Bipolar Loop Recovery for Piezoelectric Imprint Reduction

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Solution Overview

Problem

Piezoelectric devices experience degradation due to electrical charge accumulation at the interface between the piezoelectric layer and electrodes, leading to changes in properties like permittivity and capacitance, which affects their performance over time.

Innovation Solution

A bipolar loop recovery method is applied to the piezoelectric device, involving voltage biases with specific amplitudes and polarities that do not exceed the electric coercive field voltage, to reduce charge accumulation and restore degraded properties without causing fatigue.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If voltage pulses are applied to operate the piezoelectric device in performance mode, then the device generates physical movement and exerts force, but electrical charge accumulates at the interface between the piezoelectric layer and electrodes causing degradation

Engineering Contradiction:

Improvedevice output performanceVSAvoiddevice performance stability

Core Design Contradiction:

PowerVSReliability

Solution Approach 1:

The patent implements periodic bipolar loops between performance operation cycles. After a predetermined number of performance pulses or after a predetermined time period, a bipolar loop is applied to the piezoelectric device. This periodic recovery action prevents charge accumulation by periodically reversing the polarity, thereby maintaining device performance and reliability over extended operation.

Inventive Principle:

Principle #19Periodic action

2Reliability

If bipolar loop is applied to recover degraded performance, then charge accumulation is reduced and device properties are restored, but additional time is required for the recovery process

Engineering Contradiction:

Improvedevice performance recoveryVSAvoidrecovery operation time

Core Design Contradiction:

ReliabilityVSLoss of time

Solution Approach 1:

The bipolar loop is designed to apply voltage biases with amplitudes less than or equal to the electric coercive field voltage of the piezoelectric layer, which is a partial action compared to full performance-mode voltage pulses. This partial action is sufficient to reduce charge accumulation and restore degraded properties without requiring excessive time, thus balancing recovery effectiveness with time efficiency.

Inventive Principle:

Principle #16Partial or excessive action

3Productivity

If voltage amplitude exceeds electric coercive field voltage, then faster charge accumulation reduction occurs, but mechanical structure fatigue and degradation are caused

Engineering Contradiction:

Improverecovery speedVSAvoidmechanical structure integrity

Core Design Contradiction:

ProductivityVSStrength

Solution Approach 1:

The patent carefully controls the voltage amplitude parameter in the bipolar loop to be less than or equal to the electric coercive field voltage of the piezoelectric layer. This parameter change ensures that the recovery process is effective in reducing charge accumulation while preventing mechanical structure fatigue and degradation, thus maintaining both productivity and structural integrity.

Inventive Principle:

Principle #35Parameter changes

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 method effectively recovers and maintains the performance of piezoelectric devices by reducing charge accumulation, thereby improving their reliability and preventing mechanical structure degradation.

Implementation Method 1

A piezoelectric actuator can be utilized to create a physical movement that exerts a force on a physical part in a system under the control of an electrical signal

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

electrical charge accumulation at the interface between the piezoelectric layer and electrodes, leading to changes in properties like permittivity and capacitance... A bipolar loop recovery method is applied to the piezoelectric device, involving voltage biases with specific amplitudes and polarities that do not exceed the electric coercive field voltage, to reduce charge accumulation and restore degraded properties

Methodology Applied

Scientific EffectElectrical charge accumulation and bipolar loop recovery:

Data Source

PatentUS11856862B2Fatigue-free bipolar loop treatment to reduce imprint effect in piezoelectric device

Publication Date: 2023.12.26 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

In some embodiments, the present disclosure relates to a method in which a first set of one or more voltage pulses is applied to a piezoelectric device over a first time period. During the first time period, the method determines whether a performance parameter of the piezoelectric device has a first value that deviates from a reference value by more than a predetermined value. Based on whether the first value deviates from the reference value by more than the predetermined value, the method selectively applies a second set of one or more voltage pulses to the piezoelectric device over a second time period. The second time period is after the first time period and the second set of one or more voltage pulses differs in magnitude and/or polarity from the first set of one or more voltage pulses.