Flexible PZT-Based Row-Column Addressed 2-D PMUT Array.

Area of Science:

• Materials Science and Engineering
• Nanotechnology and Microsystems
• Acoustics and Ultrasonics

Background:

• Flexible piezoelectric micromachined ultrasound transducers (PMUTs) are crucial for advanced sensing applications.
• Existing fabrication methods often lack scalability or flexibility for wearable devices.
• Development of robust and efficient flexible PMUT arrays is essential for next-generation technologies.

Purpose of the Study:

• To report a novel row-column (RC) addressed flexible PMUT array.
• To demonstrate a top-down fabrication process suitable for flexible ultrasound devices.
• To characterize the performance of the flexible PMUT array for potential wearable applications.

Main Methods:

• Utilized a top-down fabrication process involving a temporary carrier wafer and deep reactive ion etching (DRIE).
• Employed sol-gel processed lead zirconate titanate (PZT) thin film (0.8 μm) as the active piezoelectric material.
• Integrated a 14 μm polyimide passive layer and fabricated sidewalls using reactive ion etching (RIE).

Main Results:

• Achieved resonance frequencies of 2.7 MHz (in-air) and 2.1 MHz (underwater) as measured by Laser Doppler Vibrometer (LDV).
• Demonstrated an in-air sensitivity of 1.2 nm/V with a 5-V DC bias.
• Measured an underwater pressure response of 40 Pa/V at 1 cm with a 10-V DC bias.

Conclusions:

• The fabricated flexible PMUT array exhibits promising performance characteristics.
• The device maintains functionality under bending (8-mm radius), indicating suitability for wearable applications.
• Further optimization is suggested for enhanced performance in shallow-depth underwater sensing.