Charge Control of Ionic Polymers

Abstract

Ionomeric polymer metal composites can be used as transducers characterized by high strain and low force. They are created by bonding a thin conductive electrode to the surfaces of an ionomeric polymer. Much of the work in the past has focused on using a voltage across the thickness of the polymer to produce mechanical motion. That work has often demonstrated that the mechanism of transduction within the polymer was associated with the accumulation of charge in the polymer. This thesis will discuss the use of current as a means to better control the accumulation of charge. Better control of the charge will provide more reliable control of the mechanical motion of the polymer.

The data presented in this thesis demonstrates that the response of an ionomeric polymer to a current input is repeatable. The repeatability is a desirable result; however, using current to actuate the polymers also produces back relaxation in the response. Examination of the back relaxation reveals a low frequency non-linearity. The nonlinearity is quantified by the fact that the gain associated with the back relaxation does not increase linearly with an increase in input current. There is also a change in the response at certain voltage thresholds. For example, when the voltage across the polymer exceeds 3 V, the rate of back relaxation increases. The repeatability of the response will aid in implementing reliable control of the polymer, but the non-linearities in the back relaxation will provide a considerable challenge in developing a model to be used in control.