Bulletin of the American Physical Society
APS March Meeting 2015
Volume 60, Number 1
Monday–Friday, March 2–6, 2015; San Antonio, Texas
Session D44: Invited Session: Mechanical Metamaterials |
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Sponsoring Units: GSNP GSOFT Chair: Pedro Reis, Massachusetts Institute of Technology Room: 214D |
Monday, March 2, 2015 2:30PM - 3:06PM |
D44.00001: From form to feel: using origami design principles to shape mechanics Invited Speaker: Christian Santangelo |
Monday, March 2, 2015 3:06PM - 3:42PM |
D44.00002: Mechanical metamaterials for cloaking Invited Speaker: Martin Wegener We review our experiments on mechanical metamaterials for cloaking. This includes two-dimensional graded laminate elastic metamaterials for broadband cloaking of flexural waves in thin plates, three-dimensional pentamode metamaterials and modifications thereof, e.g., for three-dimensional core-shell cloaks, and direct coordinate transformations of discrete hexagonal lattices. We suspect that the latter mimic inhomogeneous and anisotropic Cosserat metamaterial distributions. Polymer structures with sub-micrometer feature sizes are fabricated by galvo-scanner dip-in three-dimensional direct-laser-writing optical lithography, macroscopic structures by a commercially available three-dimensional printer. [Preview Abstract] |
Monday, March 2, 2015 3:42PM - 4:18PM |
D44.00003: Mechanical Metamaterials with Negative Compressibility Transitions Invited Speaker: Adilson Motter When tensioned, ordinary materials expand along the direction of the applied force. In this presentation, I will explore network concepts to design metamaterials exhibiting negative compressibility transitions, during which the material undergoes contraction when tensioned (or expansion when pressured). Such transitions, which are forbidden in thermodynamic equilibrium, are possible during the decay of metastable, super-strained states. I will introduce a statistical physics theory for negative compressibility transitions, derive a first-principles model to predict these transitions, and present a validation of the model using molecular dynamics simulations. Aside from its immediate mechanical implications, our theory points to a wealth of analogous inverted responses, such as inverted susceptibility or heat-capacity transitions, allowed when considering realistic scales. References: Z.G. Nicolaou and A.E. Motter, J. Stat. Phys. 151(6), 1162 (2013); Z.G. Nicolaou and A.E. Motter, Nature Materials 11, 608 (2012). [Preview Abstract] |
Monday, March 2, 2015 4:18PM - 4:54PM |
D44.00004: Performance through Deformation and Instability Invited Speaker: Katia Bertoldi Materials capable of undergoing large deformations like elastomers and gels are ubiquitous in daily life and nature. An exciting field of engineering is emerging that uses these compliant materials to design active devices, such as actuators, adaptive optical systems and self-regulating fluidics. Compliant structures may significantly change their architecture in response to diverse stimuli. When excessive deformation is applied, they may eventually become unstable. Traditionally, mechanical instabilities have been viewed as an inconvenience, with research focusing on how to avoid them. Here, I will demonstrate that these instabilities can be exploited to design materials with novel, switchable functionalities. The abrupt changes introduced into the architecture of soft materials by instabilities will be used to change their shape in a sudden, but controlled manner. Possible and exciting applications include materials with unusual properties such negative Poisson's ratio, phononic crystals with tunable low-frequency acoustic band gaps and reversible encapsulation systems. [Preview Abstract] |
Monday, March 2, 2015 4:54PM - 5:30PM |
D44.00005: Programmable and Frustrated Mechanical Metamaterials Invited Speaker: Martin van Hecke Most metamaterials to date consist of periodic lattices of unit cells that work together in harmony. Here we demonstrate how frustration leads to new functionality. First we discuss 2D mechanical metamaterials whose response to uniaxial compression can be programmed by lateral confinement, allowing monotonic, nonmonotonic, and hysteretic behavior. These functionalities arise from a broken rotational symmetry which causes a highly nonlinear competition between two mutually incompatible modes of deformation. Second we show how to create non-periodic 3D metamaterials, leading to a wealth of novel functionalities, including mechanical pattern recognition. By perturbing the stacking order in these material we incorporate frustration which leads to multistable behavior. [Preview Abstract] |
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