Fluid sensor and methods

Abstract

A fluid sensor for use in an environment having an ambient temperature has a field-effect transistor (FET) comprising a functionalized semiconductor nano-wire, an integral heater disposed proximate to the field-effect transistor to heat the field-effect transistor to an elevated temperature relative to the ambient temperature, and integral thermal insulation disposed to maintain the field-effect transistor at the elevated temperature.

1 . A fluid sensor for use in an environment having an ambient temperature, the fluid sensor comprising: 
 a) a field-effect transistor (FET) comprising a functionalized semiconductor nano-wire,    b) an integral heater disposed proximate to the field-effect transistor to heat the field-effect transistor to an elevated temperature relative to the ambient temperature, and    c) integral thermal insulation disposed to maintain the field-effect transistor at the elevated temperature.    
   
   
       2 . The fluid sensor of  claim 1 , wherein the functionalized semiconductor nano-wire comprises silicon.  
   
   
       3 . The fluid sensor of  claim 2 , wherein the silicon of the functionalized semiconductor nano-wire is doped to provide a predetermined conductivity type.  
   
   
       4 . The fluid sensor of  claim 1 , wherein the functionalized semiconductor nano-wire comprises a catalyst.  
   
   
       5 . The fluid sensor of  claim 4 , wherein the catalyst comprises a material capable of interacting with a fluid to be sensed and effecting a change of an electrical characteristic of the field-effect transistor (FET).  
   
   
       6 . The fluid sensor of  claim 4 , wherein the catalyst comprises a metallic catalyst.  
   
   
       7 . The fluid sensor of  claim 4 , wherein the catalyst is a material selected from the list consisting of platinum, palladium, iridium, rhenium, ruthenium, gold, silver, and mixtures or alloys or compounds thereof; carbon; tungsten, titanium, tin, zinc, and oxides thereof; organometallic compounds containing elements from the group consisting of cobalt, iron, and nickel; and transition metal complexes containing elements from Groups IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB of the Periodic Table of Elements.  
   
   
       8 . The fluid sensor of  claim 4 , wherein the catalyst comprises a porous thin layer of catalyst material.  
   
   
       9 . The fluid sensor of  claim 8 , wherein pores of the porous thin layer of catalyst material extend at least partially through the thin layer of catalyst material.  
   
   
       10 . The fluid sensor of  claim 4 , wherein the catalyst comprises a mesh formed by thin filaments of catalyst material.  
   
   
       11 . The fluid sensor of  claim 1 , wherein the functionalized semiconductor nano-wire comprises a silicon nano-wire functionalized with a material capable of interacting with a fluid to be sensed and effecting a change of an electrical characteristic of the field-effect transistor (FET).  
   
   
       12 . The fluid sensor of  claim 1 , wherein the functionalized semiconductor nano-wire comprises a silicon nano-wire functionalized with a catalyst selected from the list consisting of: platinum, palladium, iridium, rhenium, ruthenium, gold, silver, and mixtures or alloys or compounds thereof; carbon; tungsten, titanium, tin, zinc, and oxides thereof; carbon; tungsten, titanium and oxides thereof; organometallic compounds containing elements from the group consisting of cobalt, iron, and nickel; and transition metal complexes containing elements from Groups IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB of the Periodic Table of Elements.  
   
   
       13 . The fluid sensor of  claim 1 , further comprising a substrate for supporting the field-effect transistor.  
   
   
       14 . The fluid sensor of  claim 13 , wherein the field-effect transistor and the substrate are formed from a layer of silicon on an insulator (SOI).  
   
   
       15 . The fluid sensor of  claim 14 , wherein the field-effect transistor and the substrate are formed from a layer of silicon on an insulator layer comprising silicon oxide.  
   
   
       16 . The fluid sensor of  claim 13 , wherein the integral thermal insulation is disposed on the substrate.  
   
   
       17 . The fluid sensor of  claim 13 , wherein the integral heater is disposed on the substrate.  
   
