Patent ID: 8783101
Filing Date: 2014-07-22
Classification: G01N

Abstract:
1. A capacitive humidity sensor having a substantially linear response and capable of detecting relative humidity in a full range of 0 to 100% relative humidity, the humidity sensor comprising: an aluminum substrate forming one electrode of the capacitive humidity sensor; an anodic aluminum oxide thin film formed from at least a portion of the aluminum substrate and having a thickness of 2-20 μm formed on a portion of the aluminum substrate, the anodic aluminum oxide film having channels with a channel diameter from 10 nm to 100 nm configured to adsorb water vapor from an ambient environment; and a porous metal layer formed on a portion of the anodic aluminum oxide film formed on the aluminum substrate, the porous metal layer forming a second electrode of the capacitive humidity sensor, the aluminum substrate, anodic aluminum oxide thin film and porous metal layer having undergone heat treatment to produce a substantially linear humidity versus capacitance sensor response, wherein said heat treatment is selected from one of the following conditions: a) annealing at a temperature of 85° C. for 5-50 hours at 90% relative humidity; b) annealing at a temperature of 90° C. for 5-50 hours in dry air; or c) immersion in boiling water at a temperature of 100° C. for 10-100 minutes; and wherein a response time of said capacitive humidity sensor is less than 6 seconds when the channel diameter is larger than 10 nm.