Capacitive Touch Force Sensing via Stiffness Ratio Optimization
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Solution Overview
Problem
Existing force/touch input devices are limited in accurately determining the position and intensity of applied force, which restricts their flexibility and usability.
Innovation Solution
A capacitive input device with a pliable component having bending stiffness overlaid on a compressible layer, where the ratio of bending to compression stiffness spreads the compressed region across multiple force receiver electrode locations, allowing for accurate interpolation of force data.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single compressible layer is used in force/touch input devices, then the device structure is simple, but the measurement precision of force position and intensity is limited
Solution Approach 1:
The compressible layer is divided into multiple sub-layers (first compressible layer and second compressible layer) with different compression stiffness values. This segmentation allows each sub-layer to contribute differently to force distribution, enabling more precise measurement of force position and intensity while maintaining a relatively simple overall structure.
Solution Approach 2:
Different regions of the compressible structure have different compression stiffness values. The first compressible layer has a first compression stiffness and the second compressible layer has a second compression stiffness, creating local variations in mechanical properties to achieve precise force mapping across the sensing surface.
2Measurement precision
If the bending stiffness to compression stiffness ratio is not optimized, then the compressed region concentrates on fewer electrode locations, but the force data interpolation accuracy decreases
Solution Approach 1:
The patent optimizes the ratio of bending stiffness to compression stiffness to ensure that when force is applied, the compressed region spreads across a sufficient number of force receiver electrode locations. This parameter optimization enables accurate interpolation of force data while maintaining device adaptability for various input scenarios.
3Measurement precision
If the compressed region is spread out over multiple electrode locations, then force data interpolation is enabled for accurate position determination, but the device complexity increases
Solution Approach 1:
The compressible layer is segmented into multiple sub-layers that collectively distribute the compressed region across multiple electrode locations. This segmentation approach enables force data interpolation for accurate position determination without requiring an excessive number of individual sensor elements, thus balancing precision with 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
Enables precise determination of force coordinate position and magnitude, enhancing the usability and accuracy of user interface inputs.
Implementation Method 1
a pliable component having a bending stiffness, the pliable component configured to deflect in response to force applied to an input surface
Implementation Method 2
a pliable component having a bending stiffness... configured to deflect in response to force applied
Implementation Method 3
a compressible layer having a compression stiffness... the resulting compressed region is spread out over a plurality of force receiver electrode coordinate locations
Data Source
AI summary
A device and method for operating a capacitive touch screen input device configured to sense input objects and their applied force in a sensing region, the device including a pliable component having an input surface and characterized by a bending stiffness, and first and second arrays of sensor electrodes. The input device further includes a third array of sensor electrodes and a spacing layer disposed between the third array. The pliable component is characterized by a compressive stiffness and configured to deform in response to a force applied to the input surface and to deflect the second array of sensor electrodes towards the third array of sensor electrodes, wherein the deformation of the input surface and the deflection of the second array of sensor electrodes is a function of the ratio of the bending stiffness of the pliable component and the compressive stiffness of the spacing layer.