Origami for experts – Leaves and solar sails

Like in nature ...

Space-savingly folded and protectively enclosed, young leaves wait in the buds of the trees for budding.

The hornbeam (Carpinus betulus L.) allows the basic structure of the fold to be easily recognized even in the unfolded leaf. The parallel folds never abut the connecting axis at a 90° angle. They are kinematically coupled to each other: if one fold is pulled apart, the others open independently as well.

The Japanese space scientist Koryo Miura originally discovered the principle of these "curved folds" on crumpled paper. At the vertices, three mountain folds always meet with a valley fold - or, conversely, three valley folds meet with a mountain fold. The analogy to the hornbeam leaf was described only in 1998.

... so in technology

Miura invented a solar sail structure, which has since been known as the Miura fold. It is space-saving, stable and resilient, and can be unfolded in a single continuous movement. Studies on hornbeam leaves and other biological systems later inspired further development of the system.

Image captions

The bud of a hornbeam unfolds.

"Straight fold": when unfolding, both folds must be opened separately.

Curved fold: If one of the folds is opened, the second fold unfolds automatically with it.

Miura fold: With just one movement, the compact structure opens to form a surface.

Text of the information board in the Botanical Garden