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A virtual prototype focussed ultrasound surgery (FUS) transducer has been developed with finite element analysis (FEA) (OnScale, Redwood City, CA, USA) comprising a single piezocermic element and an acoustic Fresnel lens. The piezoceramic is supported by microbaloon filled epoxy to approximate an air backing. The transducer housing and Fresnel lens materials are photopolymer resins of the type used in mask stereolithography (mSLA) printers. The design is optimised in FEA for the materials used in the Fresnel lens and the active piezoceramic layer. Six piezoceramic materials produced by Meggitt A/S (Kvistgaard, Denmark) were characterised in FEA and the acoustic properties of the photopolymer resins were measured using a standard pulse-echo approach to find their sound speed and frequency-dependent attenuation. The piezoceramic materials characterised spanned four major types: soft (PZ29); hard (PZT4); a specialised composition for high intensity focused ultrasound (HIFU) (PZ54); and low acoustic impedance, porous (PZ36HD). Acoustic impedance matching between the active material and the lens allowed the porous piezoceramic with lower piezoelectric and coupling coefficients to reach a higher intensity, spatial peak temporal average, (I SPTA ) at the focus (3.6 kWcm−2) than the hard PZT (2.46 kWcm−2). The focal intensity improved when HIFU and soft PZT were used, producing 5.69 kWcm−2 and 6.35 kWcm−2respectively.

Additive manufacturing (AM) offers opportunities to design more complex shapes of the Ti-6Al-4V parts commonly used in high-power ultrasonic surgical devices. Moreover, AM metal printing will be essential to the realization of miniature ultrasonic devices incorporating internal structures for minimally invasive surgical procedures. However, it is necessary first to verify the ultrasonic vibrational behavior of devices with three-dimensional (3D) printed metal parts. Therefore, two different prototype devices are fabricated, with CNC machined mill annealed and 3D printed Ti-6Al-4V parts. Both devices, an ultrasonic bone needle and a miniature ultrasonic scalpel, incorporate complex geometries but can be manufactured using subtractive processes so that the comparative effects of 3D printing on the vibrational performance of the devices can be elucidated. The metal microstructure is investigated through measurements of longitudinal and shear acoustic velocities and scanning electron microscopy. Comparisons of electrical impedance, frequency and modal responses, and the vibrational response at increasing levels of excitation enable evaluation of the efficacy of incorporating 3D printed Ti-6Al-4V parts. Results show that whereas the bone needle exhibited comparable vibrational responses for the measurement techniques used, the 3D printed bone cutting device exhibited a more dense modal response and developed cracks at high excitation levels.

Minimally invasive surgery offers opportunities for reduced morbidities, faster postoperative recovery, and reduced costs, and is a major focus of surgical device innovation. For ultrasonic surgical devices, which offer benefits of high precision, low force, and tissue selectivity in surgical procedures, there exist laparoscopic ultrasonic shears for minimally invasive surgeries that combine tissue cutting with vessel hemostasis and sealing functions. Another approach to laparoscopy that could enable new procedures, and increase the sites of surgeries that could be reached by an ultrasonic device, involves integrating a miniature ultrasonic tool with a flexible surgical robot. However, miniaturization presents challenges in delivering the ultrasonic vibrational energy required to cut hard and soft tissues, partly due to the concomitant small volume of piezoelectric material. This article aims to provide insights into the trade-offs between transducer size, volume of piezoceramic material, resonance frequency, and the achievable displacement amplitude of devices that, consistent with current ultrasonic surgical tools, are based on a bolted Langevin transducer (BLT) and tip. Different configurations of BLTs are studied, including a cascaded version, simple bar versions, and BLTs with different front mass geometries. Results show that a BLT with a larger number of piezoceramic rings exhibits a higher coupling coefficient ${k}_{\text {eff}}$ but with the compromise of a lower mechanical ${Q}$ and stronger nonlinear response at increasing excitation levels. Displacement amplitude is reduced considerably when a BLT is excited at a higher harmonic, where the PZT rings are maintained at a nodal plane, and the resonance frequency shift at increasing excitation levels increases significantly. The electromechanical and dynamic characteristics of a cascaded transducer excited in its third longitudinal mode (L3) are almost equivalent to a much shorter version of a BLT driven at the same frequency but in its first longitudinal mode (L1), showing that a cascaded BLT can be a realistic proxy for studying the dynamics of small BLT devices. A new figure of merit is proposed that is the product of ${Q}$ , ${k}_{\text {eff}}^{{2}}$ , and gain, which $\vphantom {\sum ^{R}}$ accounts for the gain of cylindrical BLTs which is shown not to be unity. It also proves effective as it incorporates the key factors affecting the achievable displacement amplitude of a BLT, including for BLTs with gain profiles in the front mass. The order of highest to lowest amplitude of a series of six gain-profile BLTs matches the order estimated by the figure of merit. It is shown that a BLT with a stepped profile front mass can achieve displacement that has the potential to cut hard or soft tissue and exhibits the smallest shifts in resonance frequency at increasing excitation levels.

