Harvard researchers have designed a new foldable, self-actuated 3D material that can be continuously controlled and reprogrammed to change size, volume, and shape. The study appeared March 11 in Nature Communications and offers a glimpse into the material that was inspired by an origami technique called snapology. The material is scalable from the nanoscale to the meter-scale and could be used to make anything from surgical stents to portable pop-up domes for disaster relief.
When folded flat, the total volume of the material is reduced by up to 100-fold while still being able to withstand the weight of an elephant before popping right back up ready for the next task. We spoke to the study’s first author Johannes T.B. Overvelde from Harvard’s School of Engineering and Applied Sciences about the material.
ResearchGate: Can you offer a simple explanation of the material?
Johannes T.B. Overvelde: The structure is inspired by an origami technique called snapology, and is made from extruded cubes with 24 faces and 36 edges. Like origami, the cube can be folded along its edges to change shape. In the article we demonstrate, both theoretically and experimentally with a centimeter-scale prototype, that the cube can be deformed into many different shapes by folding certain edges, which act like hinges. We furthermore embedded pneumatic actuators (air pockets) into the structure, which can be programmed to deform specific hinges, changing the cube’s shapes and size, and removing the need for external force.
RG: How do you control the material? How easily could it be shaped and changed in real-time?
JO: Through analytical analysis we identified that the structure has exactly three degrees of freedom (i.e. there are three ways in which the structure can deform). By strategically placing and pressurizing the embedded actuators, we were able to control and deform the structure along these three degrees of freedom. The large assembly of extruded cubes (4x4x4) contained a total of 96 actuators, 32 for each degree of freedom, which we pressurized manually using three syringes. The structure responded directly, such that the deformed states could be achieved within a few seconds. Moreover, when releasing the pressure, the energy stored in the elastic hinges immediately pushed the structure back to its initial fully expanded state.
RG: What inspired the material’s design?
JO: The current work was initially inspired by snapology, a type of modular unit-based origami invented by Heinz Strobl in which paper ribbons are used to create complex geometric extruded polyhedra. While snapology provided the geometric starting point for our research, we focused on the foldability of these structures and how this can lead to new designs for transformable metamaterials (see here for more information on snapology).
