CMUT With Substrate-Embedded Springs For Non-Flexural Plate Movement

Area of Science:

• Materials Science
• Mechanical Engineering
• Electrical Engineering

Background:

• Conventional capacitive micromachined ultrasonic transducers (CMUTs) exhibit limited displacement due to plate flexure and non-active anchored areas.
• This reduces overall transduction efficiency and deviates from ideal piston transducer behavior.

Purpose of the Study:

• To propose and validate a novel CMUT structure that achieves piston-like top plate translation.
• To enhance CMUT efficiency and fill-factor by redesigning the mechanical structure.

Main Methods:

• Utilized finite element analysis (FEA) for designing and simulating the proposed CMUT structure.
• Fabricated prototype single-element transducers and 1-D arrays using a simple 3-mask process.
• Characterized fabricated devices through electrical impedance measurements and acoustic pressure testing.

Main Results:

• Simulations predicted fractional bandwidths over 100% in immersion and >90% average plate displacement.
• Fabricated prototypes demonstrated resonant behavior and achieved a peak-to-peak acoustic pressure of 1.5 MPa.
• The novel design confirmed piston-like plate movement and improved fill-factor compared to conventional CMUTs.

Conclusions:

• The proposed CMUT structure successfully replicates ideal piston transducer functionality.
• This design offers significantly improved efficiency and performance by avoiding plate flexure.
• The simplified fabrication process and enhanced performance make it suitable for advanced ultrasonic applications.