Curved Touch Sensor Electrode Strain Compensation

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Solution Overview

Problem

Thermoforming two-dimensional touch sensor panels into three-dimensional curved surfaces often results in strain and non-uniform touch electrodes, leading to distortion and inconsistent touch sensing performance due to the curvature and thermoforming process.

Innovation Solution

Designing a two-dimensional touch sensor panel with non-uniform area touch electrodes based on expected strain patterns for a given curved surface, and thermoforming it into a three-dimensional panel with uniform area touch electrodes, ensuring equal surface areas and reduced distortion through strain mapping and iterative adjustments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If a two-dimensional touch sensor panel with uniform area touch electrodes is thermoformed into a three-dimensional curved surface, then the manufacturing process is simple, but the touch electrodes become non-uniform and distorted

Engineering Contradiction:

Improvethermoforming process simplicityVSAvoidtouch electrode uniformity

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by pre-calculating and pre-distorting the two-dimensional touch electrode pattern according to the expected strain distribution during thermoforming. The non-uniform areas in the 2D pattern are deliberately designed to compensate for the distortion that will occur when formed into the three-dimensional curved surface, ensuring uniform touch electrode areas in the final product.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the parameter of touch electrode area from uniform (in the 2D pattern) to non-uniform (in the 2D pattern) to achieve uniformity in the final 3D formed product. This parameter transformation is based on strain analysis and finite element method calculations that predict the distortion behavior during thermoforming.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If the touch sensor panel is formed with highly curved surfaces, then the device design flexibility is improved, but the touch sensing performance becomes inconsistent

Engineering Contradiction:

Improvecurved surface design flexibilityVSAvoidtouch sensing consistency

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent applies local quality by making each touch electrode in the two-dimensional pattern have a locally adjusted area based on its position and the local strain characteristics. The non-uniform distribution of electrode areas in the 2D pattern compensates for the varying strain levels at different locations during thermoforming, ensuring uniform electrical properties and consistent touch sensing performance across the entire curved surface.

Inventive Principle:

Principle #3Local quality

3Device complexity

If uniform area touch electrodes are achieved in the three-dimensional panel, then the touch signal processing is simplified, but the two-dimensional pattern requires complex non-uniform design

Engineering Contradiction:

Improvetouch signal processing complexityVSAvoidtwo-dimensional pattern design

Core Design Contradiction:

Device complexityVSEase of manufacture

Solution Approach 1:

The patent replaces manual or trial-and-error mechanical design of the two-dimensional pattern with computational methods. Finite element method calculations and strain analysis are used to automatically generate the optimal non-uniform two-dimensional electrode pattern that will produce uniform three-dimensional electrodes after thermoforming, thereby simplifying the overall manufacturing process despite the complex-looking 2D pattern.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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 approach minimizes distortion and ensures uniform touch signal processing, simplifies algorithms, and reduces dynamic range requirements for sensing circuitry, enhancing the reliability and consistency of touch sensing on highly curved surfaces.

Implementation Method 1

a two dimensional touch sensor panel can be thermoformed (or curved by another process) to a three-dimensional touch sensor panel

Methodology Applied

Scientific EffectThermoforming:

Data Source

PatentUS11983370B2Spherical or highly curved touch-sensitive surfaces

Publication Date: 2024.05.14 APPLE INC

AI summary

A two dimensional touch sensor panel can be thermoformed or curved by another process to a three-dimensional touch sensor panel, and the three-dimensional touch sensor panel can be laminated to a three-dimension surface having a highly curved or spherical shape. In some examples, thermoforming a two-dimensional touch sensor panel into a three-dimensional touch sensor panel can result in strain of the touch electrodes, and can result in non-uniform three-dimensional touch electrodes (distortion of the two-dimensional touch electrode pattern). The strain can be a function of the curved touch-sensitive surface and/or process related mechanical strain from thermoforming. In some examples, a three-dimensional touch sensor panel can be formed with uniform area touch electrodes using a two-dimensional touch sensor panel pattern with non-uniform area touch electrodes in accordance with the strain pattern expected for a given curved surface and thermoforming technique.