Gas Sensor Module Using pH Shift for Selective Low-ppm Detection
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Solution Overview
Problem
Current gas sensors face limitations in selectivity and sensitivity, particularly in detecting specific gases at low concentrations, due to crosstalk phenomena and lower sensitivity compared to the human olfactory system, making it difficult to accurately sense gases like volatile organic acids and ammonia at ppm levels.
Innovation Solution
A gas sensor module that dissolves target gases in an aqueous solution to sense pH changes, utilizing ion pairs with matching dissociation constants, and includes an electrochemical sensor with a working and reference electrode to enhance selectivity and sensitivity, with adjustable initial pH and ion concentrations for optimized sensing ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If semiconductor type gas sensor or electrochemical gas sensor is used, then gas sensing function is provided, but sensing selectivity is limited due to crosstalk phenomenon
Solution Approach 1:
The patent introduces an aqueous solution as an intermediary medium between the target gas and the sensor. The target gas first dissolves in the aqueous solution, undergoes chemical reaction to change pH, and then the pH change is detected by the electrochemical sensor. This intermediary approach eliminates direct crosstalk between different gases while maintaining detection capability.
Solution Approach 2:
The patent changes the detection parameter from direct gas concentration measurement to pH value measurement. By measuring the pH change of the aqueous solution caused by target gas dissolution and chemical reaction, the system achieves higher selectivity since pH is specifically affected by the target gas rather than other coexisting gases.
2Measurement precision
If conventional gas sensor is used, then gas detection is provided, but sensitivity is lower than human olfactory organ and difficult to sense gas at or below ppm level
Solution Approach 1:
The patent utilizes the phase transition of target gas from gas phase to dissolved state in aqueous solution. This phase change concentrates the target gas molecules in the liquid phase, enhancing the detection signal and enabling sensitivity at sub-ppm levels that exceeds human olfactory capability.
Solution Approach 2:
The patent replaces conventional direct electrical sensing mechanisms with a chemical-mechanical-chemical detection pathway: gas dissolution in liquid, chemical reaction causing pH change, and electrochemical detection of pH. This substitution enables higher sensitivity by leveraging the amplification effect of chemical reactions.
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 module achieves high selectivity and sensitivity in detecting target gases, such as volatile organic acids and ammonia, by leveraging pH changes in the aqueous solution, allowing for accurate determination of gas concentrations and improved resolution down to sub-ppm levels, effectively addressing the limitations of existing sensors.
Implementation Method 1
senses a pH change of the aqueous solution that occurs due to the target gas being dissolved in the aqueous solution
Implementation Method 2
dissolving the target gas in an aqueous solution to sense a pH change of the aqueous solution
Implementation Method 3
uses a method of sensing an amount of ions generated due to oxidizing/reducing a gas dissolved in an electrolyte
Data Source
AI summary
A gas sensor module, a refrigerator having the same and a control method for the refrigerator. In another aspect, in a gas sensor module, ion pairs are pre-dissolved in an aqueous solution while the amount thereof and pH of an initial aqueous solution may be adjusted to adjust a sensing range and sensitivity with respect to a target gas to be sensed. In another aspect, the gas sensor module senses the amount of target gas includes an aqueous solution in which ion pairs of a substance having the same dissociation constant as the target gas are dissolved, and senses a pH change of the aqueous solution that occurs due to the target gas being dissolved in the aqueous solution.