Sensor platform using a horizontally oriented nanotube element

• US 20050053525A1
• Filed: 05/12/2004
• Published: 03/10/2005
• Est. Priority Date: 05/14/2003
• Status: Active Grant

• Current Assignee: Nantero Incorporated
• Original Assignee: Nantero Incorporated
• Inventors: Bertin, Claude L., Vogeli, Bernhard, Segal, Brent M., Rueckes, Thomas, Jaiprakash, Venkatachalam C., Brock, Darren
• Granted Patent: US 7,780,918 B2
• Time in Patent Office: Days
• US Class Current: 422/88
• CPC Class Codes: B82Y 15/00 Nanotechnology for interacting, sensing or actuating, e.g. quantum dots as markers in protein assays or molecular motors
• CPC Class Codes: G01N 27/4146 involving nanosized elements, e.g. nanotubes, nanowires
• CPC Class Codes: G11C 13/025 using fullerenes, e.g. C60, or nanotubes, e.g. carbon or silicon nanotubes
• CPC Class Codes: Y10S 977/902 Specified use of nanostructure
• CPC Class Codes: Y10S 977/904 for medical, immunological, body treatment, or diagnosis
• CPC Class Codes: Y10S 977/92 Detection of biochemical
• CPC Class Codes: Y10S 977/921 Of toxic chemical
• CPC Class Codes: Y10S 977/922 Of explosive material
• CPC Class Codes: Y10S 977/924 using nanostructure as support of dna analysis
• CPC Class Codes: Y10T 29/43 Electric condenser making
• CPC Class Codes: Y10T 29/49082 Resistor making

Abstract

Sensor platforms and methods of making them are described, and include platforms having horizontally oriented sensor elements comprising nanotubes or other nanostructures, such as nanowires. Under certain embodiments, a sensor element has an affinity for an analyte. Under certain embodiments, such a sensor element comprises one or more pristine nanotubes, and, under certain embodiments, it comprises derivatized or functionalized nanotubes. Under certain embodiments, a sensor is made by providing a support structure; providing a collection of nanotubes on the structure; defining a pattern within the nanotube collection; removing part of the collection so that a patterned collection remains to form a sensor element; and providing circuitry to electrically sense the sensor'"'"'s electrical characterization. Under certain embodiments, the sensor element comprises pre-derivatized or pre-functionalized nanotubes. Under certain embodiments, sensor material is derivatized or functionalized after provision on the structure or after patterning. Under certain embodiments, a large-scale array includes multiple sensors.

Claims

1. A sensor platform, comprising

a sensor element comprising a patterned collection of a plurality of nanotubes and having an electrical characterization;

a support structure for supporting the sensor element so that it may be exposed to a fluid;

control circuitry to electrically sense the electrical characterization of the sensor element so that the presence of a corresponding analyte may be detected.

2. The sensor platform of claim 1 wherein the sensor element also comprises at least one nanowire.

3. The sensor platform of claim 1 wherein the patterned collection of a plurality of nanotubes is a lithographically defined, patterned collection of a plurality of nanotubes.

4. The sensor platform of claim 1 wherein the sensor element has an affinity for the corresponding analyte.

5. The sensor platform of claim 4 wherein the sensor element comprises at least one pristine nanotube.

6. The sensor platform of claim 4 wherein the sensor element comprises at least one nanotube that is derivatized to have or to increase the affinity.

7. The sensor platform of claim 4 wherein the sensor element comprises at least one nanotube that is functionalized to have or to increase the affinity.

8. The sensor platform of claim 1 wherein the sensor element has an affinity for at least two analytes and wherein the plurality of nanotubes includes at least two types of nanotubes, a first type having an affinity for a first analyte and a second type having an affinity for a second analyte.

9. The sensor platform of claim 4 wherein the support structure includes a channel and wherein the sensor element is suspended to span the channel.

10. The sensor platform of claim 9 wherein the support structure includes a conductive electrode positioned in the channel, and wherein the sensor element is deflectable in response to the control circuitry to contact the electrode so that a gating effect of the nanotubes in the sensor element may be electrically detected.

