Title page for ETD etd-01062004-120129

Type of Document Master's Thesis
Author Mudarri, Timothy C.
URN etd-01062004-120129
Title A Novel Use for Ionic Polymer Transducers for Ionic Sensing in Liquid
Degree Master of Science
Department Mechanical Engineering
Advisory Committee
Advisor Name Title
Leo, Donald J. Committee Chair
Robertshaw, Harry H. Committee Member
Shires, Peter K. Committee Member
  • electroactive polymer
  • ionic polymer
  • electrochemical biosensor
  • ion sensing
Date of Defense 2003-12-18
Availability unrestricted
Ionic electroactive polymers have been developed as mechanical sensors or actuators, taking advantage of the electromechanical coupling of the materials. This research attempts to take advantage of the chemomechanical and chemoelectrical coupling by characterizing the transient response as the polymer undergoes an ion exchange, thus using the polymer for ionic sensing. Nafion™ is a biocompatible material, and an implantable polymeric ion sensor which has applications in the biomedical field for bone healing research. An ion sensor and a strain gauge could determine the effects of motion allowed at the fracture site, thus improving rehabilitation procedures for bone fractures.

The charge sensitivity of the material and the capacitance of the material were analyzed to determine the transient response. Both measures indicate a change when immersed in ionic salt solutions. It is demonstrated that measuring the capacitance is the best indicator of an ion exchange. Relative to a flat response in deionized water (±2%), the capacitance of the polymer exhibits an exponential decay of ~25% of its peak when placed in a salt solution. A linear correlation between the time constant of the decay and the ionic size of the exchanging ion was developed that could reasonably predict a diffusing ion. Tests using an energy dispersive spectrometer (EDS) indicate that 90% of the exchange occurs in the first 20 minutes, shown by both capacitance decay and an atomic level scan. The diffusion rate time constant was found to within 0.3% of the capacitance time constant, confirming the ability of capacitance to measure ion exchange.

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