DIELECTROPHORETIC ASSEMBLY OF COLLOIDS IN TOGGLED AC FIELDS
| Author(s) | Reed, Kaelan | |
| Date Accessioned | 2017-09-12T19:57:58Z | |
| Date Available | 2017-09-12T19:57:58Z | |
| Publication Date | 2017-05 | |
| Abstract | The dielectrophoretic directed self-assembly of colloidal particles is a rapid, tunable, and simple method for the production of materials with phononic and photonic band gaps. However, under the application of a constant AC electric fi eld, particles become kinetically trapped in non-equilibrium structures containing numerous defects which interfere with the desired phononic and photonic properties. This problem is ampli ed by anisotropic particles as they must translationally and rotationally align to assemble into equilibrium structues. To resolve this limitation of dielectrophoretic self-assembly, a method to anneal kinetically trapped con gurations to an equilibrium state is needed. Before exploring an approach to improve the order of structures formed by dielectrophoretic directed self-assembly, a well-documented method for producing planar electrodes, and their use in the construction of a dielectrophoretic sample cell is presented. Furthermore, the high voltage circuit used to generate the applied AC electric fi eld is introduced and thoroughly characterized. This experimental setup is then used to investigate the use of toggled AC electric elds to assemble polystyrene colloids into crystalline structures free of defects. The time evolution of the macroscopic structures and the long-time microscopic structures formed under the influence of toggled AC electric fi elds are discussed for three colloidal suspensions: 1 m polystyrene spheres dispersed in a density mismatched H2O-based medium, in a density matched H2O/D2O-based medium, and polystyrene dicolloids in a density mismatched H2O-based medium. The rst of these suspensions suggests toggling is not necessary to construct equilibrium structures from isotropic particles with weak interactions. When the 1 m particles are suspended in a density matched solution, only localized ordering is observed indicating gravity is an integral force in the formation of macroscopic colloidal crystals through dielectrophoretic self-assembly. Finally, the dicolloidal suspension exhibits an increase in order when a toggled eld is applied at a frequency of 0.1 Hz rather than a constant eld. This suggests toggled elds make it possible to improve the order of these particles, which are particular difficult to assemble due to their anisotropy. | en_US |
| Advisor | Eric M. Furst, Ph.D. | |
| Program | Chemical Engineering | |
| URL | http://udspace.udel.edu/handle/19716/21648 | |
| Publisher | University of Delaware | en_US |
| Keywords | Chemical Engineering, DIELECTROPHORETIC, COLLOIDS, AC FIELDS | en_US |
| Title | DIELECTROPHORETIC ASSEMBLY OF COLLOIDS IN TOGGLED AC FIELDS | en_US |
| Type | Thesis | en_US |