11. The sensor platform of claim 10 further including an upper electrode positioned above the sensor element.

12. The sensor platform of claim 1 including a fluidic separator in fluid communication with the sensor platform to deliver a fluid potentially having the analyte.

13. The sensor platform of claim 1 wherein the sensor element rests flat on the support structure.

14. The sensor platform of claim 1 wherein the sensor element is reusable in that, after exposure to the corresponding analyte, the sensor element can be substantially returned to its pre-exposure state by applying a voltage.

15. The sensor platform of claim 1 further comprising a conductive element located apart from the sensor element so that the conductive element and the sensor element are in a capacitive relationship.

16. The sensor platform of claim 15 wherein the sensor element is on one side of an insulating layer, and the conductive element is on another side of the insulating layer.

17. The sensor platform of claim 15 wherein the control circuitry comprises current-mirror circuitry to allow a capacitance associated with the conductive element and the sensor element to be measured.

18. The sensor platform of claim 17 wherein the control circuitry comprises a reference capacitor to allow measurement of the capacitance associated with the sensor element and the conductive element relative to the capacitance of the reference capacitor.

19. The sensor platform of claim 18 wherein the reference capacitor comprises both a second collection of nanotubes and a second conductive element that is separate from the second collection of nanotubes, so that the second collection of nanotubes and the second conductive element are in a capacitive relationship.

20. The sensor platform of claim 1 further comprising a first conductive element contacting the sensor element at a first point and a second conductive element contacting the sensor element at a second point so that an electric current can run through the sensor element between the first and second conductive elements.

21. The sensor platform of claim 20 wherein the control circuitry comprises current-mirror circuitry to allow the resistance between the first and second contact points to be measured.

22. The sensor platform of claim 21 wherein the control circuitry comprises a reference resistor to allow measurement of the resistance between the first and second contact points relative to the resistance of the reference resistor.

23. The sensor platform of claim 22 wherein the reference resistor comprises a second collection of nanotubes, and third and fourth conductive elements that contact the sensor element at separate points so that an electric current can run through the second collection of nanotubes between the third and fourth conductive elements.

24. A large-scale array of sensor platforms wherein the array includes a large plurality of sensor platform cells, each cell comprising

a sensor element comprising a patterned collection of a plurality of nanotubes and having an electrical characterization;

a support structure for supporting the sensor element so that it may be exposed to a fluid;

control circuitry to electrically sense the electrical characterization of at least one sensor element so that the presence of a corresponding analyte may be detected.

25. The large-scale array of claim 24 wherein the sensor element comprises at least one nanowire.

26. A sensor platform, comprising

a sensor element comprising a patterned collection of a plurality of nanotubes and having an electrical characterization;

a support structure for supporting the sensor element;

a conductive element located apart from the sensor element to form a structure in which the conductive element and sensor element are in a capacitive relationship;

control circuitry to electrically sense an electrical value reflecting a capacitance associated with the sensor element and the conductive element.

27. The sensor platform of claim 26 wherein the sensor element comprises at least one nanowire.

28. The sensor platform of claim 26 wherein the sensor element is in one side of an insulating layer, and the conductive element is a conductive pad on another side of the insulating layer.

29. The sensor platform of claim 26 wherein the sensor element is substantially surrounded by support structure material so that it is not substantially exposed to potential contact with a fluid.

30. A large-scale array of sensor platforms wherein the array includes a plurality of sensor platform cells, each of which comprises

a sensor element comprising a patterned collection of a plurality of nanotubes and having an electrical characterization;

a support structure for supporting the sensor element;

a conductive element located apart from the sensor element to form a structure in which the conductive element and sensor element are in a capacitive relationship;

control circuitry to electrically sense an electrical value reflecting the capacitance associated with the sensor element and the conductive element.

31. The large-scale array of claim 30 wherein the sensor element comprises at least one nanowire.

32. A sensor platform, comprising

a sensor element comprising a patterned collection of a plurality of nanotubes and having an electrical characterization;

a support structure for supporting the sensor element;

first and second conductive elements that contact the sensor element at separate locations;

control circuitry to electrically sense a value reflecting the resistance associated with the passage of current between the conductive elements through at least a portion of the sensor element.

