Microfluidic Chlorine Sensor Using Colorimetric Detection
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Solution Overview
Problem
Current methods for measuring chlorine concentration in aqueous solutions, such as in swimming pools and municipal water, are either costly, require skilled operators, or are not suitable for field use due to pH interference and inability to differentiate between free and combined chlorine, leading to inaccurate disinfection efficiency and taste/odor issues.
Innovation Solution
A microfluidic device that mixes a solution sample with an indicator dye to produce a reduced dye concentration indicative of chlorine levels, allowing for optical measurement of free, combined, and total chlorine concentrations without the need for pH compensation, using separate modules for free and combined chlorine measurement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If amperometric methods are used to measure free chlorine continuously, then measurement precision is improved, but device complexity and cost increase, and operator skill requirements increase
Solution Approach 1:
The patent replaces complex electrochemical amperometric sensors with a simpler colorimetric system using indicator dyes and optical detection. The chemical reaction between chlorine and dye produces a color change that can be measured optically, eliminating the need for complex electrochemical cells and skilled operators while maintaining measurement capability
Solution Approach 2:
The patent changes the measurement parameter from electrical current (amperometric) to optical absorbance (colorimetric). By measuring the absorbance of light at specific wavelengths before and after the dye-chlorine reaction, the system achieves continuous chlorine monitoring with simpler, more cost-effective equipment
2Device complexity
If non-selective electrode ORP method is used, then device complexity is reduced, but measurement precision deteriorates due to inability to differentiate free and combined chlorine
Solution Approach 1:
The patent uses different indicator dyes with specific selectivity for different chlorine forms. DPD dye specifically targets free chlorine, while orthotolidine dye responds to combined chlorine, allowing differentiation of chlorine types through selective chemical reactions rather than relying on non-selective electrical potential measurements
Solution Approach 2:
The patent employs colorimetric detection where different dyes undergo characteristic color changes when reacting with different chlorine forms. DPD turns pink in the presence of free chlorine, while orthotolidine produces a blue-green color with combined chlorine, enabling visual and instrumental differentiation of chlorine types through color measurement
3Ease of operation
If DPD method is used for continuous chlorine monitoring, then ease of operation is improved, but reliability deteriorates due to reagent instability and narrow measurement range
Solution Approach 1:
The patent creates a multi-functional measurement system that can measure free chlorine, combined chlorine, and total chlorine using different dye combinations. The system can switch between measurement modes and use multiple dyes (DPD, orthotolidine, methyl orange) to handle different chlorine concentration ranges and water matrix conditions, enhancing reliability while maintaining ease of operation
Solution Approach 2:
The patent implements dynamic measurement capabilities where the system can adapt measurement parameters based on sample characteristics. Flow rates, reaction times, and dye concentrations can be adjusted to optimize measurements for different chlorine levels and water types, making the system both easy to operate and reliable across varying conditions
4Ease of manufacture
If traditional colorimetric methods are used, then cost is reduced, but measurement precision deteriorates due to pH interference requiring compensation
Solution Approach 1:
The patent introduces pH buffer solutions as intermediaries that control and stabilize the pH environment during the dye-chlorine reaction. By buffering the reaction medium, the system eliminates pH interference without requiring complex pH measurement and compensation systems, maintaining both low cost and high measurement precision
Solution Approach 2:
The patent optimizes reaction parameters including pH, temperature, and dye concentration to maximize the specificity and sensitivity of the colorimetric reaction. By controlling these parameters through buffered solutions and standardized procedures, the system achieves accurate chlorine measurements without expensive pH compensation equipment
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
Provides a cost-effective, user-friendly, and accurate continuous monitoring of chlorine levels, reducing pH interference and enabling real-time measurement of free, combined, and total chlorine, improving disinfection efficiency and water quality.
Implementation Method 1
expose an oxidant containing solution to a known amount of a dye which can be oxidised by the oxidant to produce an amount of an oxidised dye that is proportional to the amount of oxidant in solution
Implementation Method 2
the oxidised dye absorbs light at different wavelength(s) than the parent dye and a reduction in absorbance of the parent dye or an increase in absorbance of the oxidised dye can be used to measure the amount of oxidant in solution
Data Source
AI summary
A microfluidic device for measuring an amount of an oxidant in a solution is disclosed. The device includes a microfluidic substrate configured to mix a solution sample to be analysed with an indicator dye solution containing an indicator dye under conditions suitable for some of the indicator dye to react with any oxidant in the solution to produce an oxidant measurement solution having a reduced indicator dye concentration that is indicative of the amount of oxidant in the solution, the microfluidic substrate including an optical reading window through which the reduced indicator dye concentration in the oxidant measurement solution can be measured optically.