WO2000039570A2 - Capteur de detection de petites concentrations d'une substance cible - Google Patents
Capteur de detection de petites concentrations d'une substance cible Download PDFInfo
- Publication number
- WO2000039570A2 WO2000039570A2 PCT/US1999/030540 US9930540W WO0039570A2 WO 2000039570 A2 WO2000039570 A2 WO 2000039570A2 US 9930540 W US9930540 W US 9930540W WO 0039570 A2 WO0039570 A2 WO 0039570A2
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- sensitive layer
- chemical sensitive
- sensor
- target matter
- piezoresistive
- Prior art date
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Classifications
-
- G—PHYSICS
- G01—MEASURING; TESTING
- G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
- G01N27/00—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means
- G01N27/02—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance
- G01N27/04—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance
- G01N27/041—Investigating or analysing materials by the use of electric, electrochemical, or magnetic means by investigating impedance by investigating resistance of a solid body
Definitions
- This invention relates generally to gas and chemical sensors and more particularly to a micro-electromechanical system for detecting very small concentrations of a target matter.
- sensors are presently in use to detect various types of gases and chemical compounds . Such sensors range from the common household smoke detector to those designed to detect deadly nerve gases . Many of these applications require sensors that are sensitive and relatively small in size.
- a need has arisen for a compact, light weight, low power, high sensitivity sensor capable of detecting chemical concentrations in gas and liquid phases with sub-ppb sensitivity.
- the present invention provides a sensor that addresses these needs .
- a gas sensor is constructed to detect and measure concentrations of a target matter in either a microenvironment or in normal applications.
- a piezoresistive layer is mechanically coupled to a selected chemical sensitive layer.
- the target matter reacts with the chemical sensitive layer and creates an induced strain in the chemical sensitive layer.
- the chemical sensitive layer is coupled to the piezoresistive material in a manner such that the reaction of the chemical sensitive layer to the target matter (the induced strain) applies stress to the piezoresistive material.
- This applied stress typically results in a change in resistance of the piezoresistive material. This change is resistance may be used to indicate the concentration of the target matter that is interacting with the chemical sensitive layer.
- Embodiments of the invention provide numerous technical advantages.
- sensors incorporating teachings of the present invention may be manufactured as micro-electromechanical systems (MEMS) for use in both microenvironments and normal environments.
- MEMS micro-electromechanical systems
- a MEMS chemical sensitive single crystal silicon cantilever design is used which has no moving parts, therefore making the embodiment simple and compact .
- Another technical advantage is the use of a chemical sensitive layer with selected sensitivity to specific gases, liquids, and chemical species. The use of this chemical sensitive layer in combination with a piezoresistive material allows for sub-ppb sensitivity.
- Still further technical advantages of the present invention include the use of a chemical sensitive sensor cantilever and non-chemical sensitive reference cantilever pair to compensate for environmental transients.
- one embodiment provides multichannel capability to detect multiple types of gases, liquids or chemical species.
- sensors incorporating the present invention may be used in outdoor sensor networks and handheld applications due to their ruggedness, compactness, low weight, low power requirements, and low cost.
- Sensors formed in accordance with teachings of the present invention may be used for continuous monitoring of a target matter while remaining unsaturated during the useable lifetime of the sensor.
- Sensors incorporating teachings of the present invention are also capable of operating as stand alone sensors or as components of networked arrays of diverse sensors.
- Other technical advantages are readily apparent to one skilled in the art from the following figures, descriptions, and claims.
- FIGURE 1 is a schematic drawing in elevation showing a sensor incorporating one embodiment of the present invention
- FIGURE 2 is a schematic drawing showing an isometric view of the sensor of FIGURE 1 and an electrical circuit for obtaining data from the sensor;
- FIGURE 3 is a schematic drawing in elevation showing portions of a micro-electromechanical system for detecting very small concentrations of a selected target matter in accordance with teachings of the present invention
- FIGURE 4 is a plan view of a portion of the micro- electromechanical system of FIGURE 3 ;
- FIGURE 5 is a schematic drawing of a sensing system incorporating another embodiment of the present invention.
- FIGURES 1 through 5 of the drawings like numerals being used for like and corresponding parts of the various drawings.
- target matter shall mean a gas, vapor, liquid, chemical species, or any other type of matter which is sought to be detected.
- ppm shall stand for "part per million” .
- the phrase “part per million” shall mean that for every one million parts of a certain medium (i.e. air), there is only one part of the target matter.
- the “part” can be any representative amount of a substance, such as a molecule or a certain volume.
- ppb and ppt stand for "part per billion” and “part per trillion”, respectively. The meaning of these phrases is clear from the meaning of "part per million”, discussed above.
