Degree
Doctor of Philosophy (PhD)
Department
Chemical Engineering
Document Type
Dissertation
Abstract
Colloidal particles are nano/micro meter-sized particles dispersed in a fluid medium and serve as diverse building blocks for assembling complex structures. The ease of tunability of the shape, size, and interparticle interactions of colloidal particles facilitates their assembly into rich structures and phases that mirror the assembly process of atomic systems. Often regarded as "big atoms" colloidal particles provide an ideal model system for investigating complex phenomena in condensed matter, such as crystallization and nucleation. While the assembly of colloids under thermodynamic equilibrium has been extensively studied, recent interest has shifted toward exploring colloids in non-equilibrium conditions to create dynamic assemblies and drive motion. Achieving the structure and functionality of living matter in synthetic materials requires understanding the underlying principles governing non-equilibrium systems. This Ph.D. dissertation presents strategies to assemble and propel colloidal particles by applying magnetic fields as a source of energy to form dynamic structures under out-of-equilibrium conditions.
Firstly, we achieve magnetic field-guided assembly using colloidal particles as building blocks that range from isotropic spheres to shape-anisotropic particles, resulting in a diverse array of assembled structures. By tuning the magnetic field configuration, we achieve dynamic control over interparticle magnetic interactions, which can be either attractive or repulsive. The in situ tunability of the interparticle interactions through magnetic fields allows for reversible transitions of isotropic spherical colloidal particles between different assembled structures, including crystals, fractal clusters, and low-density Wigner glass. In addition, we investigated the assembly and melting transitions for particles of varying shapes and showed distinct differences in the melting transition depending on the shape anisotropy of the particles.
Secondly, we employ magnetic fields to precisely control the motion of non-spherical microellipsoids particles near a substrate. We demonstrate the contactless capture and transport of cargo particles due to the generation of mobile microvortices by the rotational motion of microellipsoids. To demonstrate the capabilities of microellipsoids as functional microrobots and perform biomedical tasks such as targeted delivery, we developed a feedback-controlled navigation scheme for microellipsoids to transport cargo to the desired position within a complex environment. Lastly, we investigated the motion characteristics of magnetically actuated microellipsoids on topological surfaces relevant to biological environments. We also present design principles for microrobots that enable efficient and robust rolling motion on topological surfaces.
The principles and strategies for colloidal particle assembly and propulsion presented in this dissertation enhance our understanding of non-equilibrium colloidal systems, enabling the development of advanced functional materials and micro-robotic systems.
Date
7-8-2025
Recommended Citation
Gauri, Hashir M., "MAGNETIC FIELD ENABLED ASSEMBLY AND PROPULSION OF COLLOIDAL PARTICLES IN A MAGNETIC MEDIUM" (2025). LSU Doctoral Dissertations. 6874.
https://repository.lsu.edu/gradschool_dissertations/6874
Committee Chair
Bharti, Bhuvnesh
DOI
10.31390/gradschool_dissertations.6874