Stretchable Fabric Force Sensor Arrays for Curved Pressure Mapping
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Solution Overview
Problem
Existing force sensor arrays are not conformable to complex, compoundly curved shapes such as the human foot, leading to inaccurate pressure measurements and potential tissue damage from ill-fitting shoes, and they interfere with support surfaces like wheelchair seats or bed mattresses, causing erroneous force readings.
Innovation Solution
Elastically stretchable fabric-like pressure or force sensor arrays using thin, flexible individual sensors arranged in a matrix with conductive threads coated with piezoresistive material, allowing for conformability to irregular shapes and minimizing cross-talk through diode-like current-voltage transfer functions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If rigid or non-stretchable force sensor arrays are used, then manufacturing and structural stability are improved, but conformability to complex shapes and accuracy of pressure measurements deteriorate
Solution Approach 1:
The patent employs thin film piezoresistive sensor elements that are inherently flexible and can conform to complex, compoundly curved surfaces such as the human foot. These thin film sensors are embedded in a flexible substrate that allows the entire array to drap over irregular shapes while maintaining structural integrity and measurement accuracy.
Solution Approach 2:
The patent utilizes the piezoresistive effect where the electrical resistance of the sensor material changes in response to applied pressure. By measuring these resistance changes, the system can accurately determine pressure distributions on complex shapes. The flexible substrate parameters are designed to allow stretching and conforming without compromising the piezoresistive measurement capability.
2Adaptability or versatility
If stretchable conductive threads are used, then conformability to irregular shapes is improved, but cross-talk between adjacent sensors increases
Solution Approach 1:
The patent introduces insulating material as an intermediary between adjacent conductive threads and sensor elements. This insulating layer electrically isolates neighboring sensors while allowing the flexible substrate to stretch and conform to irregular shapes. The insulator prevents unwanted electrical coupling (cross-talk) between adjacent piezoresistive elements during deformation.
Solution Approach 2:
The use of thin film piezoresistive sensors with defined geometric boundaries and insulating borders ensures that when the flexible substrate stretches, the electrical fields of adjacent sensors remain confined to their respective regions, minimizing cross-talk while maintaining conformability to complex surfaces.
3Stability of the object's composition
If existing non-conformable sensor arrays are used on support surfaces, then structural stability is improved, but accuracy of force readings deteriorates due to interference with the support surface
Solution Approach 1:
The patent employs ultra-thin flexible sensor arrays that can be placed between the support surface and the body without significantly altering the mechanical properties of the support system. The thin film construction allows the sensor to conform to the interface between the support surface and body, accurately capturing pressure distributions without interfering with the natural deformation and force transmission of the support structure.
Solution Approach 2:
The patent replaces rigid, structure-interfering sensor arrays with flexible piezoresistive thin films that sense forces through electrical resistance changes rather than mechanical rigidity. This substitution allows accurate force measurement without the sensor itself becoming a mechanical obstacle that interferes with the support surface function.
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
Enables accurate measurement and mapping of forces on complex shapes like the human foot, preventing tissue damage and providing reliable data on pressure distributions without interfering with support surfaces.
Implementation Method 1
conductive threads coated with piezoresistive material
Data Source
AI summary
Force or pressure transducer arrays have elastically stretchable electrically conductive polymer threads disposed in parallel rows and columns that contact at intersections thereof a piezoresistive material which has an electrical resistivity which varies inversely with pressure or force exerted thereon to form a matrix array of force or pressure sensor elements. The threads are fixed to a single one or pair of flexible elastically stretchable substrate sheets made of thin sheets of an insulating polymer such as PVC, or for greater elasticity and conformability to irregularly-shaped objects such as human body parts, an elastically stretchable fabric such as LYCRA or SPANDEX. Elastic stretchability of the sensor arrays is optionally enhanced by disposing either or both row and column conductive threads in sinuously curved, serpentine paths rather than straight lines.