Conductive polymer based structures for a steerable catheter

Commercial steerable catheters and catheter prototypes actuated by active materials still present limitations in terms of self-sustaining capability and miniaturization. Specifications for the intravascular catheter we are developing are: bending angle up to 20 degrees, bending stiffness of a few N/m, response time of the order of seconds. Simulations with finite element method (FEM) showed these specifications can be satisfied using a polymer with active strain of 1% and elastic modulus E=4.5 GPa and a solid polymer electrolyte (SPE) matrix with E= 45 MPa. The actuator is thought to be made of a composite structure which includes polyaniline fibers, a copper wire electrode and SPE matrix. Its measured characteristics (under stimulation: -0.5/+0.8 V between fibers and copper, semiperiod 100 sec) are: active strain 0.2%, active stress 2 MPa, fiber elastic modulus 1.5 GPa, SPE elastic modulus 1-2 MPa. The major problem to realize the catheter is the stiffness of SPE, which has to be considerably augmented. Fiber active strain is below the required value, but it can be increased by proper drive. The production of fibers with a diameter of 10 microns (now 100-200 micron) will reduce the response time to the required value.