7540 Background: Targeted agent combinations for chronic lymphocytic leukemia (CLL) have resulted in safe regimens with improved progression-free survival (PFS) compared to chemoimmunotherapy. The optimal regimen and long-term outcomes remain unknown. We conducted a phase 2 study of obinutuzumab (OBIN), ibrutinib (IBR), and venetoclax (VEN) in relapsed/refractory (RR) and treatment-naïve (TN) CLL patients (pts) and report extended follow up on two previously reported cohorts (RR, TN 1) and a new cohort of identically treated TN pts (TN 2). Methods: Pts with TN or RR (≥1 prior treatment) CLL requiring treatment were eligible. Treatment was given for 14 28-day cycles (C). OBIN was started C1, IBR C2, and VEN C3 with standard dose escalation. Response was assessed 2 months (mos) after C14 (EOT) by iwCLL 2008 criteria. Minimal residual disease (MRD) was measured by 10-color flow cytometry with a cutoff of < 1x10-4. The primary endpoint was complete remission (CR) with undetectable MRD (uMRD) in blood and bone marrow at EOT. A sample size of 25 pts per cohort achieves 90% power to test the null hypothesis of 10% against 30% with 1-sided α of 10%. The Kaplan-Meier method was used to estimate PFS and overall survival (OS). Results: 75 pts were treated in 3 cohorts (Table). Data are as of 1/3/2022. In the TN 2 cohort, the overall response rate (ORR) at EOT was 96% (95% CI: 80-100) and CR with uMRD was 20% (95% CI: 7-41). The ORR for TN 1 and TN 2 combined was 90% (95% CI: 78-97) and CR with uMRD was 24% (95% CI: 13-38). Median follow up was 56 (0-65), 57 (7-63), and 30 (24-35) mos, respectively, for RR, TN 1, and TN 2. There were 3 deaths (RR = 1, TN 1 = 1, TN 2 = 1) and 6 disease progressions (RR = 4, TN 1 = 2, TN 2 = 0). Estimated 48-month PFS for TN 1 and RR cohorts were both 96% (95% CI: 72-99) and OS was 85% (95% CI: 60-95) and 100%, respectively. The estimated 24-month PFS and OS for TN 2 were both 96% (95% CI: 75-99). The most frequent adverse events were neutropenia (95%, 73% grade ≥3), leukopenia (95%, 45% grade ≥3), lymphopenia (93%, 40% grade ≥3), and thrombocytopenia (91%, 28% grade ≥3). The only grade ≥3 non-hematologic toxicity occurring at ≥20% was hypertension (85%, 39% grade ≥3). Atrial fibrillation occurred in 11% of pts. Conclusions: At extended follow-up, remissions remain durable after fixed duration OBIN, IBR, and VEN. The efficacy and acceptable safety justify further study and are being compared to IBR and OBIN in 2 phase 3 US cooperative group trials. Clinical trial information: NCT02427451. [Table: see text]

Minimally invasive surgery can potentially benefit from the use of ultrasonic devices through their high precision, low force, and tissue selectivity, thus reducing morbidity, recovery time and cost. To facilitate this, miniature ultrasonic surgical tools are required, integrated with flexible surgical robots to guide them to surgical sites inside the body. This paper presents two novel designs of miniature ultrasonic surgical devices excited by a radially polarized piezoelectric tube. One configuration employs the longitudinal mode of the tube and the other uses the breathing mode in a flextensional configuration, to achieve a longitudinal motion of the blade. Experimental results show that the vibration at the tip of the blade of the cymbal end-cap (flextensional configuration) has developed a 4-6 times higher amplitude with the same excitation than the stepped horn (longitudinal configuration), demonstrating potential for using the breathing mode of the piezoelectric tube.

