Dragonfly-inspired deployable structures: how to inflate and stay flat?

Programming the final shape of a soft inflatable structure is a nontrivial challenge. Such a task is routinely accomplished in nature, for example when the wing of an emerging dragonfly deploys over just a couple of minutes. This expansion is guided by a network of veins where hemolymph is injected and subsequently solidifies to generate rigidity.
Inspired by dragonflies, we build a model experiment to investigate inflatable deployable structures composed of a tubular network of the veins. We first mimic differential growth to fabricate wrinkled tubular structures. They comprise a soft annular core surmounted by a stiffer and thinner annulus prepared so as to yield a wrinkling instability. We then study the mechanical response of a single wrinkled tubular structure under pressure. We then characterize the in-plane expansion of the structure and study its correlation to the network geometry and the pressure applied to the system. A systematic variation of the geometric and elastic parameters allows us to search for optimal design and operational conditions for a maximal extension while minimizing the input pressure.