Quantitative Biosciences Thesis Proposal

Ethan Wold

School of Biological Sciences
Advisor: Dr. Simon Sponberg (School of Physics)

Open to the Community

Elasticity, actuation, and energy flow in insect flight

Wednesday, August 31, 2022, at 1:00 pm

Zoom Link: https://gatech.zoom.us/j/95091377319

Committee Members:

Dr. Nicholas Gravish (School of Mechanical and Aerospace Engineering, UCSD)

Dr. Gregory Sawicki (School of Mechanical Engineering, Georgia Tech)

Dr. Saad Bhamla (School of Chemical and Biomolecular Engineering, Georgia Tech)

Abstract:

Flapping flight is one of the most power-intensive forms of locomotion, yet anyone who has spent time chasing a fly understands the speed and agility of which insects are capable. Insects are the oldest and most speciose lineage of flyers, and uniquely span multiple orders of magnitude in both body size and movement frequency. As such, a natural question to ask is: why does a bumblebee flap at 200 Hz, but a butterfly only flap at 10 Hz? Scaling arguments do not explain mechanistically which aspects of an insect must adapt to facilitate a wingbeat frequency, and how they must adapt.

While wingbeat frequency can be very easily measured, it is emergent from an insect’s mechanics. Accounting for an insect’s wingbeat frequency requires careful characterization of its thorax, muscles, wings, and kinematics. Measurements of thorax material properties and muscle strains under realistic conditions are difficult to obtain, and scarce in the literature. Furthermore, flapping is actuated by muscle tissue with its own, state-dependent dynamics, which imposes constraints on the resonant mechanics of the insect. Critically, we lack 1). comparative characterization of the components of the flight apparatus in insects that span a wide range of frequencies 2). investigation of elastic elements coupled to realistic loading and actuator dynamics.

In this thesis, I propose leveraging the diversity of flapping insects to determine how wingbeat frequencies are influenced by and emerge from, interplay between morphology, elasticity, and actuation. I will measure thorax elasticity and muscle properties under realistic loading in low-frequency (moths) and high-frequency (bumblebees) insects and integrate them in the context of physics-based models of “spring-wing” systems. I aim to bound wingbeat frequencies of insects from knowledge of their constituent parts and infer mechanical properties from wingbeat frequency. Finally, I will investigate how transitions between low and high frequency flight may have occurred over evolutionary time, by eliciting real-time transitions in oscillation dynamics in live muscle.