Method and membrane applicable to implantable sensor

Claim 1

A sensor for being implanted in a human body to aid in stoichiometric analysis of an aqueous solution in said body, said solution including a gas and a stoichiometric excess of a compound reactive with said gas, said sensor comprising: an implantable electrode with an active surface; and a membrane on said electrode active surface, said membrane having a membrane surface, and including: a first stratum of hydrophilic material adjacent said electrode active surface, said first stratum being permeable to said gas and to said compound for transport to said active surface; a catalyzing agent immobilized in said first stratum for contact with said gas and said compound for promoting reaction between said compound and said gas; a peripheral edge thickness surface in said first stratum for directly contacting said solution and admitting said compound on a path of diffusion substantially parallel to said membrane and electrical surfaces; and a second stratum of hydrophobic material permeable to said compound, said second stratum of hydrophobic material being disposed adjacent to and substantially coextensive with said first stratum of hydrophilic material to reduce the rate at which said compound enters and/or is transported through said membrane to a value which is a function of the initial concentration of said compound and said solution by substantially restricting the entry of said compound into said membrane except at said peripheral edge thickness surface and to supply gas through said membrane surface to said compound diffusing at a rate relative to the rate of entry and/or transport of said compound to provide a new concentration ratio of gas to said compound within said membrane, which ratio is at least equal to a stoichiometric equivalent of said gas to said compound.

Claim 9

A method for determining the concentration of a first component present in stoichiometric excess over a reactive gas component in an aqueous solution by means of a sensor including an electrode with an active surface and a membrane having a first stratum of hydrophilic material disposed on said electrode active surface and including a peripheral edge thickness surface for directly contacting said solution to allow said first component to enter said membrane, and a membrane surface formed by a second stratum of hydrophobic material that allows said gas to enter said membrane and that contacts and substantially covers said first stratum of hydrophilic material except at said peripheral edge thickness surface, said method comprising the steps of: immobilizing a catalyzing agent in said first stratum of hydrophilic material for promoting reaction between said first component and said gas; diffusing said first component through said peripheral edge thickness surface of said first stratum of hydrophilic material on a path substantially parallel to said electrode and membrane surfaces; diffusing said reactive gas component into said first stratum of hydrophilic material through said second stratum of hydrophobic material to limit the rate of entry and/or transport of transport of said first component such that the rate of entry and/or transport of said first component is a function of the concentration of that component in said solution and is reduced relative to the rate of entry and/or transport of said gas component to provide a new ratio of said gas component to said first component at least equal to a stoichiometric equivalent; and reacting said gas component with said first component in said new ratio and detecting the concentration of unreactive gas or of the reaction product of said gas and said first component.

Claim 10

A method for determining the concentration of a first component present in stoichiometric excess over a reactive gas component in an aqueous solution by means of a sensor including an electrode with an active surface and a membrane having a first stratum of hydrophilic material disposed on said electrode active surface and including a peripheral edge thickness surface for directly contacting said solution to allow said first component to enter said membrane, and a membrane surface formed by a second stratum of hydrophobic material that allows said gas to enter said membrane and that contacts and substantially covers said first stratum of hydrophilic material except at said peripheral edge thickness surface, said method comprising the steps of: immobilizing a catalyzing agent in said first stratum of hydrophilic material for promoting reaction between said first component and said gas; diffusing said first component through said peripheral edge thickness surface of said first stratum of hydrophilic material on a path substantially parallel to said electrode and membrane surfaces; diffusing said reactive gas component into said first stratum of hydrophilic material through said second stratum of hydrophobic material to limit the rate of entry and/or transport of transport of said first component such that the rate of entry and/or transport of said first component is a function of the concentration of that component in said solution and is reduced relative to the rate of entry and/or transport of said gas component to provide a new ratio of said gas component to said first component at least equal to a stoichiometric equivalent; and reacting said gas component with said first component in said new ratio and detecting the concentration of unreactive gas or of the reaction product of said gas and said first component.