Knitted Strain Sensor Core-Surface Yarn Architecture
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Solution Overview
Problem
Existing knitted strain sensors exhibit high hysteresis, limited working range, and poor breathability, making them unsuitable for on-body applications that require accurate strain measurement up to 30-40% with stability and washability.
Innovation Solution
A knitted strain sensor element combining an electrically conducting yarn with an elastic yarn, using a plated knitting technique and a 1×1 rib stitch pattern, where the conductive yarn forms the core and the elastic yarn forms the surface, reducing mechanical and electrical hysteresis and enhancing breathability and durability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If knitted structures are used for strain sensors, then stretchability and elastic recovery are improved, but hysteresis increases and sensing performance deteriorates
Solution Approach 1:
The patent combines conductive yarn and elastic yarn into a composite plated structure where the conductive yarn forms the core and elastic yarn forms the surface. This composite construction allows the sensor to achieve both high elastic recovery (85-95%) and low hysteresis (normalized electrical hysteresis < 0.05) by leveraging the complementary properties of the two yarn types.
2Adaptability or versatility
If working range is increased to 30-40% for on-body applications, then applicability is improved, but measurement accuracy deteriorates due to non-linearity
Solution Approach 1:
The patent achieves a linear resistance-strain relationship over an extended working range of 30-40% by optimizing the plated knitting structure with specific stitch patterns (1×1 rib, 2×2 rib). This structural parameter change enables the sensor to maintain measurement accuracy across the full working range required for on-body applications.
3Measurement precision
If impregnated textiles are used to reduce hysteresis, then measurement accuracy is improved, but breathability deteriorates and washability is compromised
Solution Approach 1:
The patent extracts the hysteresis-reducing function from chemical impregnation and achieves it through mechanical plated knitting structure alone. This eliminates the need for impregnation chemicals that would compromise breathability and washability, while still achieving normalized electrical hysteresis < 0.05 through the optimized core-surface yarn arrangement.
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 results in a hysteresis-free sensor with a large working range of at least 40%, high linearity, and improved durability, suitable for on-body applications such as respiratory monitoring and limb motion tracking.
Implementation Method 1
The elastic yarn has a Young's modulus that is substantially lower than the electrically conducting yarn's Young's modulus
Implementation Method 2
an electrically conducting yarn and an elastic yarn... the electrically conducting yarn forming a core of the knitted fabric
Implementation Method 3
a strain sensor with low hysteresis and a linear response over a working range of at least 40%
Data Source
AI summary
Embodiments in this disclosure relate to a knitted strain sensor element comprising an electrically conducting yarn and an elastic yarn. The elastic yarn has a Young's modulus that is substantially lower than the electrically conducting yarn's Young's modulus. The knitted strain sensor element is knitted using a knit stitch pattern comprising knitted stitches and purled stitches on each course. preferably a rib stitch pattern, more preferably a 1×1 rib stitch pattern. The electrically conducting yarn and the elastic yarn are knitted together using a plated knitting technique forming a knitted fabric. the electrically conducting yam forming a core of the knitted fabric and the elastic yarn forming surface of the knitted fabric. Sensors. textiles and garments comprising such knitted strain sensor elements are also disclosed.