33. The sensor platform of claim 32 wherein the sensor element comprises at least one nanowire.

34. The sensor platform of claim 32 wherein the sensor element is substantially surrounded by support structure material so that it is not substantially exposed to potential contact with a fluid.

35. A large-scale array of sensor platforms wherein the array includes a plurality of sensor platform cells, each of which comprises

a sensor element comprising a patterned collection of a plurality of nanotubes and having an electrical characterization;

a support structure for supporting the sensor element;

first and second conductive elements that contact the sensor element at separate locations;

control circuitry to electrically sense a value reflecting the resistance associated with the passage of current between the conductive elements through at least a portion of the sensor element.

36. The large-scale array of claim 35 wherein the sensor element comprises at least one nanowire.

37. A method of making a sensor, comprising:

providing a support structure comprising a substrate;

providing a collection of a plurality of nanotubes on the substrate;

defining a pattern within the nanotube collection such that the pattern corresponds to a sensor element;

removing a portion of the collection so that a patterned portion of the collection remains on the substrate to form a sensor element comprising a patterned collection of a plurality of nanotubes and having an electrical characterization;

providing control circuitry to electrically sense the electrical characterization of the sensor element so that the presence of a corresponding analyte may be detected.

38. The method of claim 37 wherein the sensor element comprises at least one nanowire.

39. The method of claim 37 wherein the sensor element has an affinity for the corresponding analyte.

40. The method of claim 39 wherein the resulting sensor element comprises at least one pristine nanotube.

41. The method of claim 39 wherein the resulting sensor element comprises at least one nanotube that is derivatized to have or to increase the affinity.

42. The method of claim 39 wherein the resulting sensor element comprises at least one nanotube that is functionalized to have or to increase the affinity.

43. The method of claim 37 wherein the sensor element has an affinity for at least two analytes and wherein the plurality of nanotubes includes at least two types of nanotubes, a first type having an affinity for a first analyte and a second type having an affinity for a second analyte.

44. The method of claim 39 wherein the support structure includes a channel and wherein the sensor element is suspended to span the channel.

45. The method of claim 44 wherein the support structure includes a conductive electrode positioned in the channel, and wherein the sensor element is deflectable in response to the control circuitry to contact the electrode so that a gating effect of the nanotubes in the sensor element may be electrically detected.

46. The method of claim 45 further including an upper electrode positioned above and separated from the sensor element.

47. The method of claim 37 further including defining a fluidic separator in fluid communication with the sensor element to deliver a fluid potentially having the analyte.

48. The method of claim 37 wherein the sensor element rests flat on the substrate.

49. The method of claim 39 wherein the sensor element is reusable in that, after exposure to the corresponding analyte, the sensor element can be substantially returned to its pre-exposure state by applying a voltage.

50. The method of claim 37 wherein the collection of nanotubes is formed by growing the collection of nanotubes on the substrate using a catalyst.

51. The method of claim 50 wherein, during the growing of the collection of nanotubes, the nanotubes are derivatized to have an affinity for a corresponding analyte.

52. The method of claim 50 wherein, during the growing of the collection of nanotubes, the nanotubes are functionalized to have an affinity for a corresponding analyte.

53. The method of claim 37 wherein the collection of nanotubes is formed by depositing a solution of suspended nanotubes on the substrate.

54. The method of claim 53 wherein the nanotubes are derivatized to have an affinity for a corresponding analyte.

55. The method of claim 53 wherein the nanotubes are functionalized to have an affinity for a corresponding analyte.

56. The method of claim 37 wherein the sensor element is made of pre-derivatized nanotubes.

57. The method of claim 37 wherein the sensor element is made of pre-functionalized nanotubes.

58. The method of claim 37 further comprising derivatizing at least a portion of the pre-patterning collection of nanotubes.

59. The method of claim 37 further comprising functionalizing at least a portion of the pre-patterning collection of nanotubes.

60. The method of claim 37 further comprising derivatizing at least a portion of the patterned collection of nanotubes remaining on the substrate.

61. The method of claim 37 further comprising functionalizing at least a portion of the patterned collection of nanotubes remaining on the substrate.

62. The method of claim 37, further comprising

providing a layer of covering material on one side of a collection of nanotubes;

removing a portion of the covering material to expose a portion of the collection.

