Advancing non-destructive testing with CMUT-based ultrasound imaging system: from submerged materials to industrial applications

Abdalla, Mohamed (2026) Advancing non-destructive testing with CMUT-based ultrasound imaging system: from submerged materials to industrial applications. PhD thesis, University of Glasgow.

Abstract

Capacitive Micromachined Ultrasonic Transducers (CMUTs) have emerged as a powerful alternative to conventional piezoelectric transducers for ultrasonic sensing and imaging, offering significant advantages in bandwidth, scalability, and CMOS process compatibility. However, their widespread deployment in non-destructive testing (NDT) and underwater sensing has been hindered by the reliance on bulky laboratory instrumentation, limited electronic integration, and inconsistent performance in submerged environments. This thesis presents the complete design, fabrication, and experimental validation of a miniaturised, low-power CMUT-based ultrasonic imaging and measurement system, developed to enable compact, field-deployable, and energy-efficient NDT applications.

At the core of this work is a custom-designed front-end electronic platform that integrates signal generation, amplification, acquisition, and digital processing within a single compact architecture. The printed circuit board (PCB) developed in this study provides tunable DC biasing, programmable pulse generation, and wideband amplification through dedicated analogue signal paths. The system incorporates a field-programmable gate array (FPGA) for deterministic timing control, high-speed sampling, and real-time signal processing using 14-bit, 125 MSPS analogue-to-digital converters. This integration eliminates the dependence on conventional laboratory hardware such as oscilloscopes, Bias-T, and waveform generators, achieving full system autonomy with dramatically reduced size, cost, and power consumption. Extensive experimental investigations were conducted to optimise CMUT excitation parameters, including the effects of pulse width (10–80 ns), frequency (2.5–5 MHz), polarity, and DC–AC signal interplay. The results reveal that the CMUT achieves optimal performance near 3 MHz with pulse widths above 30 ns, providing strong signal amplitude and reduced harmonic distortion. The removal of the Bias-T network further enhanced transmission efficiency and improved the signal-to-noise ratio. The system was validated through a series of underwater and NDT experiments employing both pulse–echo and pitch–catch configurations, demonstrating high measurement repeatability with standard deviations below 0.12 mm and coefficients of variation under 0.01%. The developed platform was subsequently extended into a fully functional ultrasonic imaging system, featuring FPGA-based A-, B-, and C-scan processing integrated with a motorised 3D scanning stage repurposed from an Ultimaker printer. Imaging experiments on submerged stainless-steel and aluminium specimens successfully identified geometric features, surface defects, and embedded structures with submillimeter accuracy, confirming the capability of the proposed system for underwater material inspection and defect detection.

In summary, this thesis delivers four primary contributions: the development of a compact, miniaturised PCB for CMUT biasing and signal control; an FPGA-based digital architecture for deterministic ultrasonic timing and acquisition; systematic CMUT characterisation and performance optimisation under submerged conditions; and the successful implementation of a portable CMUT-based NDT and imaging system. Collectively, these innovations advance the state of the art in ultrasonic engineering by demonstrating that CMUT-based systems can achieve high precision, reliability, and autonomy in real-world inspection and underwater applications.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Additional Information: Due to copyright issues this thesis is not available for viewing.
• Subjects: T Technology > T Technology (General)
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Supervisor's Name: Heidari, Professor Hadi
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-85762
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 19 Feb 2026 13:40
• Last Modified: 19 Feb 2026 13:40
• Thesis DOI: 10.5525/gla.thesis.85762
• URI: https://theses.gla.ac.uk/id/eprint/85762

Related URLs

• Conference proceeding