Multilayer Piezoelectric Actuator for Low-Power Bone Conduction

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Solution Overview

Problem

Individuals with conductive hearing loss often do not benefit from conventional hearing aids due to ear canal issues, malformed ears, or single-sided deafness, and bone conduction devices face challenges with power requirements and mechanical force generation.

Innovation Solution

A bone conduction device utilizing a multilayer piezoelectric element with passive layers and a mass component, which generates mechanical force for skull vibration using lower voltage electrical signals, reducing power consumption and improving force transmission.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional hearing aids are used for conductive hearing loss, then air conduction amplification is provided, but the device is unsuitable for individuals with ear canal inflammation, malformed ears, or single-sided deafness

Engineering Contradiction:

Improvesuitability for various hearing loss typesVSAvoidear canal inflammation and infection

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the acoustic air conduction system with a bone conduction system. Instead of transmitting sound through the ear canal and eardrum, the device uses a piezoelectric actuator to generate mechanical vibrations that are transmitted directly through the skull bones to the cochlea, bypassing the problematic ear canal and middle ear structures

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent introduces a bone conduction transducer as an intermediary between the sound signal and the cochlea. This transducer converts electrical signals into mechanical vibrations that are transmitted through the skull bones, serving as a mediator that avoids direct interaction with the inflamed or malformed ear canal structures

Inventive Principle:

Principle #24Intermediary (Mediator)

2Force

If bone conduction devices are used to bypass ear canal issues, then mechanical force is transmitted to the skull, but high power requirements and insufficient mechanical force generation occur

Engineering Contradiction:

Improvemechanical force for skull vibrationVSAvoidpower consumption

Core Design Contradiction:

ForceVSPower

Solution Approach 1:

The patent changes the electrical parameters by using low-voltage drive signals (1-5V) instead of high-voltage signals. This is achieved by optimizing the piezoelectric material properties and device geometry to achieve sufficient mechanical force output at low voltage, thereby reducing power consumption while maintaining adequate bone conduction force

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent employs composite piezoelectric structures combining multiple piezoelectric layers with different properties. This composite approach allows the device to generate higher mechanical force output from low-voltage inputs by leveraging the synergistic effects of different piezoelectric materials and their optimized layer configurations

Inventive Principle:

Principle #40Composite materials

3Power

If piezoelectric actuators are designed for bone conduction, then mechanical force is generated, but device complexity increases with multilayer structures

Engineering Contradiction:

Improvepower consumptionVSAvoidmultilayer piezoelectric structure

Core Design Contradiction:

PowerVSDevice complexity

Solution Approach 1:

The patent divides the piezoelectric actuator into multiple thin layers, each contributing to the overall mechanical force generation. This segmentation allows the device to achieve sufficient force output at low voltage while maintaining a compact and manageable structure. Each layer can be independently optimized and the modular design simplifies manufacturing and assembly

Inventive Principle:

Principle #1Segmentation

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 device effectively converts sound signals into mechanical force for skull vibration, providing hearing assistance with reduced power requirements and improved comfort, suitable for various types of hearing loss including single-sided deafness.

Implementation Method 1

The piezoelectric layers are configured to deform in response to application thereto of electrical signals

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

a mass component attached to the multilayer piezoelectric element so as to move in response to deformation of the piezoelectric element

Methodology Applied

Scientific EffectInertia: Inertia

Implementation Method 3

The coupling transfers mechanical forces generated by the multilayer piezoelectric element and the mass component to the recipient's skull

Methodology Applied

Scientific EffectMechanical force transmission: Mechanical Force

Data Source

PatentEP3829194B1Piezoelectric actuator and bone conduction device comprising the piezoelectric actuator

Publication Date: 2026.04.15 COCHLEAR LIMITED

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Figure 3A~3B

AI summary

piezoelectric actuator comprises a piezoelectric element comprising two stacked layers. The two stacked layers comprise: a piezoelectric layer, and a passive layer mounted to the piezoelectric layer. The piezoelectric layer is configured to deform in a longitudinal direction in response to application thereto of electrical signals generated based on the received sound signals, so that the centers of both layers deflect in a direction normal to the longitudinal direction.