45 results about "Chemiresistor" patented technology

A chemical-sensing apparatus is formed from the combination of a chemical preconcentrator which sorbs and concentrates particular volatile organic chemicals (VOCs) and one or more chemiresistors that sense the VOCs after the preconcentrator has been triggered to release them in concentrated form. Use of the preconcentrator and chemiresistor(s) in combination allows the VOCs to be detected at lower concentration than would be possible using the chemiresistor(s) alone and further allows measurements to be made in a variety of fluids, including liquids (e.g. groundwater). Additionally, the apparatus provides a new mode of operation for sensing VOCs based on the measurement of decay time constants, and a method for background correction to improve measurement precision.

An inverse analysis method for characterizing diffusion of vapor from an underground source of volatile contaminant using data taken by an in-situ sensor. The method uses one-dimensional solutions to the diffusion equation in Cartesian, cylindrical, or spherical coordinates for isotropic and homogenous media. If the effective vapor diffusion coefficient is known, then the distance from the source to the in-situ sensor can be estimated by comparing the shape of the predicted time-dependent vapor concentration response curve to the measured response curve. Alternatively, if the source distance is known, then the effective vapor diffusion coefficient can be estimated using the same inverse analysis method. A triangulation technique can be used with multiple sensors to locate the source in two or three dimensions. The in-situ sensor can contain one or more chemiresistor elements housed in a waterproof enclosure with a gas permeable membrane.

A flexible chemiresistor (CR) sensor for sensing a molecule of interest in a fluid (liquid or gas) is provided. The flexible CR sensor comprises a flexible chemiresistor (CR) module. The flexible CR module comprises a flexible substrate such polyethylene terephthalate (PET), polyethylene naphthalate (PEN) or polyimide (PI), and a thin film nanoparticle assembly assembled on the flexible substrate. The thin film nanoparticle assembly comprises metal or metal alloy core, ligand-capped nanoparticles and molecular linkers connecting the nanoparticles. The flexible CR sensor and an intelligent pattern recognition engine can be incorporated in a handheld device that can detect a molecule of interest in a fluid (e.g., a liquid or gas) accurately, rapidly, and without false positives. Any sensing array nanomaterial, pattern recognition, and compact/or electronic hardware can be integrated to achieve a desired detection limit and response speed.

A multi-pin chemiresistor for use in microchemical sensors. A pair of free-standing, bare wires is supported by an electrically insulating support, and are oriented parallel to each other and spaced closely together. A free-standing film of a chemically sensitive polymer that swells when exposed to vapors of a volatile chemical is formed in-between the pair of closely-spaced wires by capillary action. Similar in construction to a thermocouple, this “chemicouple” is relatively inexpensive and easy to fabricate by dipping the pair of bare wires into a bath of well-mixed chemiresistor ink. Also, a chemiresistor “stick” is formed by dipping an electrically insulating rod with two or more linear or spiral-wrapped electrical traces into the bath of well-mixed chemiresistor ink, which deposits a uniform coating of the chemically sensitive polymer on the rod and the electrical traces. These “sticks” can be easily removed and replaced from a multi-chemiresistor plug.

The present invention relates to a composition for sensor films used for detecting chemical analytes within sensors, such as polymer-absorption chemiresistors (i.e. conductometric sensors). The present invention provides sensor film compositions that have greater temperature stability and sensitivity to chemical analytes, as well as methods of making these sensor films. Sensor film compositions according to the present invention include a crosslinked siloxane polymer comprising a monomer having a hydrocarbon side group with greater than or equal to two carbon atoms and a plurality of conductive particles distributed within the polymer. Alternate preferred embodiments distribute an oil comprising siloxane having at least one side group with greater than or equal to two carbons through a crosslinked siloxane polymer, wherein the oil is distributed through a crosslinked polysiloxane copolymer. Further, conductive particles having a N₂ adsorption of between about 8 to about 25 m²/g provide enhanced sensor film performance.

The present invention provides a chemiresistor-based sensor for measuring the presence or amount of analyte in an electrolyte solution; said chemiresistor comprising (i) a chemiresistor film wherein the impedance of said nanoparticle film changes in the presence of an analyte; and (ii) two electrically conducting electrodes in electrical contact with said nanoparticle film; wherein said electrically conducting electrodes are adapted to be connected to a device for measuring the impedance of said chemiresistor film under a voltage signal and wherein the impedance of the double layer capacitor formed by the two electrically conducting electrodes in the presence of the electrolyte solution, is larger than the impedance of the chemiresistor film either before or after exposure of the chemiresistor film to the analyte. A method of using said chemiresistor-based sensor to measure the presence or amount of analyte is also provided. Further provided is a method of determining the partition coefficient of an analyte using said chemiresistor-based sensor.

The present invention is a chemiresistor for qualitative and quantitative analysis of chemical species that consists of a very thin film of particles, nanoclusters, deposited on an insulating substrate and contacted by electrodes. The particles have a metallic core, preferably spheroidal, that is less than 5 nm in diameter and surrounded by an monolayer ligand shell ranging in thickness from 0.4 nm to 2 nm. The Coulomb blockade effects upon which the invention operates result in nonlinear current-voltage characteristics which dramatically improves sensitivity with much lower power dissipation. One property of the ligand shell is that its chemical composition can be chosen to be especially receptive to a particular chemical vapor.

