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AC Frequency-based Cyclical Electrical Stimulation of Hydrogel Microactuators Open Access


Other title
AC Frequency
Dynamic Mechanical Properties
Dielectric Barrier
Numerical Modeling
Type of item
Degree grantor
University of Alberta
Author or creator
Saunders, Joseph RC
Supervisor and department
Dr. Walied Moussa, Department of Mechanical Engineering
Examining committee member and department
Dr. Dan Sameoto, Department of Mechanical Engineering, UofA
Dr. Subir Bhattacharjee, Department of Mechanical Engineering, UofA
Dr. Ziad Saghir, Department of Mechanical and Industrial Engineering, Ryerson University
Dr. Alidad Amirfazli, Department of Mechanical Engineering, Lassonde School of Engineering
Department of Mechanical Engineering

Date accepted
Graduation date
Doctor of Philosophy
Degree level
The continuing interest in Lab-on-a-Chip technologies and Point-of-Care diagnostics systems is driving the development of supporting components for microfluidic regulation. Optimally the microfluidic regulation components would operate cyclically with a minimum input power, could be precisely controlled in specific locations, and wouldn’t require bulky external components. One potential microactuator that could satisfy these requirements is an electrically stimulated hydrogel microactuator to provide a swelling and deswelling response. A hydrogel’s temporal performance is also enhanced at reduced length scales, its fabrication is amenable to mass fabrication processes, and knowledge exists for macroscale cyclical bending. However, electrical stimulation at the microscale in a closed system would need to overcome electrolyte electrolysis effects and electrochemical reactions at electrodes. In this thesis, several aspects of an electrically stimulated hydrogel microactuator that undergoes cyclical swelling have been analyzed. Firstly, the chemical and electrical field dynamics were numerically investigated through application of a yet uninvestigated cycling polarity electrical field, which highlighted the need for increased applied electric fields, and reduced hydrogel dimensions and modulus. Secondly, the hydrogel’s dynamic mechanical properties were investigated to ascertain the straining frequency’s effect on the hydrogel’s viscoelastic state, and quantifiable moduli were identified with appropriate mechanical stiffness for microactuation. These two studies provided system design parameters to maximize performance. Thirdly, to overcome electrolysis and electrochemical reactions a dielectric layer was introduced over the electrodes. This system modification required the unprecedented use of AC frequencies for stimulation and necessitated an analysis, both analytically and experimentally, of the characteristic AC frequency needed to successfully demonstrate and maximize hydrogel microactuation. The system’s frequency-varying capacitance, impedance, and apparent power were also investigated. Lastly, the hydrogel microactuator’s operation under cyclical electrical stimulation, achieved through pulse width modification, was successfully demonstrated and investigated for up to three cycles of actuation. The system was subjected to increasing electric fields to demonstrate a maximum true strain of ~27% with response times
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
Saunders, J.R., and W. Moussa,”Cyclical electrical stimulation of hydrogel microactuators employing Parylene-N coated electrodes” IEEE Journal of Microelectromechanical systems, In Press, DOI: 10.1109/JMEMS.2013.2268382Saunders, J.R., and W. Moussa, “AC frequency-based electrical stimulation of hydrogel microactuators employing Parylene-N coated electrodes” Sensors and Actuators B: Chemical, vol. 182, pp. 761-773, 2013.Saunders, J.R., and W. Moussa, “Dynamic mechanical properties and swelling of photopolymerized anionic hydrogels” Journal of Polymer Science B: Polymer Physics, 50:16, pp. 1198-1208, 2012.Saunders, J.R., S. Abu-Salih, and W. Moussa, “Parametric Chemo-Electro-Mechanical Modeling of Smart Hydrogels”, Journal of Theoretical and Computational Nanoscience, 5:10, pp. 1961-1975, 2008.Saunders, J.R., S. Abu-Salih, T. Khaleque, S. Hanula, and W. Moussa, “Modeling Theories of Intelligent Hydrogel Polymers”, Journal of Theoretical and Computational Nanoscience, 5:10, pp. 1942-1960, 2008.

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