Using origami design principles to fold reprogrammable mechanical metamaterials

Science ◽  
2014 ◽  
Vol 345 (6197) ◽  
pp. 647-650 ◽  
Author(s):  
Jesse L. Silverberg ◽  
Arthur A. Evans ◽  
Lauren McLeod ◽  
Ryan C. Hayward ◽  
Thomas Hull ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Compressive Modulus ◽  
Unit Cell ◽  
Lattice Defects ◽  
Programmable Matter ◽  
Nanometer Size ◽  
Scale Free ◽  
Mechanical Metamaterials ◽  
Geometric Character ◽  
Crystallographic Structures

Although broadly admired for its aesthetic qualities, the art of origami is now being recognized also as a framework for mechanical metamaterial design. Working with the Miura-ori tessellation, we find that each unit cell of this crease pattern is mechanically bistable, and by switching between states, the compressive modulus of the overall structure can be rationally and reversibly tuned. By virtue of their interactions, these mechanically stable lattice defects also lead to emergent crystallographic structures such as vacancies, dislocations, and grain boundaries. Each of these structures comes from an arrangement of reversible folds, highlighting a connection between mechanical metamaterials and programmable matter. Given origami’s scale-free geometric character, this framework for metamaterial design can be directly transferred to milli-, micro-, and nanometer-size systems.

Microstructures and Mechanical Property of Ni Processed by High-Pressure Torsion and Their Evolution upon Annealing

2006 ◽  
Vol 114 ◽  
pp. 45-50 ◽  
Author(s):  
Zhi Qing Yang
Keyword(s):  
High Pressure ◽  
Grain Boundaries ◽  
Room Temperature ◽  
High Pressure Torsion ◽  
Small Difference ◽  
Dynamical Evolution ◽  
Peripheral Region ◽  
Lattice Defects ◽  
Grain Sizes ◽  
Xrd And Tem

XRD, TEM, microhardness and thermal analysis were carried out on a series of Ni samples produced by high-pressure torsion (HPT). The evolution of microstructures and their inhomogeneity were investigated. The local microstrain showed dynamical oscillations as a function of the HPT rotations, demonstrating dynamical evolution of lattice defects during the procedure. Both XRD and TEM showed that a small difference in grain sizes remains even after 5 revolutions of HPT with smaller grain sizes at the peripheral region of the sample. The higher microhardness at the peripheral region is the result of the smaller grain sizes and the higher density of lattice defects, compared with the central region. Thermal treatment at a heating rate of 20K/min from room temperature to 473K did not result in decreased microhardness, but increased by about 10% for samples treated with not more than 3 rotations of HPT. The increase in microhardness was attributed to further grain refinement, the formation of a larger fraction of high-angle grain boundaries and grain boundaries being closer to equilibrium after recovery.

scholarly journals Bio-Inspired Active Skins for Surface Morphing

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Yujin Park ◽  
Gianmarco Vella ◽  
Kenneth J. Loh
Keyword(s):  
Deformation Mechanism ◽  
Unit Cell ◽  
Material Behavior ◽  
Two Dimensional ◽  
New Class ◽  
Mechanical Metamaterials ◽  
Unique Material ◽  
Out Of Plane ◽  
Unit Cells ◽  
Significant Attention

AbstractMechanical metamaterials that leverage precise geometrical designs and imperfections to induce unique material behavior have garnered significant attention. This study proposes a Bio-Inspired Active Skin (BIAS) as a new class of instability-induced morphable structures, where selective out-of-plane material deformations can be pre-programmed during design and activated by in-plane strains. The deformation mechanism of a unit cell geometrical design is analyzed to identify how the introduction of hinge-like notches or instabilities, versus their pristine counterparts, can pave way for controlling bulk BIAS behavior. Two-dimensional arrays of repeating unit cells were fabricated, with notches implemented at key locations throughout the structure, to harvest the instability-induced surface features for applications such as camouflage, surface morphing, and soft robotic grippers.

Grain boundaries and lattice defects in YBa2Cu3O7−x ceramics

1987 ◽  
Vol 5 (11-12) ◽  
pp. 425-428 ◽  
Author(s):  
Wen Shulin ◽  
Feng Jingwei ◽  
Song Xingyun ◽  
Lu Lisheng ◽  
Li Chenghong ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Lattice Defects

scholarly journals Elasticity Approach to Predict Shape Transformation of Functionally Graded Mechanical Metamaterial under Tension

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3452
Author(s):  
Mohammad Javad Khoshgoftar ◽  
Ali Barkhordari ◽  
Sajjad Seifoori ◽  
Mohammad Javad Mirzaali
Keyword(s):  
Elastic Stiffness ◽  
Theory Of Elasticity ◽  
Functionally Graded ◽  
Unit Cell ◽  
Uniaxial Tensile ◽  
Geometrical Parameters ◽  
Design Strategies ◽  
Shape Transformation ◽  
Complex Deformation ◽  
Mechanical Metamaterials

