Lamb Wave Resonator for Fluid Element Detection
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Solution Overview
Problem
Conventional devices for detecting elements in fluid environments, such as those using surface acoustic waves, face challenges including high production costs due to the need for piezoelectric substrates and energy loss in aqueous environments, limiting their sensitivity and usability.
Innovation Solution
The device employs a piezoelectric stack with odd-numbered longitudinal upper electrodes and a single lower electrode to generate and measure symmetrical Lamb waves, allowing for effective detection of elements in a fluid medium without generating acoustic waves in the liquid, thereby enhancing sensitivity and reducing production costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If surface acoustic waves (SAW) are used for detection in fluid environments, then the device can operate in aqueous media, but energy loss occurs in water which greatly reduces sensitivity
Solution Approach 1:
The patent replaces surface acoustic waves (mechanical waves propagating along the surface) with Lamb waves (volume waves propagating through the thickness of the piezoelectric layer). This substitution changes the wave mode from surface-bound to volume-based, allowing the acoustic energy to be confined within the piezoelectric layer rather than propagating into the liquid medium, thereby reducing energy loss and improving detection sensitivity
Solution Approach 2:
The patent changes the wave propagation parameter by using Lamb waves with specific symmetry properties (antisymmetrical modes) that have displacement patterns perpendicular to the piezoelectric layer surface. This parameter change ensures that the acoustic waves do not propagate into the liquid, confining energy within the solid piezoelectric medium and preventing energy loss to the fluid environment
2Ease of manufacture
If piezoelectric substrates are used to generate Lamb waves, then detection in fluid environments becomes possible, but production costs increase due to non-standard substrate requirements
Solution Approach 1:
The patent segments the device into distinct functional layers: a standard silicon substrate, a piezoelectric layer deposited on top, and electrode structures. This segmentation allows the use of inexpensive, widely-available silicon substrates while adding piezoelectric functionality through thin-film deposition, making the device compatible with conventional microelectronics manufacturing processes
Solution Approach 2:
The patent employs a composite structure combining silicon substrate with piezoelectric materials (such as aluminum nitride or zinc oxide) deposited as thin films. This composite approach leverages the mechanical and thermal properties of silicon while incorporating the piezoelectric properties needed for Lamb wave generation, enabling cost-effective production through standard semiconductor manufacturing techniques
3Loss of energy
If antisymmetrical Lamb waves are used to prevent acoustic wave propagation in liquid, then energy loss is reduced, but only antisymmetrical modes are sufficiently slow which limits wave type options
Solution Approach 1:
The patent applies different electrode configurations to different regions of the piezoelectric layer to selectively generate specific Lamb wave modes. By localizing the excitation pattern (using interdigitated electrodes with specific finger arrangements and polarities), the device can excite antisymmetrical Lamb waves in targeted areas while maintaining the ability to operate in fluid environments
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
This approach enables efficient detection of elements in a fluid medium by maximizing elastic energy in the resonant structure, improving sensitivity and allowing direct use in aqueous environments, while being cost-effective and easy to produce.
Implementation Method 1
The resonator comprises means for generating Lamb waves... a piezoelectric stack delimited by two longitudinal lateral surfaces, the means for generating and measuring comprising an odd number of longitudinal upper electrodes... two adjacent upper electrodes having an opposite polarity
Implementation Method 2
The Lamb wave is a volume wave which can propagate in a plate, i.e. in a solid medium of very small thickness compared with its lateral dimensions. There are two types of Lamb waves, symmetrical Lamb waves and antisymmetrical Lamb waves.
Implementation Method 3
detection of elements in an aqueous environment can be performed by using the variation of the resonance frequency of an acoustic resonator... signals representative of the resonance frequency of the resonator
Implementation Method 4
When the device is immersed in several different fluid environments, molecules are liable to hybridize on the receptors grafted on each resonator. Should a molecule hybridize, the latter becomes attached to the resonator and modifies the resonance frequency thereof.
Data Source
AI summary
A device for detecting elements in a fluid environment includes at least one acoustic resonator having a surface designed for fixing of elements. The resonator is configured for generating and measuring Lamb waves fostering generation of symmetrical Lamb waves. The device analyzes the resonance frequency of the resonator to determine the variation of the resonance frequency of the symmetrical Lamb waves representative of the presence of the elements.