63. The method of claim 37, further comprising

providing a first layer of a first covering material on one side of a collection of nanotubes;

providing a second layer of a second covering material on one side of a collection of nanotubes;

removing a portion of the second covering material;

annealing portions of the first and second covering materials.

64. The method of claim 37 further comprising providing a conductive element located apart from the sensor element so that the sensor element and the conductive element have a capacitive relationship.

65. The method of claim 64 further comprising providing an insulating layer between the conductive element and the sensor element.

66. The method of claim 64 wherein the control circuitry comprises current-mirror circuitry to allow a capacitance associated with the conductive element and the sensor element to be measured.

67. The method of claim 64 further comprising providing a reference capacitor to allow measurement of the capacitance associated with the sensor element and conductive element relative to the capacitance of the reference capacitor.

68. The method of claim 67 wherein the reference capacitor comprises both a second collection of nanotubes and a second conductive element that is separate from the second collection of nanotubes, so that the second collection of nanotubes and the second conductive element have a capacitive relationship.

69. The method of claim 37 further comprising providing a first conductive element that contacts the sensor element at a first point and providing a second conductive element that contacts the sensor element at a second point, so that an electric current can run through the sensor element between the first and second conductive elements.

70. The method of claim 69 wherein the control circuitry comprises current-mirror circuitry to allow the resistance between the first and second contact points to be measured.

71. The method of claim 69 further comprising providing a reference resistor to allow measurement, relative to the resistance of the reference resistor, of the resistance associated with current running through the sensor element between the first and second conductive elements.

72. The method of claim 71 wherein the reference resistor comprises both a second collection of nanotubes and a third conductive element and a fourth conductive element that contact the second collection of nanotubes at separate points, so that an electric current can run through the sensor element between the third and fourth conductive elements.

73. A method of making a capacitive structure, comprising

providing a support structure comprising a substrate;

providing a collection of a plurality of nanotubes on the support structure;

defining a pattern within the collection of nanotubes such that the pattern corresponds to a sensor element;

removing a portion of the collection so that patterned portion of the collection remains on the substrate to form a sensor element comprising a patterned collection of a plurality of nanotubes and having an electrical characterization;

providing a conductive element located apart from the sensor element to form a structure in which the conductive element and sensor element are in a capacitive relationship;

providing control circuitry to electrically sense a capacitance associated with the conductive element and the sensor element.

74. The method of claim 73 wherein the sensor element comprises at least one nanowire.

75. The method of claim 73 further comprising providing an insulating layer between the conductive element and the sensor element.

76. The method of claim 73 further comprising providing covering material in contact with the sensor element so that it is not substantially exposed to potential contact with a fluid.

77. A method of making a resistive structure, comprising

providing a support structure comprising a substrate;

providing a collection of a plurality of nanotubes on the substrate;

defining a pattern within the collection of nanotubes such that the pattern corresponds to a sensor element;

removing a portion of the collection so that patterned portion of the collection remains on the substrate to form a sensor element comprising a patterned collection of a plurality of nanotubes and having an electrical characterization;

providing first and second conductive elements that contact the sensor element at separate locations;

providing control circuitry to electrically sense a value reflecting the resistance associated with the passage of current between the conductive elements through at least a portion of the sensor element.

78. The method of claim 77 wherein the sensor element comprises at least one nanowire.

79. The method of claim 77 further comprising providing covering material in contact with the sensor element so that it is not substantially exposed to potential contact with a fluid.

80. A sensor platform, comprising

a sensor element comprising a patterned collection of a plurality of nanowires and having an electrical characterization;

a support structure for supporting the sensor element so that it may be exposed to a fluid;

control circuitry to electrically sense the electrical characterization of the sensor element so that the presence of a corresponding analyte may be detected.

81. The sensor platform of claim 80 wherein the sensor element also comprises at least one nanotube.

82. The sensor platform of claim 80 wherein the patterned collection of a plurality of nanowires is a lithographically defined, patterned collection of a plurality of nanowires.

