Filamentous Strain Sensor with Carbon Nanotube Bundles
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Solution Overview
Problem
Existing filamentous strain sensors are limited in detecting large stretch-contraction strains due to fragility and narrow measurement ranges, as they can be torn under great strain and have limited durability.
Innovation Solution
A strain sensor element with a first conductive portion formed from twisted carbon nanotube bundles and a second elastic conductive portion covering the first, which includes a resin composition and a conductive strip helically wound around the first portion, allowing for parallel and series connections that change resistance values with strain, enhancing detection accuracy and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conductor phase is formed by carbonizing the organic polymer material, then conductivity is achieved, but the sensor becomes torn when great strain is applied
Solution Approach 1:
The patent uses a composite structure consisting of carbon nanotube bundles (first conductive portion) embedded in an elastic conductive polymer matrix (second conductive portion). The carbon nanotubes provide strength and conductivity, while the elastic polymer provides flexibility and prevents tearing, resolving the contradiction between durability and resistance to tearing.
Solution Approach 2:
The patent creates different regions with different properties: the first conductive portion (carbon nanotube bundles) provides high strength and conductivity, while the second conductive portion (elastic polymer) provides flexibility and elasticity. This local differentiation allows the sensor to withstand great strain without tearing while maintaining conductivity.
2Measurement precision
If the first conductive portion is continuous, then low resistance is achieved, but the sensor cannot detect great stretch-contraction strain
Solution Approach 1:
The first conductive portion is intentionally made discontinuous with gaps between carbon nanotube bundle segments. These gaps allow the sensor to undergo large deformations without breaking the overall conductive path, enabling detection of great stretch-contraction strain while maintaining measurement precision through the elastic polymer's conductivity.
Solution Approach 2:
The discontinuous structure allows dynamic adjustment of the conductive path during deformation. As the sensor stretches, the gaps open and close, and the conductive polymer maintains electrical connection, enabling the sensor to adapt to large strain ranges while maintaining detection accuracy.
3Reliability
If the second conductive portion is made elastic and conductive, then great strain detection is enabled, but the structure becomes more complex
Solution Approach 1:
The patent merges the functions of elasticity and conductivity into a single second conductive portion made of elastic conductive polymer. This eliminates the need for separate elastic and conductive components, reducing structural complexity while enabling great strain detection.
Solution Approach 2:
The second conductive portion serves multiple functions simultaneously: it provides elasticity for large deformation, maintains conductivity for electrical connection, and prevents tearing of the overall structure. This multi-functionality reduces the number of components needed and simplifies the overall device structure.
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 strain sensor element effectively detects large stretch-contraction strains with improved accuracy and durability by changing resistance values through the combination of carbon nanotube bundles and an elastic conductive layer, preventing tearing and maintaining reliability under tension.
Implementation Method 1
a first conductive portion (1) that is filamentous and formed from carbon nanotube bundles twisted together
Implementation Method 2
a second conductive portion (2) that covers a peripheral surface of the first conductive portion (1) and is elastic and conductive
Implementation Method 3
the resistance value between both ends of the strain sensor element changes when the strain sensor element stretches or contracts
Data Source
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AI summary
Provided is a filamentous strain sensor element capable of detecting a relatively great stretch-contraction strain. The strain sensor element of which resistance value changes in response to stretch and to contraction in a longitudinal direction, includes: a first conductive portion that is filamentous and formed from a carbon nanotube bundle; and a second conductive portion that covers a peripheral surface of the first conductive portion and is elastic and conductive, in which the first conductive portion is discontinuous at one or a plurality of positions.