ii To my loving wife and wonderful parents.iii ACKNOWLEDGMENTS First and foremost I would like to thank my research advisor Dr. Eric Nuxoll for his support, brilliant advice, professionalism and endless patience. He has been a great mentor throughout my doctoral studies at the University of Iowa since I became his first graduate student. Besides overall research skills, I learned much more including how to address a problem in a practical way, determine priorities and most importantly how to express and defend ideas. I have had the privilege to work with very talented undergrad students Matthew Gosse and Derek Baerenwald, who directly contributed to this project. I am also grateful to Yasuhiro Nishii, a visiting scholar from Japan, for his partial contributions to this work and continued work forward with this project. Guiding and mentoring these bright individuals was an exciting opportunity and also a great experience for me. Others who have helped me along the way include my fellow research group members Ann O'Toole, Joel Coffel, Erica Bader and Bryce Hundley. iv I am incredibly grateful to my parents who have always supported me. I have been blessed to be born in a loving family that has fully encouraged and enabled me to achieve my dreams. Finally, no words can express my thankfulness to Khushbu, my wife, who always stood by me throughout this journey. Without her encouragement and motivation I would not have pursued the education to the length I have.v ABSTRACT Solutes are often most efficiently deployed in discrete pulses, for example in the delivery of herbicides or drugs. Manual application of each pulse can be labor-intensive, automated application of each pulse can be capital intensive, and both are often costly and impractical. Barrier-Mediated Pulsatile Release (BMPR) systems offer a materialsbased alternative for automated pulsatile drug delivery, without pumps, power supplies, or complex circuitry. While earlier materials-based approaches such as delayed-release microcapsules are limited to two or three pulses due to the independent nature of each pulse's timing control, BMPR systems link the timing of each pulse to the previous pulse.Each dose of drug is sequestered in its own stimuli-sensitive depot, releasing only upon contact with the stimulant. These depots are stacked with sacrificial barriers in between, each of which block the stimulant for a predetermined time. For instance, layers of soluble drug may be separated by degradable polymer layers. Water, as the stimulant, will erode the polymer layer over a fixed period of time, followed by quick dissolution and release of the underlying drug and the start of degradation for the next polymer layer.This example, however, is quickly limited by irregular polymer erosion, a single stimulant (water), and difficulty in scaling delay times.The research work presented in this thesis reports the development of a generalized BMPR system which overcomes those limitations. Model drugs (methylene blue and methyl orange) were immobilized in a pH-sensitive ...
