Flexible Acoustic Sensor Stack for Reliable Curved-Surface Sensing

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Solution Overview

Problem

Existing flexible acoustic sensors, particularly in foldable devices, face challenges with signal strength and reliability due to their flexible and pliable nature, leading to performance limitations in fingerprint sensing and other biometric applications.

Innovation Solution

A method for fabricating flexible acoustic sensing apparatuses involves using a thin-film transistor device with a flexible substrate, coating a copolymer material to form a piezoelectric layer, and applying an electrode layer, followed by a laser liftoff process to separate the stack from a glass substrate, with protective layers to maintain cohesion and protect against mechanical stresses.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If flexible substrate is used for acoustic sensors, then adaptability to curved surfaces is improved, but signal strength and reliability deteriorate

Engineering Contradiction:

Improveadaptability to curved surfacesVSAvoidsignal strength and reliability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The patent employs a composite structure consisting of multiple functional layers including flexible substrate, piezoelectric layer, electrode layer, and protective layers. This composite material approach maintains flexibility while enhancing signal strength and reliability through the coordinated properties of each layer, directly resolving the contradiction between adaptability and reliability.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The patent utilizes thin film structures for the piezoelectric layer and electrode layer deposited on flexible substrate. These thin films maintain the flexibility needed for curved surfaces while providing sufficient acoustic sensing capability, thereby achieving both adaptability and reliability simultaneously.

Inventive Principle:

Principle #30Flexible shells and thin films

2Reliability

If protective layers are added to maintain cohesion, then reliability is improved, but device complexity increases

Engineering Contradiction:

Improveintegrity of sensor stackVSAvoidfabrication process complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The protective layers are applied at specific stages during the fabrication process before certain subsequent steps. This preliminary action ensures the sensor stack maintains its integrity throughout manufacturing without requiring complex post-processing or rework, thereby improving reliability while managing fabrication complexity.

Inventive Principle:

Principle #10Preliminary action

3Ease of manufacture

If laser liftoff process is used to separate from glass substrate, then ease of manufacture is improved, but risk of mechanical damage increases

Engineering Contradiction:

Improveseparation from glass substrateVSAvoidmechanical stresses and damage

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent employs protective layers as intermediary elements that shield the sensor stack during the laser liftoff process. These protective layers absorb and distribute the mechanical stresses generated during separation from the glass substrate, thereby facilitating easy manufacture while preventing damage to the delicate sensor components.

Inventive Principle:

Principle #24Intermediary (Mediator)

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 enables high-resolution acoustic sensing on curved surfaces, improving sensor performance and reliability in flexible devices by maintaining the integrity of the sensor stack and reducing fabrication costs.

Implementation Method 1

performing a poling process on the coated copolymer material to produce a piezoelectric layer, wherein the piezoelectric layer is configured to, responsive to receipt of an acoustic signal, provide an electrical signal

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

performing a laser liftoff (LLO) to separate the glass substrate from the TFT device having the flexible substrate

Methodology Applied

Scientific EffectLaser ablation: Laser Ablation

Data Source

PatentUS20260032398A1Flexible acoustic sensor systems and fabrication thereof

Publication Date: 2026.01.29 QUALCOMM INC

AI summary

Fabrication and processing of flexible acoustic sensor systems and various configurations of sensor stacks associated therewith are disclosed. In some embodiments, a method for fabrication of a flexible acoustic sensing apparatus may include: obtaining a stack of materials on a glass wafer, the stack of materials including: a thin-film transistor (TFT) component having a flexible substrate; a piezoelectric component on the TFT component, the piezoelectric component configured to, responsive to receipt of an acoustic signal, provide an electrical signal to one or more receiver elements having associated circuitry on the TFT component; and an electrode component on the piezoelectric component, the electrode component including one or more acoustic transmitter elements configured to transmit one or more acoustic signals; performing a laser liftoff (LLO) process to separate the stack of materials from the glass wafer; and implementing at least a portion of the stack of materials with a display component.