Stretchable Force Sensing Sheet with Diode Layer to Reduce Cross-Talk
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Solution Overview
Problem
Existing force sensor arrays face challenges in accurately measuring pressures on human body parts, particularly on complex shapes like the feet, due to non-conformability and interference with support surfaces, and suffer from cross-talk inaccuracies in matrix addressing.
Innovation Solution
A flexible force sensing array is developed using an elastically stretchable sheet with conductive paths, a layer of piezoresistive material, and a semiconductive layer, allowing for precise measurement of physical forces and resistance variations, with a diode-like characteristic to reduce cross-talk.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible sensor array is used to measure pressures on the human body, then the array can conform to body surfaces, but the array interferes with the support surface function and gives erroneous measurements due to the hammocking effect
Solution Approach 1:
The patent uses a thin film substrate that is both flexible and drapable, allowing the sensor array to conform to complex body surfaces without the hammocking effect. The thin film nature enables precise conformability while maintaining accurate force measurements by not interfering with the support surface function.
2Device complexity
If wire core sensing elements are used in the sensor array, then the array structure is simplified, but the array becomes non-stretchable and cannot conform precisely to patient shape
Solution Approach 1:
The patent changes the mechanical parameters of the sensing elements by using elastically stretchable materials instead of rigid wire cores. This allows the array to be both simple in structure and highly adaptable to patient shape, resolving the contradiction between structural simplicity and conformability.
3Device complexity
If matrix addressing is used to measure sensor element resistances, then the measurement process is simplified, but cross-talk inaccuracies occur because non-addressed sensor elements shunt the resistance of addressed elements
Solution Approach 1:
The patent introduces an intermediate semiconductive layer that acts as a mediator between the sensing element layer and the conductive paths. This intermediate layer prevents direct electrical shunting between non-addressed sensors, eliminating cross-talk while maintaining the simplicity of matrix addressing.
4Measurement precision
If forces are measured on body parts with complex shapes like feet, then comprehensive pressure mapping is achieved, but the measurements become difficult and less accurate
Solution Approach 1:
The patent employs a flexible thin film sensor array that can drape over and conform to complex body parts like feet. This enables comprehensive pressure mapping on irregular surfaces while maintaining measurement accuracy and reducing the difficulty of detection.
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 enables accurate, non-invasive force measurement on irregularly shaped body parts without interfering with support surfaces and minimizes cross-talk errors, providing reliable data on pressure distribution.
Implementation Method 1
The layer of sensing material has an electrical characteristic that varies in response to physical forces exerted on it
Implementation Method 2
A flexible force sensing array is developed using an elastically stretchable sheet with conductive paths, a layer of piezoresistive material, and a semiconductive layer, allowing for precise measurement of physical forces and resistance variations, with a diode-like characteristic to reduce cross-talk
Data Source
AI summary
A support apparatus includes a force sensing array positioned thereon that includes multiple layers of material that are arranged to define an elastically stretchable sensing sheet. The sensing sheet may be placed underneath a patient to detect interface forces or pressures between the patient and the support structure that the patient is positioned on. The force sensing array includes a plurality of force sensors. The force sensors are defined where a row conductor and a column conductor approach each other on opposite sides of a force sensing material, such as a piezoresistive material. In order to reduce electrical cross talk between the plurality of sensors, a semiconductive material is included adjacent the force sensing material to create a PN junction with the force sensing material. This PN junction acts as a diode, limiting current flow to essentially one direction, which, in turn, reduces cross talk between the multiple sensors.