Title: Integrated biological and chemical sensors
Abstract: An array of piezoelectric resonators used in a sensor device in order to identify chemical and biological agents. The resonators can operate as bulk acoustic wave (BAW), surface acoustic wave (SAW), or Love mode devices. The sensor device integrates gravimetric, calorimetric, thermal gravimetric, voltage gravimetric and optical detection methods into one sensor system, improving the accuracy of identifying hazardous agents. For gravimetric detection, dual-mode resonators provide simultaneous calorimetric and gravimetric data, one type from each mode. Resonators with heaters on the surfaces will provide thermal gravimetric data. An optical detector can be used to analyze the optical signal from the surface of a coated resonator. Additionally, voltage gravimetric measurements can be made with an electric field set up between the resonator and an external electrode. Thermal voltage gravimetric measurements can be made by adding an integrated heater on the resonator with an external electrode. An alarm can be activated upon the identification of a hazardous agent. The sensor device can utilize other valuable information, including traceable time, GPS location, and variables related to temperature, humidity, air speed, and air direction.
Patent Number: 6,955,787 Issued on 10/18/2005 to Hanson
| Inventors:
|
Hanson; William Paynter (1107 Sherwood Dr., Carlisle, PA 17013)
|
| Appl. No.:
|
684301 |
| Filed:
|
October 11, 2003 |
| Current U.S. Class: |
422/50; 29/592; 29/592.1; 29/594; 73/1.01; 73/1.02; 73/1.82; 73/1.83; 73/23.2; 73/53.01; 73/54.41; 73/61.49; 73/570; 73/579; 422/56; 422/57; 422/68.1; 422/82.01; 422/82.02; 422/83; 422/88; 422/98; 436/43; 436/63; 436/147; 436/149; 436/150; 436/151; 436/155 |
| Intern'l Class: |
G01N 021/00; G01N 031/22; G01N 015/06; G01N 033/00; G01N 033/48 |
| Field of Search: |
422/50,56,57,681,820.1,820.2,83,88,98
436/43,63,147,149,150,151
73/101,102,182,183,232,530.1,544.1,614.9,570,579
29/592,592.1,594
|
References Cited [Referenced By]
U.S. Patent Documents
| 3164004 | Jan., 1965 | King.
| |
| 4748367 | May., 1988 | Bloch et al.
| |
| 5065140 | Nov., 1991 | Neuburger.
| |
| 5411709 | May., 1995 | Furuki et al.
| |
| 5696422 | Dec., 1997 | Hanson.
| |
| 5744902 | Apr., 1998 | Vig.
| |
| 5852229 | Dec., 1998 | Josse et al.
| |
| 5936150 | Aug., 1999 | Kobrin et al.
| |
| 5992215 | Nov., 1999 | Caron et al.
| |
| 6044332 | Mar., 2000 | Korsah et al.
| |
| 6076406 | Jun., 2000 | Blair et al.
| |
| 6085576 | Jul., 2000 | Sunshine et al.
| |
| 6293136 | Sep., 2001 | Kim.
| |
| 6379623 | Apr., 2002 | Mays, Jr.
| |
| 6432362 | Aug., 2002 | Shinar et al.
| |
Primary Examiner: Warden; Jill
Assistant Examiner: Sines; Brian
Attorney, Agent or Firm: Gaskin; Mary J.
Claims
1. An integrated sensor device for use in identifying biological and chemical
agents, the sensor device comprising:
(a) an array of piezoelectric resonators having electrodes, each of the resonators
operating in a mode selected from the group consisting of a single mode and a dual mode:
(b) two or more different sensor coatings, each one disposed on one of the resonators,
the sensor coatings collectively designed to differentially absorb to one or more
of the biological and chemical agents for measuring orthogonal physical properties;
(c) one or more heater elements, each one integrated to one of the piezoelectric resonators;
(d) a control circuit for exciting the piezoelectric resonators and for measuring
frequency and impedance;
(e) a control circuit configured for varying the temperature of the heater elements
and for measuring the temperature, frequency and impedance of the resonators at
a plurality of temperatures in order to generate data for use in thermal-gravimetric
analysis; and
(f) means for analyzing data collected from the control circuits to identify
the biological and chemical agents.
