Force Sensor Using Low Resistivity Moderator Layers
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Solution Overview
Problem
Conventional force sensing devices rely on contact resistance, which makes them sensitive to changes in mechanical properties of interfacing materials, leading to instability in environmental conditions such as temperature changes.
Innovation Solution
A force sensing device with a first and second electrode layer of moderate and high resistivity, respectively, separated by an air gap and connected via low resistivity moderator layers, minimizing contact resistance and relying on macroscopic contact area for current flow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional force sensors use contact resistance as the key mechanism, then a changing resistance can be generated to detect force, but the sensor becomes sensitive to mechanical interface material changes (hardness, roughness) and environmental conditions (temperature), leading to instability
Solution Approach 1:
The patent introduces an air gap as an intermediary between the first and second electrode layers. This air gap acts as a mediator that eliminates direct contact between the electrodes, thereby removing the contact resistance mechanism that causes sensitivity to mechanical interface changes. The air gap allows force detection through macroscopic contact area changes while maintaining stability against environmental variations.
Solution Approach 2:
The patent replaces the mechanical contact resistance mechanism with an electrical field-based measurement mechanism. Instead of relying on physical contact and the resulting contact resistance, the invention uses changes in macroscopic contact area to modulate the electrical field and current flow between the electrodes, thereby detecting force without the instability associated with contact resistance.
2Power
If the first and second electrode layers are brought into direct contact under applied force, then current flow can be generated, but the current flow becomes dependent on contact resistance which varies with mechanical properties and environment
Solution Approach 1:
The air gap serves as an intermediary that allows current flow to be generated through field effects rather than direct contact. This intermediary structure enables power generation while eliminating the reliability issues associated with contact resistance variations.
Solution Approach 2:
The patent changes the fundamental parameter from contact resistance (which varies with mechanical properties) to macroscopic contact area (which provides stable, repeatable changes). By measuring current flow as a function of contact area rather than contact resistance, the system achieves both power generation and stability.
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 provides a stable force sensing device that is not dependent on contact resistance, maintaining accuracy across varying environmental conditions by using low resistivity moderator layers to control current flow based on macroscopic contact area changes.
Implementation Method 1
said first conductive material and said second conductive material each comprise a material having a substantially low resistivity, said low resistivity being lower than said first resistivity and said second resistivity, such that, when said first and second conductive materials are brought into contact under an applied force, the current flow between said first and second conductive materials is dependent on contact area between said first and second moderator layers
Data Source
AI summary
A force sensing device, comprises a first electrode layer comprising a material having a first resistivity and a second electrode layer comprising a pressure sensitive material having a second resistivity. The second resistivity is relatively high compared to the first resistivity. The first and second electrode layers are configured to be brought together under an applied force. A first conductive material is applied to the first electrode layer and a second conductive material is applied to the second electrode layer to produce first and second moderator layers, respectively. The first and second conductive materials each comprise a material having a resistivity lower than the first and second resistivities, such that, when the first and second conductive materials are brought into contact under the applied force, the current flow between the first and second conductive materials is dependent on the contact area between the first and second moderator layers.