Piezoresistive Strain Sensing in Foldable OLED Displays

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Solution Overview

Problem

Flexible electronic display panels face challenges in sensing strain and managing configuration changes due to bending, which can lead to degradation over time, including deformation, delamination, and moisture absorption, without effective monitoring and alert systems.

Innovation Solution

Incorporating piezoresistive sensors into the display panel to measure strain, with a display controller that determines bend angles and updates the panel's configuration, such as toggling power modes or alerting for replacement, based on recorded strain history.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If flexible display panels are used to enable bending and folding, then adaptability and versatility are improved, but reliability deteriorates due to strain-induced degradation

Engineering Contradiction:

Improvebending capabilityVSAvoidpanel durability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The system performs preliminary monitoring of strain accumulation before critical damage occurs. Piezoresistive sensors continuously measure strain in the flexible display panel, and the controller tracks historical strain data to predict potential degradation issues before they manifest as actual failures, enabling preventive maintenance actions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements a feedback loop where piezoresistive sensors provide real-time strain measurements to the controller, which then adjusts operational parameters or alerts users based on accumulated strain history. This closed-loop feedback mechanism allows the system to adapt to bending stresses and mitigate degradation through configuration changes.

Inventive Principle:

Principle #23Feedback

2Reliability

If strain monitoring systems are added to flexible display panels, then reliability is improved through degradation detection, but device complexity increases

Engineering Contradiction:

Improvedegradation detection capabilityVSAvoidsensor integration

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The piezoresistive sensors serve multiple functions: they monitor strain for reliability assessment, detect bend angles for configuration management, and provide data for both preventive maintenance and operational optimization. This multi-functionality reduces the need for separate sensor systems and justifies the added complexity through enhanced system capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The flexible display panel performs self-diagnosis through integrated piezoresistive sensors that continuously monitor its own strain conditions. The controller analyzes this self-generated data to detect degradation, manage configurations, and alert users, enabling the system to monitor and manage its own health without external intervention.

Inventive Principle:

Principle #25Self-service

3Reliability

If continuous strain monitoring is implemented, then reliability is improved through early degradation detection, but energy consumption increases

Engineering Contradiction:

Improvecontinuous monitoring accuracyVSAvoidsensor power consumption

Core Design Contradiction:

ReliabilityVSUse of energy by moving object

Solution Approach 1:

Instead of truly continuous monitoring, the system uses periodic strain measurements at defined intervals and event triggers (such as during bending operations or configuration changes). This periodic sampling approach maintains reliable degradation detection while significantly reducing the average power consumption compared to uninterrupted continuous monitoring.

Inventive Principle:

Principle #19Periodic action

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

Enhances operational features by managing power and detecting degradation, thereby extending the lifespan of flexible display panels by monitoring strain and adjusting operations accordingly.

Implementation Method 1

receiving sensor signals from one or more piezoresistive sensors disposed in the electronic display panel, determining an amount of strain in the electronic display panel based on the received sensor signals

Methodology Applied

Scientific EffectPiezoresistive effect: Piezoresistive Effect

Data Source

PatentUS11488499B2Strain sensing in foldable displays

Publication Date: 2022.11.01 SYNAPTICS INC

AI summary

A method and apparatus for sensing strain in a flexible electronic display. In some implementations, a display controller may be coupled to an electronic display panel. The display controller is configured to receive sensor signals from one or more piezoresistive sensors disposed in the electronic display panel, determine an amount of strain in the electronic display panel based on the received sensor signals, determine a bend angle of the electronic display panel based on the determined amount of strain, and update a configuration of the electronic display panel based at least in part on the determined bend angle. In some implementations, the electronic display panel may be an organic light-emitting diode (OLED) display panel. In some implementations, the electronic display panel may include a polycrystalline silicon (poly-Si) backplane disposed on a flexible substrate, where each of the piezoresistive sensors includes one or more strain gauges formed on the poly-Si backplane.