2. The sensor device of claim 1 wherein the piezoelectric resonators are made
from a piezoelectric crystal selected from the group consisting of quartz, lithium
niobate, lithium tantalate, langasite and gallium orthophosphate.
3. The sensor device of claim 1 wherein the array of piezoelectric resonators
can operate as a device selected from the group consisting of a bulk acoustic wave
(BAW) device, a surface acoustic wave (SAW) device, and a Love mode device.
4. The sensor device of claim 1 wherein each of the sensor coatings is made from
a material selected from the group consisting of metal, metallic alloy, polymer,
ceramic, carbon, nano-structure, or gold nano-particles.
5. The sensor device of claim 1 which further includes an external electrode
arranged to set up an electrical field between one of the resonators and the external electrode.
6. The sensor device of claim 1 wherein at least one of the sensor coatings disposed
on a resonator is capable of fluorescing and which further includes an optical
source and an optical detector arranged to probe the fluorescing sensor coating.
7. The sensor device of claim 6 wherein the resonator further includes gold nano panicles.
8. The sensor device of claim 1 which further includes at least one of measurement
means selected from the group consisting of a clock, a GPS receiver, a thermometer,
a barometer, and an anemometer.
9. The sensor device of claim 1 which further includes an alarm means.
10. A method for identifying biological and chemical agents comprising the steps of:
(a) selecting an array of piezoelectric resonators operating in a mode selected
from the group consisting of a single mode and a dual mode, at least one of the
resonators having a heater element integrated thereto;
(b) applying a sensor coating to two or more of the resonators, the sensor coatings
collectively designed to differentially absorb to one or more of the biological
and chemical agents;
(c) exposing the piezoelectric resonators to a substance containing one or more
suspected chemical and biological agents;
(d) electrically exciting the piezoelectric resonators;
(e) measuring the frequency and impedance of the piezoelectric resonators;
(f) measuring the temperature of the heater element;
(g) activating the heater element;
(h) controlling the temperature of the heater element at a plurality of temperatures;
(i) measuring the frequency and impedance of the piezoelectric resonators at
the plurality of temperatures;
(j) measuring the temperature of the heater element at the plurality of temperatures;
(k) analyzing the data collected from steps (e), (f), (i) and (j);
(l) using the results of step (k) to identify a specific biological or chemical agent.
11. The method of claim 10 wherein the piezoelectric reaonators are made from
a piezoelectric crystal selected from the group consisting of quartz, lithium niobate,
lithium tantalate, langasite and gallium orthosphosphate.
12. The method of claim 10 wherein the array of piezoelectric resonators can
operate as a device selected from the group consisting of a bulk acoustic wave
(BAW) device, a surface acoustic wave (SAW) device, and a Love mode device.
13. The method of claim 10 wherein each of the sensor coatings is made from a
material selected from the group consisting of metal, metallic alloy, polymer,
ceramic, carbon, nano-structure, or gold nano-particles.
14. The method of claim 10 wherein step (k) includes analyzing orthogonal physical properties.
15. The method of claim 10 which further includes;
(m) arranging an external electrode between one of the resonators and the external
electrode in order to set up an electrical field;
(n) measuring the mass loss;
(o) integrating the results of the measurements into steps (k) and (l).
16. The method of claim 10 which further includes:
(m) applying a sensor coating capable of fluorescing on one of the resonators;
(n) arranging an optical source and an optical detector to probe the fluorescing
sensor coating;
(o) measuring the fluorescence;
(p) integrating the results of the measurements into steps (k) and (l).
17. The method of claim 10 which further includes one or more of the following steps:
(m) measuring time;
(n) using a GPS receiver to ascertain location, including latitude, longitude,
and altitude;
(o) measuring temperature;
(p) measuring humidity;
(q) measuring air speed and direction.
18. The method of claim 10 which further includes:
(m) means for activating an alarm when a hazardous biological and chemical agent
is identified.
19. The sensor device of claim 1 wherein some of the electrodes of the resonators
are coated with nano particles.
