Remotely communicating, battery-powered nanostructure sensor devices Number:7,522,040 from the United States Patent and Trademark Office (PTO) owispatent

Title: Remotely communicating, battery-powered nanostructure sensor devices

Abstract: A portable sensor device incorporates a low-power, nanostructure sensor coupled to a wireless transmitter. The sensor uses a nanostructure conducting channel, such as a nanotube network, that is functionalized to respond to a selected analyte. A measurement circuit connected to the sensor determines a change in the electrical characteristic of the sensor, from which information concerning the present or absence of the analyte may be determined. The portable sensor device may include a portable power source, such as a battery. It may further include a transmitter for wirelessly transmitting data to a base station.

Patent Number: 7,522,040 Issued on 04/21/2009 to Passmore,   et al.

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Inventors:	Passmore; John Loren (Berkeley, CA), Gabriel; Jean-Christophe P. (Pinole, CA), Star; Alexander (Albany, CA), Joshi; Vikram (San Francisco, CA), Skarupo; Sergei (San Francisco, CA)
Assignee:	Nanomix, Inc. (Emeryville, CA)
Appl. No.:	11/111,121
Filed:	April 20, 2005

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Related U.S. Patent Documents

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	Application Number	Filing Date	Patent Number	Issue Date
	60652883	Feb., 2005
	60564248	Apr., 2004

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Current U.S. Class:	340/540 ; 324/71.1; 340/539.26; 340/603; 340/628; 340/632
Current International Class:	G08B 21/00 (20060101)
Field of Search:	340/603,540,506,539.12,539.11,539.26,573.1,628,629,630,631,632,541 324/71.1 422/98,82.02,82.03 257/253,347,401,414 73/105

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Primary Examiner: La; Anh V
Attorney, Agent or Firm: Weaver Austin Villeneuve & Sampson LLP

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Parent Case Text

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CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority pursuant to 35 U.S.C. .sctn. 119(e) to provisional application Ser. No. 60/564,248, filed Apr. 20, 2004, and to provisional application Ser. No. 60/652,883, filed Feb. 15, 2005, which applications are specifically incorporated herein, in their entirety, by reference.

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Claims

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What is claimed is:

1. A remote sensor device, comprising: a nanostructure sensor comprising a nanostructure conducting channel between a source electrode and a drain electrode, wherein the nanostructure sensor is configured to respond to an analyte; a measurement circuit operatively connected to the nanostructure sensor, the measurement circuit configured to provide a signal indicating a response of the nanostructure sensor to the analyte; and a transmitter operatively connected to the measurement circuit, the transmitter configured to wirelessly transmit the signal, wherein the nanostructure sensor, the measurement circuit, and the transmitter are assembled together in a portable unit.

2. The remote sensor device of claim 1, further comprising a portable power source connected to provide power to the measurement circuit.

3. The remote sensor device of claim 2, wherein the portable power source is selected from the group consisting of a battery, a solar cell, and a fuel cell.

4. The remote sensor device of claim 1, wherein the measurement circuit further comprises a processor configured to determine an amount of the analyte based on the signal from the nanostructure sensor.

5. The remote sensor device of claim 1, wherein the nanostructure conducting channel comprises a nanotube.

6. The remote sensor device of claim 1, wherein the nanostructure conducting channel comprises a network of randomly-oriented nanotubes.

7. The remote sensor device of claim 6, wherein the source electrode comprises a plurality of fingers interdigitated with fingers of the drain electrode.

8. The remote sensor device of claim 1, further comprising a functionalization material disposed adjacent to the nanostructure conducting channel.

9. The remote sensor device of claim 8, wherein the functionalization material comprises a material selected from palladium and polyethylene imine.

10. The remote sensor device of claim 1, further comprising an encapsulation material covering the nanostructure conducting channel, the source electrode, and the drain electrode, wherein the encapsulation material is configured to control a diffusion rate of the analyte through the encapsulating material.

11. The remote sensor device of claim 1, further comprising a base under the nanostructure conducting channel, the source electrode, and the drain electrode, wherein the base is selected from a semiconducting material and an insulating material.

12. The remote sensor device of claim 11, further comprising a passivation layer interposed between the nanostructure conducting channel and the base.

13. The remote sensor device of claim 11, further comprising a diffusion blocking layer interposed between the base and at least one of the source and drain electrodes.

14. The remote sensor device of claim 13, wherein the diffusion blocking layer comprises a Si.sub.3N.sub.4 layer.

15. The remote sensor device of claim 13, further comprising a conditioned surface layer overlying the diffusion blocking layer.

