Humidity Indicator Material Using Segmented Fibrous Sheets
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Solution Overview
Problem
Existing humidity indicator devices are complex to manufacture, prone to erroneous results, and not suitable for miniature applications, as they require manual work and cannot reliably detect temporary exposure to elevated relative humidity or liquid water, especially when the humidity has dropped below the critical level by the time of inspection.
Innovation Solution
A fibrous sheet laminated with a hot-melt adhesive and impregnated with a water-soluble dye and deliquescent salt, allowing for the formation of a colored solution that is absorbed by a second fibrous sheet, providing irreversible detection of elevated relative humidity and liquid water, even if the conditions have temporarily ceased.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If conventional humidity indicator devices are used, then they can detect humidity levels, but they are complex to manufacture and require manual work
Solution Approach 1:
The device is divided into two separate fibrous sheets: a first sheet containing the indicator composition (dye and deliquescent salt) and a second sheet that acts as the indicator element. This segmentation allows each sheet to be manufactured independently and simplifies the overall manufacturing process while maintaining functionality.
Solution Approach 2:
The first and second fibrous sheets are combined through lamination to form an integrated indicator device. The indicator composition in the first sheet interacts with moisture to form a colored solution that is absorbed by the second sheet, creating a unified detection system that is simple to manufacture yet effective.
2Reliability
If conventional humidity indicator devices are used, then they can indicate humidity exposure, but they are prone to erroneous results when humidity temporarily exceeds then drops below critical levels
Solution Approach 1:
The indicator composition in the first sheet is prepared in advance to detect and respond to humidity exposure. When moisture is present, the deliquescent salt dissolves the dye to form a colored solution that is immediately absorbed by the second sheet, capturing the humidity exposure event before it can be lost or reversed.
Solution Approach 2:
The device uses color change as the detection mechanism. The indicator composition contains a dye that, when dissolved by moisture-activated deliquescent salt, produces a visible color change on the second fibrous sheet. This color change provides a permanent visual record of humidity exposure that cannot be reversed even if humidity levels subsequently drop.
3Adaptability or versatility
If conventional humidity indicator devices are used, then they can detect humidity, but they are not suitable for miniature applications
Solution Approach 1:
By dividing the indicator device into two separate fibrous sheets with distinct functions, the design achieves miniaturization. The first sheet contains the reagent system while the second sheet provides the visual indicator, allowing the entire device to be compact yet maintain reliable detection functionality for miniature applications.
4Reliability
If reversible humidity indicators are used, then they can indicate current humidity levels, but they fail to indicate temporary past exposure to high humidity
Solution Approach 1:
The indicator system is designed to capture and permanently record humidity exposure events. The deliquescent salt and dye combination in the first sheet reacts to moisture by forming a colored solution that is absorbed by the second sheet, creating an irreversible visual record that preserves information about past humidity exposure even after conditions normalize.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables reliable, automatic detection of elevated relative humidity and liquid water, suitable for mass production and miniature applications, with the indicator material maintaining a positive detection result even after conditions have normalized.
Implementation Method 1
an indicator composition which comprises (c1) a water-soluble dye and, optionally, (c2) a deliquescent salt
Implementation Method 2
permeation of an aqueous solution from said first fibrous sheet to said second fibrous sheet is allowed
Data Source
AI summary
The present invention provides an indicator material suitable for detecting relative humidity exceeding a specific limit value and/or liquid water comprising (a) a first fibrous sheet containing an indicator composition which comprises a water-soluble dye and, optionally, a deliquescent salt, in finely divided form, and (b) a second fibrous sheet laminated to one surface of said first fibrous sheet by means of a hot-melt adhesive that does not cover the entire surfaces laminated to each other such that permeation of an aqueous solution from said first fibrous sheet to said second fibrous sheet is allowed. The invention also provides an indicator device comprising said indicator material on a carrier and a process for the manufacture of said indicator material and said indicator device.