Surface Acoustic Wave Sensor with Rotated Y-Cut LiTaO3 Substrate
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Solution Overview
Problem
The sensitivity of surface acoustic wave sensors is limited by the structure of the surface acoustic wave element, and there is a need for improved detection of minute mass changes using SH-type surface acoustic waves.
Innovation Solution
A surface acoustic wave sensor with a rotated Y-cut LiTaO3 substrate and Au electrodes of specific normalized thickness, along with a reaction membrane and optional bonding and protective layers, is used to enhance sensitivity and accurately detect target substances by measuring frequency changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional surface acoustic wave elements are used, then the sensor structure is simple, but the sensitivity is limited and cannot detect minute mass changes effectively
Solution Approach 1:
The patent applies parameter changes by optimizing the normalized thickness of the Au electrode layer to specific ranges (0.5-2.0% for Rayleigh waves, 1.5-3.5% for SH waves) and selecting specific Euler angles (0° to 18° or 58° to 180°) for the Y-cut LiTaO3 substrate. These parameter optimizations enable the sensor to detect minute mass changes with high sensitivity while maintaining a relatively simple structure.
Solution Approach 2:
The patent utilizes mechanical vibration by employing surface acoustic waves (Rayleigh waves or SH waves) propagating through the LiTaO3 substrate. The interdigital transducers generate these mechanical vibrations, and the mass applied to the reaction membrane modifies the wave propagation characteristics, enabling detection through frequency or velocity changes.
2Measurement precision
If the electrode thickness is increased to improve signal strength, then the detection capability improves, but the normalized thickness becomes too large which reduces sensitivity
Solution Approach 1:
The patent resolves this contradiction by establishing optimal ranges for the normalized thickness parameter. For Rayleigh waves, the normalized thickness is optimized to 0.5-2.0%, and for SH waves, it is optimized to 1.5-3.5%. These parameter values balance the signal strength from sufficient electrode material with the sensitivity requirement of keeping the normalized thickness within optimal limits.
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 sensor achieves high sensitivity and precise detection of target substances by effectively utilizing SH-type surface acoustic waves, even when immersed in liquids, with the optimized structure allowing for reliable measurement of minute mass changes and temperature variations.
Implementation Method 1
electrodes, principally containing Au, for exciting a surface acoustic wave
Implementation Method 2
a piezoelectric substrate and a reaction membrane, placed thereon
Data Source
AI summary
A surface acoustic wave sensor for detecting a target substance by measuring the change in frequency due to the mass applied to a reaction membrane placed on a surface acoustic wave element having high sensitivity due to the improvement of the surface acoustic wave element structure. The surface acoustic wave sensor includes an SH-type surface acoustic wave and a rotated Y-cut LiTaO3 substrate having Euler angles (0°, 120° to 140°, 0°±5°); electrodes principally containing Au, for exciting a surface acoustic wave, the electrodes being arranged on the LiTaO3 substrate; and a reaction membrane bound to a target substance or a binding substance bound to the target substance covering the electrodes arranged on the LiTaO3 substrate. The interdigital transducers have a normalized thickness of about 3.0% to about 5.0%, the normalized thickness being determined by normalizing the thickness of the interdigital transducers by the wavelength of the surface acoustic wave.