Intermittently refuelable implantable bio-oxidant fuel cell

Abstract

An implantable biologically acceptable miniature fuel cell that is intermittently refuelable through one or more percutaneously positioned refueling ports. Refueling occurs by injection, preferably by hypodermic, typically annually. No transcutaneous leads or refueling stoma or tubes are employed. The cell is a bio-oxidant cell, as distinct from being a bioautofuel cell, having a silicone membrane coating over at least one external cathode surface permitting oxygen and water molecules to diffuse there through while preventing exit of organic fuel or oxidation-reduction by-products. Carbohydrate fuels are disclosed with glycerol being preferred from among it, glucose, sorbitol and mixtures. A variety of cathode and anode compositions are disclosed with Pt-black anodes and carbon-black cathodes being preferred. A high fuel to O.sub.2 concentration ratio is important to prevent O.sub.2 -parasitic effect on the anode. A high IS buffer is employed as the electrolyte, in the range of above 0.2 M, preferably 0.3-1.0 M, with a pH of above about 6.0, preferably 7.0-7.8. The cells produce approximately 0.14 watt-hr/gm and 0.16 watt-hr/ml, have operated satisfactorily in vitro for 225 days without refueling and are still running, 458 days with refueling, and satisfactorily in vivo for 55 days in baboon subjects without refueling.