Thin LN-LT YBAR Structure for Low-Loss Liquid Acoustic Sensing
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Solution Overview
Problem
Current film bulk acoustic resonators (FBARs) face challenges in liquid sensing due to high acoustic losses and require electric contacts on both sides of the piezoelectric membrane, limiting their usability in liquid environments.
Innovation Solution
The development of a Y-cut film bulk acoustic resonator (YBAR) with a piezoelectric plate attached to a substrate, featuring a floating back-side conductor pattern and a sensing layer, which allows for shear mode operation without electric fields in the sample medium, enabling high sensitivity and robustness in liquid environments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If FBARs use extension mode vibrations, then they can operate at high frequencies, but they cannot be used for liquid sensing due to high acoustic losses
Solution Approach 1:
The patent changes the vibration mode parameter from extension mode to shear mode, and changes the crystal cut orientation to Y-cut, which enables the resonator to operate in liquid environments with reduced acoustic losses while maintaining high frequency operation
Solution Approach 2:
The patent uses a composite structure combining Y-cut lithium niobate piezoelectric plate with specific electrode configurations and sensing layers, creating a resonator that combines high frequency capability with liquid environment compatibility
2Ease of operation
If FBARs require electric contacts on both sides of the piezoelectric membrane, then they can be electrically actuated, but their usability in liquid environments is limited
Solution Approach 1:
The patent removes the back-side electric contacts from the liquid-exposed surface, extracting the source of electrical interference and allowing the resonator to operate robustly in liquid environments while maintaining electrical actuation capability through front-side contacts only
3Measurement precision
If acoustic energy is transferred to the sample medium, then sensing can occur, but the flow becomes interrupted and sensitivity is reduced
Solution Approach 1:
The patent changes the acoustic mode from extension to shear mode, which fundamentally alters the coupling mechanism between the resonator and sample medium, enabling sensitive detection with minimal acoustic energy transfer that does not interrupt flow
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 YBAR sensor achieves high sensitivity and robustness in liquid environments with minimal acoustic energy transfer to the sample medium, allowing for uninterrupted flow and precise detection of target species, with frequency shifts measurable even for single molecular layers.
Implementation Method 1
a piezoelectric plate attached to a substrate
Implementation Method 2
shear mode operation without electric fields in the sample medium
Data Source
AI summary
Acoustic sensor devices and sensor systems are disclosed. An acoustic sensor device includes a piezoelectric plate having a front surface and a back surface. A floating back-side conductor pattern is formed on the back surface. A first and second front-side conductor patterns are formed on a portion of the front surface opposite the back-side conductor pattern. A sensing layer is formed over all or a portion of the floating back-side conductor pattern.