Two-way actuation of graphene oxide arising from quantum mechanical effects

Abstract

Using density functional theory (DFT) calculations, two stable phases were found for several graphene oxide (GO) crystals with linearly aligned epoxy groups. Upon electron injection, they exhibit two-way actuation behavior. This two-way actuation is named by the observations that one piece of monolayer GO crystal is able to expand or contract upon electron injection, namely, contraction of the stable phase, and expansion of the meta-stable phase. The obtained maximum in-plane strains are as high as 8% and −5%. Such large deformation in opposite directions obtained from a single piece GO material offers unique opportunities in designing highly tunable and integrated actuators for microelectromechanical or nanoelectromechanical systems.

Machine Learning for Shape Memory Graphene Nanoribbons and Applications in Biomedical Engineering

“…The electronic re-arrangement around the zigzag interfaces bends the 2D layer at angle α, as shown by the optimized DFT structure also represented in Figure 1. According to [31], the GO sheet presents two phases around α = 104°and 133° [31,32], corresponding to lattice constants of a lat ∼ 16 Å and 18.5 Å. The two phases are separated by ∼100 meV.…”

“…Additionally, GO can endow with shape memory behavior to nanocomposites [27,28] for bone repair with minimal invasive surgery [29], and electrical actuators with low power consumption [30], essential for many applications in bioengineering. Recently, first-principle calculations have shown that GO with highly ordered epoxy groups can experience shape memory effect on its own without the presence of a polymer matrix [31,32] and can experience recoverable strain rates up to 14%. Applications for such shape memory nanomaterials include resonators, artificial muscles, and molecular robots [33], among many others.…”

Studies of Shape Memory Graphene Nanostructures via Integration of Physics-based Modelling and Machine Learning

“…The optimized structure is bent at the carbon-oxygencarbon row, with angle α, and defines zigzag interfaces with the oxygen row of atoms. According to [13], the GO sheet posses two phases around α = 104 • and 133 • [13,14], corresponding to lattice constants of a lat ∼ 16 Å and 18.5 Å. The two phases are separated by an energy of ∼ 100 meV.…”

“…It is well known now that GO by itself, without the presence of a matrix, can also exhibit shape memory effects. It has been reported that a GO with highly ordered oxygen epoxide groups can experience recoverable strain rates up to 14%, paving the way for such applications as shape memory devices at the nanoscale dimensions [13,14], resonators, artificial muscles, and molecular robots [15]. The GO sheet presents stable phases at two different lattice constants, separated by ∼ 100 meV in the energy vs lattice constant space.…”

Mechanical and electromechanical properties of functionalized hexagonal boron nitride nanosheet: A density functional theory study

“…Studies show that the graphene oxide bandgap under tensile stress is reduced due to the weakening of C-O hybridization. 17,[60][61][62] To properly understand the electrical properties of OH-BNNS under uniaxial tensile strain, the electron density of states and the bandgap of OH-BNNS with 20% and 60% hydroxyl coverage ratios under strains of 0.05 and 0.10 are presented in Figs. 6(a)-6(d).…”