Phases and Actuation of Superparamagnetic Soft Matter

Brisbois, Chase

doi:https://doi.org/10.21985/n2-9vd9-3950

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Phases and Actuation of Superparamagnetic Soft Matter

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External manipulation of soft matter underlies a multitude of advancements in far-from-equilibrium materials. The application of magnetic fields has proven tremendouslybeneficial due to its ability to impart rapid and precise changes throughout soft magnetic systems. This has led to scientists and engineers to develop composite materials that take advantage of the characteristics of soft condensed matter with those of magnetic nanoparticles to achieve novel properties not possible in the absence of a magnetic field. Using a combination of theory, experiments, and simulation, we describe how magnetic fields affect the state of distinct colloidal nanostructures composed of superparamagnetic particles suspended in a liquid environment. This dissertation is composed of two parts that each investigate a superparamagnetic system first with a static field and then with a dynamic field. Part One focuses on magnetoelastic membranes in precessing magnetic fields. In the fast precession regime, we uncover buckling mechanisms that affect membrane actuation. By lowering the precession frequency, we found dynamic steady-states where membrane locomotion could be achieved. In Part Two, we explore the effects of magnetic fields on magnetic crystal phases and morphology. We show how magnetic coupling directly affects the morphology of superparamagnetic rods in static magnetic fields. Driving such rods to precess will impart positional ordering to a layered (smectic) liquid crystal phase. In these works, we have striven to develop simple mathematical relationships between pertinent system properties and dimensionless control parameters in order to confer physical intuition to the reader.

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