Self-contained tubular bending actuator driven by conducting polymers

The low voltage operation and relatively high strain response of conducting polymer actuators has made their use in tubular actuators such as actively steerable catheter tips of interest. Previous work has shown that bending can be achieved by simply coating a commercial catheter with conducting polymer and patterning. However, these actuators require an external electrolyte to operate. This work presents instead a self-contained tubular actuator in which all ion conduction between active polymer layers occurs internally. The conducting polymer PEDOT provides the active deformation to control its maneuverability and actuation. To form the body of the actuator and an electrolyte medium to enable transfer of ions during the actuation of conducting polymer, a highly ionically conductive interpenetrating polymer network composed of ionically conductive polyethylene oxide and stretchable nitrile butadiene rubber (NBR) is used. This compliant medium also enables a tight radius of curvature. Laser micromachining is used to pattern PEDOT on the surface. A 0.95 mm diameter device is shown to achieve a 22 mm radius of curvatures under activation of 2 V. A closed form beam bending model for tubular trilayer actuators is derived which predicts the radius of curvature as a function of applied voltage and free strain. This model enables easy prediction of deflection, as is demonstrated. (C) 2016 Elsevier B.V. All rights reserved.