Sensitivity control for nanotube sensors

Abstract

Nanostructure sensing devices for detecting an analyte are described. The devices include nanostructures connected to conductive elements, all on a substrate. Contact regions adjacent to points of contact between the nanostructures and the conductive elements are given special treatment. The proportion of nanostructure surface area within contact regions can be maximized to effect sensing at very low analyte concentrations. The contact regions can be passivated in an effort to prevent interaction between the environment and the contact regions for sensing at higher analyte concentrations and for reducing cross-sensing. Both contact regions and at least some portion of the nanostructures can be covered with a material that is at least partially permeable to the analyte of interest and impermeable to some other species to tune selectivity and sensitivity of the nanostructure sensing device.

1 . An electronic system for detecting analytes, comprising: 
 a signal processing unit;    a first nanostructure sensing device circuit in communication with the signal processing unit.    
     
     
         2 . The electronic system of  claim 1 , wherein the first nanostructure sensing device circuit comprises: 
 an electrical supply;    a first nanostructure sensing device operatively connected to the electrical supply; and    a meter operatively connected to the electrical supply, wherein the meter is configured to measure an electrical characteristic of a circuit comprising the electrical supply and the first nanostructure sensing device.    
     
     
         3 . The electronic system of  claim 2 , wherein the first nanostructure sensing device comprises: 
 a substrate;    at least one nanostructure disposed over the substrate;    a first conductive element disposed over the substrate and making a first connection to a first nanostructure, the first connection providing electrical communication between the first conducting element and the first nanostructure;    a second conductive element disposed over the substrate and making a second connection to a first nanostructure, the second connection providing electrical communication between the second conducting element and the first nanostructure;    contact regions adjacent to the connections between the conductive elements and the first nanostructure; and    inhibiting material covering at least the contact regions.    
     
     
         4 . The electronic system of  claim 3 , wherein the nanostructure sensing device further comprises a portion of the first nanostructure wherein the portion is at least partially free of inhibiting material.  
     
     
         5 . The electronic system of  claim 3 , wherein the nanostructure sensing device further comprises a gate electrode.  
     
     
         6 . The electronic system of  claim 3 , wherein the inhibiting material is impermeable to at least one species.  
     
     
         7 . The electronic system of  claim 3 , further comprising functionalization on at least one nanostructure sensing device.  
     
     
         8 . The electronic system of  claim 7 , wherein the functionalization for a first nanostructure sensing device is different from the functionalization for a second nanostructure sensing device.  
     
     
         9 - 41 . (canceled)  
     
     
         42 . A nanotube sensor, comprising: 
 a silicon substrate;    a plurality of carbon nanotubes disposed over the substrate;    a first metal electrode in physical and electrical contact with a first nanotube;    a second metal electrode in physical and electrical contact with the first nanotube;    contact regions adjacent to points of the physical contact between the metal electrodes and the first nanotube; and    an inhibiting material on at least the contact regions.    
     
     
         43 - 46 . (canceled)  
     
     
         47 . An electronic system, comprising a plurality of nanostructure devices, wherein each nanostructure device comprises: 
 a substrate;    at least one nanostructure disposed over the substrate;    a first conductive element disposed over the substrate and making a first connection to a first nanostructure, the first connection providing electrical communication between the first conducting element and the first nanostructure;    a second conductive element disposed over the substrate and making a second connection to a first nanostructure, the second connection providing electrical communication between the second conducting element and the first nanostructure;    contact regions adjacent to the connections between the conductive elements and the first nanostructure;    passivation material covering at least the contact regions; and    a portion of the first nanostructure that is at least partially free of passivation material.    
     
     
         48 . The electronic system of  claim 47 , wherein at least a portion of the plurality of nanostructure devices further comprises a gate electrode.  
     
     
         49 . The electronic system of  claim 47 , wherein the passivation material is impermeable to at least one species.  
     