Description
FIELD OF THE INVENTION
The present invention relates to biological and chemical sensors integrating
several physical measurements of target agents.
BACKGROUND OF THE INVENTION
The fast and accurate identification of biological and chemical agents is not
only of great interest within the sensor community, but performs a public service
by saving lives. The wide dissemination of inexpensive and accurate sensor systems
with very low or zero false alarm rates is critical in order to respond to terrorist
threats or accidental exposures. False alarms are very costly and could lead to
dilatory responses to subsequent real terrorist threats and accidental exposures.
The effectiveness of the first responders depends upon their knowing what hazardous
substance has been detected, the concentration of the hazardous substance and the
time of the initial exposure. A sensor system which is fast, inexpensive and accurate,
and with a low false alarm rate, is critical in both military and civilian applications.
The false alarm rate can be reduced significantly through the use of multiple
orthogonal detection methods. Orthogonal methods detect different physical characteristics
of a target agent or substance. For example, optical and gravimetric effects are
orthogonal. Gravimetric effects result from mass changes on the resonator, while
optical techniques look at the interaction of electromagnetic radiation.
For example, U.S. Pat. No. 5,744,902 to Vig describes detectors using a dual-mode
sensor using both a gravimetric and a calorimetric analysis of chemical/biological agents.
However, other than gravimetric and calorimetric, none of the prior art
detection systems integrates two or more orthogonal measurements (selected from
the following methods: gravimetric, calorimetric, thermal gravimetric, voltage
gravimetric, and optical detection methods) into one sensor system, thereby substantially
improving the identification of hazardous agents and reducing the false alarm rate.
SUMMARY OF THE INVENTION
The present invention provides an array of piezoelectric resonators, which are
used as a "laboratory" for measuring mechanical, physical and chemical effects.
The array can be manufactured from a single resonator, or individual resonators
can be formed into an array, depending on the application.
The resonators in the array can be arranged into configurations for each test.
For gravimetric detection, dual-mode resonators will provide simultaneous calorimetric
and gravimetric data, one type from each mode. Resonators with heaters on the surfaces
will provide thermal gravimetric data. Further, the heaters can make the resonators
"self-cleaning." An optical detector can be used to analyze the optical signal
from the surface of a coated resonator; incorporating gold-nano particles into
the coating and the electrode of the resonator can enhance the optical signal.
Additionally, voltage gravimetric measurements can be made with an electric field
set up between the resonator and an external electrode. Thermal voltage gravimetric
measurements can be made by adding an integrated heater on the resonator with an
external electrode.
The array of piezoelectric resonators can operate as bulk acoustic wave (BAW),
surface acoustic wave (SAW), or Love mode devices.
The integration of gravimetric, calorimetric, thermal gravimetric and optical
analytical methods into one sensor system greatly reduces the false alarm rate
for detecting chemical and biological agents. For example, after the optical sensor
provides data to identify a target agent, the resonators can be used to determine
its concentration.
The sensors can be used in buildings and open spaces to monitor terrorist threats
for Homeland Security and to identify hazardous waste in environmental applications.
They can be used to monitor chemical and biological agents in military and commercial
settings. Further, they can be used to detect toxic mold in buildings.
It is an object of the present invention to provide a sensor system capable of
detecting a wide variety of chemical and biological agents and concentrations,
with an extremely low false alarm rate.
Another object of the present invention is to combine two or more orthogonal
detection methods based on gravimetric, calorimetric, thermal gravimetric, voltage
gravimetric, and optical measurements.
Still another object of the present invention is to provide a sensor system
which is fast and accurate, yet inexpensive.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a top view of an array of bulk acoustic wave (BAW) devices.
FIG. 2 is a cross-sectional side view of the array of the BAW devices illustrated
in FIG. 1 taken along line 2—2.
FIG. 3 is a cross-sectional side view of a BAW device, with an external electrode plate.
FIG. 4 is a cross-sectional side view of a BAW device integrated with a fluorescent
optical detector system.
FIG. 5 is a representational top view of an array of SAW devices.
