Capacitive Force Sensing with Elastomeric Dielectric Layer
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Solution Overview
Problem
Existing force/proximity input devices have limitations in sensitivity and accuracy due to the limitations of current force sensors, which restrict their flexibility and usability.
Innovation Solution
The implementation of an elastomeric layer and a layer of rigid spacer dots between force transmitter and receiver electrodes, where the elastomer fills the volume between the spacer dots in response to applied force, changing the effective dielectric constant and capacitance, allowing for enhanced force sensing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional force sensors are used in proximity sensor devices, then the device can detect force in the Z direction, but the sensitivity and accuracy of force sensing are limited
Solution Approach 1:
The patent replaces conventional mechanical force sensors with a capacitive sensing mechanism. The force sensor layer includes transmitter electrodes and receiver electrodes that form capacitive elements, where force applied to the input surface changes the capacitance between electrodes. This electrical field-based approach substitutes mechanical sensing with electromagnetic field sensing, achieving higher sensitivity without mechanical complexity.
Solution Approach 2:
The patent changes the sensing parameter from mechanical displacement to electrical capacitance. By measuring capacitance changes between transmitter and receiver electrodes in response to applied force, the system achieves enhanced force sensing sensitivity. The capacitive measurement parameter provides more precise detection compared to traditional mechanical sensor parameters.
2Adaptability or versatility
If force sensing capability is added to proximity sensor devices, then multi-functional input capability is achieved, but the sensitivity and accuracy remain limited by current force sensor technology
Solution Approach 1:
The patent implements a unified sensor structure where the same force sensor layer with transmitter and receiver electrodes serves multiple functions: proximity sensing, touch detection, and force sensing. This multi-functional design achieves adaptability without requiring separate specialized sensors, while the capacitive mechanism provides accurate force measurement across all functions.
Solution Approach 2:
The force sensor layer uses a composite structure combining conductive elements (transmitter and receiver electrodes) with an elastomeric layer. This composite material approach integrates multiple functional properties: the conductive elements provide electrical sensing capability while the elastomeric layer provides mechanical compliance and force transmission, achieving both versatility and precision.
3Measurement precision
If the distance between transmitter and receiver electrodes is reduced to increase capacitance sensitivity, then force sensing sensitivity improves, but the device structure becomes more complex and harder to manufacture
Solution Approach 1:
The patent uses an elastomeric layer as a flexible intermediary between the transmitter and receiver electrodes. This thin film structure allows the electrodes to be positioned in close proximity (enhancing capacitance sensitivity) while the elastomeric material provides mechanical flexibility and ease of assembly. The flexible film structure is simpler to manufacture than rigid precision-spaced electrode assemblies.
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 enables improved force imaging and usability by accurately detecting changes in capacitance and dielectric constant, facilitating better sensitivity and accuracy in force sensing.
Implementation Method 1
the elastomer fills the volume between the spacer dots in response to applied force
Implementation Method 2
changing the effective dielectric constant between the transmitter and receiver electrodes as a function of applied force
Implementation Method 3
detect changes in capacitance resulting from i) the change in distance and ii) the change in effective dielectric constant between the transmitter and receiver electrodes
Data Source
AI summary
Methods, systems and devices are described for operating an electronic system which includes a first plurality of sensor electrodes disposed in a first layer and configured to detect input objects at an input surface of the input device, the first plurality of sensor electrodes including a first subset of transmitter electrodes; a second plurality of sensor electrodes configured to detect a force imparted to the input surface and configured for capacitive coupling with the first subset of transmitter electrodes; and a compressible dielectric configured to compress in response to force applied to the input surface. The capacitive coupling between the transmitter electrodes and the second plurality of sensor electrodes is configured to vary in response to the applied force.