U.S. patent application number 12/840452 was filed with the patent office on 2012-05-10 for systems, devices, and methods for remotely interrogated chemosensor electronics.
This patent application is currently assigned to Raytheon BBN Technologies Corp.. Invention is credited to Thomas Patrick Bidigare, John Ho.
Application Number | 20120115241 12/840452 |
Document ID | / |
Family ID | 46019996 |
Filed Date | 2012-05-10 |
United States Patent
Application |
20120115241 |
Kind Code |
A1 |
Ho; John ; et al. |
May 10, 2012 |
SYSTEMS, DEVICES, AND METHODS FOR REMOTELY INTERROGATED CHEMOSENSOR
ELECTRONICS
Abstract
Systems, devices and methods for remotely interrogating sensor
electronics are described. In one embodiment, a system for
detecting and localizing chemical analytes is described. This
system includes a plurality of chemosensor electronic devices for
detecting the presence of chemical analytes. Each of these devices
includes a chemosensor for sensing chemical analytes, a
transponder, and an electronic circuit for activating the
transponder based on an output of the chemosensor. These devices
may have a cross-section area of less than 1 square micrometer. The
system also includes an interrogation device for interrogating the
plurality of devices and for receiving information on the detected
chemical analytes from devices with activated transponders, and a
processor for determining the locations of the devices with
activated transponders. These locations may be forwarded to a third
party.
Inventors: |
Ho; John; (Cambridge,
MA) ; Bidigare; Thomas Patrick; (Arlington,
VA) |
Assignee: |
Raytheon BBN Technologies
Corp.
Cambridge
MA
|
Family ID: |
46019996 |
Appl. No.: |
12/840452 |
Filed: |
July 21, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61227244 |
Jul 21, 2009 |
|
|
|
Current U.S.
Class: |
436/172 ;
422/68.1 |
Current CPC
Class: |
G08B 21/12 20130101;
G01N 21/6428 20130101; G08B 5/22 20130101; G08C 17/02 20130101;
G01N 21/77 20130101 |
Class at
Publication: |
436/172 ;
422/68.1 |
International
Class: |
G01N 21/76 20060101
G01N021/76 |
Claims
1. A device for detecting chemical analytes, comprising: a
chemosensor for sensing chemical analytes; a transponder for
receiving an interrogation signal from a remote interrogation
device and transmitting a signal to the remote interrogation device
in response to the received interrogation signal; and an electronic
circuit for activating the transponder based on an output of the
chemosensor.
2. The device of claim 1, wherein the chemosensor includes a
Type-II bilayer heterojunction.
3. The device of claim 2, wherein the Type-II bilayer
heterojunction includes a fluorescent polymer layer and a
conductive metal oxide layer.
4. The device of claim 1, wherein the chemosensor has a
cross-section area less than 1 square micrometer.
5. The device of claim 1, wherein the transponder is a radar
transponder.
6. The device of claim 1, wherein the transponder is configured for
receiving signals from the remote interrogation device from
distances of at least 250 m.
7. A method for detecting chemical analytes, comprising: sensing
chemical analytes using a chemosensor; receiving an electrical
signal from the chemosensor; activating a transponder based on the
received electrical signal; receiving an interrogation signal at
the transponder from a remote interrogation device; and
transmitting a signal from the transponder to a remote
interrogation device in response to the received interrogation
signal.
8. The method of claim 7, wherein the chemosensor includes a
Type-II bilayer heterojunction.
9. The method of claim 8, wherein the Type-II bilayer
heterojunction includes a fluorescent polymer layer and a
conductive metal oxide layer.
10. The method of claim 9, wherein the chemosensor has a
cross-section area less than 1 square micrometer.
11. The method of claim 7, wherein the transponder is a radar
transponder.
12. The method of claim 7, wherein the remote interrogation device
is located at least 250 m from the transponder.
13. A method for detection and localization of chemical analytes,
comprising: deploying a plurality of chemosensor electronic devices
in an area to detect the presence of the chemical analytes in the
area; activating a transponder in a respective device if analytes
are detected by the respective device; interrogating the plurality
of devices to receive information on the detected analytes from
devices with activated transponders; determining the locations of
the devices with activated transponders; forwarding the determined
locations to a third party.
14. The method of claim 13, wherein the chemosensor electronic
devices have a cross-section area less than 1 square
micrometer.
15. The method of claim 13, wherein the chemosensor includes a
Type-II bilayer heterojunction.
16. The method of claim 15, wherein the Type-II bilayer
heterojunction includes a fluorescent polymer layer and a
conductive metal oxide layer.
17. The method of claim 13, wherein the chemical analytes include
one of vapor-phase explosives, illegal drugs, hazardous waste,
bioagents.
18. A system for detecting and localizing chemical analytes,
comprising: a plurality of chemosensor electronic devices for
detecting the presence of the chemical analytes, wherein each
device includes a transponder that can be activated based on the
detected chemical analytes; an interrogation device for
interrogating the plurality of devices; and receiving information
on the detected chemical analytes from devices with activated
transponders; a processor for determining the locations of the
devices with activated transponders; and forwarding the determined
locations to a third party.
