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Research Papers

Bioinspired Graphene Nanogut

[+] Author and Article Information
Zhao Qin

Laboratory for Atomistic and
Molecular Mechanics (LAMM),
Department of Civil and
Environmental Engineering,
Massachusetts Institute of Technology,
77 Massachusetts Ave., Room 1-235 A&B,
Cambridge, MA 02139;
Center for Computational Engineering,
Massachusetts Institute of Technology,
77 Massachusetts Ave.,
Cambridge, MA 02139

Markus J. Buehler

Laboratory for Atomistic and
Molecular Mechanics (LAMM),
Department of Civil and
Environmental Engineering,
Massachusetts Institute of Technology,
77 Massachusetts Ave., Room 1-235 A&B,
Cambridge, MA 02139;
Center for Computational Engineering,
Massachusetts Institute of Technology,
77 Massachusetts Ave., Cambridge, MA 02139;
Center for Materials Science and Engineering,
Massachusetts Institute of Technology,
77 Massachusetts Ave.,
Cambridge, MA 02139
e-mail: mbuehler@mit.edu

1Corresponding author.

Manuscript received September 20, 2012; final manuscript received December 29, 2012; accepted manuscript posted February 12, 2013; published online August 19, 2013. Editor: Yonggang Huang.

J. Appl. Mech 80(6), 061009 (Aug 19, 2013) (6 pages) Paper No: JAM-12-1453; doi: 10.1115/1.4023641 History: Received September 20, 2012; Accepted December 29, 2012; Revised December 29, 2012

Low-dimensional nanomaterials are attractive for various applications, including damage repair, drug delivery, and bioimaging. The ability to control the morphology of nanomaterials is critical for manufacturing as well as for utilizing them as functional materials or devices. However, the manipulation of such materials remains challenging, and effective methods to control their morphology remain limited. Here, we propose to mimic a macroscopic biological system—the gut—as a means to control the nanoscale morphology by exploiting the concept of mismatch strain. We show that, by mimicking the development of the gut, one can obtain a controlled wavy shape of a combined carbon nanotube and graphene system. We show that the scaling laws that control the formation of the gut at the macroscale are suitable for ultrasmall-diameter carbon nanotubes with a diameter smaller than 7 Å but do not account for the morphology of systems with larger diameter nanotubes. We find that the deviation is caused by cross-sectional buckling of carbon nanotube, where this behavior relates to the different constitutive laws for carbon nanotube and graphene in contrast to the macroscale biological system. Our study illustrates the possibility of downscaling macroscale phenomena to the nanoscale using continuum mechanics theory, with wide-ranging applications in nanotechnology.

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Figures

Grahic Jump Location
Fig. 1

Simulation setting up and procedure. (a) Schematic figure of the system composed of a combination of a graphene ribbon and a carbon nanotube (CNT). The diameter of the CNT is d, the width of the graphene ribbon is w, the system total length is L, and the graphene ribbon is initially εL shorter than the carbon nanotube (where ε is the mismatch strain). The step-by-step simulation procedure is summarized in (b)–(d). (b) Atomistic geometry of one of the structures considered in our study. The CNT is (3,3) tube with d = 4.1 Å, the graphene ribbon is w = 15 Å, and the total length is L = 1000 Å (which is partly shown here by snapshots). The distance between the edges of the CNT and the graphene ribbon is initially 10 Å. The edges are functionalized by hydroxyl groups with the purpose of forming hydrogen bonds as a glue between the two components. As the simulation starts, the graphene ribbon is subjected to tensile strain of ε such that it reaches the same length as the CNT. (c) Graphene with prescribed strain is displaced by 8 Å in the y direction. We fix the two ends of the graphene ribbon and relax other parts of the system. The inset shows a segment with details. The hydrogen bonds are depicted in (b)–(c) by dashed lines. (d) Geometry after all constraints are removed and the system is fully relaxed. The inserted figure on the right shows the morphology of loops in the chick's gut at embryonic day 12 taken from Ref. [15] at a length-scale 106 times larger than our nanogut system (adapted and reprinted from Ref. [15] with permission from Nature Publishing Group Copyright 2011).

Grahic Jump Location
Fig. 4

Snapshots of carbon nanotubes in their initial state and at equilibrium. (a) Geometries of a (3,3) CNT (d = 4.1 Å, ɛ = 0.2, w = 28 Å), top view (left) and the shape of the cross-section. The upper snapshots show the initial geometry, and the lower snapshots show the geometry at equilibrium. (b) Geometries of CNT (5,5) (d = 6.8 Å, ɛ = 0.2, w = 28 Å), top view (left) and the shape of the cross-section (right). The upper snapshots depict the initial geometry, and the lower snapshots show the geometry at equilibrium. The graphene ribbon and the hydroxyl groups are not shown in those snapshots for clarity. (c) Total energy and number of hydrogen bonds per unit length as functions of simulation time for a (5,5) CNT (d = 6.8 Å, ɛ = 0.2, w = 28 Å). (d) Total energy and number of hydrogen bonds per unit length as functions of the simulation time for a (3,3) CNT (d = 4.1 Å, ɛ = 0.2, w = 28 Å).

Grahic Jump Location
Fig. 3

Measured geometric parameters of wavy shapes of CNT-graphene ribbon systems at equilibrium. (a) Contour length of a loop period as a function of the CNT diameter. The linear curve is fitted according to Eq. (4) and data points with d < 6.8 Å. (b) Radius of the loop at the maximum amplitude as a function of the CNT diameter and prescribed strain. The linear curve is fitted according to Eq. (5) and data points with d < 6.8 Å.

Grahic Jump Location
Fig. 2

Geometry profile of the (3,3) CNT axis as a function of simulation time. (a) Snapshots of the evolution of the geometry of the (3,3) CNT with d = 4.1 Å, ɛ = 0.2, and w = 15 Å during equilibration. The CNT axis is represented by a series of beads. The coordinate of each bead is given by the mass center of 50 neighboring carbon atoms. (b) RMSD of the all axis beads as a function of equilibration time. It is noted there is a significant jump at ∼10 ps. The simulation snapshots in panel (a) are denoted by arrows. (c) Distance profiles of the axis beads from the end-to-end connection line at different equilibration times (h as show in (a) for snapshot at 170 ps). (d) Average contour length of the loop period as a function of equilibration time for different temperatures. (e) Average radius and standard deviation at the maximum amplitude as a function of equilibration time for different temperatures.

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