An origami technique called Miura-ori has been used to demonstrate how paper tubes can be folded to produce stiff but flexible structures. With the concept of paper folding being increasingly recognized as an area of engineering research, a team from the University of Illinois at Urbana-Champaign, the Georgia Institute of Technology and the University of Tokyo have created a new “zippered tube” configuration that produces paper structures sufficiently stiff to hold weight, and that have potential applications in robotics, construction, shipping, pop-up furniture, quick-assembling emergency shelters and even space exploration.
Origami is being seen as a means to develop deployable and reconfigurable engineering systems that take advantage of their flexibility as the thin sheets can be bent and twisted easily, and also folded flat for storage and transport. As reported in the journal Proceedings of the National Academy of Sciences [Filipov et al. Proc. Natl. Acad. Sci. U.S.A. (2015) DOI: 10.1073/pnas.1509465112], the researchers were able to produce precise zig-zag folded strips of paper, before gluing two strips together to form a tube.
Although a single strip of paper is highly flexible, the coupled tubes are much stiffer and don’t fold, twist or bend in as many directions. In addition, on folding this zipper-like structure can then be easily expanded into the rigid tube configuration. As researcher Glaucio Paulino said, “The geometry is what really plays a role. We are putting two tubes together in a strange way. What we want is a structure that is flexible and stiff at the same time. This is just paper, but it has tremendous stiffness.”
Such assemblages can be deployed through a single flexible motion, and are also significantly stiffer for any other type of bending or twisting movement. In addition, assembling thin sheets into these tubular assemblages can create metamaterials that can be deployed, stiffened and tuned. This zipper configuration even using tubes with different angles of folding – by combining tubes of different geometries, it is possible to produce a range of 3D structures, while being able to change functionality in real time makes the structures adaptable and reconfigurable for different uses.
The concept involved is applicable from as small as the nanoscale, perhaps in biomedical devices, to large-scale structures, increasing the possible uses. The researchers now hope to try different combinations of tubes with different folding angles to construct new structures, and also to apply their techniques to other materials and applications.
"We are putting two tubes together in a strange way. What we want is a structure that is flexible and stiff at the same time. This is just paper, but it has tremendous stiffness.”Glaucio Paulino