19. The system of claim 18, wherein the chemosensor electronic
devices have a cross-section area less than 1 square
micrometer.
20. The system of claim 18, wherein the chemosensor devices each
include a Type-II bilayer heterojunction.
21. The system of claim 20, wherein the Type-II bilayer
heterojunction includes a fluorescent polymer layer and a
conductive metal oxide layer.
22. The system of claim 18, wherein the chemical analytes include
one of vapor-phase explosives, illegal drugs, hazardous waste,
bioagents.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent
Application No. 61/227,244, filed Jul. 21, 2009. The contents of
this application are hereby incorporated herein in their
entirety.
FIELD OF THE INVENTION
[0002] This disclosure relates generally to chemical detection, and
more particularly, the methods, systems and devices disclosed
herein relate to portable high-sensitivity high-specificity
long-standoff distance methods, systems and devices for the
detection and localization of vapor-phased explosives, illegal
drugs, hazardous waste, bioagents, or other chemical analytes.
BACKGROUND
[0003] The long standoff detection or sensing of chemical analytes
is important in many applications. In the policing of borders and
reduction or elimination of illegal drug trafficking, the detection
of chemical constituents from a large distance associated with
illegal drugs can help identify smuggling routes and perpetrators.
The detection of these chemicals could drastically improve the
border patrol's effectiveness. In biochemical warfare, the
detection or sensing of hazardous bioagents from afar is also of
high importance in order to provide early warning and identify
proper countermeasures. In today's war zones, the detection or
sensing of vapor-phase explosives with high-sensitivity is of
utmost importance, particularly, because in many war zones, the use
of improvised explosive devices (IEDs) have resulted in a large
number of deaths, e.g., more than 50% of all coalition deaths in
Iraq and Afghanistan. These deaths could be significantly reduced
if it was possible to accurately detect the presence of these IEDs
from a distance without jeopardizing the lives of human
investigators.
[0004] Most commercially-available chemical sensing devices or
systems have several drawbacks. First, these devices and systems
generally require skilled human operators, making it difficult to
deploy these devices or systems remotely and/or autonomously.
Second, these systems and devices generally only provide chemical
detection capability over a limited geographical area and are not
amenable to wide area scanning Third, these chemical detection
devices are generally too large and/or heavy to be used for covert
operations.
[0005] Vapor-phase explosives detection technology has emerged as
one of the most sensitive tools in the military's explosives
detecting arsenal. In these so-called "sniffing" explosives
detection devices, e.g., the FIDO.TM. XT portable explosives
detector (available from ICx Technologies, Massachusetts), the
detection of the chemicals/explosives is based on the attachment of
specific, known chemicals/explosives to fluorescent polymers. The
fluorescence of these polymers is dependent on the binding of
specific chemical analytes to the polymers. For example, an
explosive may cause a reduction in fluorescence of the polymers.
The polymer is excited by light from a light emitting diode (LED)
or laser. These fluorescent polymers have the property that their
photoluminescence becomes quenched as vapor-phase chemicals bind to
the surface of the fluorescent polymer. The reduced fluorescence of
the polymer film is detected by a photodetector to generate an
electrical current signal.
[0006] Despite their demonstrable success, portable explosives
detection devices such as the Fido.TM. XT also have several
drawbacks. First, in devices such as the FIDO.TM. XT, there are
significant optical losses in the transmission of photons from the
fluorescent polymer to the photodetector, yielding inefficient
chemical to electrical signal transduction. These detection devices
are difficult to miniaturize because efficient isolation of optical
signals with similar wavelengths is difficult if one wishes to have
a small micrometer-scale device. In particular, the
micro-fabrication of closely packed fluorescent polymer layers with
similar fluorescence spectra can be problematic due to the
difficulty in isolating the optical signal from each element. Of
particular relevance, commercially-available chemical detectors
cannot be deployed remotely as they do not have any remote
interrogation capabilities, and due to their size, typically are
deployed in the field with a skilled user, thereby putting lives at
risk. In particular, commercially-available chemical detection
systems and devices are not capable of being interrogated from
large distances, e.g., a few km, making them unusable for covert
detection applications, and greatly limiting the area over and
speed with which chemical analytes can be found.
SUMMARY
[0007] There exists a need for a chemical detection and
localization device which can be remotely interrogated, thereby
eliminating the need for a skilled user to accompany the device
into the field. There also exists a need for a chemical detection
and localization device that can multiplex the detection signals
from an array of fluorescent polymer sensors while maintaining high
sensitivity and high specificity.
[0008] The methods, systems and devices described herein address
these and other needs. Among other things, the methods, systems and
devices described herein address the inefficient chemical to
electrical signal transduction process described above with respect
to commercially-available chemical sensors/detectors. They add the
ability to remotely interrogate such chemical detectors. In
addition, they enable the miniaturization of chemical
sensors/detectors, thereby allowing widespread deployment of
chemical sensors/detectors in covert operations and in distributed
applications.
