Concentric PMUT Membranes for Multi-Medium Ultrasonic Detection
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Solution Overview
Problem
Existing ultrasonic transducers face challenges in efficiently operating in both air and aqueous environments with high detection accuracy, particularly at greater distances and in media with high attenuation, such as air, while maintaining compact size and flexibility across various applications.
Innovation Solution
A PMUT ultrasonic transducer with a concentric ring structure featuring varying membrane widths and a deep buried cavity, allowing for multi-frequency operation and high-power acoustic wave emission and detection, capable of rapid switching between emission and detection modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ultrasonic transducers are used, then they can operate in aqueous environments, but they suffer from high attenuation and low detection accuracy in air
Solution Approach 1:
The transducer employs different membrane sections with different acoustic impedances: a first membrane section optimized for air coupling and a second membrane section optimized for liquid coupling. This local differentiation allows the single transducer to adapt to different propagation media, achieving high detection accuracy in both air and aqueous environments without requiring separate transducers for each medium.
Solution Approach 2:
The transducer is designed with dual functionality to operate effectively in both air and liquid environments. By integrating multiple membrane sections with different acoustic properties into a single device, it achieves universal applicability across different propagation media, eliminating the need for separate transducers for air and liquid applications.
2Measurement precision
If high-frequency acoustic waves are used for detecting small objects, then detection resolution improves, but attenuation in air increases significantly
Solution Approach 1:
The first membrane section is specifically designed with acoustic impedance optimized for air coupling, allowing high-frequency waves to be effectively transmitted into air with reduced attenuation. This localized optimization enables the system to maintain high detection resolution for small objects while minimizing energy loss in the air propagation path.
3Volume of moving object
If the transducer size is reduced for compact applications, then flexibility improves, but detection accuracy at greater distances deteriorates
Solution Approach 1:
The membrane is segmented into multiple sections with different acoustic impedances, allowing each section to contribute to different aspects of the detection function. This segmentation enables a compact overall structure while maintaining the acoustic performance needed for distant detection, as each segment is optimized for its specific function rather than requiring a single large uniform structure.
4Device complexity
If single-frequency transducers are used, then device simplicity is maintained, but multi-frequency operation capability is lost
Solution Approach 1:
Different membrane sections are designed with different acoustic impedances that resonate at different frequencies. The first membrane section is optimized for higher frequencies while the second is optimized for lower frequencies, allowing the single transducer structure to effectively operate across a broad frequency range without requiring multiple separate transducer elements.
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 PMUT transducer achieves high detection accuracy and sensitivity in high-attenuation media like air, with rapid response and compact size, enabling applications such as distance measurement and focused ultrasonic treatments.
Implementation Method 1
piezoelectric effects (piezoelectric MUTs, PMUTs)
Implementation Method 2
membranes capable of vibrating in both acoustic waves transmission condition and acoustic waves reception condition
Implementation Method 3
acoustic waves (in particular, ultrasounds at a frequency comprised between 20 kHz and 100 MHz) in fluid (liquid or gaseous) and/or solid propagation media
Data Source
AI summary
PMUT acoustic transducer formed in a body of semiconductor material having a face and accommodating a plurality of first buried cavities, having an annular shape, arranged concentrically with each other and extending at a distance from the face of the body. The first buried cavities delimit from below a plurality of first membranes formed by the body so that each first membrane extends between a respective first buried cavity of the plurality of first buried cavities and the face of the body. A plurality of piezoelectric elements extend on the face of the body, each piezoelectric element extending above a respective first membrane of the plurality of first membranes. The first membranes have different widths, variable between a minimum value and a maximum value.