Meeting Abstract
Flapping flight at the centimeter scale is one of the most energetically demanding modes of locomotion, which has led to the evolution of a resonant flight system for efficient elastic energy storage and return. In this configuration, the power muscles deform a stiff, parallel elastic exoskeleton that indirectly strains the elastic wing hinge to drive the wing. The wing hinge has been implicated in energy storage due to the presence of resilin – the most elastically efficient biological protein yet discovered. Cross-bridges have also been identified as potential storage sources. Because these materials have relatively low stiffness and displacement amplitudes (0.46 mm in downstroke power muscles), it is possible that other structures play significant roles in energy storage as well. Therefore, to understand the energetic consequences of this actuation method, we characterized the dynamic material properties of the thoracic exoskeleton in the hawkmoth Manduca sexta. We isolated the exoskeleton and drove sinusoidal length sweeps from 0.1 to 90 Hz with physiological amplitudes. To fully deform the thorax requires 1.2 N, which is 50% of the power muscles’ maximum force output. This corresponds to approximately 100% of in vivo force generation. The thorax was 70% elastically efficient across a wide range of frequencies and amplitudes. This lead to a total body-mass specific power return of 5 W kg-1, which reduces inertial power demands by 20%. In conclusion, inertial power can be reduced by an additional 80% and this value may be constrained by the in vivo muscular force output. This work lays the foundation for developing a mechanical representation of the flight apparatus for better quantification of indirectly actuated, resonant flight energetics.