[0009] In one aspect, the invention relates to a device for
detecting chemical analytes. The device includes a chemosensor for
sensing chemical analytes. The chemical analytes include one of
vapor-phase explosives, illegal drugs, hazardous waste, and
bioagents. The device also includes a transponder for receiving an
interrogation signal from a remote interrogation device and
transmitting a signal to the remote interrogation device in
response to the received interrogation signal. The device further
includes an electronic circuit for activating the transponder based
on an output of the chemosensor. In some embodiments, the
chemosensor includes a Type-II bilayer heterjunction, and this
junction includes a fluorescent polymer layer and a conductive
metal oxide layer. In some embodiments, the chemosensor has a
cross-section area less than 1 square micrometer. In some
embodiments, the transponder is a radar transponder. In some
embodiments, the remote interrogation device is located at least
250 m from the transponder of the device.
[0010] In another aspect, the invention relates to a method for
detecting chemical analytes. The chemical analytes include one of
vapor-phase explosives, illegal drugs, hazardous waste, and
bioagents. The method includes sensing chemical analytes using a
chemosensor, receiving an electrical signal from the chemosensor,
activating a transponder based on the received electrical signal,
receiving an interrogation signal at the transponder from a remote
interrogation device, and transmitting a signal from the
transponder to a remote interrogation device in response to the
received interrogation signal. In some embodiments, the chemosensor
includes a Type-II bilayer heterjunction, and this junction
includes a fluorescent polymer layer and a conductive metal oxide
layer. In some embodiments, the chemosensor has a cross-section
area less than 1 square micrometer. In some embodiments, the
transponder is a radar transponder. In some embodiments, the remote
interrogation device is located at least 250 m from the
transponder.
[0011] In a third aspect, the invention relates to a method for the
detection and localization of chemical analytes. The chemical
analytes include one of vapor-phase explosives, illegal drugs,
hazardous waste, and bioagents. The method includes deploying a
plurality of chemosensor electronic devices in an area to detect
the presence of the chemical analytes in the area and activating a
transponder in a respective device if analytes are detected by the
respective device. The method also includes interrogating the
plurality of devices to receive information on the detected
analytes from devices with activated transponders, and determining
the locations of the devices with activated transponders. The
method includes forwarding the determined locations to a third
party in response to this determination. In some embodiments, the
chemosensor includes a Type-II bilayer heterjunction, and this
junction includes a fluorescent polymer layer and a conductive
metal oxide layer. In some embodiments, the chemosensor has a
cross-section area less than 1 square micrometer. In some
embodiments, the transponder is a radar transponder. In some
embodiments, the remote interrogation device is located at least
250 m from the transponder.
[0012] In a fourth aspect, the invention relates to a system for
detecting and localizing chemical analytes. The chemical analytes
include one of vapor-phase explosives, illegal drugs, hazardous
waste, and bioagents. The system includes a plurality of
chemosensor electronic devices for detecting the presence of the
chemical analytes, wherein each device includes a transponder that
can be activated based on the detected chemical analytes. The
system further includes an interrogation device. The interrogation
device is for interrogating the plurality of devices, and receiving
information on the detected chemical analytes from devices with
activated transponders. The system further includes a processor.
The processor is for determining the locations of the devices with
activated transponders, and for forwarding the determined locations
to a third party. In some embodiments, the chemosensor includes a
Type-II bilayer heterjunction, and this junction includes a
fluorescent polymer layer and a conductive metal oxide layer. In
some embodiments, the chemosensor has a cross-section area less
than 1 square micrometer. In some embodiments, the transponder is a
radar transponder. In some embodiments, the remote interrogation
device is located at least 250 m from the transponder.
BRIEF DESCRIPTION OF DRAWINGS
[0013] The following figures depict certain illustrative
embodiments of the invention in which like reference numerals refer
to like elements. These depicted embodiments may not be drawn to
scale and are to be understood as illustrative of the invention and
as not limiting in any way:
[0014] FIG. 1A is an application of several remote interrogation
chemosensor devices in an area, according to an illustrative
embodiment of the invention;
[0015] FIG. 1B is a detection map that may be generated by an
interrogation device using an image formation algorithm, according
to an illustrative embodiment of the invention;
[0016] FIG. 1C is a process flow diagram for a method for detecting
chemical analytes, according to an illustrative embodiment of the
invention;
[0017] FIG. 2A is a block diagram of a first RICE device, according
to an illustrative embodiment of the invention;
[0018] FIG. 2B is a schematic diagram of an implementation of the
RICE device of FIG. 2A, according to an illustrative embodiment of
the invention;
[0019] FIG. 3 is an architecture block diagram and a picture of an
integrated circuit of a transponder for use in a RICE device such
as the RICE devices of FIGS. 2A and 2B, according to an
illustrative embodiment;
[0020] FIG. 4A is a picture of a microfabricated chemosensor chip
for use in a RICE device such as the RICE devices of FIGS. 2A and
2B that includes multiple chemosensors, according to a first
illustrative embodiment;
[0021] FIG. 4B is a schematic of a chemosensor for use in a RICE
device such as the RICE devices of FIGS. 2A and 2B or in a
chemosensor chip such as the chip of FIG. 4A, according to a second
illustrative embodiment;
[0022] FIG. 4C is a schematic of a microfabricated chemosensor with
a microLED for use in a RICE device such as the RICE devices of
FIGS. 2A and 2B or in a chemosensor chip such as the chip of FIG.
