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Method and membrane applicable to implantable sensor

  • US 4,650,547 A
  • Filed: 12/20/1985
  • Issued: 03/17/1987
  • Est. Priority Date: 05/19/1983
  • Status: Expired due to Term
First Claim
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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.

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