A Boundary Element Model for CMUT-Arrays Loaded by a Viscoelastic Medium

Area of Science:

• Acoustics
• Biomedical Engineering
• Materials Science

Background:

• Capacitive micromachined ultrasonic transducer (CMUT) arrays are crucial for medical ultrasound imaging.
• Accurate modeling of CMUTs requires considering the acoustic properties of surrounding media, including viscoelastic effects.
• Passivation layers on CMUTs, often silicon polymers, influence acoustic coupling and transducer response.

Purpose of the Study:

• To extend an existing CMUT array model by incorporating viscoelasticity effects of the propagation medium.
• To develop a new boundary matrix for simulating acoustic coupling between CMUT arrays and viscoelastic materials.
• To validate the model's predictions against experimental measurements of CMUT arrays loaded by fluids with varying viscosity.

Main Methods:

• Developed a new boundary matrix for simulating acoustic coupling with viscoelastic media.
• Implemented a 3-D Green's function for a viscoelastic half-space.
• Optimized numerical computations using vectorization and parallelization.
• Performed experimental validation using electrical impedance measurements of CMUT arrays in oils of different viscosities.

Main Results:

• The model successfully incorporates shear viscosity effects of the propagation medium.
• Observed a shift in resonance frequency and a decrease in the mechanical quality factor due to shear viscosity.
• Experimental validation showed excellent agreement with model predictions.

Conclusions:

• The enhanced model accurately accounts for shear viscosity effects in CMUT array simulations.
• This improved modeling is essential for accurate prediction of CMUT performance in applications involving viscoelastic loading, such as medical ultrasound.
• The study validates the importance of considering material viscoelasticity for CMUT transducer design and application.