4A, according to a third illustrative embodiment;
[0023] FIG. 5A is an abstraction of the bilayer heterojunction
structure of an electrical circuit of a chemosensor of a RICE
device such as the chemosensors in FIGS. 4A-4C, according to an
illustrative embodiment;
[0024] FIG. 5B is a graph of normalized current versus time for a
vapor-phase explosives detection application of a RICE device such
as the RICE devices of FIGS. 2A and 2B, according to an
illustrative embodiment; and
[0025] FIG. 6 is a process flow diagram for a method for detecting
chemical analytes using RICE device such as the RICE devices of
FIGS. 2A and 2B, according to an illustrative embodiment.
DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS
[0026] To provide an overall understanding of the invention,
certain illustrative embodiments will now be described, including
exemplary remotely interrogated chemosensor electronics (RICE)
devices and constituent components thereof. However, it will be
understood by one of ordinary skill in the art that the apparatus
described herein may be adapted and modified as is appropriate for
the application being addressed and that the systems and methods
described herein may be employed in other suitable applications,
and that such other additions and modifications will not depart
from the scope hereof.
[0027] In one embodiment, the chemical detection device is a
miniature, remotely interrogated chemosensor electronics (RICE)
device. In general, RICE devices can be deployed for any chemical
sensing application, including the detection or sensing of
vapor-phase explosives in a battlefield, illegal drugs in a border
region, or the detection or sensing of hazardous bioagents in an
urban region, as described further with respect to FIGS. 1A-1C.
Illustrative embodiments of RICE devices, methods for detecting
chemical analytes using a RICE device, and RICE device designs are
described below with respect to FIGS. 2A-6.
[0028] FIG. 1A shows an illustrative application of RICE devices
102 for detecting and localizing chemical analytes. In the
illustrative application, RICE devices 102 are deployed in an area
100 with a road 104. The RICE devices 102 are deployed by
scattering the devices on the road 104 using a manned or unmanned
vehicle such as UAV 101a, an aircraft or a ground vehicle. Once
deployed, RICE devices 102 are remotely interrogated via an
interrogation signal 110, e.g., a radar signal, emanating from an
interrogation device such as a second UAV 101b or other aircraft.
In one embodiment, the same aircraft, UAV, or ground vehicle is
used for deployment and interrogation. If chemical analytes, e.g.,
vapor-phase explosives, are detected by the RICE devices 102, each
RICE device 102 detecting the chemical analytes transmits a signal
representative of the type and/or level of chemicals detected by
the RICE device. RICE devices that detect chemical analytes are
referred to as being "activated."
[0029] Once a signal transmitted by a RICE device is received at
the interrogation device, the location of the RICE device can be
determined using a localization algorithm such as a synthetic
aperture radar (SAR) image formation algorithm. In one embodiment,
the resulting SAR image may be a combination of the locations of
many RICE devices in a particular area, from which one may create a
map representative of the location, concentration, and type of
chemicals detected. In another embodiment, the resulting SAR image
may be used for its location information alone.
[0030] FIG. 1B is a detection map 130 that may be generated by an
interrogation device using a SAR image formation algorithm based on
data obtained from RICE devices distributed in an area, such as
RICE devices 102 of FIG. 1A. Map 130 includes a road 180, house
195, and school 197. The map also includes indications of observed
chemical analytes. Specifically, the presence of a first type of
chemical is indicated by the circles on the map corresponding to
locations of activated RICE devices 190a-e. The presence of a
second type of chemical is indicated by the triangles on the map
corresponding to locations of activated RICE devices 192a-h. The
location of each responding RICE device 190a-e and/or 192a-h
represents the presence of chemicals at that location in detection
map 130. In one embodiment, such a map 130 could be used by a
vehicle in the area to avoid the parts of road 180 with explosives,
e.g., to avoid explosives that are present at the locations of RICE
devices 190b and 190c, or to determine a new route to its
destination that avoids the road 180 altogether. To that end, such
a map could be transmitted by the interrogation device to other
vehicles in the vicinity of the road 180.
