Hydrophilic Polymer Coated Waveguide for Humidity Sensing
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Solution Overview
Problem
Existing waveguide grating sensors for environmental monitoring face limitations such as low selectivity, dynamic range, accuracy, robustness, detection limit, sensitivity, and reproducibility, particularly in measuring moisture and other environmental conditions, due to issues like slow response times, non-specific refractive index changes, and susceptibility to environmental pollutants.
Innovation Solution
A waveguide with a polymer coating containing specific moieties, such as hydrophilic side-chains and crosslinked polymers, is used to enhance selectivity and sensitivity, featuring a unique spectral response for each grating, allowing for improved detection of environmental effects like humidity and pH, with a focus on higher accuracy and robustness through UV curing and optimized crosslinking.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a monolayer coating is used for humidity sensing, then the sensor can detect relative humidity changes, but the response time becomes relatively long and very high humidities cannot be measured
Solution Approach 1:
The patent changes the physical and chemical parameters of the coating material by using a polymer matrix with hydrophilic domains and hydrophobic domains, and by controlling the crosslinking density and porosity. This allows the coating to achieve both fast response time and measurement of very high humidities while maintaining good sensitivity.
Solution Approach 2:
The patent employs a composite coating structure consisting of a polymer matrix containing both hydrophilic domains (for water absorption) and hydrophobic domains (for structural stability). This composite approach enables the coating to achieve fast response to humidity changes while maintaining mechanical integrity and extending the measurable humidity range.
2Measurement precision
If a polymer coating is used to sense environmental effects, then the sensor achieves improved selectivity and sensitivity, but the preparation process becomes more complex
Solution Approach 1:
The patent applies preliminary action by pre-forming the polymer coating with the desired hydrophilic and hydrophobic domain structure before exposing it to the target analyte. The coating is pre-crosslinked and pre-structured to ensure consistent performance, which simplifies the overall manufacturing process while maintaining high selectivity and sensitivity.
Solution Approach 2:
The patent controls the preparation process by adjusting parameters such as polymer composition, crosslinking density, and coating thickness to achieve the desired balance between selectivity/sensitivity and ease of manufacture. This allows for reproducible coating formation through standardized processes.
3Measurement precision
If a thick hydrogel layer is used for sensing, then the sensor achieves high sensitivity, but it cannot be used in thin tubings and becomes susceptible to damage
Solution Approach 1:
The patent employs a thin film coating structure rather than a thick hydrogel layer. The coating is designed with appropriate thickness to maintain mechanical robustness for use in thin tubings while incorporating hydrophilic domains that provide high sensitivity to environmental changes. The crosslinked polymer network provides structural integrity.
Solution Approach 2:
The patent uses a composite polymer structure with interconnected hydrophilic and hydrophobic domains that provides both sensitivity and mechanical strength. The hydrophobic domains contribute to structural integrity and damage resistance, while the hydrophilic domains provide sensitivity to environmental effects.
4Measurement precision
If a coating with specific refractive index is used for Long Period Grating waveguides, then the sensor achieves good measurement performance, but the technology cannot be generally used on other waveguides
Solution Approach 1:
The patent develops a universal coating formulation based on polymer matrices with controlled crosslinking that can be applied to different types of waveguides (Long Period Grating, Fiber Bragg Grating, and other configurations). The coating's optical and mechanical properties can be adjusted to match different waveguide requirements, making the technology broadly applicable across multiple sensor platforms.
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 waveguide system with increased selectivity, dynamic range, accuracy, and robustness, enabling precise detection of environmental conditions with improved reproducibility and sensitivity, suitable for various applications including moisture and pH sensing.
Implementation Method 1
The polymer comprises an aliphatic chain of monomeric units, wherein at least one type of monomer contains a side-chain, in particular a hydrophilic side-chain
Implementation Method 2
The coating swells under the uptake of water
Implementation Method 3
The preparation of the sensor is cumbersome due to the slow deposition of the monolayer
Data Source
Figure 1
AI summary
The invention relates to a waveguide, comprising a grating in at least a part of the waveguide, which waveguide comprises a coating, the coating comprising a polymer, which polymer comprises an aliphatic chain, which aliphatic chain is provided with hydrophilic side-chains. The invention further relates to a sensor system comprising a waveguide according to any one of the preceding 10 claims, a light source, and a photo-detector.