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AC Frequency-based Cyclical Electrical Stimulation of Hydrogel Microactuators

  • Author / Creator
    Saunders, Joseph RC
  • 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

  • Subjects / Keywords
  • Graduation date
    2013-11
  • Type of Item
    Thesis
  • Degree
    Doctor of Philosophy
  • DOI
    https://doi.org/10.7939/R3R703
  • License
    This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.
  • Language
    English
  • Institution
    University of Alberta
  • Degree level
    Doctoral
  • Department
    • Department of Mechanical Engineering
  • Supervisor / co-supervisor and their department(s)
    • Dr. Walied Moussa, Department of Mechanical Engineering
  • Examining committee members and their departments
    • Dr. Dan Sameoto, 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
    • Dr. Subir Bhattacharjee, Department of Mechanical Engineering, UofA