- FIGURES 1 and 2 show a sensor 10 representing one embodiment of the present invention. This embodiment is simplified to show the three components of the invention and their operation.
- the first such component includes a layer 20 of a selected piezoresistive type material. Piezoresistive material 20 experiences a change in bulk resistance when stress is applied to it. Piezoresistive material 20 may be layered on or implanted in a support medium 22, or it may stand alone.
- the second such component includes a chemical sensitive layer 30.
- Chemical sensitive layer 30 is mechanically coupled or bonded to piezoresistive material 20.
- Chemical sensitive layer 30 is comprised of a material chosen to preferentially react with a selected target matter. The interaction of the target matter (not explicitly shown) with chemical sensitive layer 30 may change the physical properties of chemical sensitive layer 30, such as molar volume, morphology, and the like, and may lead to a microscopic change m the dimensions (strain) of chemical sensitive layer 30.
- the target matter may be any existing matter that reacts with a particular type of chemical sensitive layer m this way.
- the reaction m chemical sensitive layer 30 may be caused by a variety of interactions between chemical sensitive layer 30 and the target matter. These interactions may include, but are not limited to, absorption, adsorption, and amalgamation.
- sensor 10 is not limited to detecting concentrations of a target matter dispersed m the air. Sensor 10 can be used to measure a target matter concentration m a multitude of gas, liquid, and multi-phase environments.
- Chemical sensitive layer 30 is not shown m FIGURE 2 to more clearly show electrical circuit 40.
- Piezoresistive material 20 is electrically coupled to electrical circuit 40 through a pair of electrical leads 42. Electrical current may naturally flow through piezoresistive material 20, or it can be directed by electrical wiring 44. Any type of electrical circuit capable of detecting and/or measuring a change m resistance may be used m conjunction with piezoresistive material 20 and chemical sensitive layer 30.
- piezoresistive material 20 and chemical sensitive layer 30 m FIGURE 1 is only one example of many different possible configurations.
- Piezoresistive material 20 is not required to cover an entire surface of support medium 22. In fact, such a configuration may not be desired for some applications.
- Piezoresistive material 20 is preferably placed in selected areas based on the stresses induced by chemical sensitive layer 30 in response to the target material. For instance, piezoresistive material may be placed at locations where the applied stress is expected to be maximized.
- chemical sensitive layer 30 does not have to entirely cover piezoresistive material 20. It may also be placed in more than one area to obtain configurations with enhanced sensitivity.
- FIGURE 3 shows a sensor 100 representing another embodiment of the present invention. This embodiment may generally be described as a MEMS bulk micromachined piezoresistive cantilever sensor with a chemical sensitive layer. Sensor 100 incorporates the same chemical sensitive/piezoresistive principles as sensor 10, shown in FIGURE 1.
- Sensor 100 includes a cantilevered beam 122 mounted on a substrate 124.
- Substrate 124 may perform at least two different functions. One such function may be to simply provide mechanical support for the cantilevered beam 122. Substrates performing this function may be fabricated from materials such as ceramics, plastics, glass, metals, or semiconductors such as silicon (Si), germanium (Ge) , gallium arsenide (GaAs) , aluminum gallium arsenide
- AlGaAs indium phosphide
- InP indium phosphide
- CdTe cadmium telluride
- substrate 124 may perform is hosting electronic circuitry for acquiring and processing signals generated m the sensor.
- Substrates performing this function may be fabricated from materials such as silicon
- Si germanium
- Ge gallium arsenide
- GaAs gallium arsenide
- AlGaAs aluminum gallium arsenide
- InP indium phosphide
- CdTe cadmium telluride
- SiC silicon carbide
- other Group III-V or II -VI semiconductor compounds germanium (Ge) , germanium (Ge) , gallium arsenide (GaAs) , aluminum gallium arsenide (AlGaAs) , indium phosphide (InP) , cadmium telluride (CdTe) , silicon carbide (SiC) , and other Group III-V or II -VI semiconductor compounds.
- Beam 122 may serve as a support medium for one or more regions 120 of piezoresistive material implanted m beam 122.
- Piezoresistive regions 120 may comprise any type of piezoresistive material including, but not limited to, silicon doped with boron or phosphorus. However, the beam itself may also be comprised of piezoresistive material.
- Beam 122 may be made of appropriately doped silicon, Ge, GaAs, AlGaAs, SiC, diamond films, and conductive polymers such as polyimide/graphite composites.
- a chemical sensitive layer 130 is coupled or bonded to piezoresistive layer 120.
- chemical sensitive layer 130 comprises a material specifically chosen to preferentially react with a target matter.
- Beam 122 bends as a result of the stress induced by the chemical sensitive layer when exposed to the target matter.
