Flexible Surface Acoustic Wave (SAW) Magnetic Sensor Based on Terfenol-D Grating-Arrayed Thin Polymer Film

Area of Science:

• Materials Science
• Sensor Technology
• Physics

Background:

• Traditional Surface Acoustic Wave (SAW) magnetic sensors fabricated on rigid substrates are limited in their application on curved or irregular surfaces.
• Conventional designs using continuous magnetostrictive layers suffer from hysteresis and residual magnetization errors.
• There is a need for flexible magnetic sensors capable of conforming to non-planar surfaces for advanced applications.

Purpose of the Study:

• To develop and characterize a novel flexible SAW magnetic sensor.
• To investigate the impact of a grating-arrayed magnetostrictive film on sensor performance.
• To demonstrate the sensor's functionality and reliability under mechanical deformation and stress.

Main Methods:

• Fabrication of a flexible SAW magnetic sensor using a grating-arrayed Terfenol-D thin film on a 50 µm thick flexible lithium niobate (LiNbO3) substrate.
• Experimental characterization of sensor sensitivity, frequency shift, and performance dependence on grating width and film thickness.
• Validation of sensor functionality under mechanical deformation and implementation of a differential measurement method for stress compensation.

Main Results:

• Achieved high sensitivity of 85.8 kHz/mT for devices with λ-wide gratings.
• Observed a maximum frequency shift of 377 kHz at 5 mT.
• Identified optimal performance with 500 nm thick gratings and confirmed sensitivity dependence on grating width and film thickness.
• Demonstrated robust sensor performance under mechanical deformation and effective stress compensation using a differential measurement method.

Conclusions:

• The developed flexible SAW magnetic sensor with a grating-arrayed Terfenol-D film overcomes limitations of rigid sensors.
• The grating structure aids in hysteresis compensation and minimizes measurement errors.
• The sensor exhibits high sensitivity, reliable performance under stress, and is suitable for conformable sensing applications.