Nanohole Copper Electrode Fatigue Resistance

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Solution Overview

Problem

Flexible devices with metal electrodes face reliability issues due to fatigue fracture under repetitive deformation, particularly in bendable or foldable applications where cyclic deformation exceeds 1 million times, and existing methods fail to effectively control crack formation and propagation.

Innovation Solution

A metal electrode with a nanostructure featuring nanoholes and nanopillars on a polyimide substrate, where the nanopillars penetrate through nanoholes and the metal electrode is composed of copper, enhancing fatigue resistance by distributing stress and blunting crack tips.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a metal electrode is used in flexible devices, then electrical conductivity and ease of processing are improved, but fatigue fracture occurs under repetitive deformation

Engineering Contradiction:

Improvefatigue resistanceVSAvoidcrack propagation resistance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent introduces a nanohole structure into the metal electrode, creating a porous material that absorbs stress during deformation. The nanoholes act as stress concentration points that prevent crack propagation by blunting crack tips and redistributing stress, thereby improving fatigue resistance while maintaining electrical conductivity

Inventive Principle:

Principle #31Porous materials

Solution Approach 2:

The patent creates a composite structure by combining the metal electrode with the nanohole pattern, effectively creating a metamaterial with enhanced mechanical properties. This composite approach allows the metal to maintain its electrical conductivity while the nanohole structure provides improved fatigue resistance and crack propagation control

Inventive Principle:

Principle #40Composite materials

2Reliability

If nanohole structure is introduced to improve fatigue resistance, then crack propagation is controlled, but manufacturing complexity increases

Engineering Contradiction:

Improvefatigue resistanceVSAvoidnanohole structure complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the continuous metal electrode structure by introducing discrete nanoholes at specific intervals. This segmentation approach controls crack propagation by creating barriers that stop crack growth, while the regular spacing and standardized sizes of nanoholes keep the manufacturing process manageable through pattern replication

Inventive Principle:

Principle #1Segmentation

3Adaptability or versatility

If metal electrode undergoes repetitive deformation, then flexible device operation is enabled, but electrical resistance increases due to crack formation

Engineering Contradiction:

Improvedeformation capabilityVSAvoidelectrical stability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent implements beforehand cushioning by pre-introducing nanoholes into the metal electrode structure before deformation occurs. These nanoholes act as predetermined stress relief zones that absorb deformation energy and prevent the formation of harmful cracks, thereby cushioning against electrical resistance increases during repetitive bending operations

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

Data Source

PatentUS9510445B2Member for flexible element and manufacturing method thereof

Publication Date: 2016.11.29 SEOUL NATIONAL UNIVERSITY R&DB FOUNDATION

AI summary

In the present invention, a copper electrode having a nanohole structure is prepared by using a polymer substrate in the form of nanopillars in order to avoid fatigue fracture that causes degradation of electrical and mechanical properties of a flexible electrode during repetitive bending of a typical metal electrode. The nanohole structure may annihilate dislocations to suppress the initiation of fracture and may blunt crack tips to delay the propagation of damage. Therefore, the nanohole electrode exhibits very small changes in electrical resistance during a bending fatigue test.