Humidity sensor

• US 10,677,747 B2
• Filed: 02/17/2016
• Issued: 06/09/2020
• Est. Priority Date: 02/17/2015
• Status: Active Grant

• Current Assignee: Honeywell International Inc.
• Original Assignee: Honeywell International Inc.
• Inventors: Beck, Scott E., Moffat, Brian G.
• Primary Examiner(s): Sinha, Tarun
• Application Number:
  US15/551,841
• Publication Number:
  US 20180031510A1
• Time in Patent Office: 1,574 Days
• Field of Search: 7333504
• CPC Class Codes: G01N 27/225 by using hygroscopic materials

Abstract

Humidity sensors may exhibit a relatively small amount of hysteresis and/or a faster response time. In some cases, a humidity sensor may include a polymeric humidity sensing layer disposed over an electrode layer. The polymeric humidity sensing layer may include a halogenated layer disposed over the polymeric humidity sensing layer. The polymeric humidity sensing layer may, for example, include a polyimide and the halogenated layer may include a monolayer or less than a monolayer of a halogenated material such as a fluorinated material.

Claims

1. A humidity sensor comprising:

a substrate;

an electrode layer supported by the substrate, the electrode layer defining a first capacitive plate and a second capacitive plate;

a polyimide humidity sensing layer adjacent the electrode layer, the polyimide humidity sensing layer including a sensing surface and a thickness, and further including a number of openings formed within the sensing surface to increase an effective surface area of the sensing surface; and

the sensing surface of the polyimide humidity sensing layer being fluorinated to a depth that is less than the thickness of the polyimide humidity sensing layer, resulting in a fluorinated sensing surface,

wherein the electrode layer is adjacent a first side of the polyimide humidity sensing layer, and a porous platinum layer is adjacent a second opposing side of the polyimide humidity sensing layer, wherein the porous platinum layer in combination with the first capacitive plate and the second capacitive plate form a first capacitor and a second capacitor.

2. The humidity sensor of claim 1, wherein the fluorinated sensing surface is fluorinated by plasma deposition of C_xH_yF_z onto the polyimide humidity sensing layer, where x is an integer ranging from 1 to 4, y is an integer ranging from 0 to 2 and z is an integer ranging from 2 to 8.

3. The humidity sensor of claim 2, wherein the C_xH_yF_z comprises one or more of CF₄, C₂F₆, C₄F₈, CHF₃ and CH₂F₂.

4. The humidity sensor of claim 1, wherein the fluorinated sensing surface comprises a monolayer or a partial monolayer.

5. The humidity sensor of claim 1, wherein the fluorinated sensing surface comprises a heterogeneous mixture of fluorocarbons and hydrofluorocarbons.