Stretchable Fabric Sensor Arrays for Conformal Pressure Sensing

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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, especially in individuals with reduced sensation like those with diabetes.

Innovation Solution

Development of elastically stretchable fabric-like pressure sensor arrays using thin, flexible individual force sensors integrated into a matrix of rows and columns with conductive threads coated with piezoresistive material, allowing for conformability to irregular surfaces and minimizing cross-talk through diode-like circuit elements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If traditional rigid force sensor arrays are used, then measurement precision is maintained, but conformability to complex curved shapes deteriorates

Engineering Contradiction:

Improvepressure measurement accuracyVSAvoidconformability to curved shapes

Core Design Contradiction:

Measurement precisionVSAdaptability or versatility

Solution Approach 1:

The patent applies flexible thin films by integrating force sensors into a fabric substrate that can conform to curved surfaces. The fabric-based sensor array uses flexible conductive threads and elastomeric materials to maintain sensor functionality while adapting to complex geometries like the human foot, resolving the contradiction between measurement precision and conformability.

Inventive Principle:

Principle #30Flexible shells and thin films

Solution Approach 2:

The patent employs composite materials by combining piezoresistive elements with flexible fabric substrates and elastomeric coatings. This composite structure integrates the rigid sensing capability with the flexible adaptability needed to conform to curved surfaces, simultaneously achieving both measurement precision and shape conformability.

Inventive Principle:

Principle #40Composite materials

2Adaptability or versatility

If fabric-based stretchable sensors are used, then conformability to irregular shapes is improved, but measurement precision deteriorates due to elasticity

Engineering Contradiction:

Improveconformability to irregular shapesVSAvoidpressure measurement accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The patent applies parameter changes by carefully selecting and tuning the elastic properties of the fabric substrate and elastomeric materials. By controlling the stiffness, stretchability, and thickness parameters of these flexible components, the sensor maintains sufficient conformability to irregular shapes while minimizing deformation that would affect measurement precision.

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If conductive threads are closely spaced to reduce cross-talk, then measurement precision is improved, but manufacturing complexity increases

Engineering Contradiction:

Improvesignal isolation accuracyVSAvoidfabrication complexity

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent introduces insulating intermediary materials between closely spaced conductive threads to prevent electrical cross-talk. These insulating layers or coatings act as mediators that enable close spacing of conductive elements for improved measurement precision while maintaining manufacturability through standard fabric coating and lamination processes.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 mapping of pressure distributions on complex shapes, preventing tissue damage by providing timely feedback for adjusting footwear and reducing the risk of ulcers.

Implementation Method 1

each consisting of a central electrically conductive wire core covered by a layer of piezoresistive material which has an electrical resistivity that varies inversely with pressure exerted on the material

Methodology Applied

Scientific EffectPiezoresistive effect: Piezoresistive Effect

Implementation Method 2

elastically stretchable piezoresistive conductive threads

Methodology Applied

Scientific EffectElasticity: Elasticity

Data Source

PatentUS8161826B1Elastically stretchable fabric force sensor arrays and methods of making

Publication Date: 2012.04.24 PATIENTECH LLC

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.