FIG. 6 is a representational side view of the array of SAW devices.
FIG. 7 is a top detail view of a single surface acoustic wave (SAW) device.
FIG. 8 is a sectional view of the single SAW device illustrated in FIG. 7 taken
along line 8—8.
FIG. 9 is a schematic diagram illustrating the sensor device of the present invention.
FIG. 10 is a representational top view of the sensor device of the present invention,
embodied in a hand-held unit.
FIG. 11 is a representational cross-sectional side view of the sensor device
illustrated in FIG. 10 taken along line 11—11.
DESCRIPTION OF THE PREFERRED EMBODIMENT
The integrated sensors of the present invention use piezoelectrically-based resonators
designed from a piezoelectric crystal such as quartz, lithium niobate, lithium
tantalate, langasite, or Gallium Orthophosphate. The resonators can operate as
bulk acoustic wave (BAW), surface acoustic wave (SAW), or Love mode devices. In
all cases, the frequency is influenced by material deposited onto the surfaces.
When mass is deposited onto the crystal, a change in frequency of the resonator occurs.
The sensors are miniature laboratories capable of measuring mechanical, physical
and chemical effects. The sensors described herein can be used for detecting the
presence and concentration of chemical and biological agents in a medium of air
or liquids. A sensor array is formed from a number of resonators, each a multiple
(2, 3 or more) mode piezoelectric resonator, which is energy trapped, having a
highly smooth surface relative to the wavelength of the mode. Electrodes formed
on each resonator excite the resonator. A coating of nano particles (gold, carbon
or another material) can be used to enhance the absorption sites for the target
agent (and the resonator's gravimetric response), as well as the optical reflectivity
for optical detection. A sensor coating on the resonators will bond, chemically
or physically, to certain target agents. Each resonator can have a different sensor
coating; some can have no coating at all. The different sensor coatings applied
to the resonators in an array are selected so that orthogonal physical properties
can be measured, thereby allowing the user to look at the target agent from different
directions. A heating element on the resonator controls its temperature and is
used to generate data for use in thermal-gravimetric analysis (mass change with heat).
Using conventional means, the medium to be tested is concentrated and then
delivered to the surface of the crystal resonators. An excitation circuit causes
the multiple modes of the resonators to be excited at the same time so that the
mass change and temperature change can be measured independently, allowing the
mass loading to be calculated accurately. A circuit with variable drive levels
can be used to detect when the particles on the surface of the resonator become
detached. An optical sensor focused on the surface of the resonator can be used
to identify the atomic absorption wavelengths of the target agent. The optical
sensor can be transmitted, reflected or fluorescent light. A circuit measures the
power dissipated in the crystal via the heating element and can be used to determine
the heat of reaction between the target agent and the coating on the surface of
the resonator (the additional heat generated in the resonator causes a decrease
in the heat required to maintain the crystal at a predetermined temperature). A
measurement circuit is used to collect the gravimetric, calorimetric, thermal-gravimetric
and optical data. An analysis algorithm is used to determine the identify of the
target agent. A communications system is used to relay information about the detected
agent and its concentration. Finally, an alarm system can be utilized when the
target agent and/or its concentration are identified as hazardous.
As shown in Table 1 below, typically the following physical characteristics can
be measured:
| TABLE 1 |
| |
| PHYSICAL |
|
VARIABLE |
| CHARACTERISTICS |
|
CONTROL |
| MEASURED |
MEASUREMENT |
PARAMETER |
| |
| Gravimetric |
Frequency of |
None |
| (mass change) |
first mode |
| Calorimetric |
Frequency of first |
None |
| (heat generated) |
and second mode |
| Elastic Properties |
Impedance of |
None |
| of film |
first mode |
| Drive Power Effects on |
Impedance of |
Drive Power |
| Impedance of first mode |
first mode |
| Drive Power Effects on |
Frequency of |
Drive Power |
| Frequency of first mode |
first mode |
| Thermal-Gravimetric |
Frequency of |
None |
| (mass change |
first mode vs. |
| with temperature) |
temperature of resonator |
| Voltage-Gravimetric |
Frequency of |
None |
| (mass change |
first mode vs. |
| with electric field |
temperature of resonator |
| Thermal-Voltage |
Frequency of |
Temperature |
| Gravimetric (mass |
first mode, temperature |
or Voltage |
| change with electric field |
or resonator, and |
| and temperature) |
electric field |
| |
When enough physical characteristics of a target agent are measured, the accuracy
of the identification is greatly increased, resulting in zero or near-zero false
alarms. In addition, thresholds can be set to permit certain concentrations of
target agents to be tolerated, with an alarm sounding only when the concentration
reaches an unacceptable level.