     
         50 - 68 . (canceled)  
     
     
         69 . An electronic system for detecting analytes, comprising: 
 a signal processing unit;    a first sensing device in operative communication with the signal processing unit, the first sensing device comprising a substrate, at least one nanostructure disposed over the substrate and functionalized for sensitivity to at least a first analyte, and at least two conductive elements disposed adjacent the substrate and in electrical communication via the at least one nanostructure, wherein the first sensing device is configured to communicate a first signal to the signal processing unit indicative of a response to the first analyte; and    a second sensing device in operative communication with the signal processing unit, the second sensing device comprising a second nanostructure functionalized for sensitivity to at least a second analyte, wherein the second sensing device is configured to communicate a second signal to the signal processing unit indicative of a response to the second analyte.    
     
     
         70 . The electronic system of  claim 69 , wherein the signal processing unit is configured to correlate at least one of the first signal and the second signal with stored data so as to determine whether at least one of the first analyte and the second analyte is detected.  
     
     
         71 . The electronic system of  claim 70 , wherein the stored data includes sensor data from defined environments containing specific analytes.  
     
     
         72 . The electronic system of  claim 69 , wherein at least one of the first sensing device and the second sensing device further comprises a gate electrode, the gate electrode in operative communication with the signal processing unit.  
     
     
         73 . The electronic system of  claim 72 , wherein the signal processing unit is configured to correlate at least one of the first signal and the second signal with stored data so as to determine whether at least one of the first analyte and the second analyte is detected, and wherein the stored data includes sensor data from defined environments containing specific analytes correlated to sensor gate voltage values.  
     
     
         74 . The electronic system of  claim 69 , wherein at least the first sensing device further comprises at least one selected inhibiting material disposed adjacent the nanostructure, the inhibiting material configured to be substantially permeable to the first analyte.  
     
     
         75 . The electronic system of  claim 74 , wherein the least one inhibiting material is selected to be substantially impermeable to at least one different species which is distinct from the first analyte so as to reduce cross-sensitivity to the different species.  
     
     
         76 . The electronic system of  claim 75 , wherein the at least one different species which is distinct from the first analyte of interest includes the second analyte.  
     
     
         77 . The electronic system of  claim 74 , wherein the least one inhibiting material is configured to tune the selectivity of the first sensing device.  
     
     
         78 . The electronic system of  claim 69 , wherein the first sensing device further comprises a passivation material covering at least one of a portion of the conductive elements and a portion of the nanostructure.  
     
     
         79 . The electronic system of  claim 78 , wherein at least a portion of the nanostructure is exposed and substantially free of passivation material, wherein the functionalization sensitive to at least a first analyte of interest comprises a recognition layer covering at least some of the exposed portion of the nanostructure.  
     
     
         80 . The electronic system of  claim 78 , wherein the nanostructure is substantially covered by an insulating passivation material, and wherein the functionalization sensitive to at least a first analyte of interest comprises a recognition layer disposed above the passivation material, and wherein the first sensing device further comprises a gate electrode, the gate electrode in operative communication with the signal processing unit.  
     
     
         81 . The electronic system of  claim 69 , wherein the signal processing unit further includes at least one wireless connection, and wherein at least one of the first signal and the second signal is communicated to the signal processing unit though the wireless connection.  
     
     
         82 . The electronic system of  claim 69 , wherein the second sensing device further comprises: 
 a substrate;    the second nanostructure disposed over the substrate in association with the functionalization sensitive to the second analyte of interest; and    at least two conductive elements disposed adjacent the substrate and in electrical communication via at least the second nanostructure.    
     
     
         83 . The electronic system of  claim 80 , wherein the second sensing device further comprises at least one selected inhibiting material disposed adjacent the second nanostructure, the inhibiting material configured to be substantially permeable to the second analyte of interest.  
     
     
         84 . The electronic system of  claim 69 , wherein at least one of the first analyte of interest and the second analyte of interest includes a species selected from the group consisting essentially of hydrogen, carbon dioxide, and nitrous oxide.