SH-Wave Surface Acoustic Sensor for High-Viscosity Detection
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Solution Overview
Problem
Existing surface acoustic wave sensors face challenges in sensitivity, particularly when detecting particles or high-viscosity materials, leading to deterioration of sensor characteristics and reduced functionality.
Innovation Solution
A surface acoustic wave sensor configuration utilizing a high-order mode of SH waves with a piezoelectric substrate, IDT electrode, and a protection layer, where displacement at the surface of the protection layer is maximized, enhancing detection sensitivity and minimizing energy loss, even with liquid or high-viscosity materials.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Rayleigh wave or Sezawa wave with SV component displacement is used for excitation, then the sensor can detect pressure or temperature changes, but vibration energy propagates to the sample side causing large deterioration of characteristics
Solution Approach 1:
The patent changes the wave mode parameter from SV wave to SH wave, fundamentally altering the displacement characteristics. SH waves have particle displacement perpendicular to the propagation direction and parallel to the surface, eliminating the vertical component that causes energy loss to liquids. This parameter change resolves the contradiction by maintaining detection capability while preventing characteristic deterioration.
Solution Approach 2:
The patent converts the harmful effect of vertical displacement (which causes energy loss to samples) into a beneficial configuration by using SH waves where displacement is horizontal. The displacement that would otherwise be harmful is redirected to be parallel to the surface, maximizing sensitivity to mass changes while minimizing energy loss to the sample medium.
2Device complexity
If basic mode SH wave is used, then the sensor structure is simple, but detection sensitivity is insufficient for particles
Solution Approach 1:
The patent transitions from basic mode to high-order mode, adding a dimensional aspect to the wave configuration. High-order modes introduce additional displacement nodes and antinodes within the piezoelectric layer, creating regions of enhanced displacement amplitude at the surface. This dimensional enhancement increases detection sensitivity without fundamentally changing the sensor structure.
Solution Approach 2:
The patent utilizes mechanical vibration characteristics of high-order SH waves, where the displacement pattern includes multiple nodes and antinodes. The high-order mode creates larger displacement amplitudes at the surface compared to basic mode, enhancing the interaction between the acoustic wave and particle masses, thereby increasing detection sensitivity.
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 high-order mode configuration significantly increases detection sensitivity and maintains sensor functionality with minimal characteristic deterioration, compared to using basic modes or SV waves.
Implementation Method 1
surface acoustic wave sensor configured so as to be excited by the IDT electrode in a high-order mode of SH wave
Implementation Method 2
piezoelectric substrate, an IDT electrode provided on the piezoelectric substrate
Data Source
AI summary
A surface acoustic wave sensor that achieves increased detection sensitivity includes a piezoelectric substrate, an IDT electrode provided on the piezoelectric substrate, and a protection layer arranged on the piezoelectric substrate so as to cover the IDT electrode. The surface acoustic wave sensor is arranged so as to be excited by the IDT electrode in a high-order mode of an SH wave in which displacement at a surface of the protection layer and displacement near a boundary between the piezoelectric substrate and the IDT electrode have opposite directions, and the maximum displacement occurs at the surface of the protection layer.