   
       18 . The fluid sensor of  claim 13 , wherein the integral heater is disposed on the integral thermal insulation.  
   
   
       19 . The fluid sensor of  claim 13 , wherein the field-effect transistor (FET) is disposed on the substrate.  
   
   
       20 . The fluid sensor of  claim 13 , wherein the field-effect transistor (FET) is disposed on the integral thermal insulation.  
   
   
       21 . The fluid sensor of  claim 13 , wherein a portion of the substrate is removed to form an opening under the field-effect transistor (FET), the opening being at least partially aligned with the field-effect transistor.  
   
   
       22 . The fluid sensor of  claim 13 , wherein the substrate serves as a gate for the field-effect transistor.  
   
   
       23 . The fluid sensor of  claim 13 , wherein the field-effect transistor includes a gate electrically insulated from the substrate.  
   
   
       24 . The fluid sensor of  claim 13 , wherein the functionalized semiconductor nano-wire comprises a conductive catalyst electrically insulated from the substrate to provide a gate for the field-effect transistor.  
   
   
       25 . The fluid sensor of  claim 1 , further comprising at least one integral temperature sensor disposed proximate to the field-effect transistor for determining the temperature thereof.  
   
   
       26 . A fluid-sensor array, each fluid sensor of the fluid-sensor array comprising the fluid sensor of  claim 25 .  
   
   
       27 . A fluid-sensor array, each fluid sensor of the fluid-sensor array comprising the fluid sensor of  claim 1 .  
   
   
       28 . The fluid-sensor array of  claim 27 , further comprising at least one integral temperature sensor for determining a temperature thereof.  
   
   
       29 . The fluid-sensor array of  claim 27 , wherein the field-effect transistor of each fluid sensor of the array is functionalized for detecting a particular substance.  
   
   
       30 . The fluid-sensor array of  claim 27 , wherein the field-effect transistor of each fluid sensor of the array is functionalized for detecting a distinct substance.  
   
   
       31 . The fluid-sensor array of  claim 27 , wherein the field-effect transistors of a number of the fluid sensors of the array are functionalized for detecting the same substance.  
   
   
       32 . The fluid-sensor array of  claim 27 , further comprising at least one field-effect transistor not functionalized for detecting a substance, whereby at least one control device is provided.  
   
   
       33 . A fluid sensor for use in an environment having an ambient temperature, the fluid sensor comprising: 
 a) functionalized nano-scale field-effect-transistor means for detecting a fluid,    b) integral means for heating the means for detecting a fluid,    d) integral means for thermally insulating at least the means for detecting a fluid, and    e) means for supporting the means for detecting a fluid, the integral means for heating, and the integral means for thermally insulating.    
   
   
       34 . The fluid sensor of  claim 33 , wherein the integral means for heating comprises means for heating the means for detecting a fluid to an elevated temperature relative to the ambient temperature, and the integral means for thermally insulating comprises means for maintaining the means for detecting a fluid at the elevated temperature.  
   
   
       35 . The fluid sensor of  claim 33 , further comprising integral means for determining the temperature of the means for detecting a fluid.  
   
   
       36 . The fluid sensor of  claim 33 , wherein the means for detecting a fluid comprises means for detecting a gas.  
   
   
       37 . A method for fabricating a fluid sensor, the method comprising the steps of: 
 a) providing an insulating substrate,    b) depositing a layer of silicon on the insulating substrate to form a silicon-on-insulator (SOI) substrate,    c) patterning the layer of silicon to form at least one silicon nano-wire and at least one integral heater resistor,    d) forming conductive source and drain contacts, thereby combining the source and drain contacts with the semiconductor nano-wire to form a field-effect transistor,    e) functionalizing the at least one silicon nano-wire for detection of at least one gas, and    f) depositing thermal insulation disposed to maintain the field-effect transistor at an elevated temperature relative to the ambient temperature of the fluid sensor.    
   
