Ultrasonic Needles based on Mn-doped Ternary Piezocrystals

Ternary piezocrystals is the name given to a new group of single crystal piezoelectric materials that have a much higher mechanical Q and much higher energy densities than the binary compositions. Ternary piezocrystals have properties that are now sufficient for enabling their incorporation in high power ultrasonic devices. Their doped counterparts are a very recent development offering previously unavailable properties. Most importantly for high power ultrasonic transducers, they have increased the mechanical Q from around 100 to nearly 1000. However, completely new ultrasonic transducer configurations are needed to exploit fully this increased performance. Through characterisation and incorporation of doped ternary piezocrystal materials, and by capitalising on their significant potential for transducer enhancements, we will be able to create next generation high performance, high power ultrasonic devices for surgery. We will particularly investigate their integration in novel orthopaedic devices, aiming at the extremely challenging and potentially disruptive technology of ultrasonically-assisted needles. For minimally invasive, highly accurate, interventional surgery via direct penetration through bone, we will deliver devices offering the clinician entirely new and potentially transformational capabilities in a range of clinical applications including oncology, neurosurgery, orthopaedics, bone biopsy, regional anaesthesia and rheumatology. In meeting this challenge, we will develop new techniques for characterisation of the materials and create designs for novel transducers, based on the measured characteristics, for actuation of power ultrasonic surgical tools. We will research a new class of devices in the form of bone-penetrating ultrasonic needles that can be realised with doped ternary piezocrystals to permit the highly challenging surgical tasks of (i) direct delivery of therapeutic drugs to targets within or obscured by bone, (ii) gaining access within medullary canals and inside cranial sinuses/cavities for surgical procedures, and (iii) obtaining biopsies from the inside of the bone for diagnosis. Binary compositions of the new materials are already replacing conventional piezoceramics in biomedical imaging applications and adoption of these and the newer ternary compositions for other high value applications will increase as on-going efforts to scale up crystal growth techniques mature. This project will thus position the UK in the forefront of research, while simultaneously offering transformative research in ultrasonic devices for surgery.

Societal impact will be generated through the diagnostic and therapeutic uses of the needles we will create. In diagnosis, the ability to penetrate bone will be particularly useful for biopsy and will also be explored for neural procedures, in which the capability to penetrate the skull with a needle will avoid the need for a separate tool and ease transcranial access. In therapy, the possibility to inject drugs directly at the site of treatment even when the path is obstructed by bone will offer new possibilities in the markets for targeted drug delivery treatments.
Our outreach activity, aimed at showcasing ultrasonics in interventional surgery at the Glasgow Science Festival, will create impact through public awareness of the opportunities afforded by this technology. This activity will also impact our early career research team in training for and management of this activity.

Our partnership with four companies will be our basis to address economic impact in the project.

Ethicon Endo-Surgery is a multinational supplier of surgical products, including a range of ultrasound actuated devices, and a key partner for us, representing the link between our work and commercial supply to clinicians. Our academic research on ultrasonic needles will therefore have a focus on practical outcomes that will lead to commercial products. This collaboration will also create impact beyond the highly innovative development of needles to penetrate bone, in improving other surgical devices such as ultrasonic scalpels.

TRS Technologies is an international leader in the development of piezocrystals, with major supply contracts with medical imaging companies in the binary crystal compositions it pioneered. It has subsequently developed ternary piezocrystal compositions specifically for high power applications, and is now exploring doped ternary compositions and new capabilities, such as continuous crystal growth rather than growth within a crucible, to assist their commercialization and bring down costs. The research in ultrasonic needles is a first demonstrator of doped ternary piezocrystals in high power ultrasonic devices and will be highly influential in creating new commercial opportunities for these materials.

PZFlex is a software package for virtual prototyping through finite element analysis. Supplied in the UK by Weidlinger Associates Ltd, it provides specialized capabilities for the simulation of piezoelectric devices, and is in use in many major medical ultrasound imaging companies. It remains at the forefront of piezoelectric device modelling through its use in many universities. By measuring piezocrystal material properties and incorporating them in complete PZFlex models, our work will provide data for a wide range of customers of PZFlex, enabling them to incorporate these new materials across a very wide range of transducer applications.

Our work with piezocrystals and high power, low frequency ultrasound devices has application in underwater SONAR. In this domain, transducer structures and issues such as physical size and power handling capability are very similar to those in surgical tools. We have partnered with Thales Underwater Systems Ltd to deal with this through a parallel programme in the development of piezocrystal-based transducers. TUSL is also planning to sponsor UK-based work in piezocrystal growth, offering another potential commercial route to these new materials for the first time from a company within the EU.