Controlling Movement at Nanoscale: Curvature Driven Mechanotaxis

• Published in: Small (Weinheim an der Bergstrasse, Germany) Vol. 17; no. 35; pp. e2100909 - n/a
• Main Authors: Machado, Leonardo D., Bizao, Rafael A., Pugno, Nicola M., Galvão, Douglas S.
• Format: Journal Article
• Language: English
• Published: Weinheim Wiley Subscription Services, Inc 01.09.2021
• Subjects: Carbon nanotubes; Curvature; Energy gradient; Graphene; graphene nanoribbons; modeling; molecular dynamics; Nanoribbons; Nanotechnology; nano‐oscillator; Oscillators; Surface energy
• ISSN: 1613-6810; 1613-6829
• DOI: 10.1002/smll.202100909

Locating and manipulating nano‐sized objects to drive motion is a time and effort consuming task. Recent advances show that it is possible to generate motion without direct intervention, by embedding the source of motion in the system configuration. In this work, an alternative manner to controllably displace nano‐objects without external manipulation is demonstrated, by employing spiral‐shaped carbon nanotube (CNT) and graphene nanoribbon structures (GNR). The spiral shape contains smooth gradients of curvature, which lead to smooth gradients of bending energy. It is shown that these gradients as well as surface energy gradients can drive nano‐oscillators. An energy analysis is also carried out by approximating the carbon nanotube to a thin rod and how torsional gradients can be used to drive motion is discussed. For the nanoribbons, the role of layer orientation is also analyzed. The results show that motion is not sustainable for commensurate orientations, in which AB stacking occurs. For incommensurate orientations, friction almost vanishes, and in this instance, the motion can continue even if the driving forces are not very high. This suggests that mild curvature gradients, which can already be found in existing nanostructures, could provide mechanical stimuli to direct motion. Molecular dynamics simulations and modeling are used to show that spiral‐shaped graphene nanoribbons and carbon nanotubes can drive oscillatory motion, as gradients of elastic and surface energies in high curvature regions direct the nano‐oscillators toward low curvature regions. This oscillatory regime can be sustained for proper crystal orientations, in which movement is near frictionless.