Delivery vehicles that can encapsulate and release active ingredients of pre-determined volumes at the target site on-demand present a challenge in biomedical field. Due to their tunable physiochemical properties and degradation rate, polymeric particles are one of the most extensively employed delivery vehicles. Generally they are fabricated from emulsion templates. Conventional bulk emulsification technique provides little control over the characteristics of droplets generated. Thus the properties of the subsequent particles cannot be controlled. The advance of droplet microfluidics enables the generation and manipulation of designer single, double or higher-order emulsion droplets with customizable structure. These droplets are powerful and versatile templates for fabricating polymeric delivery vehicles with pre-determined properties. Due to the monodispersity of droplet templates by microfluidics, the relationship between size, size distribution, shape, architecture, elastic responses and release kinetics can be systematically studied. These understandings are of key importance for the design and fabrication of the next generation polymeric delivery vehicles with custom-made functions for specific applications. In the present work, we engineer the droplet templates generated from microfluidics to fabricate designer polymeric microparticles as delivery vehicles. We investigate and obtain the relationship between the particle size, size distribution, structure of microparticles and their release kinetics. Moreover, we also identify an innovative route to tune the particle shape that enables the investigation of the relationship between particle shape and release kinetics. We take advantage of the dewetting phenomena driving by interfacial tensions of different liquid phases to vary the droplet shape. We find that the phase-separation-induced shape variation of polymeric composite particles can be engineered by manipulating the kinetic barriers during droplet shape evolution. To predict the performance of our advanced polymer particles in practical applications, for instance, in narrow blood vessels in vivo, we also develop a novel capillary micromechanics technique to characterize the linear and non-linear elastic response of our polymer particles on single particle level. The knowledge of the mechanical properties enables the prediction as well as the design of the mechanical aspects of polymer particles in different applications. The ability to control and design the physical, chemical, mechanical properties of the delivery vehicles, and the understanding between these properties and the biological functionalities of delivery vehicles, such as the release kinetics, lead towards tailor-designed delivery vehicles with finely-designed functionalities for various biomedical applications. Our proposed electro-microfluidic platform potentially enables generation of submicron droplet templates with a narrow size distribution and nanoscaled delivery vehicles with well-controlled properties, leading to a next generation of intracellular delivery vehicles. Microfluidic-based technique has the potential to be scaled up by parallel operation. Therefore, we are well-equipped for the massive production of custom-made droplet templates of both micron-size and nanosized, and we can design the physiochemical properties and biological functionalities of the delivery vehicles. These abilities enable us to provide solutions for applications and fundamental topics where encapsulation, preservation and transportation of active ingredients are needed. / published_or_final_version / Mechanical Engineering / Doctoral / Doctor of Philosophy

Not available / text

Thesis (Ph. D.)--University of Texas at Austin, 2004. / Supervisor: Dennis G. Deppe. Vita. Includes bibliographical references.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1965. / Typescript. Vita. Description based on print version record. Includes bibliographical references.

Thesis (Ph. D.)--City University of Hong Kong, 2005. / "Submitted to Department of Electronic Engineering in partial fulfillment of the requirements for the degree of Doctor of Philosophy." Includes bibliographical references (leaves 115-128).

Thesis (PhD)--University of Stellenbosch, 2006. / Bibliography. Also available via the Internet.

M.Tech. (Mechanical Engineering) / Please refer to full text to view abstract

A theoretical and experimental study has been made of planar acousto-optic light deflectors with particular emphasis on acoustic beam steering as a means of improving device performance. The theoretical model takes into account the electrical drive characteristics of beam-steered interdigital surface acoustic wave (SAW) transducers, anisotropic diffraction of acoustic waves and the rigorous theory of the interaction between guided optical waves and high frequency surface acoustic waves. The experiments were carried out on nickel indiffused waveguides on Y-cut LiNbO₃ substrates. A four-section, three finger pair transducer array was used to launch acoustic waves with propagation direction centered at 21.8° from the Z axis. A center frequency of 200 MHz was chosen as a compromise between high acousto-optic bandwidth and ease of fabrication. The deflector had a bandwidth of more than 60 MHz and gave 44 resolvable spots with an optical wave 2.5 mm wide. The observed frequency response of the diffraction efficiency was in excellent agreement with the theory. It was concluded that beam steering is an advantageous technique for devices requiring large bandwidth and high diffraction efficiency. / Applied Science, Faculty of / Electrical and Computer Engineering, Department of / Graduate

The objective of the research presented in this thesis is to develop, implement, and demonstrate the utility of an n-sheet, state-space alternating-current thin-film electroluminescent (ACTFEL) device model. In this model, the phosphor layer is discretized into n + 1 layers, with band-to-band impact ionization, space charge creation/ annihilation, and luminescent impurity excitation/do-excitation occurring only at n sheets between the n + 1 layers. The state-space technique is a structured approach in which the ACTFEL device physics implementation is separated from the ACTFEL measurement circuit electrical response, resulting in a set of coupled, first-order differential equations which are numerically evaluated. The device physics implementation begins with electron injection from phosphor/insulator interfaces and band-to-band impact ionization. Phosphor layer space charge generation via band-to-band impact ionization and subsequent hole trapping, trap-to-band impact ionization, and shallow donor trap emission are then added to the model. Finally, impact excitation and radiative relaxation are added to the model to account for ACTFEL device optical properties. The utility of the n-sheet, state-space ACTFEL device model is demonstrated in simulations which verify hypotheses regarding ACTFEL device measured characteristics. The role of phosphor layer hole trapping and subsequent thermionic emission in SrS:Cu ACTFEL device EL thermal quenching is verified via simulation. Leaky ACTFEL device insulators are shown to produce high luminance but low efficiency. A novel space charge estimation technique using a single transferred charge curve is presented and verified via simulation. Hole trapping and trap-to-band impact ionization are shown to produce realistic overshoot in C-V curves, and each results in a different phosphor layer space charge distribution. DC coupling of the sense capacitor used in the measurement circuit to the applied voltage source is required for the generation of ACTFEL device electrical offset, as verified by simulation. Shallow donors are identified as a probable SrS:Ce ACTFEL device leakage charge mechanism. A field-independent emission rate time constant model is shown to yield realistic ZnS:Mn ACTFEL device leakage charge trends. / Graduation date: 2001

The goal of this thesis study is to develop an activated reactive evaporation (ARE) system and to demonstrate its utility by fabricating-alternating current thin-film electroluminescent (ACTFEL) oxide phosphor devices. ARE entails evaporation in an activated gas. The main ARE system components are three thermal evaporation sources, a microwave power supply, an electron cyclotron resonance plasma (ECR) source, a substrate heater/controller, a film thickness monitor, and a leak valve for gas flow control. Ga���0���:Eu ACTFEL devices are fabricated using the ARE system. The maximum Ga���O: deposition rate is approximately 2 nm/s. As-deposited films are transparent, insulating, and amorphous with an index of refraction of 1.68 and an optical bandgap of 4.25-4.9 eV. Ga���O��� films are typically amorphous until annealed above 1000��C in a furnace or by rapid thermal annealing. However, when hydrothermal annealing is employed, Ga���O��� films crystalize at temperatures as low as 450��C. Electrical and optical characterization indicates that the Ga���O���:Eu ACTFEL devices have very little charge transfer and emit very dim, orange-red electroluminescence with an emission peak of about 615 nm. / Graduation date: 2001