[0031] FIG. 1C illustrates a process flow diagram 150 for a process
or method for detecting or sensing chemical analytes used, e.g., to
generate the detection map 130 of FIG. 1B. First, a plurality of
chemosensor devices (e.g., RICE devices 102 from FIG. 1A) are
deployed into an area (step 152). These devices may be deployed by
unmanned or manned vehicles, e.g., the UAVs described in relation
to FIG. 1A. If chemical analytes are detected by these devices, the
transponder within these devices activate (step 154). The devices
are then interrogated (e.g., by an interrogation device as
described in relation to FIG. 1A) to determine whether any
chemicals of interest were detected (step 156). Activated
interrogated devices respond with a return signal including, in one
embodiment, a code indicative of the analyte detected and/or a
concentration level of the analyte. The location of the activated
devices is then determined using, e.g., synthetic aperture radar
(SAR) techniques (step 158). Information representative of location
and/or type of chemicals, e.g., a detection map, may then be
generated by the interrogation device (step 160), and this
information may be forwarded to a third party (step 162). For
example, in a military application, the information may be a map of
detected explosives that is forwarded to a convoy or other vehicle
allowing this vehicle to avoid any explosives that may be in the
vehicle's path. The information may also include codes indicative
of the analyte detected or concentration levels of the analyte. In
alternative embodiments, the information may also be forwarded to
an additional device instead of being transmitted to the
interrogation device, and this additional device may generate the
detection map.
[0032] FIGS. 2A and 2B are illustrations of embodiments of a RICE
device 200 and RICE device 250 suitable for use in the application
and methodology described above. In some embodiments, a RICE device
is fabricated to have a size on the order of that of a grain of
rice. For example, a RICE device may have a cross-section area
ranging from 0.6 micrometer squared to 1 millimeter squared.
[0033] With reference to FIGS. 2A and 2B, RICE device 200 includes
a battery 202 which provides power to electronic circuit 206,
transponder 208, and LEDs/chemosensors 204, or any combination
thereof. Battery 202 may be any suitable thin-film battery that is
capable of powering an LED, the components of electronic circuit
206, and the components of the transponder 208. LEDs/chemosensors
204 include one or more LEDs that are capable of illuminating one
or more respective chemosensors. The chemosensors themselves
include a fluorescent polymer whose fluorescence changes based upon
the level of chemicals that bind to the polymer. Examples of such
fluorescent polymers are given in U.S. Pat. Nos. 7,208,122 and
7,393,503, the contents of each of which are incorporated herein in
their entirety.
[0034] RICE device 250 includes an integrated chemosensor 255, LED
254, as well as integrated circuit (IC) radar transponder 258, IC
logic and measurement circuitry 256, thin-film battery stack 252
and microfabricated antenna 209 or 260. Each of these components
may have millimeter or micrometer dimensions and consume very
little power. This low power consumption allows a suitably
small-size thin-film battery stack to power the RICE device 200 or
250 for long periods of time. In some embodiments, LED 254 may be a
microLED with dimensions 0.2.times.0.2 by 0.5 mm and a power
consumption of 1 mW. The IC circuitry 256 may be an MSP430
microprocessor (available from Texas Instruments, Inc., in Dallas,
Tex.) with dimensions 4 mm.times.4 mm.times.1 mm, and a power
consumption of 350 microwatts. The chemosensor 255 may be a
thin-film microfabricated sensor with dimensions of approximately
0.6 mm.times.1 mm.times.0.001 mm, and a power consumption of 1 mW.
The thin-film battery stack may have dimensions of approximately 8
mm.times.8 mm.times.0.17 mm, and a power density of 200
microwatt-hours. Alternatively, RICE device 200 or 250 may use a
zinc-air battery. A typical zinc-air battery has a diameter of
about 6 mm and a thickness of about 3-4 mm, and a power density of
120 milliwatt-hours.
[0035] Those skilled in the art will realize that combinations of
the elements in RICE device 200 or 250 may be microfabricated in a
stack. For instance, the LED and the chemosensor 204 or 254 and
255, may be formed in two layers of a stack and/or the LED 254 and
the chemosensor 255 may be fabricated as a layer on top of the
thin-film battery stack 252.
[0036] The LEDs/chemosensors may be also be microfabricated or
integrated on a chip with up to 4 or 5 chemosensors per RICE
device, as shown for RICE device 250. Each chemosensor may detect
the same or different chemicals. LED 254 and chemosensors 255 (or
LED/chemosensors 204), are in communication with electronic circuit
206 and 256, while electronic circuit 206 and 256 is in
communication with transponder 208 and 258, respectively.
[0037] As indicated above, the LEDs 204 and 254 radiate the
chemosensors 204 and 255 in the RICE device 200 or 250,
respectively. If one or more analytes 210a-c are present, the
fluorescence of one or more of the chemosensors changes. In one
embodiment, this change is detected as a change in electrical
current. The electronic circuit 206 or 256 interprets this change
in electrical current as indicative of the presence of the chemical
analytes as described further below. The relationship between
electrical current and the fluorescence of the chemosensors is
described further in "Lateral organic bilayer heterojunction
photoconductors," published in Appl. Phys. Lett. 93, 063305
(2008)", the contents of which are incorporated herein in their
entirety.
