Mesoscale modeling of mechanics of carbon nanotubes: Self-assembly, self-folding, and fracture

Buehler, Markus J.

doi:10.1557/jmr.2006.0347

Cited by 192 publications

(163 citation statements)

References 64 publications

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“…Similar results have been shown in previous work for self-folding filamentous structures 44,46,48,49 enabling a direct link between continuum theory and simulation or experiment. The simplified relations given in eq.…”

Section: Analysis Of the Self-folded Fibrils: Nanorackets And Nanoringssupporting

confidence: 89%

Self-folding and aggregation of amyloid nanofibrils

2011

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Amyloids are highly organized protein filaments, rich in beta-sheet secondary structures that self-assemble to form dense plaques in brain tissues affected by severe neurodegenerative disorders (e.g. Alzheimer's Disease). Identified as natural functional materials in bacteria, in addition to their remarkable mechanical properties, amyloids have also been proposed as a platform for novel biomaterials in nanotechnology applications including nanowires, liquid crystals, scaffolds and thin films. Despite recent progress in the understanding amyloid structure and behavior, the latent selfassembly mechanism and the underlying adhesion forces that drive the aggregation process remain poorly understood. On the basis of previous full atomistic simulations, here we report a simple coarse-grain model to analyze the competition between adhesive forces and elastic deformation of amyloid fibrils. We use simple model system to investigate self-assembly mechanisms of fibrils, focused on the formation of self-folded nanorackets and nanorings, and thereby address a critical issue in linking the biochemical (Angstrom) to micrometer scales relevant for larger-scale states of functional amyloid materials. We investigate the effect of varying the interfibril adhesion energy on the structure and stability of self-folded nanorackets and nanorings and demonstrate that such aggregated amyloid fibrils are stable in such states even when the fibril-fibril interaction is relatively weak, suggesting a strong propensity towards aggregation, given that the constituting amyloid fibril lengths exceed a critical fibril length-scale of several hundred nanometers. We further present a simple approach to directly determine the interfibril adhesion strength from geometric measures. In addition to providing insight into the physics of aggregation of amyloid fibrils our model enables the analysis of large-scale amyloid plaques and presents a new method for the estimation and engineering of the adhesive forces responsible of the self-assembly process of amyloid nanostructures, filling a 2 gap that previously existed between full atomistic simulations of primarily ultra-short fibrils and much larger micrometer-scale amyloid aggregates. Via direct simulation of large-scale amyloid plaques consisting of hundreds of fibrils we demonstrate that the fibril length has a profound impact on their structure and mechanical properties, where critical fibril length-scale derived from our analysis defines the structure of amyloid plaques. A multi-scale modeling approach as used here, bridging the scales from Angstroms to micrometers, opens a wide range of possible nanotechnology applications by presenting a holistic framework that balances mechanical properties of individual fibrils, hierarchical self-assembly, and the adhesive forces determining their stability to facilitate the design of de novo amyloid materials.

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Section: Analysis Of the Self-folded Fibrils: Nanorackets And Nanoringssupporting

confidence: 89%

Self-folding and aggregation of amyloid nanofibrils

2011

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“…Our previous data for the thickness-dependent in-plane modulus of multiwalled CNT films indicated a strong dependence on the nanotube density and alignment (21), which are linked to the detailed growth details (26)(27)(28). Other approaches, such as mesoscopic simulations or atomistic models, found that CNT networks exhibit unique self-organization, including bending and bundling (29)(30)(31). Therefore, relating the nanoscale morphological details to the mechanical properties is critical.…”

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confidence: 99%

Zipping, entanglement, and the elastic modulus of aligned single-walled carbon nanotube films

Won

Gao

Panzer

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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Reliably routing heat to and from conversion materials is a daunting challenge for a variety of innovative energy technologies--from thermal solar to automotive waste heat recovery systems--whose efficiencies degrade due to massive thermomechanical stresses at interfaces. This problem may soon be addressed by adhesives based on vertically aligned carbon nanotubes, which promise the revolutionary combination of high through-plane thermal conductivity and vanishing in-plane mechanical stiffness. Here, we report the data for the in-plane modulus of aligned single-walled carbon nanotube films using a microfabricated resonator method. Molecular simulations and electron microscopy identify the nanoscale mechanisms responsible for this property. The zipping and unzipping of adjacent nanotubes and the degree of alignment and entanglement are shown to govern the spatially varying local modulus, thereby providing the route to engineered materials with outstanding combinations of mechanical and thermal properties.nanostructured materials | van der Waals | thermal interface materials | thermoelectrics | energy conversion N anostructured materials provide unique combinations of properties that promise performance breakthroughs for applications ranging from energy conversion to data storage and computation (1-4). In many cases it is the very unusual combination of two properties (2), neither of which is an extreme value when considered alone, that leads to adoption and major performance benefits. An example is the search for a mechanically compliant thermal conductor that can, for example, link semiconducting materials with the metals used for heat spreading and exchange. A particularly compelling case is thermoelectric waste heat recovery systems (3), for which the interfaces between the thermoelectric materials, electrodes, insulators, and heat exchangers must accommodate enormous, repetitive thermomechanical stress. However, nature does not provide a material combining the necessary high thermal conductivity with the required low elastic modulus (5, 6).Vertically aligned carbon nanotube (CNT) films may combine mechanical compliance with high thermal conductivity (7-18), but there have been few reports of the in-plane modulus of these films and little physical explanation for the wide range for the data (2-300 MPa) (19-25). Our previous data for the thickness-dependent in-plane modulus of multiwalled CNT films indicated a strong dependence on the nanotube density and alignment (21), which are linked to the detailed growth details (26-28). Other approaches, such as mesoscopic simulations or atomistic models, found that CNT networks exhibit unique self-organization, including bending and bundling (29-31). Therefore, relating the nanoscale morphological details to the mechanical properties is critical.Combined experimental, theoretical, and computational techniques applied to the more complex and fundamentally challenging single-walled CNT system are presented in this paper, along with the in-plane data for the modulus for sin...

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“…The fine-grained approach consists of the regular full atomistic simulations on the SWNT configuration. The other approach adopted from Buehler et al consists of approximating the structure of the SWNT as finite-sized beads connected with stiff springs (Buehler, 2006).…”

Section: Demonstrative Calculations On a Single Walled Carbon Nanotubementioning

confidence: 99%

“…In this work, we adopt the same approach and coarse-grain a 100 nm long (5,5) CNT as a 100 beads-chain with an equilibrium inter-bead separation distance of 1 nm. All the required parameters can be found in (Buehler 2006) and the dynamics of this system is simulated using LAMMPS. The time-step chosen for the dynamics is 50 fs and the production run is carried out for 10 ns.…”

Section: Coarse-grained Approachmentioning

confidence: 99%