Flexible Film Pressing Force Sensor with Recessed Support
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Solution Overview
Problem
Existing pressing force sensors with unimorph structures expend most of the applied force on deformation energy of the substrate, and resistors experience both compressive and tensile stresses, requiring symmetrical resistance changes, which complicates detection and increases costs.
Innovation Solution
A pressing force sensor with an expandable film and a support structure featuring recesses or holes, where a resistor membrane is formed on the film's surface, allowing for deformation and resistance value changes to be detected, using a bridge circuit with resistances provided by the same film to reduce variations and improve sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a unimorph structure with a rigid insulating substrate is used, then the structural stability is improved, but most of the pressing force is expended on deformation energy of the substrate, reducing detection sensitivity
Solution Approach 1:
The patent replaces the rigid insulating substrate with a flexible film that has both insulating and expandable properties. This flexible film can deform under pressing force, allowing the resistor to directly experience tensile stress and convert it into resistance changes, thereby improving detection sensitivity while maintaining structural stability through the film's inherent properties.
Solution Approach 2:
The patent employs a composite structure combining a flexible insulating film with resistor materials. This composite approach allows the film to provide both mechanical flexibility for deformation and electrical insulation, enabling efficient force transmission to the resistor while preventing unwanted electrical interference, thus resolving the contradiction between stability and sensitivity.
2Strength
If the resistor is subjected to both compressive and tensile stresses, then the structural response is improved, but symmetrical changes in resistance are required, complicating detection
Solution Approach 1:
The patent positions the resistor specifically on the tensile side of the flexible film, where it experiences only tensile stress during pressing operations. This asymmetric positioning eliminates the need to handle symmetrical resistance changes from both compression and tension, simplifying the detection circuit and signal processing while maintaining adequate structural response through the film's overall mechanics.
3Manufacturing precision
If all four resistances are provided by resistor membranes on the same film, then manufacturing variations are reduced, but the film must simultaneously provide both insulating and expandable properties
Solution Approach 1:
The patent uses a flexible film that simultaneously provides three critical functions: electrical insulation to prevent short circuits, mechanical expansion capability to transmit pressing force to the resistors, and structural support to maintain the sensor's integrity. This multi-functional material eliminates the need for separate insulating substrates and simplifies the overall structure while ensuring all four resistances are manufactured on the same film for consistent performance.
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
This configuration allows for low-cost, high-sensitivity detection of pressing forces with reduced power consumption and the ability to differentiate between compressive and tensile stresses, while minimizing the impact of temperature changes.
Implementation Method 1
a piezoelectric film disposed along the film. The piezoelectric film has two kinds of use. First, a sensor using a resistor like the pressing force sensor according to the present invention consumes current when detecting a pressing force
Implementation Method 2
a pressing force detecting resistor membrane formed on a portion of a main surface of the film... the film is expanded with the pressing force detecting resistor membrane. As a result, the pressing force detecting resistor membrane is deformed, and a change in resistance value of the pressing force detecting resistor membrane corresponding to the deformation is detected
Data Source
AI summary
A pressing force sensor that includes an expandable and contractible film, pressing force detecting resistor membranes formed on a portion of a main surface of the film, and a support disposed along the main surface of the film. The support is provided with recesses or holes with openings located in areas where the pressing force detecting resistor membranes on the main surface of the film are located. In the pressing force sensor, when a pressing force is exerted on the main surface of the film, the film is expanded with a pressing force detecting resistor membrane. As a result, the pressing force detecting resistor membrane is deformed, and a change in resistance value of the pressing force detecting resistor membrane corresponding to the deformation is detected.