The present invention can be embodied in a bulk acoustic wave (BAW) array
10,
such as the one shown in FIG. 1 and FIG. 2. Formed on a single crystal quartz wafer
11 is an arrangement of BAW resonator plates
12. The BAW resonator
plates
12 can be round, as shown, or can have another shape, such as square
or hexagonal. The BAW resonator plates
12 can be arrayed in a 3×4 array,
as shown, or can be arrayed 2×2, 2×n, 3×3, 3×n, 4×4, or
4×n. The BAW resonator plates
12 have contoured surfaces to improve
the short term stability of the resonators by reducing the noise flow.
Depending on its position in the BAW array
10, each BAW resonator
has either a top edge electrode
13 or a top center electrode
14 (on
the top side of the crystal quartz wafer
11), as well as with a bottom edge
electrode
15 or a bottom center electrode
16 (on the bottom side
of the crystal quartz wafer
11). The electrodes
13,
14,
15,
16 can be coated with nano particles (e.g., gold) to enhance the absorption
of the target agent as well as the optical reflectivity.
Some of the BAW resonator plates
12 will have been coated with a sensor
coating
17, the sensor coatings
17 having been collectively designed
to differentially absorb to a specific chemical or biological agent, mass loading
the resonator and giving off heat in the reaction. The heat of reaction can be
detected by operating the resonator on two modes, using one mode which is temperature
compensated (changes very little with temperature) and another which has a large
temperature coefficient. For example, a BAW resonator operating on the third overtone
C mode, designed with minimum frequency shift over the temperature range can be
used with a third overtone B mode over the same temperature range designed to have
a large frequency shift with temperature. A third overtone C mode, designed with
minimum frequency shift over a temperature range, could be used with a fundamental
C mode, designed to have a higher frequency shift over the same temperature range.
The material used for each sensor coating
17 can be a metal, metallic
alloy, polymer, ceramic, carbon, nano-structure, or gold nano-particle. A different
coating
17 can be used on each BAW resonator plate
12 in order to
detect different target agents.
The BAW sensor array
10 shown in FIG. 1 and FIG. 2 also shows the integrated
heater element
18 on two of the BAW resonator plates
17. The heater
element
18 can be used to control the temperature of the BAW resonators.
In addition, thermal gravimetric data detectors
19 can be used to monitor
the current or voltage through the heater element
18 in order to determine
the heat of reaction between the thin film and the target agent; the heat generated
in the reaction will decrease the amount of heat required to maintain the resonators
at a predetermined temperature. The heater elements
18 can also be used
to "self-clean" the resonators and regenerate sensor coatings
17 which have
become saturated.
Data collected from the BAW resonator plates
12 includes gravimetric/calorimetric
data, thermal-gravimetric data. In addition, information related to the elastic
properties of the monolayer can be determined from the loss in the BAW resonators.
Further, a circuit with variable drive levels can detect when the particles on
the surface become detached.
FIG. 3 shows another embodiment of the present invention. A portion of the crystal
quartz wafer
11 has a BAW resonator plate
12, with a top electrode
20 and a bottom electrode
21, which can be coated with nano particles
to enhance the absorption of the target agent. The BAW resonator plate
12
has been coated with a sensor coating
17 to bind with a specific chemical
or biological agent. A heater element
18 can be used to control the temperature
of the BAW resonator plate
12. An external electrode plate
22 has
been arranged to set up an electrical field between the top electrode
20
and the external electrode plate
22, which provides for the voltage gravimetric
measurement of mass loss with applied electric field.
