We consider the opening of Bauhinia seeds pods as a mechanical phenomenon that results from intrinsic geometry induced by growth/shrinkage. The pod wall architecture is such that dehydration causes the buildup of internal stresses. A small external perturbation then leads to the fast snapping from closed- flat state to an open-chiral one, a snapping that spreads the seeds.

I will present an analytical, numerical and experimental study of pod opening behavior. In particular, we study how the observed equilibrium helical configurations are determined by the differential shrinkage of the pod wall. We extend the model beyond the parameters of the Bauhinia pod, predicting a wide variety of non-trivial configurations, and demonstrate how the geometrical and mechanical principles studied, can be used to design “soft actuators”. Finally, we propose that these principles play an important role in shape selection during self assembly of different macromolecules.