Humidity sensor element containing polyphenylsulfone
View Patent ↗A humidity sensor element for a humidity sensing device includes a rigid, p doped silicon substrate, a non-porous terminal on one side of the substrate, a porous terminal on a second side of the substrate, and a layer of polyphenylsulfone between the porous terminal and the substrate. The sensor elements displays improved linear response with humidity changes and very low hysteresis.
1. A sensor element for measuring humidity and which comprises a substrate of doped silicon, said substrate defining opposite first and second sides; a non-porous first terminal layer located on said first side of said substrate; a porous or permeable second terminal layer located on said second side of said substrate; and a humidity-sensitive sensor layer located between said substrate and said second terminal layer, said sensor layer comprising polyphenylsulfone.
2. A sensor element according to claim 1 , wherein said non-porous first terminal layer is composed of dual layers of chromium and gold.
3. A sensor element according to claim 2 , including a first layer of silicon oxide located between said substrate and said first terminal layer for adhering said first terminal layer to said substrate.
4. A sensor element according to claim 3 , including a second layer of silicon oxide located between said substrate and said sensor layer for adhering said sensor layer to said substrate.
5. A sensor element according to claim 4 , including an anchoring layer between said second layer of silicon oxide and said sensor layer.
6. A sensor layer element according to claim 5 , wherein said anchoring layer comprises aminosilane.
7. A sensor layer element according to claim 5 , wherein said anchoring layer comprises an amino polyamic acid.
8. A sensor element according to claim 5 , wherein said second terminal layer is made of gold.
9. A sensor element according to claim 8 , including an anchoring layer of tetraethyoxysilane/mercaptosilane between said sensor layer and said second terminal layer.
10. A sensor element according to claim 5 , wherein said second terminal layer is made of dual layers of chromium and gold.
11. A sensor element according to claim 5 , wherein said second terminal layer is formed of lampblack in a binder.
12. A sensor element according to claim 11 , wherein said binder is selected from the group consisting of polyethersulfone, a soluble aramid and a soluble polyimide.
13. A sensor element according to claim 12 , wherein said binder is a soluble aramid formed of a condensation product of bis(4-aminophenyl) ether and isophthaloyl chloride.
14. A sensor element according to claim 12 , wherein said binder is a soluble polyimide formed of a condensation product of 3,3′,4,4′-benzophenone tetracarboxylic diahydride and 5(6)-amino-1-(4-aminophenyl)-1,3,3′trimethylindane.
15. A sensor element according to claim 1 , including a vapor-permeable coating layer covering said second terminal layer.
16. A sensor element according to claim 1 , wherein said substrate is composed of p-doped silicon.
17. A sensor element according to claim 1 , wherein said sensor layer is between about 1 and 3 microns in thickness.
18. A sensor element according to claim 1 , wherein said sensor layer consist essentially of polyphenylsulfone.