3:00–4:00 pm
Please join us:
Melody Lim’s PhD Thesis Defense
Friday, January 28 at 3:00 PM CDT
ACOUSTICALLY LEVITATED GRANULAR MATTER
The properties of small particle clusters can differ dramatically from the bulk phases of the same constituents. For conditions out of equilibrium, new pathways and physical principles for cluster formation and reconfiguration emerge. These principles underlie phenomena from molecular assembly to the formation of planets from granular matter. In this thesis, we introduce acoustic levitation as a platform to experimentally probe the formation of small structures in a controlled environment far from equilibrium. Scattered sound establishes short-range, shape-dependent attractions between millimeter-scale particles. In this substrate-free, underdamped environment, six or seven particles cluster into shapes that resemble flowers and turtles, while hundreds of particles self-assemble into granular droplets with strikingly fluid-like behavior. Particle shape directly controls acoustic forces, with particles preferring to make contact along sharp edges. Detuning the acoustic trap generates active fluctuations that drive cluster rearrangements, droplet spinning and splitting, and soft hinge-like motions, creating a tunable active granular material. Our results open up new possibilities for non-invasively manipulating macroscopic particles, tuning their interactions and directing their assembly.
Committee Members:
Heinrich Jaeger (chair)
Daniel Fabrycky
Sidney Nagel
Vincenzo Vitelli
Melody will be a postdoctoral fellow at the Kavli Institute at Cornell for Nanoscale Science, advised by Itai Cohen and Paul McEuen, where she will continue working on far-from-equilibrium self-assembly.