   
       38 . The method of  claim 37 , wherein the silicon-layer patterning step c) is performed by nanolithography.  
   
   
       39 . The method of  claim 37 , wherein the silicon-layer patterning step c) is performed using a lithography method selected from the list consisting of nano-imprint lithography, electron-beam lithography, ion-beam lithography, deep-UV lithography, and X-ray lithography.  
   
   
       40 . The method of  claim 37 , wherein the step d) of forming conductive source and drain contacts is performed by nanolithography.  
   
   
       41 . The method of  claim 37 , wherein the step d) of forming conductive source and drain contacts is performed using a lithography method selected from the list consisting of nano-imprint lithography, electron-beam lithography, ion-beam lithography, deep-UV lithography, and X-ray lithography.  
   
   
       42 . The method of  claim 37 , wherein the step of functionalizing the at least one silicon nano-wire comprises depositing a quantity of a material capable of interacting with a fluid to be sensed and effecting a change of an electrical characteristic of the field-effect transistor (FET).  
   
   
       43 . The method of  claim 37 , wherein the step of functionalizing the at least one silicon nano-wire comprises depositing a quantity of catalyst on the silicon nano-wire.  
   
   
       44 . The method of  claim 37 , wherein the step of functionalizing the at least one silicon nano-wire comprises depositing on the silicon nano-wire a quantity of a catalyst selected from the list consisting of: platinum, palladium, iridium, rhenium, ruthenium, gold, silver, and mixtures or alloys or compounds thereof; carbon; tungsten, titanium, tin, zinc, and oxides thereof; organometallic compounds containing elements from the group consisting of cobalt, iron, and nickel; and transition metal complexes containing elements from Groups IIIA, IVA, VA, VIA, VIIA, VIIIA, IB, IIB of the Periodic Table of Elements.  
   
   
       45 . The method of  claim 37 , wherein the step of functionalizing the at least one silicon nano-wire includes forming a gate for the field-effect transistor (FET).  
   
   
       46 . The method of  claim 37 , further comprising the step of removing at least a portion of the substrate under the field-effect transistor (FET).  
   
   
       47 . The method of  claim 46 , wherein the step of removing at least a portion of the substrate is performed by etching the back side of the substrate to form an opening at least partially aligned with the field-effect transistor (FET).  
   
   
       48 . The method of  claim 37 , further comprising the steps of patterning the semiconductor film and forming a junction to make a diode with known temperature-dependent electrical characteristics, whereby an integral temperature sensor is formed.  
   
   
       49 . A fluid sensor fabricated by the method of  claim 48 .  
   
   
       50 . A method of using the fluid sensor of  claim 49 , comprising the steps of: 
 a) associating with each of two or more fluids to be sensed a different operating temperature range effective for sensing the fluid to be sensed,    b) sensing a temperature of the fluid sensor by operating the integral temperature sensor, and    c) actuating the integral heater to adjust the temperature of the fluid sensor to within a selected operating temperature range, whereby one of the two or more fluids to be sensed is selected for sensing.    
   
   
       51 . A fluid sensor fabricated by the method of  claim 37 .  
   
   
       52 . An integrated circuit comprising the fluid sensor of  claim 51 .  
   
   
       53 . A fluid-sensor array, each fluid sensor of the fluid-sensor array being fabricated by the method of  claim 37 .  
   
   
       54 . An integrated circuit comprising the fluid-sensor array of  claim 53 .  
   
   
       55 . A method of using a fluid sensor having an integral heater and an integral temperature sensor, the method comprising the steps of: 
 a) associating with each of two or more fluids to be sensed a different operating temperature range effective for sensing the fluid to be sensed,    b) sensing a temperature of the fluid sensor by operating the integral temperature sensor, and    c) actuating the integral heater to adjust the temperature of the fluid sensor to within a selected operating temperature range, whereby one of the two or more fluids to be sensed is selected for sensing.