[0038] Electronic circuit 206 or 256 includes circuitry for
detecting the change in electrical current from the
LEDs/chemosensors 204, or 254 and 255, circuitry for comparing the
detected electrical current to a predetermined threshold electrical
current or a prior/historical electrical current, and circuitry for
transmitting an electronic signal representative of the comparison
to transponder 208 or 258. The predetermined electrical current
level(s) may include typical values of electrical current expected
to be detected by the circuitry for a particular LED light
strength, particular battery power level, and particular
chemosensor (i.e., for a particular analyte and polymer or any
combination thereof). The prior/historical current values include
past values of electrical current detected from the chemosensor and
previously stored in memory by the circuitry. In such embodiments,
the devices analyze a rate of change of current as opposed to a
particular current level. Electronic circuit 206 or 256 also
includes other suitable electronic components, e.g., differential
amplifiers and comparators for comparing the detected electrical
current to the threshold or prior/historical current, processors or
other logic circuitry (e.g., an Application Specific Integrated
Circuit (ASIC)) for controlling or guiding the operation of the
electronic circuit, and memory elements (e.g., ROM, RAM, or EEPROM)
for storing, among other things, the threshold current or
prior/historical current level(s).
[0039] Transponder 208 or 258 includes electronics for receiving
and transmitting signals. The electronics includes a receiver for
receiving interrogation signals, a transmitter for transmitting
signals, and other electronic circuitry. The other electronic
circuitry includes a processor 256, for processing the received
signals and transmitting signals in response to the received
signals, an electronic tag which may be activated by the remote
interrogation device 212, or by the electronic circuit 206 or 256
of RICE device 200 or 250, respectively, and an antenna 209 or 260,
for receiving interrogation signals and transmitting signals in
response to the interrogation signals.
[0040] Transponder 208 or 258 is configured to be remotely
interrogated by interrogation device 212 via interrogation signal
214. Interrogation device 212 may be deployed in a manned vehicle
or UAV such as UAV 101a and/or 101b described in relation to FIG.
1A above. The interrogation signals may range from very-high
frequency (VHF) signals to Ka-band signals, or may be RADAR
signals. If the interrogation signal 214 is a RADAR signal,
transponder 208 or 258 is referred to as a radar transponder.
[0041] The electronic tag of the transponder 208 or 258 is
activated or "on" if the detected electrical current from the
chemosensor, when compared to the threshold electrical current or
rate of change in electrical current, signifies the presence of
chemicals such as vapor-phase explosives. The electronic tag of the
transponder 208 or 258 is deactivated or "off" if the detected
electrical current or rate of change of electrical current from the
chemosensor signifies the absence (or relative absence) of
chemicals.
[0042] If interrogation signal 214 is present, and if the
electronic tag in transponder 208 or 258 is activated or "on",
transponder 208 or 258 transmits a signal representative of the
detected electrical current (or presence of chemicals) to
interrogation device 212. In one embodiment, the response signal
may be a stream of binary numbers, e.g., 000, 010, 011, etc.,
modulated onto a carrier wave. Each binary number encodes
information representative of the detected chemicals. In other
embodiments, the response signal is the received signal's
frequency, or the received signal's frequency divided by 2. For
instance, an activated transponder could receive a signal at a
particular frequency, divide the received signal's frequency by 2,
and transmit a signal with this halved frequency to the
interrogation device. For instance, if the interrogation signal
frequency generated by the interrogation device to the transponder
is approximately 450 Mhz, transponder 208 or 258 may transmit a
signal to the interrogation device at approximately 225 Mhz. In
general, the transponder 208 or 258 and interrogation device may
use any suitable transmission frequency for the signal, e.g.,
ranging from a few MHz to several GHz.
[0043] The transmitted signal from the RICE device transponder 208
or 258 allows the interrogation device to determine from the
received signal (1) the location of the RICE device 200 or 250 and
(2) the presence of chemicals at that location. In one embodiment,
device localization is performed using a synthetic aperture radar
(SAR) image formation technique. With this approach, a "heat map"
of the ground is generated such that, e.g., bright pixels
correspond to RICE devices which are activated and have detected a
chemical of interest. SAR processing algorithms enable resolutions
(i.e., RICE device/analyte location accuracies) of 1 ft or
better.
[0044] In one embodiment, the transponder 208 or 258 may be
remotely interrogated from distances of a few meters up to 15 km.
In another embodiment, the remote interrogation distance may be
between approximately 250 m and approximately 10 km. Those skilled
in the art may alter this "stand-off" distance by appropriately
sizing the transponder receiver and transmitter, as well as the
antenna on the interrogation device. Such a design may involve the
use of a RADAR system design equation that relates the design of
the transponder (e.g., receiver size, antenna size, transmission
power, transmission energy, etc.) to the stand-off distance. A
radar transponder generally has a range of a few meters to 15 km,
e.g., 250 m, and consumes approximately 1 mW of transmission
power.
