Chemical apparatus and process disinfecting – deodorizing – preser – Analyzer – structured indicator – or manipulative laboratory... – Means for analyzing gas sample
Reexamination Certificate
1999-06-22
2004-06-22
Warden, Jill (Department: 1743)
Chemical apparatus and process disinfecting, deodorizing, preser
Analyzer, structured indicator, or manipulative laboratory...
Means for analyzing gas sample
C422S082010, C422S082020, C422S082030, C422S083000, C204S412000, C204S415000, C204S416000, C204S418000, C204S431000, C436S149000, C436S151000
Reexamination Certificate
active
06752964
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a novel class of vapor sensors with tunable properties. More particularly, this invention relates to vapor sensors modified by the addition of a compatible small molecule of low volatility, i.e., a plasticizer.
BACKGROUND OF THE INVENTION
There is considerable interest in developing chemically sensitive sensors that are capable of detecting the presence of a particular chemical analyte in a fluid. Because the fluid is typically air, such sensors act as electronic noses, “smelling” the presence of a particular airborne molecule. These sensors are often fabricated from a polymeric organic material that is capable of absorbing a chemical analyte which comes in contact therewith, wherein absorbance of the analyte causes the polymeric material to expand or change, thereby modifying the electrical properties of the sensor. Variability in the ability to absorb an analyte results in variability in the detectable signal produced. Such organic polymer-based sensors have found use in a variety of different applications and devices including, for example, devices that function as analogs of the mammalian olfactory system (see, U.S. Pat. No. 5,571,401, which issued to Lewis et al, Lundström et al.,
Nature
352:47-50 (1991) and Shurmer and Gardner,
Sens. Actuators
B 8:1-11 (1992)), bulk conducting polymer films (Barker et al.,
Sens. Actuators
B 17:143 (1994) and Gardner et al.,
Sens. Actuators
B 18:240 (1994)), surface acoustic wave devices (Grate et al.,
Anal. Chem.
67:2162 (1995), Grate et al.,
Anal. Chem.
65:A987 (1993) and Grate et al,
Anal. Chem.
65:A940 (1993)), fiber optic micromirrors (Hughes et al.,
J. Biochem. and Biotechnol.
41:77 (1 993)), quartz crystal microbalances (Chang et al.,
Anal. Chim. Acta
249:323 (1991)) and dye impregnated polymeric coatings on optical fibers (White et al,
Anal. Chem.
68:2191 (1996)). To date, however, many of the sensors employed in the above-described devices have been fabricated from limited numbers of polymeric components and, therefore, are limited in the responses they are capable of producing.
Further, today's technology lags far behind the ability of canines or humans to detect or distinguish between chemical analytes. As a consequence, certain work is limited by the suitability of animals or humans to execute tasks. For example, quality control of food products can require production line employees to smell each item. Unfortunately, the ability of individuals to adequately discriminate odors diminishes after a short period of time, e.g., in about two hours. In addition, mammalian olfactory senses are limited in their ability to identify certain vapors. For example, water vapor is not detectable by smell. FurthFurther, mammalian olfactory senses are limited to identifying gaseous components, with no ability to identify or “smell” solutes in liquids.
Recent studies have shown that arrays of chemically sensitive sensors, such as those disclosed in U.S. Pat. No. 5,571,401, formed from a library of expandable insulating organic polymers containing a conductor such as carbon black, are broadly responsive to a variety of analytes, yet allow classification and identification of organic vapors through application of pattern recognition methods. (Lonergan et al.,
Chem. Mater.
8:2298 (1996)). To date, these array elements have been fabricated from a relatively small number of approximately 10-20 organic polymers, with a single distinct polymer backbone composition in each sensor element. Although a limited number of polymeric sensor compositions might be chosen to perform optimally for specific applications, attempts to perform complex applications, such as to mimic the sense of olfaction, in which the sensing task is time dependent or is not defined in advance of the sensor array construction, will almost certainly require use of polymeric sensor libraries that are far more extensive and compositionally diverse than those presently known.
In general, plasticizers are organic compounds added to polymers to facilitate processing and to increase the flexibility and toughness of the polymeric product. Among the more important plasticizers are nonvolatile organic liquids and low melting solids such as phthalates, adipate and sebacate esters, polyols such as ethylene glycol and tricresyl phosphates.
U.S. Pat. No. 4,948,490, which issued to Venkatasetty, discloses a single cell electrochemical sensor utilizing a conducting polymeric solid electrolyte film. These conducting polymeric films such as polyethylene oxide, polypropylene oxide and polyvinylidine fluoride can be used with a plasticizer. A preferred plasticizer is polyethylene glycol dimethyl ether. The plasticizer is added to the mixture to increase ionic conductivity by converting some or substantially all of the structure from crystalline to a plasticized amorphous form.
In addition, U.S. Pat. No. 4,587,101, discloses a fluorescence oxygen sensor having a plasticized polymer with fluorescent indicator molecules embedded within the polymer. In operation, the presence of the oxygen reduces the intensity of the fluorescent indicator substance, thus facilitating detection.
European Patent Application No. 0 794 428, published Sep. 10, 1997, describes sensors capable of distinguishing between enantiomers. The sensor comprise a pair of spaced apart contacts and a conducting polymer material spanning the gap. The polymer has chiral sites in the polymer material formed by incorporating optically active counter ions such as camphor sulfonic acid.
WO 99/00663, published Jan. 7, 1999, the contents of which are incorporated by reference herein, discloses a sensor in which at least a first and second organic polymer are combined to form an organic polymer blend. The sensor will preferably provide a signal that is not linearly related to the mole fraction of at least one of the organic polymers used to produce the organic polymer blend.
In view of the foregoing, and despite the advances disclosed in WO 99/00663, there still remains a need for novel methods for producing large libraries of radically sensitive sensors having tunable properties, each of which are capable of producing a detectable response in the presence of an analyte of interest. The present invention fulfills this and other needs.
SUMMARY OF THE INVENTION
In accordance with the present invention, a novel organic polymer-based sensor is provided with tunable properties capable of detecting the presence of an analyte in a fluid, thereby providing a detectable response. As used herein, the term “fluid” includes gases, vapors, solids, and liquids. As used herein, the term “tunable” refers to tailoring a sensor to a specific application with specific types of polymers and constituents thereof. In certain embodiments, the sensor comprises an organic mixture and a detector operatively associated with the mixture. In one embodiment, the organic mixture comprises a compatible molecule of low volatility (a plasticizer) combined with an insulating organic polymer or a conducting organic polymer. In another embodiment, the organic mixture comprises a plasticizer combined with an organic polymer blend of a first organic polymer and a second organic polymer. In certain embodiments, the first or second polymers are both insulating polymers. In still another embodiment, the organic mixture comprises a plasticizer combined with an organic polymer formed from a first organic monomer and a second monomer. In yet another embodiment, the organic mixture comprises a plasticizer combined with an interpenetrating network comprising a first organic polymer and a second organic polymer formed from an organic monomer polymerized in the presence of the first organic polymer.
In another embodiment of the present invention, an electrically conductive material, which can be a single electrically conductive material or a mixture of two or more electrically conductive materials, is added to the organic mixture, such as an insulating organic polymer. In a preferred embodiment, the electrically conductive m
Grubbs Robert H.
Lewis Nathan S.
Matzger Adam J.
California Institute of Technology
Handy Dwayne K.
Townsend and Townsend / and Crew LLP
Warden Jill
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