The New Jersey Institute of Technology's
Electronic Theses & Dissertations Project

Title:	Field induced assembly of particulate systems
Author:	Shah, Kinnari
View Online:	njit-etd2017-051 (xv, 76 pages ~ 1.9 MB pdf)
Department:	Department of Mechanical and Industrial Engineering
Degree:	Doctor of Philosophy
Program:	Mechanical Engineering
Document Type:	Dissertation
Advisory Committee:	Ravindra, N. M. (Committee co-chair) Rao, I. Joga (Committee co-chair) Nadimpalli, Siva P.V. (Committee member) Lee, Eon Soo (Committee member) Jaffe, Michael (Committee member)
Date:	2017-01
Keywords:	Self-assembly Dielectophoresis Droplet Lab-on chip Air-liquid interface Transmission probability
Availability:	Unrestricted
Abstract:	The primary focus of the first part of this dissertation is to study the AC field-driven assembly of monodisperse silica and glass particles on liquid - liquid interface and forming a liquid film of uniform thickness having arrangement of particles on it. This liquid film with arrangement of regular particles can be converted into a solid film by curing top UV curable liquid. Here, electric field is used as a tool to facilitate AC field-driven assembly. The work describes the assembly of different size of regular particles and effective development of solid film. It is also shown that particles of two dissimilar sizes and dielectric properties can be assembled on Air-liquid interface and form assembly of dual particles with ring structure. In this work, two dissimilar particles are trapped between an interface and AC electric field is applied to particle suspensions in a gap between the top and bottom electrodes. In order to exploit the concept of dual particle assembly, mixture of glass particles and plastic latex particles are studied. It is noticeable that the lateral dipolar force leads two particles to either repel or attract. This force of repulsion and attraction between particles depend on their polarizabilities and the intensity of the force. Finally, rapid and effective formation of ring structure of dual particles is shown. The study is also extended for mixture of particles that are less than 10 μm. In all cases, it is observed that smaller particles act as the binder for larger particles and form dual particle ring structure since they have a reverse polarizability. In the third part of this dissertation, AC electric field is used to assemble the particles on the freely suspended single floating droplet on immiscible liquid. Particles on the droplet can be levitated and assembled at the pole or equator due to dielectric properties and conductivity of particles and liquid medium when low frequency is applied. Under high frequency, particles drag towards the pole or equator due to Clausius Mossotti factor of particle and droplet. The high and low frequency are distinguished by crossover frequency. Here, crossover frequency is investigated experimentally and assembly of the different particles at the pole or equator of the droplet is shown. At any initial location of the particle and considering the very low frequency, flow deceases with increase in frequency - this is studied experimentally. A diffusing particle is subjected to a variety of collisions that leads to a random or Brownian motion. Assembly of particles of various sizes with various viscous media are studied in the first and second part. It is experimentally observed that Brownian motion decreases with increase in particle size. The aim of this study is to highlight the visualization of Brownian motion and compute the transmission probability from inner to outer region under the conditions of varying viscosity, particle size and temperature. The obtained results are validated with Stokes-Einstein equation and Fang and Ning’s experimental and theoretical work. It is shown that the transmission probability increases with decrease in viscosity and particle size and increase in temperature.