83. The sensor platform of claim 80 wherein the sensor element has an affinity for the corresponding analyte.

84. The sensor platform of claim 83 wherein the sensor element comprises at least one pristine nanowire.

85. The sensor platform of claim 83 wherein the sensor element comprises at least one nanowire that is derivatized to have or to increase the affinity.

86. The sensor platform of claim 83 wherein the sensor element comprises at least one nanowire that is functionalized to have or to increase the affinity.

87. The sensor platform of claim 80 wherein the sensor element has an affinity for at least two analytes and wherein the plurality of nanowires includes at least two types of nanowires, a first type having an affinity for a first analyte and a second type having an affinity for a second analyte.

88. The sensor platform of claim 83 wherein the support structure includes a channel and wherein the sensor element is suspended to span the channel.

89. The sensor platform of claim 88 wherein the support structure includes a conductive electrode positioned in the channel, and wherein the sensor element is deflectable in response to the control circuitry to contact the electrode so that a gating effect of the nanowires in the sensor element may be electrically detected.

90. The sensor platform of claim 89 further including an upper electrode positioned above the sensor element.

91. The sensor platform of claim 80 including a fluidic separator in fluid communication with the sensor platform to deliver a fluid potentially having the analyte.

92. The sensor platform of claim 80 wherein the sensor element rests flat on the support structure.

93. The sensor platform of claim 80 wherein the sensor element is reusable in that, after exposure to the corresponding analyte, the sensor element can be substantially returned to its pre-exposure state by applying a voltage.

94. The sensor platform of claim 80 further comprising a conductive element located apart from the sensor element so that the conductive element and the sensor element are in a capacitive relationship.

95. The sensor platform of claim 94 wherein the sensor element is on one side of an insulating layer, and the conductive element is on another side of the insulating layer.

96. The sensor platform of claim 94 wherein the control circuitry comprises current-mirror circuitry to allow a capacitance associated with the conductive element and the sensor element to be measured.

97. The sensor platform of claim 96 wherein the control circuitry comprises a reference capacitor to allow measurement of the capacitance associated with the sensor element and the conductive element relative to the capacitance of the reference capacitor.

98. The sensor platform of claim 97 wherein the reference capacitor comprises both a second collection of nanowires and a second conductive element that is separate from the second collection of nanowires, so that the second collection of nanowires and the second conductive element are in a capacitive relationship.

99. The sensor platform of claim 80 further comprising a first conductive element contacting the sensor element at a first point and a second conductive element contacting the sensor element at a second point so that an electric current can run through the sensor element between the first and second conductive elements.

100. The sensor platform of claim 99 wherein the control circuitry comprises current-mirror circuitry to allow the resistance between the first and second contact points to be measured.

101. The sensor platform of claim 100 wherein the control circuitry comprises a reference resistor to allow measurement of the resistance between the first and second contact points relative to the resistance of the reference resistor.

102. The sensor platform of claim 101 wherein the reference resistor comprises a second collection of nanowires, and third and fourth conductive elements that contact the sensor element at separate points so that an electric current can run through the second collection of nanowires between the third and fourth conductive elements.

103. A large-scale array of sensor platforms wherein the array includes a large plurality of sensor platform cells, each cell comprising

a sensor element comprising a patterned collection of a plurality of nanowires and having an electrical characterization;

a support structure for supporting the sensor element so that it may be exposed to a fluid;

control circuitry to electrically sense the electrical characterization of at least one sensor element so that the presence of a corresponding analyte may be detected.

104. The large-scale array of claim 103 wherein the sensor element comprises at least one nanotube.

105. A sensor platform, comprising

a sensor element comprising a patterned collection of a plurality of nanowires and having an electrical characterization;

a support structure for supporting the sensor element;

a conductive element located apart from the sensor element to form a structure in which the conductive element and sensor element are in a capacitive relationship;

control circuitry to electrically sense an electrical value reflecting the capacitance associated with the sensor element and the conductive element.

106. The sensor platform of claim 105 wherein the sensor element comprises at least one nanotube.

107. The sensor platform of claim 105 wherein the sensor element is in one side of an insulating layer, and the conductive element is a conductive pad on another side of the insulating layer.

108. The sensor platform of claim 105 wherein the sensor element is substantially surrounded by support structure material so that it is not substantially exposed to potential contact with a fluid.

