Advances in fabrication technologies are enabling the production of architected materials with unprecedented properties. Most such materials are characterized by a fixed geometry, but in the design of some materials it is possible to incorporate internal mechanisms capable of reconfiguring their spatial architecture, and in this way to enable tunable functionality. Inspired by the structural diversity and foldability of the prismatic geometries that can be constructed using the snapology origami technique, here we introduce a robust design strategy based on space-filling tessellations of polyhedra to create three-dimensional reconfigurable materials comprising a periodic assembly of rigid plates and elastic hinges. Guided by numerical analysis and physical prototypes, we systematically explore the mobility of the designed structures and identify a wide range of qualitatively different deformations and internal rearrangements. Given that the underlying principles are scale-independent, our strategy can be applied to the design of the next generation of reconfigurable structures and materials, ranging from metre-scale transformable architectures to nanometre-scale tunable photonic systems.
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This work was supported by the Materials Research Science and Engineering Center under NSF Award number DMR-1420570. K.B. also acknowledges support from the National Science Foundation (CMMI-1149456-CAREER). We thank M. Mixe and S. Shuham for assistance in the fabrication of the cardboard prototypes, and R. Wood for the use of his laboratory.
Space-filling and periodic assemblies of convex polyhedra are used as a template to construct prismatic architected materials. After selecting a space-filling tessellation, we focus on a unit cell and separate the polyhedra while ensuring that the normals of all periodically-placed face pairs remain aligned. We then extrude the edges of the polyhedra in the direction normal to their faces to construct the extruded unit cell, which is then used to form the architected material.
Three prototypes of the 3D prismatic architected materials were constructed using cardboard for the rigid faces and double-sided tape for flexible hinges. Depending on the space-filling assembly of polyhedra used as a template, the resulting architected material has different deformation modes or is completely rigid.
To alter the reconfigurability of the architected materials, we reduce their connectivity by extruding only selected face pairs of the unit cell, while making the remaining faces rigid. As an example, the architected material based on the space-filling assembly of truncated octahedra can made reconfigurable by extruding only 6 of its faces and making the remaining 8 faces rigid.
A variety of qualitatively different deformation modes can be achieved in the proposed prismatic architected materials besides shear, including internal reconfigurations that do not alter the macroscopic shape of the materials, and uniform expansion along one or two principal directions.
Using multi-material additive manufacturing we fabricated two of the proposed prismatic architected materials. The faces were fabricated using a rigid material, while the hinges were given a finite size and printed using a softer material. The two architectures that were printed are characterized by respectively zero and one deformation modes.
About this article
Nature Reviews Materials (2017)