Tungsten Oxide Nanoparticle Gas Sensor for Methanol Detection

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Solution Overview

Problem

Existing combustible gas sensors face challenges in measuring high concentrations of gases like methanol, carbon monoxide, and ammonia due to low sensitivity and safety concerns, particularly in thick gas atmospheres where thermal conductivity sensors are ineffective and infrared absorption sensors are expensive.

Innovation Solution

A method using a tungsten oxide nanoparticle-containing film with a pair of electrodes, exposed to visible light, which measures electric resistance changes to determine gas concentration, avoiding the need for heating and enhancing sensitivity to reductive gases without the risks associated with thermal sensors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If thermal conductivity sensors are used to measure high concentration combustible gases, then safety is improved (no ignition risk), but sensitivity deteriorates (low sensitivity to gases with thermal conductivities near air)

Engineering Contradiction:

ImprovesafetyVSAvoidsensitivity

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent replaces the thermal conductivity measurement mechanism with a photoconductive mechanism. Instead of measuring thermal properties, the sensor uses a semiconductor layer that changes electrical resistance when exposed to light in the presence of combustible gases. This substitution allows detection of gases like methanol, carbon monoxide, and ammonia that have thermal conductivities similar to air, while maintaining safety by operating without high-temperature heating elements.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the detection parameter from thermal conductivity to electrical resistance. By measuring resistance changes in a semiconductor layer under light exposure rather than thermal conductivity changes, the sensor achieves high sensitivity to reductive gases while avoiding the ignition risks associated with thermal measurement methods.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If infrared absorption sensors are used to measure high concentration combustible gases, then sensitivity is improved, but cost deteriorates (expensive due to special optical parts)

Engineering Contradiction:

ImprovesensitivityVSAvoidcost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent replaces expensive infrared optical components with a simple semiconductor layer and basic light source. The photoconductive sensor uses readily available materials and standard electronic components, dramatically reducing manufacturing cost while maintaining high sensitivity to combustible gases through resistance measurement.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

Solution Approach 2:

The patent substitutes the complex infrared absorption measurement system with a simpler photoconductive resistance measurement system. Instead of requiring specialized infrared detectors and optical paths, the sensor uses a semiconductor layer whose electrical resistance changes in response to gas exposure under light, eliminating the need for expensive optical parts.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Reliability

If thermal conductivity sensors are used in high concentration gas atmospheres, then safety is improved, but measurement capability deteriorates (cannot measure high concentrations accurately)

Engineering Contradiction:

ImprovesafetyVSAvoidmeasurement capability

Core Design Contradiction:

ReliabilityVSMeasurement precision

Solution Approach 1:

The patent changes from thermal conductivity measurement to photoconductive resistance measurement. This parameter change enables accurate measurement of high gas concentrations because the resistance change in the semiconductor layer is proportional to gas concentration without the saturation and safety limitations inherent in thermal conductivity-based methods.

Inventive Principle:

Principle #35Parameter changes

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

This approach allows safe and sensitive measurement of high concentrations of combustible gases, including methanol, carbon monoxide, and ammonia, with improved safety and reduced sensitivity saturation, while being less affected by moisture and not requiring expensive optical components.

Implementation Method 1

exposing said film to light

Methodology Applied

Scientific EffectLight absorption: Absorption (EM radiation)

Implementation Method 2

measuring electric resistance change of said film before and after exposing said film to light

Methodology Applied

Scientific EffectPhotoconductivity: Photoconductivity

Data Source

PatentUS11609201B2Method for measuring combustible gas concentration, combustible gas sensor, and combustible gas sensor production process

Publication Date: 2023.03.21 KK TOSHIBA

AI summary

The embodiments provide a method making it possible to safely and inexpensively measure concentrations of combustible gases, such as methanol, at room temperature even in high concentration atmospheres, and also provide a sensor making it possible to carry out the above measurement method. The measurement method comprises:arranging a film containing nanoparticles of tungsten oxide and a pair of electrodes which are separated from each other and which individually keep in contact with said film in said atmosphere,exposing said film to light,measuring electric resistance change of said film before and after exposing said film to light, and determining said concentration based on said change.