16. The remote sensor device of claim 13, wherein the conditioned surface layer comprises an SiO2 layer.

17. The remote sensor device of claim 1, wherein the nanostructure sensor comprises a plurality of electrically isolated sensors configured to respond to the analyte.

18. The remote sensor device of claim 1, wherein the nanostructure sensor comprises a plurality of electrically isolated sensors configured to respond to different analytes.

19. The remote sensor device of claim 1, wherein the nanostructure sensor comprises at least a first nanostructure capacitor element disposed spaced-apart from at least a corresponding second capacitor element.

20. The remote sensor device of claim 1, wherein one or more of the nanostructure sensor, at least a portion of the measurement circuit and at least a portion of the transmitter is included in an integrated circuit chip.

21. The remote sensor device of claim 1, wherein the measurement circuit includes an analog-to-digital converter, and wherein the nano structure sensor communicates directly to the analog-to-digital converter without intermediate signal amplification.

22. The remote sensor device of claim 8, wherein the functionalization material is patterned to cover a portion of the nanostructure conducting channel and to leave a remaining part of the nanostructure conducting channel exposed to the analyte.

23. The remote sensor device of claim 11, wherein the base comprises a porous material, wherein the porous material comprises a plurality of channels configured to permit suction to be applied across the base.

24. A system for collecting information regarding a remote analyte, the system comprising: a sensor device, comprising a nanostructure sensor comprising a nanostructure conducting channel between a source electrode and a drain electrode, a measurement circuit operatively connected to the nanostructure sensor configured to provide a signal indicating a response of the nanostructure sensor to an analyte, a wireless transmitter operatively connected to the measurement circuit; and a base station comprising a wireless receiver located remotely from the sensor device and configured to wirelessly receive the signal from the sensor device.

25. The system of claim 24, further comprising a portable power source for the sensor device.

26. The system of claim 24, further comprising a plurality of sensor devices each comprising a nanostructure sensor, wherein the base station is configured to wirelessly receive signals from the plurality of sensor devices indicating a response of each sensor to analytes.

27. The system of claim 24, wherein the base station further comprises a transmitter adapted for wirelessly relaying the signal to a second remote station.

28. The system of claim 24, wherein the base station further comprises an output device adapted for providing a user with information concerning an amount of analyte measured by the sensor device.

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Description

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BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to chemical sensors for remote monitoring, using nanostructures as low-power sensor elements.

2. Description of Related Art

Advances in integrated circuit technology have enabled complex computers to be made small, lightweight, and relatively inexpensively, often as integrated microprocessors. In addition, they can be made to consume relatively small amounts of power. Computers in this class are not as sophisticated as state-of-the-art personal computers, but are powerful enough to process 16-bit data and do floating-point arithmetic. Because they require so little power, they can be used in devices that run on batteries for relatively long periods of time. Thus, for example, they are useful for applications as diverse as burglar alarms and cell phones.

At the same time, modern communications technology enables computers to exchange information wirelessly. Various protocols for radio communication allow data transmitters to use radio spectrum for brief periods of time in limited regions of space. Using such protocols, computers can communicate using weak radio transmitters that transmit and receive in short pulses. This approach minimizes the power requirements of radio communication. As a result, battery-powered devices can transmit data wirelessly to base stations, while remaining in operation for a relatively long period of time without changing or recharging their batteries. Such devices can be used together as a network of remotely located computers.

One important application for a sensor remote network is monitoring of conditions over a wide area. The use of batteries and radio communication eliminates the need to install wires to connect widely deployed monitors. For example, remote battery-powered sensors are known for monitoring electromagnetic radiation along the length of electric power lines, or the monitoring of water quality over a wide area, using distributed optical sensors. However, it is generally believed that a power source is needed to recharge the batteries to maintain such remote sensors operational for sufficiently long periods.

One type of sensor is a chemical sensor, which measures the presence or absence of a chemical species. A variety of chemical sensors are known in the art; for example optical sensors and catalytic bead sensors. Sensors of this type are often relatively inexpensive, sensitive and specific to particular chemicals. However, they are large, and often operate at high temperature, and require large amounts of power. Another type of chemical sensor is a surface acoustic wave detector. These sensors are often smaller and lighter, but they often respond to a range of chemicals rather than to a specific chemical. Yet another type of chemical sensor is a field-asymmetric ion mobility spectrometer. These sensors are often small, but require large amounts of power, and they are relatively expensive. They are often reasonably specific sensors, but often they are not very sensitive. This list is not exhaustive of the known chemical sensors. It is meant to illustrate that the types of sensors differ widely with respect to their size, sensitivity, resolution, specificity, power requirements, cost, and other properties. Most sensors are not appropriate for use in low-cost, battery-powered, remotely communicating devices.