[0045] As described below with respect to FIG. 3, radar
transponders can be microfabricated to have a cross-section area of
roughly 2.5 square millimeters (e.g., 0.75 mm.times.3.25
mm.times.0.25 mm), and use much less power--approximately 10
mW--than other types of transponders. In contrast to radar
transponders, state of the art passive radio frequency ID (RFID)
tags have a range that of roughly 20 meters, and a size of
approximately 4 square millimeters, and consume much more power
than a radar transponder. Active RFID tags are typically even
larger (e.g., 85 mm.times.54 mm.times.4.5 mm) and consume even more
power than passive RFID tags, though they have a range of about 200
meters.
[0046] FIG. 3 illustrates a block diagram 300 of a divide-by-2
transponder architecture along with a photograph of an IC
implementing a RICE device transponder for an embodiment of the
RICE device transponder, such as transponders 208 or 258 in FIGS.
2A and 2B, respectively. The transponder receives an interrogation
signal with frequency .about.450 MHz. The transponder subsequently
filters (e.g., using a 450 MHz Band Pass Filter (BPF)) and
amplifies (e.g., using a Low-Noise Amplifier (LNA)) this signal.
The filtered and amplified signal is then passed through a
divide-by-two digital electronic circuit. In some embodiments, the
signal can be phase-shift modulated. After the division-by-two
and/or modulation stages, the resulting signal is filtered (e.g.,
using a 225 MHz Low Pass Filter (LPF)), amplified (e.g., using a
Low-Noise Amplifier (LNA)) and transmitted to the interrogation
device.
[0047] This divide-by-2 transponder block diagram architecture 300
provides sufficient isolation between transmit and receive to keep
the device from self-oscillating. The transponder's transmitted
signal is coherent, i.e., of the same phase as the interrogation
signal, thereby allowing the interrogation device to coherently
process the transmitted signal to determine both the range and
cross-range components of the RICE device's location. Transponder
architecture 300 can be microfabricated, e.g., on BiCMOS SiGe, to
have sizes of less then 3 square millimeters as shown in integrated
circuit 350. Depending on the signal frequencies, such a
transponder can be miniaturized even further. That is, at higher
frequencies, the electronic components may be made even
smaller.
[0048] With continued reference to FIGS. 2A, 2B and 3, the battery
lifetime of transponder 208, 258 (and thus, RICE device 200 or 250)
is generally limited by the power consumption of the low noise
amplifier (LNA). While very low power amplifiers (with power
consumptions of less than approximately 1-10 mW) are suitable for
this application, operating even LNAs continuously could limit the
endurance of the device to a few hours if only low power density
thin-film batteries 202 or 252 are used. In some embodiments, sleep
cycling techniques can be applied to the processor of transponder
208 or 258 to significantly extend the endurance of the device, to
several weeks or longer. These techniques use very low-power (with
power consumptions of less than tens of microwatts) clocks and
digital logic circuitry that typically energize the amplifier only
at points in time when the device is responding to the
interrogation device 212.
[0049] Additionally, or alternatively, prolonged battery lifetimes
for transponder 208 or 258 may be obtained by using an
interrogation device 212 with significant power density incident at
the transponder 208 or 258. This generally requires either higher
interrogation device 212 transmission power, greater interrogation
device 212 antenna gain, or shorter standoff ranges for
interrogation. For instance, sufficient power density incident at
the transponder 208 or 258 allows the interrogation device 212 to
more directly awaken transponder without requiring the amplifier
(e.g., LNA) to be awakened from a sleep cycle.
[0050] FIG. 4A shows an illustration of a microfabricated
chemosensor chip 400, including a plurality of chemosensors 402 for
detecting or sensing chemical analytes. Chemosensor chip 400 could
be a component of RICE devices 200 or 250 described above with
respect to FIGS. 2A and 2B. The chemosensors 402 have
micrometer-scale dimensions, and are illuminated by one or more LED
light sources (not shown). In some embodiments, the LEDs may be
microLEDs. The combination of a microLED with a chemosensor chip
300 may be part of a RICE device such as LED/chemosensors 204 in
RICE device 200 in FIG. 2A. This implementation is discussed
further with respect to FIG. 4C.
[0051] FIG. 4B shows a block diagram of a chemosensor 450. Such a
chemosensor, is similar to the chemosensors 402 illustrated in FIG.
4A above and includes a Type-II bilayer heterojunction. This
bilayer heterojunction includes a fluorescent polymer layer 406 and
a metal oxide layer 408, e.g., SnO.sub.2. The Type-II bilayer
heterojunction itself is deposited on planar electrodes 410a and
410b that enable the application of an electric field to the
heterojunction using a battery 414. The heterojunction also
includes an insulating layer 412 such as glass. Further description
of Type-II bilayer heterojunctions may be found in Chapter 6 of
"Organic Lateral Heterojunction Devices for Vapor-phase Chemical
Detection", a Ph.D. Thesis by John Ho, published by the
Massachusetts Institute of Technology in June 2009. The contents of
this document, including Chapter 6, are hereby incorporated herein
in their entirety.
