CO.sub.2 sensor using a hydrophilic polyurethane matrix and process for manufacturing

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:

• 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.

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:

• 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.