It is desirable, therefore, to provide a remote sensing device with wireless communication capability, that is both compact and inexpensive. It is further desirable to provide a device that can operate for extended periods on a limited power resource.

SUMMARY OF THE INVENTION

The invention provides a wireless sensor device in which a chemical sensing function is performed by electronic devices made with functionalized nanostructures. The functionalized nanostructure sensors are optimized to be low-cost, low-power, small, sensitive, and selective.

Although sensor systems described herein are particularly suitable for efficient operation by battery power, the typically low power consumption of nanosensor devices having aspect of the invention provides embodiments suitable for operation either using conventional power sources used in portable/remote electronics (e.g., battery, solar cell, miniature fuel cell) and/or using alternative energy resources, such as a thermocouple, radio-frequency energy, electrochemical interactions, supercapacitors, energy scavenging mechanisms, or the like, or combinations thereof. The term "power resource" includes both conventional power sources and also such alternative energy resources.

As used herein, a "nanostructure" is any structure which has at least one dimension smaller than 100 nm. Examples include, but are not limited to, multiwalled nanotubes, single-walled nanotubes, carbon nanotubes, carbon onions, semiconductor nanowires, metal nanowires, nanorods, nanocrystals, and nanoparticles. Examples further include the list of nanostructures provided in the patent application Publ. No. 2002/0117659, by Lieber et al., which is herein incorporated in its entirety by reference.

In certain embodiments having aspects of the invention, an electronic device, such as a nanosensor, may comprise at least one nanostructure is disposed on a substrate. In addition, at least two conducting elements are disposed on the substrate, such that each conducting element is in electrical communication with the at least one nanostructure. In some embodiments of the invention, an additional conducting element, referred to as a gate electrode, is provided such that it is not in electrical communication with the at least one nanostructure, but such that there is an electrical capacitance between the gate electrode and the at least one nanostructure.

Alternative embodiments having aspects of the invention may be configured as a nanostucture capacitive sensor. For example, a nanostructure sensor may comprise an assembly including at least a first nanostructure capacitor element disposed spaced-apart from at least a corresponding second capacitor element, the capacitor elements communicating with circuitry to permit measurement of at least a capacitance and/or impedance of the assembly. The nanostructure element (and/or other adjacent elements) may be functionalized to provide a capacitance response to at least an analyte of interest.

Various alternative device structural arrangements may be employed without departing from the spirit of the invention. For example, an electronic device, such as a nanosensor, may comprise a layered assembly including at least one nanostructure disposed between at least a pair of spaced-apart boundary layers, in which the boundary layers have at least a conductive portion in communication with the nanostructure. In another example, an electronic device, such as a nanosensor, may comprise a generally elongate rod-like assembly including at least one nanostructure disposed between at least a core element and a shell element, the core and shell having at least a conductive portion in communication with the nanostructure.

Examples of nanostructure electronic devices are provided, among other places, in patent application Ser. No. 10/656,898 filed Sep. 5, 2003 entitled "Polymer Recognition Layers For Nanostructure Sensor Devices", and in application Ser. No. 10/704,066, filed Nov. 7, 2003 entitled "Nanotube-Based Electronic Detection Of Biomolecules" (now published as US 2004-0132070), both of which are incorporated herein, in their entirety, by reference.

Conducting elements may be included in communication with circuitry to measure an electrical, magnetic, electrochemical, electromechanical and/or electromagnetic property of the nanostructure sensor. Any suitable property may provide the basis for sensor sensitivity so as to permit detection and/or measurement of at least one sensor signal, for example, electrical resistance, electrical conductance, current, voltage, capacitance, impedance, transistor "on" current, transistor "off" current, transistor hysterisis or phase change, or transistor threshold voltage. Those skilled in the art will appreciate that other properties may also readily be measured by employment of associated circuitry. Accordingly, this list is not meant to be restrictive of the types of properties that can be measured.

