Mechanical behaviour of implantable electrodes

A team of materials scientists is supporting the development of Networked Implantable Neuroprostheses (NNPS) Systems on an NIHBioengineering Research Partnership. The Materials Group is leading the material and structural evaluation, analysis, and testing of implantable electrodes and interconnects that form part of the NNPS. Currently the potential use of silver cored Drawn Filled Tube (DFT) cables as electrodes is being investigated. The response of various configurations of the DFT cables to static and cyclic mechanical loading imposed during long-term implantation is being studied. DFT cables with 25% and 41% silver core with various cable configurations (1x7, 1x19, 7x7, 7x19) have been tested. Monotonic tensile tests were performed and the fracture surfaces of the cables were observed under scanning electron microscope to reveal the fracture mechanisms involved. Fully reversed cyclic tests of the cables were conducted in a flex tester under various strain loading conditions in order to determine the fatigue behaviour of the cables both in the low cycle and high cycle regime. The fatigue behaviour of the cables was modelled using the Coffin-Manson-Basquin relationship.