Motion via Bistability in Viscous Fluids*

We study the behavior of bistable beams in viscous media and their application to aquatic locomotion. Specifically, we exploit asymmetric actuation of bistable beams, which leads to a nonreciprocal deformation path. As an example, we use double pinned axially compressed bistable beams. We actuate the beam asymmetrically by imposing an angular position on one of the beam extremities.

Using a combination of numerical simulations and experiments, we find that when the beam is surrounded by a viscous fluid, the position of the stable states is not impacted. However, a higher moment is needed to deform the beam compared to air. Importantly, the beam motion non-reciprocity results in thrust in the axial direction, and, therefore, propulsion. The thrust increases with increasing beam compression.