PRINTED HYGROSCOPIC ELECTRODES FOR LOW-COST CAPACITIVE RELATIVE HUMIDITY SENSORS

• US 20200132616A1
• Filed: 10/31/2018
• Published: 04/30/2020
• Est. Priority Date: 10/31/2018
• Status: Active Grant

• Current Assignee: Xerox Corporation (Xerox Holdings Corp.)
• Original Assignee: Palo Alto Research Center, Inc. (Xerox Holdings Corp.)
• Inventors: Pierre, Adrien, Doris, Sean Emerson, Schwartz, David Eric
• Granted Patent: US 11,143,615 B2
• Time in Patent Office: Days
• CPC Class Codes: G01N 27/225 by using hygroscopic materials
• CPC Class Codes: G01N 27/605 for determining moisture content, e.g. humidity

Abstract

A capacitive relative humidity sensor includes a first electrode and a second electrode, where at least the one of the electrodes is a water-permeable electrode. The electrodes act in conjunction with a water-sensitive hygroscopic dielectric material. The design enables low-cost and simple fabrication of fast-responding and stable relative humidity sensors using digital fabrication techniques.

Claims

1. A method of forming a capacitive relative humidity sensor comprising:

optionally pre-treating a water absorptive dielectric layer;

depositing a first electrode on at least a portion of a surface of the water absorptive dielectric layer; and

depositing a second electrode on at least a portion of another surface of the water absorptive dielectric layer, wherein at least one of the first electrode and the second electrode is comprised of a water permeable material.

2. The method according to claim 1 wherein the second electrode is deposited across an entire surface of the water absorptive dielectric layer.

3. The method according to claim 1 wherein one of the deposition methods is one of inkjet printing and aerosol printing.

4. The method according to claim 1 wherein the water permeable material is a PEDOT:

PSS material.

5. The method according to claim 1 wherein a dielectric constant of the water absorptive dielectric layer changes with humidity, causing changes in capacitance between the first electrode and the second electrode.

6. The method according to claim 1 wherein a geometric parameter of the water adsorptive dielectric layer changes with humidity, causing changes in capacitance between the first electrode and the second electrode.

7. The method according to claim 1 further including treating the water absorptive dielectric prior to depositing the water permeable electrode, to increase the wetting of the water absorptive dielectric and/or to control the extent and rate of water uptake by the water absorptive dielectric layer.

8. The method according to claim 1 further including depositing a non-water absorptive dielectric between at least a portion of one of the surfaces of the water absorptive dielectric and one of the first electrode and the second electrode.

9. The method according to claim 1 further including

providing a carrier substrate;

the water absorptive dielectric layer being deposited on a surface of the carrier substrate; and

separating the water absorptive dielectric layer from the carrier substrate.

10. A method of forming a capacitive relative humidity sensor comprising:

depositing a first electrode on at least a portion of a substrate;

depositing a water absorptive dielectric layer on at least a portion of the first electrode;

optionally pre-treating the water absorptive dielectric layer; and

depositing a second electrode on at least a portion of the water absorptive dielectric layer, wherein the second electrode layer is made of a water permeable material.

11. The method according to claim 10 wherein one of the deposition methods is one of inkjet printing and aerosol printing.

12. The method according to claim 10 wherein the water permeable material is a PEDOT:

PSS material.

13. The method according to claim 10 wherein a dielectric constant of the water absorptive dielectric layer changes with humidity, causing changes in capacitance between the first electrode and the second electrode.

14. The method according to claim 10 wherein a geometric parameter of the water adsorptive dielectric layer changes with humidity, causing changes in capacitance between the first electrode and the second electrode.

15. A capacitive relative humidity sensor, comprising:

a water absorptive dielectric layer having a first surface and a second surface;

a first electrode positioned in contact with at least a portion of the first surface of the water absorptive dielectric layer; and

a second water-permeable electrode positioned in contact with at least a portion of the second surface of the of the water absorptive dielectric layer.

16. The capacitive relative humidity sensor according to claim 15 wherein the first electrode is a non-water permeable material.

17. The capacitive relative humidity sensor according to claim 15 wherein the first electrode is a water permeable material.

18. The capacitive relative humidity sensor according to claim 15 wherein the second electrode is deposited across an entire surface of the water absorptive dielectric layer.

19. The capacitive relative humidity sensor according to claim 15 wherein the deposition of the first and/or second electrodes is by one of inkjet printing and aerosol printing.

20. The capacitive relative humidity sensor according to claim 15 wherein the water permeable material is a PEDOT:

PSS material.

21. The capacitive relative humidity sensor according to claim 17 wherein the water permeable material is a PEDOT:

PSS material.

22. The capacitive relative humidity sensor according to claim 15 further including treating the water absorptive dielectric prior to depositing the water permeable electrode, to increase the wetting of the water absorptive dielectric and/or to control the extent and rate of water uptake by the water absorptive dielectric layer.

23. The capacitive relative humidity sensor according to claim 15 further including a non-water absorptive dielectric between at least a portion of one of the surfaces of the water absorptive dielectric and one of the first electrode and the second electrode.