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UBC Theses and Dissertations

Fabrication and non-linear modeling of conducting polymer-based actuators : toward catheter and tactile display applications Farajollahi, Meisam


The low voltage operation and relatively high strain response of conducting polymer actuators have made their use in different applications of great interest. In this thesis, modeling and characterization of the chemoelectromechanical behaviour of the linear freestanding and bending trilayer conducting polymer-based actuators are presented. In the modeling approach, a combination of state space representation and a two-dimensional RC transmission line was employed to develop the time domain model. Electrical and ionic conductivities and also Young’s modulus versus oxidation state were measured and incorporated into the model. Significant changes in conductivity and Young’s modulus make using a non-linear model necessary for accurate modeling. Implementation of the non-linear functions for electrical and mechanical properties in the model is one of the major advantages of the modeling approach. Capability of the model to predict the linear strain and radius of curvature for bending trilayer actuators versus time and position with good agreement with experiments are shown in this thesis. Voltage drop along the length of the film, away from the attachment point and the variation in electrical conductivity with state of charge along this length necessitated the use of a 2D non-linear model to obtain effective predictions of response for the film dimension used. Tubular actuators using conducting polymers as the active material for a catheter application are developed. Laser micromachining to pattern the actuators is demonstrated. A 0.95 mm diameter device is shown to achieve a 22 mm radius of curvature under activation of 2 V. A closed form beam bending model for trilayer actuators with tubular and rectangular cross sections is derived. These formulations predict the radius of curvature as a function of applied voltage and free strain considering different Young’s modulus for conducting polymer layers. This derivation is also useful for other multilayer actuators. The force generated by trilayer actuators is an important parameter which is investigated in this work. Mathematical derivation and simulations are employed to determine this parameter. Some solutions and their effects on force generated by trilayer actuators are presented to show how the force can be enhanced for tactile interface application.

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