Chemistry: analytical and immunological testing – Optical result
Reexamination Certificate
2000-02-18
2003-11-18
Snay, Jeffrey (Department: 1743)
Chemistry: analytical and immunological testing
Optical result
C422S082060, C422S082080
Reexamination Certificate
active
06649416
ABSTRACT:
FIELD OF THE INVENTION
This invention generally relates to sensors and methods for detecting analytes. More particularly, this invention relates to optical sensors, sensor arrays, sensing systems and sensing methods for intelligent sensing and detection of unknown materials by way of real-time feedback and control of sampling conditions.
BACKGROUND OF THE INVENTION
U.S. Pat. No. 4,859,864 to Smith discloses an air bubble sensor that employs light emitting diode (LED) light sources, phototransistor detectors, and displays or alarms for detecting the presence of bubbles in a fluid sample.
U.S. Pat. No. 5,674,751 to Jaduszliwer, et al. disclose a hydrazine fuel fiber optic sensor that employs a diode laser pulsed light source, a calorimetric fiber optic sensor system, and a photodetector to detect changes in spectral absorption due to ppb levels of hydrazine fuel.
U.S. Pat. No. 5,445,795 to Lancaster, et al. disclose a portable optical sensor for detecting volatile organic compounds (VOCs) in vapors and aqueous media. The disclosed device comprises a vapochromic sensor formed from transition metal complex salts, a sensor chamber, a vacuum pump for drawing samples into the chamber, a light source for illuminating the sensor, a light detector responsive to light reflected from the vapochromic sensor, and a detection means for determining a color change in the sensor due to the presence of VOCs. In one disclosed embodiment for fuel tank sensing, the sensor, an LED illuminating light source, and a photodiode detector with an optical band-pass filter are all housed within the sensor chamber and a photodiode feedback signal is provided to a control means for adjusting a fuel metering valve via signal processing electronic circuitry. Other embodiments employ a bi-color LED that can be modulated between two wavelengths and gated detection electronics in the detector is synchronized with LED driver current to monitor small changes in reflected signals at both wavelengths.
U.S. Pat. No. 5,116,759 to Klainer, et al. discloses a vapor or liquid chemical sensor where analytes pass into a sampling cell where they contact sensing solutions for detection. The disclosed device comprises a single illumination source, an optional semi-permeable analyte membrane, a chamber with one or more analyte-sensitive solutions contained in a reservoir cell, a sample signal detector for detecting optical changes in the cell due to the analyte, and an optional reference signal detector for background signal correction. Reagent and sampling pumps are also disclosed for continuously flushing the cell with analyte and solution reagent. The disclosed device employs diodes, lasers or lamps as an excitation source, optically responsive analyte sensing solutions, detectors, and conventional electronic circuitry that are known in the art. In a preferred embodiment, an LED is the preferred light source and a photodiode is the preferred detector. Other embodiments disclose a light source sensor, a source stabilizer, a detector stabilizer, and a temperature sensor and compensator circuitry for feedback, monitoring and stabilizing the light source and detector. Disclosed embodiments include an A/D interface, alarms, display, recorders or plotters for readout, a computer and software.
Persaud and Dodd (
Nature v
. 299, pp. 352-355, Sep. 23, 1982) disclose an electronic nose comprised of semi-selective sensors in a cross-reactive sensor array designed to mimic a mammalian olfactory system. The disclosed sensors comprise commercially available semiconductor transducer gas sensors that exhibit a conductance change when the adsorb ambient vapors. The disclosed sensors were capable of detecting vapors at high concentrations ranging from 0,1 to 10 mols per liter of air. The response time for these sensors ranged from 1 to 3 minutes. Measurements made with various sensor parings demonstrated selectivity toward a number of analyte vapors at high concentrations.
U.S. Pat. No. 5,512,490 to Walt and Kauer disclose a fiber optic sensor with semi-selective sensors in a cross-reactive sensor array that employs spectral recognition patterns for identifying and detecting a variety of analytes. The reference teaches thin film sensors formulated by mixing polymers with dye compounds. The sensors are immobilized on either a solid planar translucent or transparent substrate or a fiber optic fiber or bundle. In a preferred embodiment, the substrate is a transparent optical fiber bindle in which sensors are placed on the ends of optical fibers or groups of such fibers. The sensing system taught by this reference utilizes an arc lamp excitation source, an optical train comprising a series of lenses, filters which are sequentially switched to provide for changes in both excitation light wavelength and emitted light wavelength, and a CCD camera detector which captures spatial images of the fluorescence intensity of individual sensor elements at various wavelengths. The measured responses of individual sensors to analytes are combined to form a pattern of spectral responses over time that are unique to a specific analyte. Spectral response patterns are stored in a library and the response patterns generated from unknown samples are compared with library patterns to identify and detect target analytes. Either light intensity or wavelength may be employed for analyte determinations
U.S. Pat. No. 5,063,164 to Goldstein discloses a biomimetic sensor for detecting airborne toxins. The disclosed device comprises a porous, semi-transparent substrate which is sufficiently transmissive to light to permit detection of transmitted light by an LED and photodiode and is impregnated with a self-regenerating sensor. The sensor allegedly mimics the human response to toxins with regard to sensitivity and affinity by employing a molecular encapsulant that contains a chemical sensor reagent. The disclosed device provides for detecting a change in optical density of the sensor which is dependent on toxin concentration and time of exposure. For dilute analyte levels, extended exposure times are required for adequate sensitivity and detection.
Smardzewski [
Talanta
35(2):95-101(1988)] discloses a multi-element optical waveguide sensor for detecting analytes in fluids which comprises eight fiber optic waveguides each circumferentially coated with sensing material, an array of eight sequentially-activated LEDs optically coupled to the waveguide assembly, and a single detector or array of multiple detectors, photomultiplier tubes or photodiodes, optically coupled to the waveguide assembly. Samples are passed over the outer surface of the coated waveguides and color changes produced by analyte interaction with the coating are monitored. In the disclosed method, each channel is sampled sequentially with measurements made on a single channel before moving to a subsequent channel. In the disclosed method the LEDs are pulsed on and off with switching times of at least one millisecond during measurements. The device provides for sensor signal output to be visually displayed or input to a microprocessor pattern-recognition algorithm. CMOS analog switches/multiplexers are used in feedback loops to control automatic gain-ranging, light-level adjustment and channel-sequencing. The detection limit and sensitivity of the disclosed device and method are limited to ppm levels.
Kopola, et al. [
SPIE
, Fiber Optic Sensors, v. 586, pp. 204-210 (1985)] disclose an eight channel spectrophotometer for measuring spectral reflectance at discrete wavelengths. The disclosed device comprises eight different LED light sources that cover a wavelength range between 480 nm and 1500 nm, a reference and measurement photodiode detector, a temperature controller, a fiber optic probe, signal conditioning electronics, microprocessor controller, and a display and plotter interface. In the disclosed method, measurements of both a reference LED output signal and sample LED output signal, which is modulated by the presence of an analyte, are simultaneously made with a single LED source and
Kauer John S.
White Joel E.
Creehan R. Dennis
Resnick David S.
Snay Jeffrey
Trustees of Tufts College
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