[0052] In one embodiment, the Type-II bilayer heterojunction is
constructed by spin-casting a fluorescent polymer that is sensitive
to a particular explosive on top of a second, more conductive thin
film metal oxide layer. Thus, the sensors themselves are capable of
miniaturization and on-chip integration with other microfabricated
structures, e.g., with transponder 350 (FIG. 3). Furthermore, the
resulting micrometer dimensions allow for close-packed, multiplexed
LED/chemosensor chips, e.g., 400 in FIG. 4A that can detect a wide
range of chemical analytes.
[0053] FIG. 4C shows a schematic of a chemosensor with a microLED
structure 470. MicroLEDs are small in size, making them suitable
for microfabrication and inclusion into the RICE devices discussed
herein. For instance, microLEDs may be integrated with other
microelectronic circuit such as a microprocessor, amplifier, ASIC,
or field-programmable gate array (FPGA). Structure 470 includes a
chemosensor 472 and microLED light source 474. The microLED light
source 474 includes an anode 476 and a cathode 478, which are on
either side of light emitting junction 480. Light from LED light
source 474 passes through transparent substrate 482a before
reaching transparent substrate 482b of chemosensor 472. Chemosensor
472 also includes sensor electrodes 488a and 488b, metal oxide
layer 484, and fluorescent polymer 486. The fluorescence of the
polymer 486 changes based on the chemical analytes the structure
470 is exposed to, and this change in fluorescence is sensed as a
change in resistance, and effectively, a change in the voltage or
current sensed across electrodes 488a and 488b.
[0054] FIG. 5A illustrates an abstraction of the bilayer
heterojunction structure to an electrical circuit. Battery 510
provides for an electric field across an LED/chemosensor chip,
shown in the figure as a variable chemoresistor 502. The effective
resistance of chemoresistor 502 is dependent upon the level of LED
light irradiating the chemosensor from the LED, the temperature of
the Type-II bilayer heterojunction, the level of chemicals attached
to the fluorescent polymer, and the strength of the electric field
applied by battery 510. Effectively, this chemosensor has a tunable
dynamic range which can be adjusted by changing operating
conditions (battery voltage, temperature, etc.) to make the sensors
more or less sensitive to a particular chemical/anaylte.
[0055] FIG. 5B illustrates a graph of normalized current 503 versus
time 504 for a vapor-phase explosives detection application. At
Time=T, vapor-phased explosives are attached to a fluorescent
polymer in the Type-II bilayer heterojunction structure. As more
explosives attach to the fluorescent polymer, the resistance of the
chemoresistor 502 becomes large, resulting in an
exponentially-decaying normalized chemoresistor current 506. The
exponentially-decaying waveform may have a different morphology if
a different fluorescent polymer is used in the bilayer
heterojunction. In one embodiment, if electronic circuit 512 senses
that the value of the normalized chemoresistor current 506 is less
than the value of the threshold chemoresistor current 509,
electronic circuit 512 transmits the signal to transponder 514. The
comparison of the two currents may be performed using any suitable
electronic means, e.g., a differential amplifier, or a comparator
circuit. The transponder may then transmit information to a remote
interrogation device as described above in relation to FIGS. 1A-2B.
In an alternative embodiment, a signal is only sent to the
transponder when a rate of change of current passes a threshold
rate that is determined based on a prior current level.
[0056] FIG. 6 illustrates a process flow diagram 600 for a process
or method for detecting chemical analytes. Chemicals are first
sensed using an LED/Chemosensor (step 602). The LED/Chemosensor may
be implemented as described above in relation to FIGS. 4A-4C. The
electrical signal, e.g., a current, from the chemosensor is
received by the electronic circuit (step 604). This circuit may be
implemented as described in relation to electronic circuit 512
(FIG. 5A).
[0057] The received electronic signal is then processed by the
electronic circuit (step 606). For instance, the electronic circuit
may compare the received electrical current signal to a threshold
electrical current or prior/historical current level(s) stored in a
memory device in the electronic circuit, and transmit the results
of this comparison as a second electrical signal to a transponder.
Or as described above, the electronic circuit may compare the rate
of change of the electrical current to a threshold determined based
on a prior current level.
[0058] If an interrogation signal is received by the transponder
from a remote interrogation device (step 608), then the transponder
of the device, if it had detected a chemical of interest, transmits
a signal representative of the sensed chemical to the remote
interrogation device (step 610). On the other hand, if an
interrogation signal is not received, the transponder does not
transmit a signal (step 612).
[0059] There are several advantages achieved by the various
embodiments described herein with respect to FIGS. 1A-6B. Among
other advantages, with microfabricated photoconductive sensors
which are electrically isolated and integrated with microfabricated
transponders, the chemical detection device can be miniaturized,
deployed in large numbers, and can be interrogated remotely from
substantial distances.
[0060] The invention may be embodied in other specific forms
without departing from the spirit or essential characteristics
thereof. The forgoing embodiments are therefore to be considered in
all respects illustrative, rather than limiting of the
invention.
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