EAP Based Steerable Catheters

1 Ionic Polymer—Metal Composite (IPMC) Based Steerable Catheters 

The Ionic Polymer-Metal Composite (IPMC) is a type of EAP actuator whose use in active catheters has been studied the most [19-22, 27, 28]. An IPMC consists of a polymer electrolyte sandwiched between two thin metal layers and typically has an elastic modulus of 0.1 GPa [10]. Common polymer electrolytes are perfluorinated alkenes with anionic-group-terminated side chains, such as Nafion and Flemion or styrene/divinylbenzene based polymers with ionic groups substituted from phenyl rings [10]. 

IPMC actuators exhibit a typical strain of 0.5 %, strain rate of 3 %/s and a typical stress of 3 MPa. They are actuated at potentials of 10 V [42]. The performance of these actuators has been improved by using various combinations of cations [23-25] and different types of electrodes, such as platinum-copper [26]. In this chapter a brief overview of different designs and test procedures using this type of actuators is presented, as similar approaches could also be employed in conjugated polymer driven devices. IPMC based steerable catheters are further described in another chapter of this book. 

Onishi et al. proposed a tube of IPMC as a microactuator for active catheters [21]. Their suggested device is a perfluorocarboxylic acid (ion exchange polymer) tube 

Jong et al. modelled, fabricated and tested an IPMC strip actuator for inclusion into a low cost active tip bending system for a catheterscope [22]. Platinized Nafion 117 membranes with thicknesses of 170 pm were employed. The authors studied the force generated by the IPMC actuators and found that additional force may be required in order to overcome bending resistance from the catheterscope sheathing, capillary forces of attraction within wet ducts and viscous fluids. Encapsulation of the design was suggested to avoid gas production from hydrolysis [22]. 

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