Conjugated Polymer Based Steerable Catheters

The electrolyte can be a liquid, a gel or a solid. Solid polymer electrolyte is a complex of high molecular weight polymers and metal salts and a gel is a liquid solution of metal salts trapped in a cross-linked soluble polymer matrix [12], 

Conjugated polymer actuators are good candidates for driving active catheters, due to their low voltage ( 2 V), high strain (typically 2 % or greater), low cost and biocompatibility [42]. The relatively high stiffness of these materials (elastic moduli of 1 GPa [42]), also makes them suitable for use as active catheter drive elements. 

1 Intravascular Microcatheters Steered by Conjugated Polymer Actuators 

In the first configuration, the CP/SPE/CP sandwich stracture is inserted inside the catheter walls. Polypyrrole doped with benzensulfonate anions (PPy/BS ) with an elastic modulus of450 MPa and active strain of 1 % was assumed to be the CP element, and a layer containing Cu(C104)2 with a modulus of 45 MPa was considered as the SPE. In the second configuration, the walls of the catheter are assumed to be made of the CP fibres/SPE matrix composite material. The CP fibres may be PPy or PANi extruded microfibres. In the simulation the fibres were assumed to have the same active and passive properties as their film form. The overall mechanical characteristics of the composite structure are as follows Young modulus 247 MPa, shear modulus 37 MPa and electrochemical strain 1 % [13]. 

The authors of this chapter are investigating active catheter designs similar to those of Mazzoldi, De Rossi and colleagues that are described in the previous section, but employed to rapidly scan the tip of the catheter to enable high-resolution 3-D imaging via optical 

---

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. 

---