CAREER: The exceptional biomechanics of legged locomotion in the microcosmos

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This Faculty Early Career Development (CAREER) project combines biological experiments, mathematical modeling, and physical modeling to reveal the performance capabilities and constraints of legged locomotion in small invertebrates. When viewed on a relative scale, the fastest legged animals on the planet are the smallest of invertebrates. Organisms such as beetles, cockroaches, and mites are capable of running at speeds of tens to hundreds of body lengths per second. These remarkable feats of movement at the microscopic scale are enabled by strong limbs, robust foot attachment mechanics, and resilient exoskeleton structures that give these organisms locomotor capabilities vastly different from their larger counterparts. Yet smaller organisms also have to contend with incredibly complex and unstructured substrates that can impose step-to-step height variations equal to or larger than their leg length. This research will develop general principles of legged locomotion in complex environments which could contribute to the development of new legged robots that can move more effectively in unstructured environments. In parallel with the research aims, educational experiences for K-12, undergraduate, and academic professionals to better integrate living systems literacy into engineering curriculum will be developed. These activities include funded summer research experiences for underrepresented students in collaboration with a local Title 1 high school. At the college level, course development, hands-on training for undergraduate and graduate students, and interdisciplinary workshops for researchers in engineering and biology will be implemented. The overall goal of these efforts is to enable engagement, communication, and collaboration between engineers and biologists, facilitated through living systems literacy. This research project uses modeling and experiment to develop new geometric and dynamic scaling principles for legged locomotion in centimeter- and millimeter-scale organisms. Experiments will be performed with invertebrates that vary in size by four orders of magnitude in mass (the American cockroach, the Argentine ant, and the mite). To develop geometric scaling principles between animal morphology and natural substrates, a new experimental substrate-scanning platform to identify the three-dimensional topography of natural substrates will be developed. To study the dynamic scaling principles of force production and acceleration, new force measurement platforms to measure the ground-reaction forces involved in microscale legged locomotion will be developed. These experiments will be supported by physical modeling and computational modeling to elucidate scaling laws for dynamic and geometric phenomena in legged locomotion. The combination of experiments, modeling, and theory will improve our understanding of the biomechanics of microscale legged locomotion. The overall aim of this work is to contextualize the regimes of legged locomotion across the microscopic to macroscopic scales. The research and educational aims of this work are highly interdisciplinary. Graduate and high-school students will receive extensive training in biomechanics, physics, and engineering. Students will present results of these studies at robotics, physics, and biology conferences, and the outcomes will be published in interdisciplinary journals. Thus, the broader impacts include more focused understanding of legged biomechanics, new inspiration for legged robots, new understanding of natural substrates, and training of interdisciplinary scientists. This project was co-funded by the Physiological Mechanisms and Biomechanics Program in the BIO Division of Integrative Organismal Systems, the BIO Division of Biological Infrastructure Innovation Program, and the Biomechanics and Mechanobiology Program in the Engineering Directorate’s Civil, Mechanical, and Manufacturing Innovation Division.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.