Development and Evaluation of Alloys for the Electrodes for Functional Electrical Stimulation to Appropriate for the Long Term Implantation

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Alloys for the electrodes for FES(Functional Electrical Stimulation)were developped and evaluated to appropriate for thelLong term implantation. And following results were obtained.1. Development of New Alloy : A database for alloy designing was created. And ingots of some high-manganese high-nitrogen austenitic stainless steels were producted experimentaly. Relation between reduction and elongation or reduction of area of these alloys were tested. And, it was confirmed that the alloy named NAS106N(6mass%Mn, 10mass%Ni, 22mass%Cr, 2mass%Mo, 0.4mass%N)shows the most superior properties. And thin wire rope for FES electrodes were made by this alloy.2. Evaluation of FES Electrodes made by New Alloy : Magunetization curves of FES wires made by newly developed alloy NAS106N, stainless steell SUS316L and cobalt-chromium based alloy NAS604PH were measured. NAS106N and NAS604PH shows the superior non-magnetic properties than SUS316L, Fatigue life of electrodes made by NAS106N, NAS605PH, SUS316L in air and 0.9%NaCl saline solution were also measured by dual-driven rotating-bending test. NAS106N has higher fatigue life than SUS316L and NAS604PH at all experimental condition in air and high at stress conditions in saline solution. On the other hand, fatigue lives of SUS316L and NAS106 were lower than NAS604PH at low stress condition in saline solution.Accordingly, NAS106N will be promising material for FES electrodes but to prevent the fretting corrosion should be the problem to be solved.