Measuring the Electric Properties of Thin Film Shape Memory Polymers in Simulated Physiological Conditions

Shape memory polymers (SMP) exhibit unique physical properties attractive for potential application in medical devices. These materials can assume a rigid solid state but soften after exposure to saline solution and heat, a feature which may aid the implantation process. Exposure to the biological environment leads to fluid absorption by the polymer coating resulting in the desired change in mechanical properties. The fluid uptake, however, also results in a change of electric properties that need to be taken into account when designing electrical components integrated with SMP. We developed procedures based on electrochemical impedance spectroscopy (EIS) to study the electric properties of saline-soaked SMP coatings. With these, we can observe the softening process as well as long-term electrical behavior. Simple circuit models are used to model the coating properties and calculate relative permittivity and electrical resistivity of the SMP material.