Date of Award
Master of Science in Chemical Engineering
Washkewicz College of Engineering
The quest for new smart materials with engineered properties and desired functionalities has driven scientists into the domain of nanotechnology over the past 30 years. Particles with anisotropic properties as a result of their geometry, chemical patterning or surface functionality have been envisioned as building blocks for advanced materials. By tuning the anisotropic interactions engendered by anisotropic particles, one potentially could manipulate the dynamic pathways for assembly.
The work described in this thesis considers the response of an ellipsoidal colloid particle to a nearby AC electrode polarized at ~0.1 – 4 kV/m and ~0.1 – 3 kHz. The ellipsoidal particle, which had a surface sulfate functional group, was dispersed in 10^-6M NaCl. The particle experienced typical electric-field induced responses, including electro-rotation and electro-orientation at low frequency - 100Hz - with an electric field intensity of 2500V/m. For instance, the particle (lying) was observed to frequently try to align its longer axis parallel to the electric field. We quantified the ellipsoid’s response by tracking its position and orientation with and without an electric field. The translational diffusion coefficient without and with electric field was calculated to be in the range of (7.625 – 39.2750) × 10^-3µm2/s and (0.725 – 305.525) × 10^-3µm2/s respectively. Surprisingly, the ellipsoid was also observed to propel in the direction normal to the electric field, which we believe to be a first for such a system. We proposed that the propulsion is a result of broken symmetry in the electrohydrodynamic (EHD) flow due to non-symmetric ellipsoid shape of our particle.
Obasanjo, Cornelius Adebowale, "The Response of an Ellipsoidal Colloid Particle in an AC Field" (2016). ETD Archive. 940.