The re-entrant structures are among the simple unit cell designs that have been widely used in the design of mechanical metamaterials. Changing the geometrical parameters of these unit cell structures, their overall elastic properties (i.e., elastic stiffness and Poisson’s ratio), can be simultaneously tuned. Therefore, different design strategies (e.g., functional gradient) can be implemented to design advanced engineering materials with unusual properties. Here, using the theory of elasticity and finite element modeling, we propose a fast and direct approach to effectively design the microarchitectures of mechanical metamaterials with re-entrant structures that allow predicting complex deformation shapes under uniaxial tensile loading. We also analyze the efficiency of this method by back calculating the microarchitectural designs of mechanical metamaterials to predict the complex 1-D external contour of objects (e.g., vase and foot). The proposed approach has several applications in creating programmable mechanical metamaterials with shape matching properties for exoskeletal and soft robotic devices.

Structural Units and Energy of Grain Boundaries in GaN

2003 ◽  
Vol 798 ◽  
Author(s):  
Jun Chen ◽  
Pierre Ruterana ◽  
Gerard Nouet
Keyword(s):  
Grain Boundaries ◽  
Atomic Structure ◽  
Boundary Plane ◽  
Unit Cell ◽  
Wurtzite Structure ◽  
Structural Units ◽  
Weber Potential

ABSTRACTThe energy of coincidence grain boundaries in wurtzite structure was investigated with the Stillinger-Weber potential after modification for GaN. A boundary can have two interfaces with a different period corresponding to the edge and diagonal of the unit cell of coincidence site lattices for rotations around [0001] in the range 0–60°. Their energy depends mainly on the atomic structure of the dislocation cores used for the boundary plane reconstruction. As a function of the structure units in the period, the energy of the edge and diagonal shows two minima which are observed for the edge boundaries.

On the Role of Schottky Disorder on the Stability and Structure of (100) Twist Grain Boundaries in Nio

1983 ◽  
Vol 24 ◽  
Author(s):  
D. Wolf
Keyword(s):  
Grain Boundaries ◽  
Point Defects ◽  
Coincidence Site Lattice ◽  
Unit Cell ◽  
Twist Boundary ◽  
Site Lattice ◽  
Metastable Structures ◽  
The Stability ◽  
Twist Boundaries

ABSTRACTRecent calculations on (100) coincidence-site lattice (CSL) twist boundaries in the NaCl structure have shown that without point defects these boundaries are only marginally stable. Following an earlier suggestion that point defects are the likely source for the considerable stability of these boundaries observed experimentally for Mgo and NiO, Tasker and Duffy have shown recently that the creation of a Schottky pair can, indeed, stabilize a (100) twist boundary in NiO. In this article a variety of configurations in which one or more Schottky pairs have been created in the perfect CSL or anti-CSL unit cell are investigated. It is concluded that many metastable structures may exist which differ mainly with respect to their different interfacial mass densities and the relative translation of the two halves of the bicrystal.

scholarly journals Harnessing the anisotropic multistability of stacked-origami mechanical metamaterials for effective modulus programming

2018 ◽  
Vol 29 (14) ◽  
pp. 2933-2945 ◽  
Author(s):  
Sattam Sengupta ◽  
Suyi Li
Keyword(s):  
Adaptive Systems ◽  
Three Dimensional ◽  
Unit Cell ◽  
Effective Modulus ◽  
Stable States ◽  
Mechanical Metamaterials ◽  
Principal Axes ◽  
Unit Cells ◽  
Multiple Unit ◽  
Parametric Analyses

This study examines a three-dimensional, anisotropic multistability of a mechanical meta material based on a stacked Miura-ori architecture, and investigates how such a unique stability property can impart stiffness and effective modulus programming functions. The unit cell of this metamaterial can be bistable due to the nonlinear relationship between rigid-folding and crease material bending. Such bistability possesses an unorthodox property: the arrangement of elastically stable and unstable equilibria are different along different principal axes of the unit cell, so that along certain axes the unit cell exhibits two force–deformation relationships concurrently within the same range of deformation. Therefore, one can achieve a notable stiffness adaptation via switching between the two stable states. As multiple unit cells are assembled into a metamaterial, the stiffness adaptation can be aggregated into an on-demand modulus programming capability. That is, via strategically switching different unit cells between stable states, one can control the overall effective modulus. This research examines the underlying principles of anisotropic multistability, experimentally validates the feasibility of stiffness adaptation, and conducts parametric analyses to reveal the correlations between the effective modulus programming and Miura-ori designs. The results can advance many adaptive systems such as morphing structures and soft robotics.

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