- the resistance of piezoresistive layer 120 is changed. This change m resistance can then be detected and/or measured using an electrical circuit (not explicitly shown) .
- This electrical circuit is coupled to piezoresistive layer 120 through the use of one or more bonding pads 140. Bonding pads 140 are used to support the wires of the electric circuit, and to maintain the connection of these wires to piezoresistive layer 120. Evaporated metals with low electrical conductivity may be used as bonding pads 140.
- FIGURE 4 shows a sensing system 200 incorporating teachings of the present invention. Sensing system 200 comprises two cantilevered beams. One beam is a signal beam 210 and the other is a reference beam 220.
- beams 210 and 220 are "U" -shaped double cantilever beams, however, any type of beam or membrane supported in any way could also be used. As described above, the "U" -shaped beam may be used so that electrical current directed into one leg 123a of the "U" will flow out of the other leg 123b.
- Signal beam 210 comprises one or more piezoresistive regions (not explicitly shown) and a chemical sensitive layer (not explicitly shown) . However, reference beam 220 does not include a chemical sensitive layer. Reference beam 220 does includes one or more piezoresistive regions (not explicitly shown) .
- Signal beam 210 and reference beam 220 are preferably coupled to an electrical circuit 230 through the use of bonding pads 140, as shown in FIGURE 5.
- Electrical circuit 230 is used to detect and/or measure the change in resistance of the piezoresistive material of signal beam 210. Through the use of electrical circuit 230, the output of signal beam 210 is referenced to the output of reference beam 220.
- the use of a signal/reference pair eliminates system drift due to changes in ambient conditions in the monitoring environment. These ambient conditions include, but are not limited to, temperature, humidity, vibration, and the deposition of nontarget matter.
- electrical circuit 230 comprises a Wheatstone bridge to measure the resistance change of signal beam 210.
- the configuration of a Wheatstone bridge is well known in the art, so it will not be described in detail here.
- the Wheatstone bridge includes four main sources of resistance. These sources of resistance are two resistors 232, signal beam 210, and reference beam 220. Signal beam 210 is connected in one arm of the Wheatstone bridge, and reference beam 220 is connected in another arm of the bridge.
- Electrical circuit 230 also includes a voltage source 234.
- the change in resistance of the piezoresistive material of signal beam 210 is determined by measuring the output voltage of electrical circuit 230. Connecting reference beam 220 as one of the resistors eliminates common mode noise and interfering effects, and provides for an accurate measurement of the change in resistance of the piezoresistive material of signal beam 210.
- the output voltage is amplified using an amplifier 236.
- the amplified voltage reading is then sent, via an interface 240, to a digital or analog output device.
- a digital or analog output device examples of such devices are a digital signal processor 242, a central processing unit 244, and an analog output device 246.
- the analog or digital output device may include a database that correlates a measured voltage or change in resistance with a certain concentration of the target matter. The analog or digital output device may then display or transmit the measured concentration to a user.
- Embodiments of the present invention may be used as dosimeters to measure the total exposure to a target matter, as well as being used as detectors. By integrating the signal response over time, the total amount of the target matter that reacts with a chemical sensitive layer in that time interval can be determined.
- the present invention may be used as a continuous monitoring detector to measure a change in the concentration of a target matter.
- a detector incorporating teachings of the present invention may make continuous samples over successive time intervals of a user-specified duration. The incremental change in resistance of the piezoresistive material is measured over the time interval. The output may then be specified in terms of a change in the target matter concentration over each time interval or as a total dose measurement by integrating the response over an extended period of time.
- a system incorporating the present invention is capable of detecting changes in concentration in the ppt range.
- saturation is proportional to the product of the target matter concentration and the exposure time. That is to say, saturation is achieved when the chemical sensitive layer is fully reacted with the target matter, and no more target matter can be absorbed.
- the exposure time required for saturation increases.
- a MEMS chemical sensitive cantilever detector exposed to ambient target matter concentrations at the ppb level will last one thousand times longer than when exposed to target matter concentrations at the ppm level .
- sensors representing an embodiment of the present invention may be arranged in a multichannel functional array (not explicitly shown) .
- a multichannel functional array allows each individual sensor to have maximum sensitivity to a precise target matter.
- an array may be used to detect a variety of different target matters.
- an array could be used to detect a variety of different types of explosives and chemical weapon agents.
- the present invention can theoretically be used to detect any type of target matter.
- the only requirement is that the chemical sensitive layer react with the target matter so as to apply a stress to the piezoresistive material.
- the MEMS chemical sensitive cantilever detector shown in FIGURES 3 and 4 , has been used to demonstrate detection of mercury (Hg) vapor and volatile organic compounds (VOCs) such as alcohols, acetone, and benzene with sub-ppb sensitivity.
