  Structural instability is a hazard that leads to catastrophic failure and is
generally avoided through special designs. A trend, however, has emerged over
the past decades pointing to the harnessing of mechanisms with instability.
Inspired by the snapping of a hair clip, we are finessing the unique
characteristics of the lateral-torsional buckling of beams and the snap-through
of pre-buckled dome-like thin-wall structures in a new field: the in-plane
prestressed mechanism. Analyses reveal how the 2D-3D assembly of an in-plane
prestressed actuator (IPA) is achieved and how the post-buckling energy
landscape is pictured. Combining them with soft robotics, we show that the
inclusion of a bistable IPA can enormously enhance the performance of an
underwater fish robot as well as inspire a finger-like soft gripper.
