Flexible Strain Gauge Layer Structure for Stable Resistor Formation
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Solution Overview
Problem
Strain gauges with flexible substrates face instability in gauge characteristics due to challenges in forming stable resistors, leading to issues with gauge factor, temperature coefficient of resistance, and resistance temperature coefficient.
Innovation Solution
A strain gauge design featuring a flexible substrate with a functional layer of metal, alloy, or metal compound, a resistor made of chromium or nickel, and an insulating resin coating, which promotes crystal growth and improves adhesion, stability, and resistance to oxidation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible substrate is used for the strain gauge, then the strain gauge can be applied to curved or flexible surfaces, but the resistor formation becomes unstable and gauge characteristics become unstable
Solution Approach 1:
A functional layer is introduced as an intermediary between the flexible substrate and the resistor. This functional layer serves as a mediator that promotes stable crystal growth of the resistor material while accommodating the flexibility of the substrate, thereby resolving the contradiction between substrate flexibility and resistor stability.
Solution Approach 2:
The strain gauge employs a composite structure consisting of multiple layers: flexible substrate, functional layer, and resistor layer. This composite material approach allows each layer to contribute its specific properties - the substrate provides flexibility, the functional layer promotes crystal growth, and the resistor layer provides stable electrical characteristics.
2Reliability
If a functional layer is added to promote crystal growth, then resistor stability improves, but the device structure becomes more complex
Solution Approach 1:
The functional layer is designed to perform multiple functions simultaneously: it promotes crystal growth of the resistor material, provides a stable interface between the flexible substrate and resistor, and contributes to the overall mechanical stability of the strain gauge structure. This multi-functionality justifies the additional layer by delivering multiple benefits from a single component.
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 solution enhances the stability of gauge characteristics, achieving a gauge factor of 10 or more and temperature coefficients within the range of -1000 ppm/°C to +1000 ppm/°C, while reducing pinholes and surface unevenness, thus improving the strain gauge's performance.
Implementation Method 1
a functional layer formed of a metal, an alloy, or a metal compound, on one surface of the substrate... promotes crystal growth
Implementation Method 2
an insulating resin layer with which the resistor is coated
Data Source
Figure 1~2
Figure 3A~3B
Figure 3C~4
AI summary
A strain gauge includes a flexible substrate; a functional layer formed of a metal, an alloy, or a metal compound, on one surface of the substrate; a resistor formed of material including at least one from among chromium and nickel, on one surface of the functional layer; and an insulating resin layer with which the resistor is coated.