Baromorphs: pneumatic shape morphing elastomers

Although bending a sheet of paper into a cylinder or a conical hat is quite easy, bending the same sheet in two simultaneous directions is not possible without crumples. However Nature is full of structures that are initially planar, but adopt complex 3D shapes as they grow. The secret of lettuce leaves? Differential growth: some regions, or some directions grow faster than the others.
Non-homogeneous growth with electroactive sheets could be a solution (see below). With the baromorphs, we chose the second strategy: non-isotropic growth. A network of channels is embedded inside an elastomer plate. Upon pressure, the channel tend to expend. This expansion is much higher across their section than along their length. Such growth is not compatible anymore with a planar geometry and the structure adopts a 3D shape that can be tuned by the pressure. In this example of material intelligence, the information is encoded the design of the channels.
What kind of shapes can be obtained with such technique? The simplest examples are domes or saddles obtained with circular of radial channels, respectively. In theory any reasonably smooth 3D shape can nevertheless be obtained by combining these two elementary geometries.
What applications do we envision? Soft robotics, and more specifically, equipments for disabled persons, adaptable furniture, but also deployable structures for space applications.

Publication :

E. Siéfert, E. Reyssat, J. Bico & B Roman, Bio-inspired pneumatic shape-morphing elastomers, Nature Materials, 2018.

https://doi.org/10.1038/s41563-018-0219-x

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