The invention relates to “solid state” chemiresistor sensors with electric control of the affinity of a chemosensitive material. The configurations of the present invention enable the fast regeneration of the sensor after analyte binding, which therefore increases selectivity. In one embodiment the chemiresistor sensor is implemented as a multi-electrode chemiresistor, comprising 4 electrodes for the separate measurement of the resistance of the chemosensitive material and the contact resistance, and 2 further electrodes to control the redox state of the chemosensitive sensor material, thereby facilitating fast and effective regeneration of the sensor.

A chemiresistor sensor probe for detecting target analytes. The probe includes a body having a first control surface and a second control surface recessed within the first. A sensor film comprises numerous conductive particles disposed upon the second surface. The film swells upon absorbing one or more analytes for which it has an affinity, thus causing the conductive particles to become more dispersed and increasing the resistance between the particles. The thickness of the film is equal to the distance between the first surface and the second surface, thus permitting the thickness to be controlled by varying the distance between the control surfaces. The robustness of the sensor probe is enhanced by placing a porous or mesh electrode along with, or in place of, a chemical binding agent between the film and the terminals. The robustness is also improved by placing a diode in series with the sensor circuit.

Nanoparticle-fibrous membrane composites are provided as tunable interfacial scaffolds for flexible chemical sensors and biosensors by assembling gold nanoparticles (Au NPs) in a fibrous membrane. The gold nanoparticles are functionalized with organic, polymeric and/or biological molecules. The fibrous membranes may include different filter papers, with one example featuring a multilayered fibrous membrane consisting of a cellulose nanofiber (CN) top layer, an electrospun polyacrylonitrile (PAN) nanofibrous midlayer (or alternate material), and a nonwoven polyethylene terephthalate (PET) fibrous support layer, with the nanoparticles provided on the fibrous membranes through interparticle molecular/polymeric linkages and nanoparticle-nanofibrous interactions. Molecular linkers may be employed to tune hydrogen bonding and electrostatic and/or hydrophobic/hydrophilic interactions to provide sensor specificity to gases or liquids. The sensors act as chemiresistor-type sensors. A preferred implementation is a sweat sensor.

The sensitivity of a chemiresistor sensor can be dynamically tuned using mechanical strain. The increase in sensitivity is a smooth, continuous function of the applied strain, and the effect can be reversible. Sensitivity tuning enables the response curve of the sensor to be dynamically optimized for sensing analytes, such as volatile organic compounds, over a wide concentration range.

The invention relates to a sensor assembly to detect and quantify organic and/or inorganic mercury compounds, including elemental mercury that may be present in gases or liquids, such as natural gas, air, condensates, crude oil, refined petroleum gas or liquids, and water including connate water, condensed water and water containing hydrate inhibitor(s). The sensor assembly includes a housing having a flow channel defined by an inlet, a sensor array, and an outlet. The sensor array is based on the differential sorption properties measured using a surface acoustic wave (SAW) sensor array, a chemiresistor array, or a combination of the two.

Compositions for sensor films used for detecting chemical analytes within sensors, such as polymer-absorption chemiresistors (i.e., conductometric sensors) are provided. Robust sensor film compositions that have low resistance, high conductivity, and greater temperature stability and sensitivity to chemical analytes are provided, as well as methods of making these sensor films. Such sensor film compositions include a matrix having a polymer resin and a plurality of conductive particles comprising an axial-geometry conductive particle. Exemplary axial-geometry conductive particles comprise graphene, such as a carbon nanotube. Blends of conductive particles are also contemplated, including blends of axial-geometry conductive particles, such as carbon nanotubes, and carbon black.

The present invention relates to a method of altering the sensitivity and/or selectivity of a chemiresistor sensor, to a sensor and a sensor array produced by such method.

A chemiresistor sensor system that compensates for changes in resistance caused by changes in ambient temperature, thereby increasing the accuracy of the sensor system's ability to detect target analytes. The sensor system generally includes a first resistor, a second resistor, and a load regulator or switch that is sensitive to changes in ambient temperature. At least one of the first resistor and the second resistor is a sensing element having a resistance that changes in response to the presence of one or more of the analytes. The switch manages an electrical load across the first resistor and the second resistor. The switch prevents passage of the electrical load across the first and/or second resistor when the ambient temperature is at a first value. The switch permits passage of the electrical load across the first and/or second resistor when the ambient temperature is at a second value.

The present disclosure relates to a composition for sensor films used for detecting chemical analytes within sensors, such as polymer-absorption chemiresistors (i.e., conductometric sensors). The present disclosure provides robust sensor film compositions that have low resistance, high conductivity, and greater temperature stability and sensitivity to chemical analytes, as well as methods of making these sensor films. Sensor film compositions according to the present disclosure include a matrix having a polymer resin comprising siloxane and a plurality of conductive particles including at least two distinct species.