109. A large-scale array of sensor platforms wherein the array includes a plurality of sensor platform cells, each of which comprises

a sensor element comprising a patterned collection of a plurality of nanowires and having an electrical characterization;

a support structure for supporting the sensor element;

a conductive element located apart from the sensor element to form a structure in which the conductive element and sensor element are in a capacitive relationship;

control circuitry to electrically sense an electrical value reflecting the capacitance associated with the sensor element and the conductive element.

110. The large-scale array of claim 109 wherein the sensor element comprises at least one nanotube.

111. A sensor platform, comprising

a sensor element comprising a patterned collection of a plurality of nanowires and having an electrical characterization;

a support structure for supporting the sensor element;

first and second conductive elements that contact the sensor element at separate locations;

control circuitry to electrically sense a value reflecting the resistance associated with the passage of current between the conductive elements through at least a portion of the sensor element.

112. The sensor platform of claim 111 wherein the sensor element comprises at least one nanotube.

113. The sensor platform of claim 111 wherein the sensor element is substantially surrounded by support structure material so that it is not substantially exposed to potential contact with a fluid.

114. A large-scale array of sensor platforms wherein the array includes a plurality of sensor platform cells, each of which comprises

a sensor element comprising a patterned collection of a plurality of nanowires and having an electrical characterization;

a support structure for supporting the sensor element;

first and second conductive elements that contact the sensor element at separate locations;

control circuitry to electrically sense a value reflecting the resistance associated with the passage of current between the conductive elements through at least a portion of the sensor element.

115. The large-scale array of claim 114 wherein the sensor element comprises at least one nanotube.

116. A method of making a sensor, comprising:

providing a support structure comprising a substrate;

providing a collection of a plurality of nanowires on the substrate;

defining a pattern within the nanowire collection such that the pattern corresponds to a sensor element;

removing a portion of the collection so that patterned portion of the collection remains on the substrate to form a sensor element comprising a patterned collection of a plurality of nanowires and having an electrical characterization;

providing control circuitry to electrically sense the electrical characterization of the sensor element so that the presence of a corresponding analyte may be detected.

117. The method of claim 116 wherein the sensor element comprises at least one nanotube.

118. The method of claim 116 wherein the sensor element has an affinity for the corresponding analyte.

119. The method of claim 118 wherein the nanowires are pristine nanowires.

120. The method of claim 118 wherein the nanowires are derivatized to have or to increase the affinity.

121. The method of claim 118 wherein the nanowires are functionalized to have or to increase the affinity.

122. The method of claim 116 wherein the sensor element has an affinity for at least two analytes and wherein the plurality of nanowires includes at least two types of nanowires, a first type having an affinity for a first analyte and a second type having an affinity for a second analyte.

123. The method of claim 118 wherein the support structure includes a channel and wherein the sensor element is suspended to span the channel.

124. The method of claim 123 wherein the support structure includes a conductive electrode positioned in the channel, and wherein the sensor element is deflectable in response to the control circuitry to contact the electrode so that a gating effect of the nanowires in the sensor element may be electrically detected.

125. The method of claim 124 further including an upper electrode positioned above and separated from the sensor element.

126. The method of claim 116 further including defining a fluidic separator in fluid communication with the sensor element to deliver a fluid potentially having the analyte.

127. The method of claim 116 wherein the sensor element rests flat on the substrate.

128. The method of claim 118 wherein the sensor element is reusable in that, after exposure to the corresponding analyte, the sensor element can be substantially returned to its pre-exposure state by applying a voltage.

129. The method of claim 116 wherein the collection of nanowires is formed by growing the collection of nanowires on the substrate using a catalyst.

130. The method of claim 129 wherein, during the growing of the collection of nanowires, the nanowires are derivatized to have an affinity for a corresponding analyte.

131. The method of claim 129 wherein, during the growing of the collection of nanowires, the nanowires are functionalized to have an affinity for a corresponding analyte.

132. The method of claim 116 wherein the collection of nanowires is formed by depositing a solution of suspended nanowires on the substrate.

