Lead-Free Piezoelectric Composite for Flexible Wearable Sensors

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Solution Overview

Problem

Current piezoelectric materials for wearable devices face challenges such as high weight, stiffness, brittleness, and limited design flexibility due to the use of lead-based ceramics, and lower piezoelectric performance in polymer materials, which hinders the development of flexible and efficient human-machine interaction devices.

Innovation Solution

A lead-free piezoelectric composite is developed, comprising a polymeric matrix with a dielectric constant greater than 30 and greater than 10 vol.% of a lead-free piezoelectric material, such as barium titanate or potassium sodium niobate, dispersed throughout, achieving an elastic modulus of less than 1 GPa and a piezoelectric coefficient d33 of greater than 20 pC/N, enabling higher flexibility and blocking forces.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If lead-based piezoelectric ceramics are used, then piezoelectric constants are improved, but weight and toxicity increase

Engineering Contradiction:

Improvepiezoelectric constantsVSAvoidweight

Core Design Contradiction:

PowerVSWeight of moving object

Solution Approach 1:

The invention extracts and removes the harmful lead component from piezoelectric ceramics, replacing it with lead-free ceramic particles dispersed in a polymer matrix. This extraction eliminates the weight and toxicity issues while preserving the piezoelectric functionality through the ceramic particles.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The invention creates a composite material system combining polymer and lead-free ceramic particles. The polymer matrix provides flexibility and light weight, while the ceramic particles contribute piezoelectric properties, achieving a balance between performance and the removed harmful characteristics.

Inventive Principle:

Principle #40Composite materials

2Power

If piezoelectric ceramics are used, then piezoelectric constants are improved, but mechanical flexibility and design adaptability deteriorate

Engineering Contradiction:

Improvepiezoelectric constantsVSAvoidmechanical flexibility

Core Design Contradiction:

PowerVSAdaptability or versatility

Solution Approach 1:

The composite structure combines the rigidity and piezoelectric properties of ceramic particles with the flexibility of the polymer matrix. This allows the material to be formed onto curved surfaces and integrated into flexible wearable devices while maintaining acceptable piezoelectric performance.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention creates local piezoelectric functionality within the flexible polymer matrix by dispersing ceramic particles throughout the material. This allows different regions to have appropriate properties for their specific functions while maintaining overall material flexibility.

Inventive Principle:

Principle #3Local quality

3Object-affected harmful factors

If lead-free piezoelectric ceramics are used, then toxicity is reduced, but piezoelectric constants deteriorate

Engineering Contradiction:

ImprovetoxicityVSAvoidpiezoelectric constants

Core Design Contradiction:

Object-affected harmful factorsVSPower

Solution Approach 1:

The composite material combines lead-free ceramic particles with a polymer matrix to achieve a synergistic effect. The lead-free ceramics provide non-toxic piezoelectric functionality, while the polymer enhances flexibility and processability, compensating for the lower piezoelectric constants of lead-free ceramics.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The invention optimizes parameters such as ceramic particle size, volume fraction, and polymer matrix composition to maximize piezoelectric performance in the lead-free composite system, achieving acceptable d33 values despite using non-toxic materials.

Inventive Principle:

Principle #35Parameter changes

4Adaptability or versatility

If piezoelectric polymer materials are used, then mechanical flexibility is improved, but piezoelectric response deteriorates

Engineering Contradiction:

Improvemechanical flexibilityVSAvoidpiezoelectric response

Core Design Contradiction:

Adaptability or versatilityVSPower

Solution Approach 1:

The invention creates a composite where polymer provides the flexible matrix and dispersed piezoelectric ceramic particles provide the electromechanical coupling. This combination achieves both mechanical flexibility for wearable applications and sufficient piezoelectric response for functional performance.

Inventive Principle:

Principle #40Composite materials

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

The composite provides enhanced mechanical flexibility and piezoelectric properties, reducing the thickness and manufacturing cost of wearable devices while maintaining performance at higher filler loadings and lower processing temperatures, making it suitable for flexible sensor applications and wearable devices.

Implementation Method 1

Flexible lead-free piezoelectric composites with high piezoelectric charge constant values

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a polymeric matrix having a dielectric constant greater than 30 at 20° C.

Methodology Applied

Scientific EffectDielectric polarization: Dielectric

Data Source

PatentUS20220158075A1Flexible and low cost lead-free piezoelectric composites with high d33 values

Publication Date: 2022.05.19 SABIC GLOBAL TECHNOLOGIES BV

AI summary

Lead-free piezoelectric composites and methods of making and uses thereof are described. The lead-free piezoelectric composites have high flexibility and high piezoelectric properties.