior of a single MWCNT and the strain-mechanism simultaneously. Furthermore this configuration points out an efficient mode of future CNT-based actuators.