Capacitive Shear Force Detection Using Substrate Translation
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Solution Overview
Problem
Existing proximity sensor devices have limited accuracy and complex construction in detecting applied forces, which restricts their ability to determine user input effectively, limiting their flexibility as input devices.
Innovation Solution
The use of a configuration with at least one sensor electrode on a first substrate that translates relative to a second substrate upon force application, forming variable capacitances with conductive portions, allowing for improved detection of tangential, normal, and rotational force components applied to the sensor surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If strain gauge load cells or piezoelectric crystal force transducers are used to detect applied force, then force detection capability is provided, but construction complexity increases and accuracy is limited
Solution Approach 1:
The patent replaces mechanical force sensors (strain gauges, piezoelectric crystals) with a capacitive sensing system. The first substrate with force sensor electrodes forms variable capacitors with conductive portions on the second substrate. When force is applied, the first substrate translates relative to the second substrate, changing the capacitance values. This electrical field-based measurement system eliminates complex mechanical sensor construction while providing accurate force detection through capacitance changes.
2Adaptability or versatility
If capacitance measurement is used to estimate applied force, then force detection is enabled, but accuracy is limited due to contact area changes only
Solution Approach 1:
The patent divides the sensing system into multiple force sensor electrodes (first, second, third, and fourth electrodes) arranged in specific patterns on the first substrate. Each electrode forms its own variable capacitor with corresponding conductive portions on the second substrate. By measuring capacitance changes from multiple segmented electrodes, the system can distinguish between different force components (normal, tangential, rotational) rather than just measuring total contact area, significantly improving force estimation accuracy and versatility.
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 enhances the ability of input devices to determine various force components, providing increased input functionality and accuracy for user interactions.
Implementation Method 1
A plurality of force sensor electrodes are disposed on the first substrate such that they overlap conductive portions of the second substrate and form variable capacitances with the conductive portions. A force applied to the input surface resulting in a translation of the first substrate relative to the second substrate changes the distance between (and/or the area of overlap between) the plurality of force sensor electrodes and the conductive portions of the second substrate.
Data Source
AI summary
An input device having a sensing region overlapping an input surface includes a first substrate, a second substrate physically coupled to the first substrate, and a sensor electrode disposed on the first substrate and configured to detect input objects in the sensing region. A first force sensor includes a first electrode disposed on the first substrate and a first conductive portion of the second substrate capacitively coupled with the first electrode. The first conductive portion is configured to move relative to the first electrode such that a first variable capacitance of the first force sensor changes in response to force applied to the input surface in a first direction parallel to the touch surface.