Flexible Humidity Sensor With Moisture Barrier Layer
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Solution Overview
Problem
Flexible humidity sensors face challenges in maintaining accuracy and response time due to water vapor absorption by both the dielectric layer and the flexible substrate, leading to variations in capacitance that are not solely attributed to humidity changes.
Innovation Solution
A humidity sensor design incorporating a moisture absorption prevention layer with a low water vapor transmission rate, covering the substrate and electrodes, and featuring hydrophobic patterns and a dielectric layer to minimize substrate moisture absorption, thereby isolating capacitance changes to humidity variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible polymer substrate is used to support the capacitor, then the sensor achieves flexibility and wearability, but water vapor is absorbed by the substrate causing capacitance variations that reduce measurement accuracy
Solution Approach 1:
A moisture absorption prevention layer is introduced as an intermediary component between the flexible substrate and the dielectric layer. This layer acts as a mediator that blocks water vapor transmission while maintaining the flexibility of the overall structure, thereby preventing substrate moisture absorption from affecting capacitance measurements.
Solution Approach 2:
The patent employs composite material structures including the moisture absorption prevention layer made from materials such as Al2O3, ZnO, ZrO2, TiO2, HfO2, SiOx, SiNx, or SiOxNy. These composite materials provide both the barrier function against moisture and compatibility with the flexible substrate, resolving the contradiction between flexibility and measurement precision.
2Speed
If the dielectric layer is made thin to improve response time, then the sensor responds faster to humidity changes, but the sensor becomes more sensitive to substrate moisture absorption, reducing accuracy
Solution Approach 1:
The moisture absorption prevention layer serves as a protective intermediary that enables the use of thin dielectric layers without compromising accuracy. By blocking moisture at the substrate interface, it allows the dielectric layer to be sufficiently thin for fast response while preventing the sensitivity issue that would otherwise arise from substrate moisture absorption.
Solution Approach 2:
The moisture absorption prevention layer provides preliminary protection against moisture ingress before it can reach the dielectric layer and electrodes. This preemptive barrier prevents the harmful effects of moisture absorption, allowing the thin dielectric structure to function accurately and respond rapidly to humidity changes.
3Measurement precision
If hydrophobic patterns are added to the dielectric layer to prevent moisture accumulation, then measurement accuracy improves, but device complexity increases
Solution Approach 1:
Hydrophobic patterns are applied locally to specific regions of the dielectric layer rather than uniformly across the entire structure. This localized approach provides moisture prevention where most needed while maintaining simplicity in other areas, thus improving measurement precision without excessively increasing device complexity.
Solution Approach 2:
The hydrophobic patterns modify the surface energy parameters of the dielectric layer, creating regions with different wettability characteristics. This parameter change enables moisture to be directed away from critical sensing areas, improving accuracy while the patterned approach keeps the overall device complexity manageable.
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 provides a humidity sensor with high accuracy and rapid response time by preventing substrate moisture absorption, ensuring that capacitance changes are primarily due to humidity, thus enhancing dynamic accuracy and reaction rate.
Implementation Method 1
the moisture absorption prevention layer may have a water vapor transmission rate (WVTR) less than that of each of the flexible substrate and the dielectric layer
Implementation Method 2
a humidity sensitive dielectric layer formed on a flexible support to absorb or desorb water vapor according to humidity of surrounding environments
Implementation Method 3
featuring hydrophobic patterns and a dielectric layer to minimize substrate moisture absorption
Data Source
AI summary
A humidity sensor is provided. The humidity sensor includes a flexible substrate, a moisture absorption prevention layer covering the flexible substrate, a dielectric layer on the moisture absorption prevention layer, hydrophobic patterns on the dielectric layer, a first electrode between the moisture absorption prevention layer and the dielectric layer, and a second electrode spaced apart from the first electrode between the moisture absorption prevention layer and the dielectric layer. The first electrode has a thickness greater than that of the moisture absorption prevention layer.