Front-End Amplified polyCMUTs for Acoustic Emission Sensing of Carbon Fiber Reinforced Polymer

Thursday, May 8, 2025: 8:30 AM
Room 15 (Vancouver Convention Centre)
Mr. Jinhao Lu , The University of British Columbia, Vancouver, BC, Canada
Dr. Martin Angerer , The University of British Columbia, Vancouver, BC, Canada
Mr. Jonas Welsch , The University of British Columbia, Vancouver, BC, Canada
Prof. Robert Rohling , The University of British Columbia, Vancouver, BC, Canada
Prof. Edmond Cretu , The University of British Columbia, Vancouver, BC, Canada
Non-destructive test (NDT), particularly through acoustic emission (AE) sensing, plays a critical role in ensuring the structural health and integrity of various systems. However, traditional AE sensors based on piezoelectric materials are bulky, expensive, and limited in bandwidth, hindering their large-scale use in modern applications. In contrast, capacitive micromachined ultrasonic transducers (CMUTs) offer broader bandwidth, smaller form factors, and easier integration. The emerging technology of polymer-based capacitive micromachined transducers (polyCMUTs) allows for further cost reduction and rapid prototyping and fabrication times utilizing state-of-the-art microfabrication techniques.

In this study, we designed, fabricated, and integrated polyCMUT AE sensors with pre-amplifier integration to improve sensitivity, signal transmission and noise levels over longer distances. The electronics, including a bias tee and a charge amplifier (1 pC/V gain), were optimized for low noise, achieving an input-referred noise density of 2.33 nV/√Hz using the OPA818 operational amplifier.

Testing the passive polyCMUT sensors according to ISO 24543:2022(E) demonstrated a broad bandwidth (150 kHz to 1.7 MHz, with resonance at 1.3 MHz) and a tunable sensitivity, at levels comparable to commercial AE sensors. The pre-amplifier-integrated system achieved an off-resonance sensitivity of 3V/nm and an input-referred noise density of 2.8 nV/√Hz with an equivalent gain of 40 dB.

Our polyCMUT sensors have a significantly lower acoustic impedance (3.5 MRayl) compared to traditional piezoelectric AE sensors (~30MRayl). Our lower impedance leads to much better acoustic coupling with carbon fiber reinforced polymer (CFRP), which has an impedance of about 4 MRayl. This, combined with the sensor's compact design (20 x 14 x 5 mm³), cost-effectiveness, and scalability, makes our pre-amplified polyCMUT AE sensors a promising solution for large-scale monitoring of CPRP, especially in aerospace applications such as unmanned aerial vehicles (UAVs) and aircrafts.

See more of: UBC & DLR - Sensor Technology
See more of: Aeromat Technical Program