FIG. 4 shows the present invention integrated with an optical detector. A portion
of the crystal quartz wafer
11 has a BAW resonator plate
12 with
a top electrode
20 and a bottom electrode
21, which can be coated
with nano particles to enhance optical reflectivity. The top electrode
20
on the BAW resonator plate
12 has been coated with a sensor coating
23
which is capable of fluorescing. The optical detector system consists of an optical
source
24, such as an organic light emitting diode (OLED), a separation
barrier, or shield
25, and an optical detector
26, arranged to detect
the fluorescence of biological or chemical agents adsorbed onto the top electrode
20 on the BAW resonator plate
12. The optical detector system is
used to identify the atomic absorption wavelengths of the target agent.
The present invention can also be embodied in a surface acoustic wave (SAW) array
27, such as the one shown in FIGS. 5 through 8. A surface acoustic wave
device, such as the one shown, is formed from a quartz crystal designed to support
high-frequency acoustics oscillators, which are sensitive to surface effects. The
SAW array
27 shown in FIG. 5 and FIG. 6 has a surface acoustic wave (SAW)
substrate
28. Each SAW resonator has an input electrode
29 and an
output electrode
30 coupled to the substrate
28. A sensor coating
32 can cover a portion of the substrate
28 (as shown) or can cover
the electrodes
29,
30 and the entire upper planar surface of the
substrate
28, so long as the sensor coating
32 material would not
corrode the electrodes
29,
30.
The SAW resonator can be arrayed in a 3×4 SAW array
27, as shown,
or can be arrayed 2×2, 2×n, 3×3, 3×n, 4×4, or 4×n.
The electrodes
29,
30 can be coated with nano particles (e.g., gold)
to enhance the absorption of the target agent as well as the optical reflectivity.
Each of the SAW resonators in the SAW array
27 can have a different sensor
coating
32 designed to chemically attach to a specific chemical or biological
agent, mass loading the resonator and giving off heat in the reaction.
The SAW array
27 shown in FIGS. 5 and 6 has integrated heater elements
33 encircling the electrodes
29,
30 of several of the SAW
resonators. The heater elements
33 can be used to control the temperature
of the SAW resonators. In addition, the current or voltage through the heater elements
33 can be monitored to determine the heat of reaction, which will decrease
the amount of heat required to maintain the resonators at a predetermined temperature.
Heat from the heater elements
33 can also be used to "self-clean" the resonators
and regenerate sensor coatings
32 which have become saturated.
As shown in FIG. 6, the SAW substrate
28 is thermally insulated by stand-offs
35.
A single SAW resonator
36 is shown in detail in FIG. 7 and FIG. 8. The
input
electrode
29 and output electrode
30, with a sensor coating
32
in between, are disposed on substrate
28. Electrode wires
31 connect
the electrodes
29,
30 to a power source (not shown). Similarly, heater
element wires
34 connect the heater element
33 to a power source
(not shown). In FIG. 8 the electrode contacts
37 and heater contacts
38
can be seen.
FIG. 9 is a schematic diagram illustrating the sensor device of the present
invention. The quartz resonator
40 is a resonator formed of a piezoelectric
material. As noted supra, the resonator can operate as a bulk acoustic wave (BAW),
surface acoustic wave (SAW), or Love mode device. The quartz resonator
40
is excited by electrical signals of varying frequency from the C-mode oscillator
41 and the B-mode or other temperature mode oscillator
42. A resistance
measurement
43 is delivered to the measurement system
44, as well
as data collected from the C-mode oscillator
41 and the temperature mode
oscillator
42. The resonator drive control can cause effects on the frequency
and impedance of the C-mode oscillator
41, which are transmitted to the
measurement system
44. A sensor coating
46 is generally applied to
the surface of the quartz resonator
40. A heater
47 can be attached
to or embedded in the surface of the quartz resonator
40. A heater control
circuit
48 controlled by heater microcontroller
49 affects the temperature
of the heater
47, controlling the temperature of the quartz resonator
40;
the temperature measurements are transmitted to measurement system
44. A
gas concentrator
50, controlled by microcontroller
51, concentrates
the target agent and forces it across the surface of the quartz resonator
40.
