Gas Sensor Thin-Film Heating Structure for Thermal Stress Cancellation

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Solution Overview

Problem

The deformation of the film structure in gas sensors due to thermal stresses caused by prolonged heating affects the detection sensitivity and stability of the sensor.

Innovation Solution

A sensor element with a double-layer structure comprising a first and second heating resistor, positioned on opposite sides of the thin film, where the thermal stresses induced by each resistor cancel each other out, preventing film deformation and ensuring stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a single heating resistor is used to heat the thin film, then the gas sensor can detect gases effectively, but thermal stresses cause deformation of the film structure and change in resistance characteristic

Engineering Contradiction:

Improvedetection sensitivityVSAvoidfilm structure stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The heating function is segmented into two separate heating resistors positioned on opposite sides of the thin film. This segmentation allows the thermal stresses to be independently controlled and canceled out, preventing film deformation while maintaining heating effectiveness for gas detection.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The second heating resistor acts as a counterweight to the first heating resistor by generating opposite thermal stresses. The thermal stress from the first resistor is canceled by the second resistor, effectively neutralizing the deformation effect while both contribute to heating the thin film.

Inventive Principle:

Principle #8Anti-weight (Counterweight)

2Measurement precision

If heating is applied to improve response and detection sensitivity, then the gas sensor becomes more sensitive, but prolonged heating causes thermal stresses leading to film deformation

Engineering Contradiction:

Improvedetection sensitivityVSAvoidfilm structure deformation

Core Design Contradiction:

Measurement precisionVSShape

Solution Approach 1:

Different regions of the thin film are heated locally by resistors positioned on opposite sides. The first heating resistor heats the lower surface while the second heating resistor heats the upper surface, creating localized thermal zones that cancel each other's deformation effects while maintaining overall heating for sensitivity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The invention utilizes thermal expansion effects by positioning heating resistors on opposite sides of the thin film. The thermal expansion stresses generated by each resistor are equal and opposite, causing them to cancel each other out and prevent net deformation of the film structure during prolonged heating.

Inventive Principle:

Principle #37Thermal expansion

3Stability of the object's composition

If a double-layer structure with two heating resistors is used, then thermal stresses cancel out and film deformation is prevented, but the device complexity increases

Engineering Contradiction:

Improvefilm structure stabilityVSAvoidheating resistor structure

Core Design Contradiction:

Stability of the object's compositionVSDevice complexity

Solution Approach 1:

Both heating resistors serve multiple functions: they generate thermal stress for cancellation, provide heating for gas detection, and their overlapping linear segments at end portions enable both stress compensation and thermal coupling. This multi-functionality reduces the need for additional compensation structures.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The harmful thermal stresses that would normally cause deformation are converted into a beneficial cancellation mechanism. By positioning the second heating resistor to generate opposite thermal stress, the harmful effect of thermal expansion is transformed into a useful stress compensation system that stabilizes the film structure.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

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 design significantly reduces thermal stress-induced deformation, stabilizing the resistance characteristics and ensuring stable performance of the gas sensor.

Implementation Method 1

The heating element can improve response of the gas sensor to gases and increase detection sensitivity

Methodology Applied

Scientific EffectJoule heating: Joule Heating

Implementation Method 2

the heat energy generated by the heating inside the gas sensor would cause thermal stresses, which may lead to a deformation of the film structure

Methodology Applied

Scientific EffectThermal stress: Thermal Expansion

Data Source

PatentUS20250297977A1Sensor element and gas sensor

Publication Date: 2025.09.25 TDK CORP

AI summary

The disclosure discloses a sensor element and a gas sensor, comprising a substrate and a thin film arranged on the substrate; The substrate is provided with a cavity and an opening in communication with the cavity; The thin film is supported on the opening and partially covers the cavity; The thin film comprises first and second heating resistors, each of which is shaped in a meander line, the first heating resistor is positioned on a side of the thin film near the cavity, and the second heating resistor is positioned on a side of the thin film away from the cavity; and a linear segment at an end portion of the first heating resistor is at least partially overlapped with a linear segment at an end portion of the second heating resistor, to allow the thermal stresses to cancel out each other.