Beyond power amplification: latch-mediated spring actuation is an emerging framework for the study of diverse elastic systems

Abstract

Rapid biological movements, such as the extraordinary strikes of mantis shrimp and accelerations of jumping insects, have captivated generations of scientists and engineers. These organisms store energy in elastic structures (e.g. springs) and then rapidly release it using latches, such that movement is driven by the rapid conversion of stored elastic to kinetic energy using springs, with the dynamics of this conversion mediated by latches. Initially drawn to these systems by an interest in the muscle power limits of small jumping insects, biologists established the idea of power amplification, which refers both to a measurement technique and to a conceptual framework defined by the mechanical power output of a system exceeding muscle limits. However, the field of fast elastically driven movements has expanded to encompass diverse biological and synthetic systems that do not have musclessuch as the surface tension catapults of fungal spores and launches of plant seeds. Furthermore, while latches have been recognized as an essential part of many elastic systems, their role in mediating the storage and release of elastic energy from the spring is only now being elucidated. Here, we critically examine the metrics and concepts of power amplification and encourage a framework centered on latch-mediated spring actuation (LaMSA). We emphasize approaches and metrics of LaMSA systems that will forge a pathway toward a principled, interdisciplinary field.

Adhesive latching and legless leaping in small, worm-like insect larvae

“…Small-legged jumping and legless-jumping systems are often powered by elastic mechanisms, typically through latching, elastic loading and release (Longo et al, 2019;Ilton et al, 2018;Sakes et al, 2016;Gronenberg, 1996;Patek, 2015;Patek et al, 2011). Worm-like, legless jumpers typically form a loop with their body by latching their anterior and posterior in place and then springing into the air when the latch is released (Fig.…”

What explains vast differences in jumping power within a clade? Diversity, ecology and evolution of anuran jumping power

“…The use of elastic mechanisms to generate movements where the maximum power output exceeds the power capacity of muscles has been documented in a number of systems (Higham & Irschick, ; Ilton et al, ; Longo et al, ; Patek et al, ; Roberts & Azizi, ). Given that muscle power varies little across anurans (Astley, ; Roberts et al, ), much of the variation we observed in jumping power is likely attributed to variation in the effectiveness of using elastic mechanisms.…”

“…These analyses suggest the high jumping power we see here is due to elastic mechanisms used to amplify muscle power. Moreover, the finding that large species seem to have higher muscle power (Astley, ; Figure S1) yet lower jumping power (Figure ) may be indicative of the fact that direct muscle actuation relies on high muscle power outputs whereas the use of elastic elements may relax selection on muscle power since muscles can operate at very slow velocities when loading (Longo et al, ).…”

“…They calculated body‐mass‐specific power and showed that it was variable across species, but they did not focus on understanding the variation in and the evolution of power per se, nor did they calculate muscle‐mass‐specific power. The latter standardization by muscle mass is the most relevant measurement for comparing power production across species (Astley, ; Longo et al, ; Roberts et al, ). Fourth, we added data for R. marina ( n = 5), previously collected (as in Moen et al, ) but (D.S.…”

A power amplification dyad in seahorses

“…Latch-mediated spring actuation (LaMSA) systems, in which slow forceful muscles are used to load an elastic element that is kept latched until it is allowed to abruptly release, have repeatedly evolved in many organisms and overcome muscle power limitations (3). LaMSA systems enable some of the fastest animal activities, powering the movements of jumping legs in fleas (4,5), the shell-breaking appendages of mantis shrimps (6,7), and the closing jaws in trap-jaw ants (8).…”