Miniature high-frequency ultrasound transducers for magnetic soft continuum robot applications

Wang, Yifei (2026) Miniature high-frequency ultrasound transducers for magnetic soft continuum robot applications. PhD thesis, University of Glasgow.

Abstract

Intracorporeal high-frequency ultrasound (US) is a potentially important modality in modern medical diagnostics, offering superior resolution for internal anatomical structures. However, conventional delivery platforms, such as needles, catheters and capsules, are often constrained by their mechanical rigidity, which limits access to complex or tortuous anatomical regions. To address these limitations, magnetic soft continuum robots (MSCRs), composed of magnetic nanoparticles embedded within a silicone matrix, are emerging as a potential solution. These soft, compliant mechanisms can be remotely manipulated and actively steered via external magnetic fields, enabling non-invasive actuation for minimally invasive medical intervention.

This thesis establishes a proof-of-concept for this novel imaging platform, detailing the development and integration of miniature high-frequency US transducers with MSCR platforms. A 15 MHz single-element transducer was fabricated utilising PINPMN-PT single crystals and a 1-3 composite structure. The research investigates the integration methodology, specifically quantifying the mechanical influence of the transducer payload on the MSCR's deflection capabilities. The functional performance of the integrated system was validated through a progressive series of experiments: preliminary lateral proximity sensing via A-scan, axial imaging via sweep scanning in silicone phantoms, and the development of a dual-element configuration capable of lateral sensing and axial imaging. The clinical feasibility of the platform was demonstrated through rotational scanning in ex vivo porcine tissue and, finally, explored via in vivo trials in a porcine model.

Concurrently, to further enhance acoustic performance, the thesis explores the application of novel piezoelectric materials. With the emergence of rare-earth doping as a strategy to optimise electromechanical properties, the efficacy of Samarium-doped PIN-PMN-PT (Sm:PIN-PMN-PT) single crystals is explored. The influence of this advanced material was evaluated by fabricating and characterising both 1-3 composite single-element transducers and 1D linear arrays. Comprehensive testing included impedance magnitude and phase analysis, pulse-echo response and sensitivity and resolution measurements. This demonstrated that Sm:PIN-PMN-PT single crystals possess superior characteristics, identifying them as an excellent candidate for MSCR integration and the next generation of medical US imaging devices.

• Item Type: Thesis (PhD)
• Qualification Level: Doctoral
• Subjects: T Technology > TJ Mechanical engineering and machinery; T Technology > TK Electrical engineering. Electronics Nuclear engineering
• Colleges/Schools: College of Science and Engineering > School of Engineering
• Supervisor's Name: Cochran, Professor Sandy and Lam, Dr. Kwok-Ho
• Date of Award: 2026
• Depositing User: Theses Team
• Unique ID: glathesis:2026-86193
• Copyright: Copyright of this thesis is held by the author.
• Date Deposited: 24 Aug 2026 08:59
• Last Modified: 24 Aug 2026 08:59
• Thesis DOI: 10.5525/gla.thesis.86193
• URI: https://theses.gla.ac.uk/id/eprint/86193

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