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A Particle Engineering Approach for the Design of Structured Microparticles Open Access


Other title
Particle Engineering Design of Structured Microparticles
Diffusion controlled microparticles formation
The Adaptive Interface Sweeping Method
Concentration profiles
Variable evaporation rate
Structured microparticles
Particle Engineering
Type of item
Degree grantor
University of Alberta
Author or creator
Boraey, Mohammed A.
Supervisor and department
Vehring, Reinhard (Mechanical Engineering)
Examining committee member and department
Lange, Carlos (Mechanical Engineering)
Martin, Andrew (Mechanical Engineering)
Finlay, Warren (Mechanical Engineering)
Abedi, Jalal (Chemical and Petroleum Engineering)
Vehring, Reinhard (Mechanical Engineering)
Department of Mechanical Engineering

Date accepted
Graduation date
Doctor of Philosophy
Degree level
The process of microparticle formation from evaporating microdroplets is the main production method for many products. For most of these applications (especially pharmaceutical ones) the properties and morphology of the final dry particle have to be precisely tailored to ensure the proper functionality of the final product. Particle engineering focuses on improving particle production processes by developing physical understanding and applying models to deliberately alter the properties of the particles. The present work discusses two aspects of the microparticle formation process, the evaporation rate and the transient concentration profiles. Although many other aspects are involved, it is thought that these two are the most influential ones. Chapter one gives a brief introduction to the process of structured microparticle formation along with the important particle physical properties and the associated challenges. Chapter two and three introduce a new particle formation theory for the formation of microparticles when diffusion is the main mechanism of mass transport. They also introduce a simplification of the theory results through a hybrid analytical/numerical model to ease the use of the results. Chapter four introduces a novel hybrid technique for calculation of the variable evaporation rate of microdroplets given knowledge of the droplet trajectory and the solvent material properties. A simplification of this approach is also proposed in the case when the trajectory data has a wide margin of uncertainty. In chapter five, the asymptotic state solution and the transient solution of the concentration profiles of an evaporating cylindrical cylinder were derived. These results are used to verify the new model proposed in chapters six and seven. Chapter six and seven propose a new numerical model (The Adaptive Interface Sweeping Method) for the calculation of the transient concentration profiles of an evaporating solution droplet. This model is capable of modeling many physical mechanisms involved in the particle formation process. It also offers a viable technique in dealing with variable material properties and evaporation rates. Chapter eight gives a brief discussion of the results introduced through the thesis and recommendations for future work.
Permission is hereby granted to the University of Alberta Libraries to reproduce single copies of this thesis and to lend or sell such copies for private, scholarly or scientific research purposes only. Where the thesis is converted to, or otherwise made available in digital form, the University of Alberta will advise potential users of the thesis of these terms. The author reserves all other publication and other rights in association with the copyright in the thesis and, except as herein before provided, neither the thesis nor any substantial portion thereof may be printed or otherwise reproduced in any material form whatsoever without the author's prior written permission.
Citation for previous publication
M.A. Boraey and R. Vehring. Diffusion controlled formation of microparticles. Journal of Aerosol Science, 67:131-143, 2014.M.A. Boraey, S. Hoe, H. Sharif, D.P. Miller, D. Lechuga-Ballesteros, and R. Vehring. Improvement of the dispersibility of spray-dried budesonide powders using leucine in an ethanol-water cosolvent system. Powder Technology, 236:171-178, 2013.A.L. Feng, M.A. Boraey, M.A. Gwin, P.R. Finlay, P.J. Kuehl, and R. Vehring. Mechanistic models facilitate efficient development of leucine containing microparticles for pulmonary drug delivery. International Journal of Pharmaceutics, 409(1-2):156-163, 2011.

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File title: A Particle Engineering Approach for the Design of Structured Microparticles
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