The data from measurement system
44 is delivered to the memory and CPU
52 for analysis and correlation. The results of the analysis are sent to
the display
53 for reading by the operator. An alarm sounds if the target
agent and/or its concentration are identified as hazardous. The antenna
55
can be used to transmit the information to a remote location.
The traceable time
56 provides the time (G.M.T.) at which a target agent
is being tested. Traceable time, with an accuracy suitable for the application,
is critical. In an application where the wind speed could be sixty miles per hour
(60 mph), the air is moving at 88 feet per second. Time synchronization within
a sensor network must be accurate enough to be usable for predicting the position
of a hazardous cloud. Time inaccuracies of 10 seconds in 60 mph wind will lead
to errors of 880 feet. Time synchronization using traceable time to 1 millisecond
will reduce this error to less than one foot.
The GPS receiver
57 gives the exact location at which the target agent
is being tested, detailing the latitude, longitude, and altitude of the test.
Environmental variables
58 provides valuable information relating
to such factors as temperature, humidity, wind or air speed, and wind or air direction.
Table 2, below, shows the characteristics measured by the present invention,
the measurement means, and the resulting measurements.
| TABLE 2 |
| |
| CHARACTERISTIC |
MEASUREMENT |
|
| MEASURED |
MEANS |
MEASUREMENT |
| |
| Gravimetric |
From C-mode |
Frequency or voltage |
| |
oscillator |
| Temperature |
From B-Mode |
Frequency or |
| |
or other tem- |
voltage → temperature |
| |
perature mode |
| |
oscillator |
| Resistance (loss) |
Resonator peak |
Slope of peak at |
| |
width |
frequency |
| Drive |
Current of crystal |
Current or voltage |
| Heater current |
Current |
Current |
| Time |
Clock |
Date and time |
| Location |
GPS Receiver |
Latitude, longitude, |
| |
|
altitude |
| Temperature |
Thermometer |
Degrees |
| Humidity |
Barometer |
Barometric pressure |
| Air speed and |
Anemometer |
Velocity and direction |
| direction |
| |
FIGS. 10 and 11 show a typical sensor device
60 of the present invention
embodied in a hand-held configuration. Disposed within a conventional rectangular
housing
61 is the sensor array
62, which can be comprised of piezoelectric-based
resonators designed from quartz, lithium, niobate, lithium tantalate, langasite,
Gallium Orthophosphate, or any piezoelectric crystal. The resonators (described
supra in more detail) in the sensor array
62 can operate as bulk acoustic
wave (BAW), surface acoustic wave (SAW), or Love mode devices. The sensor array
62 is connected electronically to the sensor array
63, which generally
consists of several circuits, including an excitation circuit for each of the multiple
modes; a circuit with variable drive levels; a circuit to provide heat; a circuit
used to measure the power dissipated in the crystal via the heater and further
used to determine the heat of reaction between the target agent and the coating
on the resonator surface; a measurement circuit used to collect data, incurring
resonant frequencies and magnitudes of impedance over a frequency range; and an
optical sensor. The sensor array electronics
62 are connected to microcontrollers
64,
65,
66,
67 and to the memory
68,
69,
which together correlate and characterize the data, comparing, for instance, the
sensed frequencies with reference frequencies. A battery
70 provides power
for operation of the hand-held embodiment
60. An antenna
71 can be
used to transmit data to a remote location.
As shown in FIG. 11, an air-borne target agent is pulled through filter
72
by air pump
73, and is then concentrated by concentrator
74. The
target agent has been forced across the sensor array
62, using a piezoelectric
fan or MEMS-based fan. Then, a pumping system
75 removes it from the hand-held
embodiment
60, forcing it out through exit filter
76. The results
of the analysis of the data related to the target agent are shown on the display
screen
77.
Although the description contains much specificity, these details should
not be construed as limiting the scope of the invention, but merely providing illustrations
of some of the presently preferred embodiments of this invention. Thus the scope
of the invention should be determined by the appended claims and their legal equivalents,
rather than by the examples given.
*