- Hg detection mercury
- VOCs volatile organic compounds
- the o chemical sensitive layer used can be a 1000 A Au film.
- photoresist can be used as the chemical sensitive layer.
Abstract
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
AU41647/00A AU4164700A (en) | 1998-12-28 | 1999-12-21 | Sensor for detecting small concentrations of a target matter |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US22139198A | 1998-12-28 | 1998-12-28 | |
US09/221,391 | 1998-12-28 |
Publications (2)
Publication Number | Publication Date |
---|---|
WO2000039570A2 true WO2000039570A2 (fr) | 2000-07-06 |
WO2000039570A3 WO2000039570A3 (fr) | 2000-11-16 |
Family
ID=22827622
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
PCT/US1999/030540 WO2000039570A2 (fr) | 1998-12-28 | 1999-12-21 | Capteur de detection de petites concentrations d'une substance cible |
Country Status (2)
Country | Link |
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AU (1) | AU4164700A (fr) |
WO (1) | WO2000039570A2 (fr) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2003067240A2 (fr) | 2001-11-13 | 2003-08-14 | Raytheon Company | Capteur permettant la detection de faibles concentrations d'un composant cible |
WO2021168441A1 (fr) * | 2020-02-21 | 2021-08-26 | Culvert Engineering Solutions, Llc | Système et dispositif de détection de produits chimiques à base de graphène |
Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5028394A (en) * | 1990-04-13 | 1991-07-02 | Bend Research, Inc. | Chemical sensors |
WO1994028372A1 (fr) * | 1993-05-25 | 1994-12-08 | Rosemount Inc. | Capteur chimique organique |
US5417100A (en) * | 1993-03-10 | 1995-05-23 | Hughes Aircraft Company | Reversible sensor for detecting solvent vapors |
US5512882A (en) * | 1991-08-07 | 1996-04-30 | Transducer Research, Inc. | Chemical sensing apparatus and methods |
US5563341A (en) * | 1995-06-07 | 1996-10-08 | Fenner; Ralph L. | Vapor pressure sensor and method |
EP0821228A1 (fr) * | 1996-07-25 | 1998-01-28 | HE HOLDINGS, INC. dba HUGHES ELECTRONICS | Capteur de composés organiques volatils |
-
1999
- 1999-12-21 AU AU41647/00A patent/AU4164700A/en not_active Abandoned
- 1999-12-21 WO PCT/US1999/030540 patent/WO2000039570A2/fr active Application Filing
Patent Citations (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US5028394A (en) * | 1990-04-13 | 1991-07-02 | Bend Research, Inc. | Chemical sensors |
US5512882A (en) * | 1991-08-07 | 1996-04-30 | Transducer Research, Inc. | Chemical sensing apparatus and methods |
US5417100A (en) * | 1993-03-10 | 1995-05-23 | Hughes Aircraft Company | Reversible sensor for detecting solvent vapors |
WO1994028372A1 (fr) * | 1993-05-25 | 1994-12-08 | Rosemount Inc. | Capteur chimique organique |
US5563341A (en) * | 1995-06-07 | 1996-10-08 | Fenner; Ralph L. | Vapor pressure sensor and method |
EP0821228A1 (fr) * | 1996-07-25 | 1998-01-28 | HE HOLDINGS, INC. dba HUGHES ELECTRONICS | Capteur de composés organiques volatils |
Non-Patent Citations (1)
Title |
---|
BATTISTONI C ET AL: "INTERACTION OF MERCURY VAPOUR WITH THIN FILMS OF GOLD" APPLIED SURFACE SCIENCE,NL,AMSTERDAM, vol. 103, no. 2, 1 October 1996 (1996-10-01), pages 107-111, XP002061342 ISSN: 0169-4332 * |
Cited By (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
WO2003067240A2 (fr) | 2001-11-13 | 2003-08-14 | Raytheon Company | Capteur permettant la detection de faibles concentrations d'un composant cible |
WO2003067240A3 (fr) * | 2001-11-13 | 2004-02-12 | Raytheon Co | Capteur permettant la detection de faibles concentrations d'un composant cible |
US6866819B1 (en) | 2001-11-13 | 2005-03-15 | Raytheon Company | Sensor for detecting small concentrations of a target matter |
WO2021168441A1 (fr) * | 2020-02-21 | 2021-08-26 | Culvert Engineering Solutions, Llc | Système et dispositif de détection de produits chimiques à base de graphène |
Also Published As
Publication number | Publication date |
---|---|
AU4164700A (en) | 2000-07-31 |
WO2000039570A3 (fr) | 2000-11-16 |
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