Laboratory for Atomistic and Molecular Mechanics LAMM

Cambridge, MA, United States

Laboratory for Atomistic and Molecular Mechanics LAMM

Cambridge, MA, United States
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Tarakanova A.,Laboratory for Atomistic and Molecular Mechanics LAMM | Buehler M.J.,Laboratory for Atomistic and Molecular Mechanics LAMM | Buehler M.J.,Massachusetts Institute of Technology
Journal of the Royal Society Interface | Year: 2012

Among a myriad of spider web geometries, the orb web presents a fascinating, exquisite example in architecture and evolution. Orb webs can be divided into two categories according to the capture silk used in construction: cribellate orb webs (composed of pseudoflagelliform silk) coated with dry cribellate threads and ecribellate orb webs (composed of flagelliform silk fibres) coated by adhesive glue droplets. Cribellate capture silk is generally stronger but lessextensiblethan viscid capture silk, and a body of phylogenic evidence suggests that cribellate capture silk is more closely related to the ancestral form of capture spiral silk. Here, we use a coarse-grained web model to investigate how the mechanical properties of spiral capture silk affect the behaviour of the whole web, illustrating that more elastic capture spiral silk yields a decrease in web system energy absorption, suggesting that the function of the capture spiral shifted from prey capture to other structural roles. Additionally, we observe that in webs with more extensible capture silk, the effect of thread strength on web performance is reduced, indicating that thread elasticity is a dominant driving factor in web diversification. © 2012 The Royal Society.


Xu Z.,Laboratory for Atomistic and Molecular Mechanics LAMM | Buehler M.J.,Laboratory for Atomistic and Molecular Mechanics LAMM | Buehler M.J.,Massachusetts Institute of Technology
ACS Nano | Year: 2010

Graphene features a two-dimensional structure, where applications from electronic building blocks to reinforced composites are emerging, enabled through the utilization of its intriguing electrical, mechanical, and thermal properties. These properties are controlled by the structural makeup of graphene, which is known to display multiple morphologies that change under thermal fluctuations and variations of its geometry. However, as of now, a systematic understanding of the relationship between the conformation of graphene and its geometry remains unknown, preventing rational bottom-up design of materials, structures, and devices. Here, we present a conformational phase diagram for rectangular graphene sheets, defined by their geometry (size and aspect ratio), boundary conditions, and the environmental conditions such as supporting substrates and chemical modifications, as well as changes in temperature. We discover the occurrence of three major structural arrangements in membrane, ribbon, and scroll phases as the aspect ratio of the graphene nanoribbon increases. A theoretical and computational analysis of governing mechanisms for each conformation is provided. © 2010 American Chemical Society.

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