Elastic biological springs are used by animals in their locomotion primarily for either power amplification or energy conservation. Power amplification, for motions like a frog jump or a mantis shrimp strike, is achieved with asymmetrical loading rates, where energy is slowly loaded into a biological spring and rapidly released. In contrast, energy-conserving movements such as running typically show symmetric loading/unloading patterns and involve a cyclic flow of energy to/from the spring. Trade-offs between power amplification and energy efficiency have been explored in a variety of animals by exploring the interplay between muscle and tendon dynamics. But despite this exploration of muscle-tendon dynamics, the role of the dynamic material properties of the biological spring itself in power/efficiency trade-offs is not yet understood. Our group is working on understanding how the high-rate and large deformation mechanics of elastic materials can impact both power output and energy efficiency of spring-driven movements. Our work addresses the fundamental materials physics of elastic mechanics, and it also informs both questions in comparative biomechanics and engineering design of spring-driven robotic systems through our network of collaborators in biology and engineering.
To investigate the trade-off between power and efficiency this summer, we will use bottlebrush elastomer materials with controlled molecular architecture. Previous work has shown that these materials can circumvent trade-offs between elastic modulus and extensibility, two properties that control the maximum stored energy density of an elastic material. We will use this elastomer material system to measure the energy efficiency and power density using a three-pronged approach building off the expertise of our group. The three major areas of expertise include traditional mechanical properties testing, novel high-rate large deformation experiments, and finite difference wave propagation simulations. Using this approach, we will establish the degree to which high power elastic movements results in a significant degradation of energy efficiency in a model elastic system
You will be part of a team of 6-8 HMC students working on a set of related projects at the intersection between physics, materials science, biology, and robotics. You will collaborate with other research groups in these disciplines across the country and you will get the opportunity to regularly present your work to a larger team. Collectively, we are working on understanding these ultra-fast elastic systems, which will have impact in the fields of evolutionary biology and micro-robotic design.