For use in distributed networks, the electrical circuit that measures an electrical property must be low-cost and low-power. Preferably, the electrical circuit comprises low-cost, low-voltage integrated circuits. Such circuits generally have limited voltage and current capacities and limited voltage and current sensitivities. As a result, it is preferred for the nanostructure sensors to have electrical resistances and electrical conductances within certain ranges. Preferably, a sensor has a resistance less than 1 M.OMEGA. and greater than 1 .OMEGA.. More preferably, a sensor has a resistance less than 100 k.OMEGA. and greater than 10 .OMEGA.. Most preferably, a sensor has a resistance less than 20 k.OMEGA. and greater than 100 .OMEGA..

In some embodiments, a nanostructure sensor is a transistor. A transistor has a maximum conductance, which is the greatest conductance measured with the gate voltage in a range, and a minimum conductance, which is the least conductance measured with the gate voltage in a range. A transistor has an on-off ratio, which is the ratio between the maximum conductance and the minimum conductance. To make a sensitive chemical sensors, a nanostructure transistor has an on-off ratio preferably greater than 1.2, more preferably greater than 2, and most preferably greater than 10. For example, a nanostructure electronic device, without the functionalization that converts the device to a sensor, may exhibit relatively high conductance at gate voltages less than about -5 V and relatively low conductance at gate voltages greater than about 0 V.

In a preferred embodiment of the invention, nanostructure electronic devices are optimized to have resistances within the preferred range of resistance and on-off ratios within the preferred range of on-off ratio. Many nanostructures are disposed on the substrate, all of them being in electrical communication with the conducting elements. In some embodiments, the many nanostructures are nanowires or nanotubes that are oriented substantially parallel. In some embodiments, the many nanostructures are nanowires or nanotubes that are oriented randomly. Methods for disposing many nanostructures are disclosed in patent application Ser. No. 10/177,929, filed Jun. 21, 2002 by Gabriel et al., which is herein incorporated by reference, in its entirety. Myriad paths are available for electrical current to flow between the conducting elements through the nanostructures. In some embodiments, each current path includes only one nanostructure; in other embodiments, each current path includes at least two nanostructures in series. The number of nanostructures, the number of current paths, and the number of nanostructures in series in a current path may be chosen to provide resistance and on-off ratio within the preferred ranges.

The nanostructure sensors utilize nanostructures which have been functionalized, which means treated with one or more recognition materials. A recognition material is a substance which is disposed on the substrate in the immediate vicinity of the at least one nanostructure or directly on the at least one nanostructure, such that the nanostructure electronic device responds electrically to a change in the concentration of a chemical species. Examples of sensing agents are provided in Publ. No. 2002/0117659 referenced hereinabove, in provisional patent application Ser. No. 60/502,485, filed Sep. 12, 2003 by Star et al., and International Application No. PCT/US04/30,136 entitled "Carbon dioxide nanoelectronic sensor", published as WO05/026,694 on Mar. 24, 2005, each of which references are herein incorporated, in their entirety, by reference. Other suitable sensing agents may also be used, as known in the art.

Functionalized nanostructure sensors are able to detect chemical species with high selectivity and high sensitivity. Furthermore, they require low amounts of power to operate. To use them in remote networked sensor devices, they should be integrated with further circuitry. The invention provides circuitry which measures an electrical property of the nanostructure sensor. An electrical property includes, but is not limited to, electrical resistance, capacitance, transistor threshold voltage, electrical current, and transistor off current. The circuitry which measures an electrical property may comprise a microprocessor, of which many examples are known in the art. In some embodiments, the circuitry further comprises an analog-to-digital converter. In some embodiments, the circuitry further comprises a regulated voltage source. The microprocessor, analog-to-digital converter, and regulated voltage source should be chosen such that they require low amounts of electrical power and such that they are low in cost.

A remotely communicating sensor device according to the invention comprises at least one functionalized nanostructure sensor, electrical circuits to measure the at least one sensor, and a communications circuit. The communications circuit comprises an antenna configured to transmit and receive radio waves and a circuit configured to control the antenna. Many examples of wireless communications circuits are known in the art, and any suitable low-power circuit may be employed. The invention is intended to be practiced with any radio communications circuit with low power requirements, for example, a circuit appropriate for extended operation in a remote battery-powered device without need for recharging.

It should be understood that, while a nanosensor may be fabricated as a discrete sensor device or sensor array, alternatively various additional components of a nanosensor apparatus having aspects of the invention may be integrated on a single "chip" or other base material (e.g., a flexible substrate), without departing from the spirit of the invention. For example additional components such as electronic circuitry, signal processors, memory devices, logic devices, photocells, optical elements, microfluidic elements, and the like may be integrated on a chip which includes one or more nanosensor devices in operative communication one or more such additional components. The integrated chip may be fabricated using techniques commonly employed for electronic integrated circuits (IC), microfluidic devices, and the like.

