Snap-through instabilities are ubiquitous in engineering, the natural sciences, and everyday life. Familiar examples include umbrellas inverting under strong wind, the rapid closure of Venus flytrap leaves to capture prey, and bistable switches in microelectromechanical systems (MEMS). Traditionally, such elastic instabilities have been viewed as failure mechanisms, as the abrupt release of stored mechanical energy at the instability threshold can damage structures. Recently, however, researchers have begun to harness this rapid energy release to generate high power output from low power input. The principle consists of slowly storing elastic energy in a structure and releasing it on demand by triggering a snap-through event.
This strategy is particularly promising for underwater locomotion and fluid propulsion at low Reynolds numbers, where achieving high instantaneous power is challenging due to the small spatial scales involved. Furthermore, according to Purcell’s scallop theorem, propulsion in low-Reynolds-number flows requires non-reciprocal motion to generate a non-zero net force, typically necessitating control of at least two degrees of freedom. Snap-through instabilities inherently provide non-reciprocity through their hysteretic and strongly nonlinear dynamics, making them attractive candidates for producing intermittent, high-power actuation in viscous flows.
This project aims to develop a fundamental understanding of the physical mechanisms governing fluid–structure interactions between snapping elastic structures and viscous flows. To this end, we conduct experiments on bistable elastic beams immersed in a viscous fluid and driven through snap-through transitions. We characterize both the structural dynamics and the induced flow field. Ultimately, this work seeks to enable engineering applications that exploit elastic snap-through to generate high flow rates or rapid propulsion at small scales, such as in microfluidic systems and soft microrobots.
