CO.sub.2 sensor using a hydrophilic polyurethane matrix and process for manufacturing
First Claim
1. A carbon dioxide sensor element comprising:
- an optical fiber having a surface portion;
a hydrophilic, gas permeable, cross-linked polymeric matrix disposed over std optical fiber surface portion, said hydrophilic polymeric matrix containing an aqueous dye-buffer solution physically entrapped in and dispersed throughout said hydrophilic polymeric matrix, said hydrophilic polymeric matrix formed from a polyurethane pre-polymer compound having a plurality of terminal isocyanate functional groups, said polyurethane pre-polymer compound being cross-linked by addition of said aqueous dye-buffer solution at room temperature; and
a layer of a gas permeable, hydrophobic material coating said hydrophilic polymeric matrix.
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Accused Products
Abstract
The carbon dioxide sensor includes a CO2 sensing matrix formed from a hydrophilic, gas permeable, cross-linked polyurethane. The polyurethane matrix is formed from a polyurethane pre-polymer mixture which cross links when mixed with an aqueous carbon dioxide buffer solution. The dye-buffer solution is physically entrapped as a homogeneous dispersion in the polymer matrix. The matrix is applied to the exposed glass core of an optical fiber, which may first be coated with a primer to allow the polyurethane matrix to bond firmly to the tip of the optical fiber. The hydrophilic polymeric matrix is preferably coated with a hydrophobic material to help avoid leaching of the dye from the matrix, and to prevent diffusion of hydronium ions into the sensing matrix. The hydrophobic polymer overcoat may thereafter be cured by heat treatment. The hydrophobic coating may also contain a light reflective material such as TiO2.
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Citations
16 Claims
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1. A carbon dioxide sensor element comprising:
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an optical fiber having a surface portion; a hydrophilic, gas permeable, cross-linked polymeric matrix disposed over std optical fiber surface portion, said hydrophilic polymeric matrix containing an aqueous dye-buffer solution physically entrapped in and dispersed throughout said hydrophilic polymeric matrix, said hydrophilic polymeric matrix formed from a polyurethane pre-polymer compound having a plurality of terminal isocyanate functional groups, said polyurethane pre-polymer compound being cross-linked by addition of said aqueous dye-buffer solution at room temperature; and a layer of a gas permeable, hydrophobic material coating said hydrophilic polymeric matrix. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method of manufacturing a carbon dioxide sensor element including an optical fiber having a surface portion covered with a hydrophilic, gas permeable, cross-linked polymeric matrix containing a homogeneous dispersion of an aqueous dye-buffer solution physically entrapped in said hydrophilic polymeric matrix, and a layer of a gas permeable, hydrophobic material coating said hydrophilic polymeric matrix, comprising the steps of:
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mixing a hydrophilic, semipermeable, pre-polymer material which cross-links in the presence of water with an aqueous dye-buffer solution, to form a homogeneous dispersion of said dye-buffer solution in said pre-polymer material and initiate cross-linking of said pre-polymer material; applying said pre-polymer material in which cross-linking has been initiated to said surface portion of said optical fiber; curing said pre-polymer material in which cross-linking has been initiated at room temperature, to form said hydrophilic, polymeric matrix on said optical fiber, and to thereby physically entrap said aqueous dye-buffer solution in said polymeric matrix; and coating said hydrophilic polymeric matrix with a layer of hydrophobic, gas permeable material. - View Dependent Claims (8, 9, 10, 11)
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12. A method of manufacturing a carbon dioxide sensor element including an optical fiber having a surface portion covered with a hydrophilic, gas permeable, cross-linked polymeric matrix containing a homogeneous dispersion of an aqueous dye-buffer solution physically entrapped in said matrix, and a layer of a gas permeable, hydrophobic material coating said hydrophilic matrix, comprising the steps of:
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mixing an aqueous dye-buffer solution with a hydrophilic, semipermeable, polyurethane pre-polymer material having a plurality of terminal isocyanate functional groups, to form a homogeneous dispersion of said dye-buffer solution in said polyurethane pre-polymer material and to initiate cross-linking of said polyurethane pre-polymer material to entrap said dye-buffer solution in said polyurethane pre-polymer material; applying said polyurethane pre-polymer material in which cross-linking has been initiated to said surface portion of said optical fiber; curing said polyurethane pre-polymer material in which cross-linking has been initiated at room temperature, to form said hydrophilic, polymeric matrix on said optical fiber, and to thereby physically entrap said aqueous dye-buffer solution in said polymeric matrix; and coating said hydrophilic polymeric matrix with a layer of hydrophobic, gas permeable material. - View Dependent Claims (13, 14, 15, 16)
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Specification