In some embodiments, a remotely communicating sensor device transmits data from a nanostructure sensor to a base station. An example of this embodiment is provided in Example A. It should be understood that remotely communicating sensor systems having aspects of the invention may include a range of alternative remote communication architectures, in addition to a remote sensor-base station embodiment. In some embodiments, multiple remotely communicating devices transmit and receive data from each other, forming a network of devices. To conserve power, in some embodiments a remote sensor may be made to transmit sensing data only intermittently, for example, at predetermined intervals or when queried by a base station or other compatible device. Some embodiments may include a plurality intercommunicating remote sensor units which may provide multiple transmission paths (e.g. for robustness), repeater station capability (e.g., for increased range with low power consumption), distributed processing, and the like.

A more complete understanding of the nanostructure sensor devices will be afforded to those skilled in the art, as well as a realization of additional advantages and objects thereof, by a consideration of the following detailed description of the preferred embodiment. Reference will be made to the appended sheets of drawings which will first be described briefly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram showing an exemplary nanosensor and associated circuit elements for a remote sensing device.

FIG. 2 is a schematic diagram showing a side view of a substrate for preparing an exemplary nanosensor device.

FIGS. 3A-B are schematic diagrams showing a side view of a substrate growing a nanotube from a catalyst particle, which illustrate the effect of a diffusion barrier.

FIG. 4 is a schematic side view showing an encapsulated nanosensor and associated circuit elements.

FIG. 5 is a schematic diagram showing an exemplary design for a nanostructure sensor using a random network of nanotubes.

FIG. 6 is a schematic circuit diagram showing an exemplary electronic circuit for a remote sensing device according to an embodiment of the invention.

FIG. 7 is a schematic circuit diagram showing an exemplary electronic circuit for a remote sensing device according to an alternative embodiment of the invention.

FIG. 8 is a chart showing an exemplary signal from an exemplary battery-powered hydrogen sensor, transmitted by a radio antenna and received by a base station.

FIG. 9 is a block diagram showing an exemplary arrangement of elements for a remote sensing system according to the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

The present invention provides a remotely communicating, low-power nanostructure sensor. The sensor is capable of operating for long periods on a limited power source, such as a small battery. In the alternative, the sensor may be powered by other low-power sources. Exemplary embodiments are described below. In the detailed description that follows, like element numerals are used to denote like elements appearing in one or more of the figures.

The remotely communicating sensor may incorporate a nanosensor comprising a nanostructure functionalized to respond to the presence of a chemical or compound. The nanosensor may be configured as a field effect transistor (FET) device, wherein the conductivity of the sensor depends on the value of an applied gate voltage, and on chemicals in the surrounding environment of the nanosensor. A nanotube may be used as a nanostructure conducting channel in a FET; such a device may be referred to as a NTFET. An exemplary architecture for a nanosensor for use with the invention is described below.

1. Nanosensor Architecture

FIG. 1. shows an electronic sensing device 100 for detecting an analyte 101 (e.g. hydrogen gas), comprising a nanostructure sensor 102. Sensor 102 comprises a substrate 104, and a conducting channel or layer 106 comprising a nanostructure material, such as a nanotube or network of nanotubes, disposed on the substrate.

The nanostructure material 106 may contact the substrate as shown, or in the alternative, may be spaced a distance away from the substrate, with or without a layer of intervening material. In an embodiment of the invention, conducting channel 106 may comprise one or more carbon nanotubes. For example, conducting channel 106 may comprise a plurality of nanotubes forming a mesh, film or network.

At least two conductive elements or contacts 110, 112 may be disposed over the substrate and electrically connected to conducting channel 106 comprising a nanostructure material. Elements 110, 112 may comprise metal electrodes in direct contact with conducting channel 106. In the alternative, a conductive or semi-conducting material (not shown) may be interposed between contacts 110, 112 and conducting channel 106. Contacts 110, 112 may comprise source and drain electrodes, respectively, upon application of a source-drain voltage V.sub.sd. The voltage or polarity of source 110 relative to drain 112 may be variable, e.g., the applied voltage may be DC, AC, pulsed, or variable. In an embodiment of the invention, the applied voltage is a DC voltage.

