Controlling Movement at Nanoscale: Curvature Driven Mechanotaxis

Abstract

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.

Self-propelled continuous transport of nanoparticles on a wedge-shaped groove track

“…17 However, manipulating the external energy gradient to maintain the motion in these active approaches increases the cost of equipment. Therefore, it is more advantageous to generate directional transport through an intrinsic mechanism, where the motion sources are embedded in the system configuration, 32 which has been proved to be achievable by recent advances. Researchers have realized the directional motion by exploiting the substrate inhomogeneity in wettability, 33,34 curvature, [35][36][37] strain, 38,39 bend, 40 structure, 41 or stiffness.…”

“…42,43 Recently, a novel spiral-shaped structure was proposed to displace nano-objects, and the results manifest that an oscillatory movement can be produced by the curvature gradient which leads to a bending energy gradient. 32 Molecular dynamics (MD) simulations proved that a nano-slider can be driven towards the hard region on a substrate with a stiffness gradient. 1 In addition, abundant studies have suggested the benefit of asymmetric wedge tracks, [44][45][46][47][48] for guiding the directional motion.…”

Oscillation of a graphene flake on an undulated substrate with amplitude gradient

“…be manipulated through changing the stiffness gradient of the substrate [16]. Additionally, the potential gradient deriving from some specially designed nanostructures, as the Archimedean-like spiral-shaped carbon nanotubes [17], provides the driving force that supports its use as a nano-oscillator.…”

Toward steering the motion of surface rolling molecular machines by straining graphene substrate

“…The free energy of nanomachines decreases as they move toward the region of the substrate which has lower temperature 23 . Galvão et al 24 demonstrated that, the curvature gradient of the substrate is able to provide mechanical stimuli to direct the motion. According to this study, the spiral-shaped substrates create gradients of bending energy which leads to the driving force on the nanomaterial located on the surface.…”