4:00–5:00 pm
Please Join us:
Ephraim Bililign's PhD Thesis Defense
Tuesday, January 31, 2023 at 4:00 pm CST
Odd dynamics of colloidal chiral matter
The symmetries that underly conventional equilibrium matter provide the grounding for continuum mechanical models. In this work, we engineer a chiral material comprised of millions of spinning colloidal magnets as a testing ground for breaking these symmetries and observing the resulting odd dynamics. By activating the fluid phase at the single unit level, we observe macroscopic flows with no counterpart in conventional fluids. Along a boundary of the fluid, we observe unidirectional free-surface waves that propagate due to an interplay between viscous and odd rotational stresses. These waves are dissipated by both surface tension and odd viscosity, an anomalous transport coefficient permitted through broken time-reversal and parity symmetries. Then, we ask a deceptively simple question: what is the effect of adding transverse interactions on the solid phase? At the system scale, non-reciprocity causes colloidal spinners to organize into crystalline whorls which sustain super-diffusive mass transport that can be controlled over orders of magnitude. By combining experimental measurements with fully-resolved hydrodynamic and minimal model simulations, we find that this phase spontaneously arises from the interplay of intrinsic odd stresses and odd elastic moduli unconstrained by energy conservation, which conspire to enable the self-propulsion of topological defects. Finally, we lift the constraint of isotropy that underlies our viscous and elastic models, enabling spatiotemporal control of the morphology of chiral matter through the time-modulation of the drive.
Committee Members:
William T. M. Irvine (Chair)
Heinrich M. Jaeger
Paul B. Wiegmann
Suriyanarayanan Vaikuntanathan