Browsing by Author "Lobmeyer, Dana M"

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    Dynamics of Magnetically Actuated Colloidal Crystals under Rotating Magnetic Fields
    (2024-03-07) Lobmeyer, Dana M; Biswal, Sibani Lisa
    Precise control at the colloidal scale is one of the most promising bottom-up approaches to fabricating new materials and/or devices with tunable and/or precisely engineered properties. Magnetic colloidal assembly offers great versatility because of the ability to externally tune particle-particle interactions and to construct a host of particle arrangements. Such a variety of structures has led magnetic colloidal assembly to also be used as experimental models, gaining insights into atomic and molecular systems. Rotating magnetic fields have particularly gained attraction in this space for their ability to create two-dimensional (2-D) colloidal crystals and tune their phase behavior through the strength of the magnetic field. However, many open questions regarding the rotational dynamics in these 2-D systems still remain open. In this thesis, field-induced particle circulation at the edge of superparamagnetic colloidal crystals is utilized for shear-induced grain boundary studies in polycrystalline materials. The underlying mechanisms of these edge flows are further investigated in sheets and clusters to fundamentally understand them and explain cluster rotation. Furthermore, the edge flows are described as a result of individual particle rotation despite the use of superparamagnetic particles. Since such particles should in theory not rotate, the magnetic relaxation time of the particles is measured and harnessed to highlight these non-ideal effects and their capability in creating previously inaccessible structures and dynamics. By discovering, measuring and harnessing a parameter previously neglected, this thesis expands the capabilities of magnetic colloidal assembly and opens the door to further expansion into novel applications.