Single-cell system using monolithic PMUTs-on-CMOS to monitor fluid hydrodynamic properties

Area of Science:

• Materials Science and Engineering
• Microelectromechanical Systems (MEMS)
• Acoustic Transduction

Background:

• Traditional fluid monitoring systems often lack compactness and multi-parameter measurement capabilities.
• Piezoelectric micromachined ultrasonic transducers (PMUTs) offer potential for miniaturized sensing applications.
• Integrating fluid property sensing directly onto a single transducer chip remains a challenge.

Purpose of the Study:

• To present a single-cell fluid sensor capable of simultaneously measuring density, viscosity, sound velocity, and compressibility.
• To demonstrate a compact and integrated fluid measurement system utilizing advanced semiconductor fabrication.
• To validate the performance and novelty of the proposed piezoelectric micromachined ultrasonic transducer (PMUT) system.

Main Methods:

• Fabrication of a two-port AlScN PMUT using a 130 nm complementary metal-oxide semiconductor (CMOS) process.
• Utilizing a unique electrode configuration for single-device input and output.
• Experimental verification through analysis of frequency shift and amplitude variation in response to fluid property changes.

Main Results:

• Achieved a high sensitivity of 482 ± 14 Hz/(kg/m³) for density and viscosity measurements.
• Successfully extracted fluid sound velocity and compressibility using acoustic measurements.
• Demonstrated novel, simultaneous extraction of multiple fluid properties from a single PMUT device.

Conclusions:

• The developed single-cell PMUT sensor offers a compact and integrated solution for multi-parameter fluid analysis.
• The high sensitivity and novel measurement capabilities represent a significant advancement over existing PMUT systems.
• This technology holds promise for various applications requiring precise and miniaturized fluid characterization.