Pressure-Based Force Sensing Using Sealed Cavity and MEMS
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Solution Overview
Problem
Conventional force and touch sensing systems in electronic devices are performance-limited in accuracy and resolution, require high-cost components, and have high power demands, making them inefficient and costly.
Innovation Solution
A pressure-based force and touch sensing system using a cavity with a pressure sensor that measures changes in cavity pressure caused by user input force, allowing for improved performance characteristics such as reduced power requirements and increased reliability, by employing micro electro-mechanical system (MEMS) components and a semi-sealed or sealed air cavity system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If capacitive-based force sensing systems are used, then force and touch sensing capability is achieved, but power consumption is high and measurement precision is limited
Solution Approach 1:
The patent replaces capacitive sensing with pressure sensing. Specifically, it uses a pressure sensor to detect changes in cavity pressure caused by touch forces, substituting the capacitive measurement mechanism with a pressure-based measurement mechanism that consumes less power and provides higher precision
Solution Approach 2:
The patent introduces a sealed cavity filled with gas (pneumatic system) between the touch surface and the pressure sensor. When force is applied to the touch surface, the cavity volume changes, causing pressure changes that are detected by the pressure sensor. This pneumatic mechanism enables high-precision force sensing with low power consumption
2Reliability
If conventional force sensing systems are used, then basic touch detection is achieved, but manufacturing cost is high due to complex components
Solution Approach 1:
The patent changes the measurement parameter from capacitance to pressure. By measuring pressure changes in a sealed cavity rather than capacitance changes, the system achieves higher reliability with simpler, more reliable pressure sensors instead of complex capacitive element assemblies
Solution Approach 2:
The patent extracts the sensing function from complex capacitive element assemblies and implements it through a simpler pressure sensor coupled with a sealed cavity. This extraction of the core sensing function to a simpler mechanism reduces component count and manufacturing complexity
3Measurement precision
If capacitive elements are used for force sensing, then touch input capability is achieved, but device complexity increases
Solution Approach 1:
The patent replaces complex capacitive element assemblies with a simple pressure sensor and sealed cavity system. The pressure sensor directly measures force-induced pressure changes without requiring complex capacitive structures, thereby reducing device complexity while maintaining or improving measurement precision
Solution Approach 2:
The pressure sensor serves multiple functions: it detects touch force magnitude, determines touch location, and can detect different touch intensities. This single pressure sensor replaces what would otherwise require multiple capacitive elements and associated circuitry, reducing overall system complexity
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 system achieves improved accuracy and reduced complexity, enabling detection of small force inputs with low noise, and reduces power consumption and costs while maintaining reliability.
Implementation Method 1
a pressure sensor coupled with the cavity and producing a cavity pressure measurement
Implementation Method 2
a moveable touch surface positioned adjacent the cavity and configured to increase the cavity pressure upon receipt of a user input force
Data Source
AI summary
An electronic device can include a force and touch sensing system. In one embodiment, an input force sensor device of an electronic device is disclosed.