ITO-Pt Thin-Film Strain Sensor for 500°C Aerospace Monitoring
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Solution Overview
Problem
Current high-temperature strain gauges have low operating temperatures (up to 200°C) and sensitivity (about 2), making them inadequate for accurately monitoring thermal stresses in aerospace components that operate in extreme conditions.
Innovation Solution
A high-temperature thin-film strain sensor with a composite indium tin oxide (ITO) and platinum (Pt) strain-sensitive grid, deposited on a substrate, forming a continuous S-shaped structure, which provides high sensitivity and stability up to 500°C, reducing the influence of thermal expansion on resistance measurements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If conventional metal foil strain gauges are used, then the structure is simple and easy to manufacture, but the operating temperature is limited to 200°C and sensitivity is low (about 2)
Solution Approach 1:
The patent uses a composite thin film structure consisting of an indium tin oxide (ITO) layer and a platinum (Pt) layer deposited in sequence. The ITO layer provides high temperature stability and electrical conductivity, while the Pt layer enhances sensitivity and strain response. This composite structure enables the strain gauge to operate at temperatures up to 500°C with a gauge factor exceeding 10, significantly improving both temperature resistance and sensitivity compared to conventional metal foil strain gauges.
Solution Approach 2:
The patent changes the material composition parameters by using ITO with specific indium oxide to tin oxide mass ratios (50:50, 90:10, or other proportions) and controls the thickness of each layer (ITO: 450-900 nm, Pt: 50-100 nm). By optimizing these parameters, the strain gauge achieves high sensitivity (gauge factor >10) and stable performance at high temperatures, resolving the contradiction between temperature capability and sensitivity.
2Measurement precision
If thin film preparation methods are used, then the sensitivity can be improved, but the manufacturing complexity increases and material selection becomes more restricted
Solution Approach 1:
The patent optimizes the deposition parameters by controlling the thickness of ITO (450-900 nm) and Pt (50-100 nm) layers, and by adjusting the indium oxide to tin oxide mass ratio in the ITO layer. These parameter optimizations enable the strain gauge to achieve high sensitivity (gauge factor >10) while maintaining compatibility with conventional thin film deposition equipment, thus improving sensitivity without excessively increasing manufacturing complexity.
Solution Approach 2:
The composite ITO-Pt thin film structure combines the advantages of both materials: ITO provides excellent temperature stability and electrical properties, while Pt enhances sensitivity and strain response. This composite approach achieves high sensitivity comparable to or better than conventional methods while using well-established thin film deposition techniques, balancing performance improvement with manufacturing feasibility.
3Temperature
If the strain gauge operates at high temperature, then thermal stress monitoring becomes possible, but temperature changes cause resistance changes and thermal expansion affects measurement accuracy
Solution Approach 1:
The composite ITO-Pt structure leverages the complementary properties of both materials: ITO has a negative temperature coefficient of resistance while Pt has a positive temperature coefficient. This compensation effect offsets each other's thermal resistance changes, stabilizing the overall resistance against temperature variations. Additionally, both materials exhibit stable thermal expansion characteristics that match the substrate, minimizing thermal expansion-induced measurement errors while enabling accurate strain measurement at temperatures up to 500°C.
Solution Approach 2:
The patent optimizes the ITO-to-Pt layer thickness ratio and indium oxide to tin oxide mass ratio to fine-tune the temperature compensation effect. By adjusting these parameters, the strain gauge achieves minimal net temperature coefficient of resistance, thereby maintaining measurement accuracy across a wide temperature range from -50°C to 500°C despite thermal expansion and resistance 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
The sensor achieves high sensitivity (gauge factor >10) and fast response time (<0.2 seconds) at 500°C, effectively measuring strain without significant thermal interference, outperforming conventional metal foil strain gauges.
Implementation Method 1
The resistance strain gauge is based on the resistance strain effect. The strain of the object being measured is obtained by detecting the change of resistance.
Implementation Method 2
ITO has a negative temperature coefficient, Pt has a positive temperature coefficient, and the positive and negative temperature coefficients of the laminated film offset each other. The resistance is relatively stable as the temperature changes
Implementation Method 3
the substrate transmits/conveys the strain of the cantilever beam to the strain-sensitive grid
Data Source
AI summary
The present disclosure relates to the field of strain sensors, and specifically relates to a high-temperature thin-film strain sensor, including a substrate and a strain-sensitive grid. The strain-sensitive grid includes an indium tin oxide layer and a platinum layer, the indium tin oxide layer is deposited on the substrate, and the platinum layer is deposited on the indium tin oxide layer. The indium tin oxide layer contains 50% by mass of indium oxide and 50% by mass of tin oxide. The high-temperature thin-film strain sensor provided by the present disclosure can be used in an environment from room temperature to 500° C., and have extremely high sensitivity at a high temperature of 500° C. Unlike the conventional metal foil strain gauge with a thickness of several microns, the high-temperature thin-film strain grid has a thickness of 500 nm, which can better convey the strain of the measured object at high temperature.