Device 100 may be operated as a gate-controlled field effect transistor, with sensor 102 further comprising a gate electrode 114. Gate 114 may comprise a base portion of substrate 104, such as a doped-silicon wafer material isolated from contacts 110, 112 and channel 106 by a dielectric layer 116, so as to permit a capacitance to be created by an applied gate voltage V.sub.g. For example, the substrate 104 may comprise a silicon back gate 114, isolated by a dielectric layer 116 comprising SiO.sub.2.

Sensor 102 may further comprise a layer of inhibiting or passivation material 118 covering regions adjacent to the connections between the conductive elements 110, 112 and conducting channel 106. The inhibiting material may be impermeable to at least one chemical species, such as to the analyte 101 or to environmental materials such as water or other solvents, oxygen, nitrogen, and the like. The inhibiting material 118 may comprise a passivation material as known in the art, such as silicon dioxide, aluminum oxide, silicon nitride, or other suitable material. Further details concerning the use of inhibiting materials in a NTFET are described in prior application Ser. No. 10/280,265, filed Oct. 26, 2002, entitled "Sensitivity Control For Nanotube Sensors" (published as US 2004-0043527 on Mar. 4, 2004) which is incorporated by reference herein.

The conducting channel 106 (e.g., a carbon nanotube layer) may be functionalized to produce a sensitivity to one or more target analytes 101. Although nanostructures such as carbon nanotubes may respond to a target analyte through charge transfer or other interaction between the device and the analyte, more generally a specific sensitivity can be achieved by employing a recognition material 120, also called a functionalization material, that induces a measurable change in the device characteristics upon interaction with a target analyte. The sensor functionalization material 120 may be selected for a specific application, such as to interact with a targeted analyte 101 to cause a measurable change in electrical properties of nanosensor device 102. For example, the functionalization material 120 may cause an electron transfer to occur in the presence of analyte 101, or may influence local environment properties, such as pH and the like, so as to indirectly change device characteristics. Alternatively or additionally, the recognition material may induce electrically-measurable mechanical stresses or shape changes in the nanostructure channel 106 upon interaction with a target analyte.

Sensitivity to an analyte or to multiple analytes may be provided or regulated by the association of a nanotube conducting channel 106 with an adjacent functionalization material 120. Specific examples of suitable functionalization materials are provided later in the specification. The functionalization material 120 may be disposed as a continuous or discontinuous layer on or adjacent to channel 106.

Device 100 may further comprise suitable circuitry in communication with sensor elements to perform electrical measurements. For example, a conventional power source may supply a source drain voltage V.sub.sd between contacts 110, 112. Measurements via the sensor device 100 may be carried out by circuitry represented schematically by meter 122 connected between contacts 110, 112. In embodiments including a gate electrode 114, a conventional power source 124 may be connected to provide a selected or controllable gate voltage V.sub.g. Device 100 may include one or more electrical supplies and/or a signal control and processing unit (not shown) as known in the art, in communication with the sensor 102.

Optionally, device 100 may comprise a plurality of sensors like sensor 102 disposed in a pattern or array, such as described in prior application Ser. No. 10/388,701 filed Mar. 14, 2003 entitled "Modification Of Selectivity For Sensing For Nanostructure Device Arrays" (now published as US 2003-0175161), which is incorporated by reference herein. Each device in the array may be functionalized with identical or different functionalization. Identical device in an array can be useful in order to multiplex the measurement to improve the signal/noise ratio or increase the robustness of the device by making redundancy. Different functionalization may be useful for providing sensitivity to a greater variety of analytes with a single device.

2. Sensor Elements

Substrate. The substrate 104 may be insulating, or on the alternative, may comprise a layered structure, having a base 114 and a separate dielectric layer 116 disposed to isolate the contacts 110, 112 and channel 106 from the substrate base 114. The substrate 104 may comprise a rigid or flexible material, which may be conducting, semiconducting or dielectric. Substrate 104 may comprise a monolithic structure, or a multilayer or other composite structure having constituents of different properties and compositions. Suitable substrate materials may include quartz, alumina, polycrystalline silicon, III-V semiconductor compounds, and other suitable materials.

Substrate materials may be selected to have particular useful properties, such as transparency, microporosity, magnetic properties, monocrystalline properties, polycrystalline or amorphous properties, or various combinations of these and other desired properties. For example, in an embodiment of the invention, the substrate 104 may comprise a silicon wafer doped so as to function as a back gate electrode 114. The wafer being coated with intermediate diffusion barrier of Si.sub.3N.sub.4 and an upper dielectric