This is a program to develop novel percutaneous electrodes for funnctional neuromuscular stimulation (FNS). Neuromuscular stimultation requires small flexible electrodes that can be inserted into individual muscles. Although the feasibility of restoring functional control has been demonstrated, the clinical use of FNS is limited, in part, by problems of electrode breakage, migration, and lack of specificity during stimulation. The program offers three primary innovations for combating these limitations. They are the following: the introduction of a Ti- 6A1-4V-ELI/Ta composite, a Ti-6A1-4V-ELI/Au composite, and tantalum as electrode lead materials; the introduction of IrO2 and Ta205 as charge injection materials; and the introduction of Dacron velours and use of low stiffness designs for preventing electrode migration. The Phase I program demonstrated flexural fatigue resistance and compatibility with Ir02 in the proposed lead materials. The Phase II program will involve the fabrication and characterization of complete FNS electrodes. Mechanical design techniques will be used to optimize electrode geometry for greater longevity. Physical characterization will include mechanical strength (tensile strength, ductility, etc.), fatigue life, microstructure, and lead impedance. Insulated electrode leads will be subjected to flexural fatigue, tensile and corrosion tests Ir02 charge injection layers will be deposited thermally (TIROF) and by sputtering (SIROF) on optimized electrode leads. Cyclic voltammetry with short and long term in vitro pulsing tests will be used to characterize charge capacity, stability and voltage transients.