133. The method of claim 132 wherein the nanowires are derivatized to have an affinity for a corresponding analyte.

134. The method of claim 132 wherein the nanowires are functionalized to have an affinity for a corresponding analyte.

135. The method of claim 116 wherein the sensor element is made of pre-derivatized nanowires.

136. The method of claim 116 wherein the sensor element is made of pre-functionalized nanowires.

137. The method of claim 116 further comprising derivatizing at least a portion of the collection of nanowires.

138. The method of claim 116 further comprising functionalizing at least a portion of the collection of nanowires.

139. The method of claim 116 further comprising derivatizing the patterned collection of nanowires remaining on the substrate.

140. The method of claim 116 further comprising functionalizing the patterned collection of nanowires remaining on the substrate.

141. The method of claim 116, further comprising

providing a layer of covering material on one side of the collection of nanowires;

removing a portion of the covering material to expose a portion of the collection.

142. The method of claim 116, further comprising

providing a first layer of a first covering material on one side of the sensor element;

providing a second layer of a second covering material on one side of the sensor element;

removing a portion of the second covering material;

annealing portions of the first and second covering materials.

143. The method of claim 116 further comprising providing a conductive element located apart from the sensor element so that the sensor element and the conductive element have a capacitive relationship.

144. The method of claim 143 further comprising providing an insulating layer between the conductive element and the sensor element.

145. The method of claim 143 wherein the control circuitry comprises current-mirror circuitry to allow a capacitance associated with the conductive element and the sensor element to be measured.

146. The method of claim 143 further comprising providing a reference capacitor to allow measurement of the capacitance associated with the sensor element and conductive element relative to the capacitance of the reference capacitor.

147. The method of claim 146 wherein the reference capacitor comprises both a second collection of nanowires and a second conductive element that is separate from the second collection of nanowires, so that the second collection of nanowires and the second conductive element have a capacitive relationship.

148. The method of claim 116 further comprising providing a first conductive element that contacts the sensor element at a first point and providing a second conductive element that contacts the sensor element at a second point, so that an electric current can run through the sensor element between the first and second conductive elements.

149. The method of claim 148 wherein the control circuitry comprises current-mirror circuitry to allow the resistance between the first and second contact points to be measured.

150. The method of claim 148 further comprising providing a reference resistor to allow measurement relative to the resistance of the reference resistor of the resistance associated with current running through the sensor element between the first and second conductive elements.

151. The method of claim 150 wherein the reference resistor comprises both a second collection of nanowires and third and fourth conductive elements that contact the second collection of nanowires at separate points, so that an electric current can run through the sensor element between the third and fourth conductive elements.

152. A method of making a capacitive structure, comprising

providing a support structure comprising a substrate;

providing a collection of a plurality of nanowires on the support structure;

defining a pattern within the collection of nanowires such that the pattern corresponds to a sensor element;

removing a portion of the collection so that patterned portion of the collection remains on the substrate to form a sensor element comprising a patterned collection of a plurality of nanowires and having an electrical characterization;

providing a conductive element located apart from the sensor element to form a structure in which the conductive element and sensor element are in a capacitive relationship;

providing control circuitry to electrically sense a capacitance associated with the conductive element and the sensor element.

153. The method of claim 152 wherein the sensor element comprises at least one nanotube.

154. The method of claim 152 further comprising providing an insulating layer between the conductive element and the sensor element.

155. The method of claim 152 further comprising providing covering material in contact with the sensor element so that it is not substantially exposed to potential contact with a fluid.

156. A method of making a resistive structure, comprising

providing a support structure;

providing a collection of a plurality of nanowires on the support structure;

defining a pattern within the collection of nanowires such that the pattern corresponds to a sensor element;

removing a portion of the collection so that patterned portion of the collection remains on the substrate to form a sensor element comprising a patterned collection of a plurality of nanowires and having an electrical characterization;

providing first and second conductive elements that contact the sensor element at separate locations;

providing control circuitry to electrically sense a value reflecting the resistance associated with the passage of current between the conductive elements through at least a portion of the sensor element.

157. The method of claim 156 wherein the sensor element comprises at least one nanotube.

158. The method of claim 156 further comprising providing covering material in contact with the sensor element so that it is not substantially exposed to potential contact with a fluid.