Sensor element and method for making the same

Claim 1

A sensor element for sensing carbon dioxide in a sample comprising: an optical fiber having a surface portion covered with a matrix made from a hydrophobic material that is permeable to carbon dioxide; and a plurality of vesicles dispersed throughout said matrix, each of said vesicles containing an aqueous sensing solution including a dye indicator which dissociates into two different species in response to the presence of carbon dioxide, an agent for modifying the equilibrium of dissociation of said dye indicator to be within a range for optimal sensitivity to said carbon dioxide, and an aqueous base for raising the pH of said aqueous sensing solution to be outside a physiological range of carbon dioxide concentration when said dye indicator is not exposed to carbon dioxide, and to be within said physiological range of carbon dioxide concentration when said dye indicator is exposed to carbon dioxide, said dye indicator being exposable to an external excitation through said matrix, and at least one species of said dye indicator producing an emission of light in response to said excitation, with said emission of light being related to the content of carbon dioxide in said sample, whereby exposure of the dye indicator to carbon dioxide will cause the equilibrium of dissociation of the indicator to be within said range for optimal sensitivity.

Claim 19

A method for making a sensor element for sensing an analyte in a sample, said sensor including an optical fiber having a surface portion covered with a matrix made from a material that is permeable to the analyte, and a plurality of vesicles dispersed throughout said matrix, each of said vesicles containing an aqueous sensing solution including a fluorescent dye indicator which has an equilibrium of dissociation into two different species which is sensitive to said analyte, comprising the steps of: adding said fluorescent dye indicator substance that is sensitive to said analyte to an aqueous solution and an agent for modifying the equilibrium of dissociation of said dye indicator substance to be within an optimal range of sensitivity to said analyte; adding an aqueous base to said aqueous solution to change the pH of said aqueous solution to be outside an optimal range of sensitivity of said dye indicator substance in said aqueous solution to form said aqueous sensing solution; adding said aqueous sensing solution to a liquid silicone matrix containing a curing inhibitor for prolonging the liquid state of said matrix; homogeneously dispersing the aqueous solution throughout said liquid matrix solution to form an emulsion of said sensing solution in a plurality of vesicles in said liquid matrix; coating said surface of said optical fiber with said emulsion; and heating said emulsion to cure said matrix of said emulsion into a solid semi-permeable membrane that is permeable to said analyte.

Claim 20

A method for making a sensor element for sensing an analyte in a sample, said sensor including an optical fiber having a surface portion covered with a matrix made from a material that is permeable to the analyte, and a plurality of vesicles dispersed throughout said matrix, each of said vesicles containing an aqueous sensing solution including a fluorescent dye indicator which has an equilibrium of dissociation into two different species which is sensitive to said analyte, comprising the steps of: adding said fluorescent dye indicator substance that is sensitive to said analyte to an aqueous solution and an agent for modifying the equilibrium of dissociation of said dye indicator substance to be within an optimal range of sensitivity to said analyte; adding an aqueous base to said aqueous solution to change the pH of said aqueous solution to be outside an optimal range of sensitivity of said dye indicator substance in said aqueous solution to form said aqueous sensing solution; adding said aqueous sensing solution to a liquid silicone matrix containing a curing inhibitor for prolonging the liquid state of said matrix; homogeneously dispersing the aqueous solution throughout said liquid matrix solution to form an emulsion of said sensing solution in a plurality of vesicles in said liquid matrix; coating said surface of said optical fiber with said emulsion; and heating said emulsion to cure said matrix of said emulsion into a solid semi-permeable membrane that is permeable to said analyte.

Claim 24

A method for making a sensor element for sensing the carbon dioxide content of a sample, said sensor including an optical fiber having a surface portion covered with a matrix made from a material that is permeable to carbon dioxide, and a plurality of vesicles dispersed throughout said matrix, each of said vesicles containing an aqueous sensing solution including polyvinylpyrrolidone and a fluorescent dye indicator responsive to carbon dioxide, comprising the steps of: adding polyvinylpyrrolidone and said fluorescent dye indicator substance that is sensitive to carbon dioxide to an aqueous solution; titrating said aqueous solution containing polyvinylpyrrolidone and said dye indicator with an aqueous base to a pH of 9 to form said aqueous sensing solution; adding said aqueous sensing solution to a liquid silicone matrix containing a curing inhibitor for prolonging the liquid state of said matrix; homogeneously dispersing the aqueous solution throughout said liquid matrix to form an emulsion of said sensing solution in a plurality of vesicles in said liquid matrix; coating said surface of said optical fiber with said emulsion in a thickness slightly more than the size of one of said vesicles; and heating said emulsion to a temperature between about 180 and 220 degrees Centigrade to cure said matrix into a solid semi-permeable membrane that is permeable to carbon dioxide.

Claim 25

A method for making a sensor element for sensing the carbon dioxide content of a sample, said sensor including an optical fiber having a surface portion covered with a matrix made from a material that is permeable to carbon dioxide, and a plurality of vesicles dispersed throughout said matrix, each of said vesicles containing an aqueous sensing solution including polyvinylpyrrolidone and a fluorescent dye indicator responsive to carbon dioxide, comprising the steps of: adding polyvinylpyrrolidone and said fluorescent dye indicator substance that is sensitive to carbon dioxide to an aqueous solution; titrating said aqueous solution containing polyvinylpyrrolidone and said dye indicator with an aqueous base to a pH of 9 to form said aqueous sensing solution; adding said aqueous sensing solution to a liquid silicone matrix containing a curing inhibitor for prolonging the liquid state of said matrix; homogeneously dispersing the aqueous solution throughout said liquid matrix to form an emulsion of said sensing solution in a plurality of vesicles in said liquid matrix; coating said surface of said optical fiber with said emulsion in a thickness slightly more than the size of one of said vesicles; and heating said emulsion to a temperature between about 180 and 220 degrees Centigrade to cure said matrix into a solid semi-permeable membrane that is permeable to carbon dioxide.