Collaborative Research: Moving with muscles vs. springs: evolutionary biomechanics of extremely fast, small systems

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Movement in biology is most often associated with motor-like mechanisms, such as muscle contractions in animals or hydraulics in plants. However, organisms have another option for generating movement: they can use motor-like mechanisms to load energy into elastic structures, such that pre-loaded, rubber band-like elastic structures generate the movement, instead of motors. Latch-mediated spring actuation generates movement largely or exclusively using stored elastic energy and incorporates latches to mediate energy release, much like controlled release of a coiled spring. This research examines how the size of an organism may determine whether movement is driven by stored elastic energy or direct motor action. Addressing this topic will improve understanding of fundamental physical limits on biological systems and how those limits influence development and evolution. Biological latch-mediated spring actuation generates among the fastest movements ever recorded, which exceed the current capabilities of human engineering to produce extremely fast movements in small, reusable devices. The discoveries from this research can help develop novel engineering devices and materials. This interdisciplinary team of research labs spans biology, physics, and materials science, and will train undergraduate, graduate, and postdoctoral researchers across four colleges and universities. The research activities will engage the broader public through a Research Experience for Teachers program each summer, alongside expansion of the Muser software program, which helps diverse undergraduates access research experiences in an equitable and transparent way. Latch-mediated spring actuation uses materials, not motors, to generate extremely fast movement in small systems. Energy is loaded into materials prior to movement and latches control loading and release of energy. This research examines the transitions between motor-driven and spring-driven movement within and across organisms. Across growth and development within species, experiments and modeling will test how mantis shrimp (Stomatopoda) maintain their mechanical capabilities and exhibit transitions between motor- and spring-driven movement across eight orders of magnitude of accelerated mass - a key predictor of the physics-based transition between effective motor- and spring-driven movement in any system. Across mantis shrimp species, variation in spring and latch components will be analyzed through statistical comparisons of the tempo (rate of evolutionary change) and mode (pattern of evolutionary change) to establish the key biomechanical factors limiting and promoting evolutionary diversification. Across the tree of life, the influence of accelerated mass and materials on origins and diversification will be tested using phylogenetic comparative analyses. Variation, transitions, and tuning of these mechanisms are informative for engineers designing small, fast, re-usable mechanisms at these extreme spatial and temporal scales. Undergraduates, graduate students, and a postdoctoral researcher will receive interdisciplinary training across the four labs. A Research Experience for Teachers program will provide interdisciplinary research experience and course development centered on these inherently engaging systems. The researchers will use, promote, and develop an open access software platform called Muser which is designed to enhance access and equity for undergraduate research experience.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.