ORIGINAL PAPER The effect of chirality on the torsion of nanotubes embedded in an elastic medium using doublet mechanics M R Ebrahimian, A Imam* and M Najafi Department of Mechanical Engineering, Science and Research Branch, Islamic Azad University, Tehran, Iran Received: 01 August 2018 / Accepted: 19 February 2019 Abstract: In this paper, the torsion of nanotubes embedded in an elastic medium is studied using doublet mechanics wherein the governing equations take the effects of scale parameter and chirality explicitly and simultaneously into account. Using this approach, it is shown that the effect of chirality is present only in the scaling theory. Thus, if the scaling characteristics of the nanotube are deemed important so is the chirality. Specifically, the effects of parameters such as the chiral angle, scale parameter, geometric properties of the nanotubes and boundary conditions are investigated in detail. It is shown that increasing the scale parameter causes an increase in the angular displacement. Also, by considering the effect of chirality, it is shown that the armchair arrangement of the nanotube has a higher torsional stiffness than the zigzag arrangement. The results of the present work are compared with the nonlocal theory, numerical methods and molecular simulations and good agreement with the latter approaches is observed. Keywords: Doublet mechanics; Chirality; Scale parameter; Torsion of nanotubes; Elastic medium PACS Nos.: 02.30.Hq; 11.30.Rd; 61.48.De; 62.20.Dc; 89.20.Kk 1. Introduction Nanotechnology has found many applications in various fields from food, medicine, medical diagnosis and biotechnology to electronics, computers, transportation and energy. Recent developments of nanostructured materials show great potential to impact energy technologies and biomedical applications, such as solar cells, environmental control, cancer diagnosis and drug delivery [1, 2]. In order to study nanoscale solids, there is a need to take the dis- crete nature of such solids into account [1]. For instance, nanotubes and nanospheres or buckyballs are engineering structures that cannot be modeled accurately without pay- ing attention to their discrete microstructures. Preparation of nanoparticles is important, because the physical and chemical properties of the nanostructures depend on the size and shapes of nanoparticles [3, 4]. Nanotubes and buckyballs are made from rolls and wraps of graphene sheets, respectively. Carbon nanotubes (CNTs) were first discovered by Iijima in 1991 [5]. A CNT can be considered as a long thin strip of an atomic plate with nanoscale diameter and microscale length which is rolled into a cylinder [1]. Sin- gle-walled carbon nanotubes (SWCNTs) have unique properties such as very high strength and very low weight. They are also very good conductors of heat and electricity. The properties of CNTs depend to a considerable extent on the chirality and underlying microstructure. For example, the electrical properties of CNTs change from semicon- ductivity to full conductivity with changes in chirality [1]. Accordingly, a number of papers [3, 6–8] have investigated the effects of chirality on the properties of SWCNTs. Nanotubes are also capable of tolerating torsional torques. Recent advances in fabrication have allowed devices to be fabricated that are able to apply a torque to CNT while measuring its mechanical and electrical responses [9]. The results obtained from the torsional study of nanotubes embedded in an elastic medium are useful in the design of nanocomposites, nanoelectromechanical systems, nanosensors, servomotors and bearings designed for use in future electrical and mechanical products. Since classical continuum mechanics is an inherently nonscale local theory, it may result in errors in the analysis *Corresponding author, E-mail: aimam@srbiau.ac.ir Indian J Phys https://doi.org/10.1007/s12648-019-01455-1 Ó 2019 IACS