Abstract
Abstract This article presents a soft cylindrical multistable origami structure based on “bendy straws,” consisting of multiple conical frusta mimicking the structure of a flexible drinking straw. These frusta are connected in such a way that the whole structure is axially multistable, having a stable compressed state in which its smallest frustum is collapsed. The bendy straw structure can also be modified so that the smallest frustum collapses only partially, keeping the structure in a bent state. We studied the geometry of a similar structure consisting of polygonal frusta instead of conical ones and used this geometry to design a nonrigidly foldable origami pattern folding into a similar origami bendy straw structure. Most of the origami structures presented so far have been modeled from rigidly foldable origami patterns: These origami structures do not rely on local deformations of the sheet and cannot use it to their advantage, whereas the nonrigid origami structure presented here features multistability. We have established that this origami structure is not only axially multistable, but that it can also be kept in a bent state, thanks to the use of pop-through defects (PTDs). The origami bendy straws studied here were made from paper (with a density of 90 g/m2) bilaminated with a 42.5 μm thick plastic film. A digital dynamometer was used to study the forces required to compress and expand a single origami bendy straw, create and reverse a PTD, and bend an origami bendy straw using PTDs.
Highlights
In a recent Focus published in Science Robotics, Rus andSung predict that origami robots will soon be developed for use as autonomous machines showing greater customizability and adaptability [1]
We studied the geometry of a similar structure consisting of polygonal frusta instead of conical ones, and use this geometry to design a non-rigidly foldable origami pattern that folds into a similar origami bendy straw structure
It is worth noting that this origami pattern is very similar to the previously presented REBO pattern [14], but we have described here how to introduce Pop-Through Defects (PTDs) in order to obtain the original bendy straw’s bent position, which has never been applied to a REBO-like pattern so far
Summary
Sung predict that origami robots will soon be developed for use as autonomous machines showing greater customizability and adaptability [1]. It is worth noting that bistability and even multistability can be observed in soft structures such as the common bendy straw, which can be either bistable or multistable as required [12] This was the starting point of our study on the design and construction of a multistable origami tube. This bendy straw structure consisting of non-identical conical frusta can be made to become axially bistable, which means that it can adopt two different states: a tall stable state and a compressed state in which its smallest frustum is inverted.
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