Mn:PIN-PMN-PT piezocrystals are under consideration for potential use in miniaturised ultrasonic scalpels for robotic minimally-invasive surgery where small size and light weight may be advantageous. Electromechanical coupling coefficient k > 0.9 for both [001] and [011] poled Mn:PIN-PMN-PT was calculated, confirming the well-recognized higher efficiency of this material when compared to standard piezoceramics. Novel transducer design strategies have been explored, and outcomes are discussed. The introduction of components with additional compliance in a standard d 31 mode transducer has been shown to drop the resonant frequency of the first longitudinal mode by more than 17%, with more than 75% improvement in tip/blade displacement. Results suggest that the combination of high performance piezocrystals with highly compliant components may be a useful route to follow to achieve our miniaturisation target.

High-Q PIC 181 hard piezoceramic and high-k Mn:PIN-PMN-PT piezocrystal thickness extensional rings have been compared for use in the actuation of an ultrasonic scalpel for robotic endo-surgery. Measured material properties have been verified with both finite element analysis and laser vibrometry, to assess the materials' suitability for high power devices. Measured material properties have been verified with both finite element analysis and laser vibrometry, to assess material's suitability for high power devices. Measurements have shown a $k_{t}=0.25$ and $Q_{m}=2200$ , and $k_{t}=0.62$ and $Q_{m}=1100$ , for PIC 181 and Mn:PIN-PMN-PT respectively. Conventional bolted Langevin-style transducers (BLTs) have been successfully designed and built to resonate at 20 kHz for both piezomaterials. Modal parameters and performance have been modelled in FEA and measured via laser doppler vibrometry. When devices were excited with $\mathbf{50\ V}_{rms}$ at L1 a displacement of: $\mathbf{8}\ \mu\mathbf{m}$ and $\mathbf{7}\ \mu \mathbf{m}$ was measured for PIC-181 and Mn:PIN-PMN-PT BLTs respectively. Results suggest that a similar resonant frequency can be achieved with a shorter and equally functional device excited by Mn:PIN-PMN-PT piezocrystals.

Targeted therapies including the engineered afucosylated anti-CD20 monoclonal antibody obinutuzumab, Bruton’s tyrosine kinase inhibitor ibrutinib, and B-cell lymphoma protein 2 inhibitor venetoclax have demonstrated significant clinical activity in chronic lymphocytic leukemia (CLL) and, based on their complementary mechanisms, are ideal for combination. However, combining venetoclax with other active agents raises safety concerns, as it may increase the risk for tumor lysis syndrome. To minimize this risk, we designed and implemented a fixed-duration regimen using sequentially administered obinutuzumab followed by ibrutinib (cycle 2) and venetoclax (cycle 3), for a total of fourteen 28-day cycles. This phase 1b study included 12 patients with relapsed or refractory CLL. We tested 3 dose levels of venetoclax and identified the doses of all 3 agents approved by the US Food and Drug Administration for use in the combination. Adverse events were consistent with known toxicities of the individual agents, with hematologic adverse events being most frequent. No clinically significant tumor lysis syndrome occurred. The overall response rate was 92% (95% confidence interval, 62%-100%), with 42% (5/12) achieving a complete remission or complete remission with incomplete marrow recovery. There were 6 patients with no detectable CLL in both the blood and bone marrow at the end of treatment. We found this regimen to be safe and tolerable in CLL, and capable of inducing deep responses, justifying future study in our ongoing phase 2 cohorts of relapsed or refractory and treatment-naive patients, as well as larger phase 3 trials currently in planning. This trial was registered at www.clinicaltrials.gov as #NCT02427451.

Orthopaedic surgery involves cutting through bone and the removal of bone, bone spurs or ligament. Ultrasonic surgical devices, employing an ultrasonically excited cutting blade, have demonstrated precision and accuracy in bone surgeries, allowing surgeons to carry out bone cutting in difficult-to-reach surgical sites. For surgical procedures in a confined space, a small surgical device has benefits, but for ultrasonic devices this results in a reduced amount of piezoceramic material in the transducer. This paper provides insights into the trade-offs between the volume of piezoceramic material, location of the piezoceramic rings, resonant frequency and the achievable vibration amplitude. Bolted Langevin-style Transducers (BLT) are adopted for this study. Experimental results show that a similar level of vibration displacement can be achieved at a much lower input voltage with a higher quantity of piezoceramic elements. However, the associated nonlinear behaviour is exacerbated. Locating the piezoceramic elements at the longitudinal displacement node is critical, in order to maximise the ultrasonic energy transfer.

Clinical, in vivo and in vitro studies have established that Low Intensity Pulsed Ultrasound (LIPUS) stimulates healing of fractured bone, but the mechanisms are not well understood. In vitro studies show cell proliferation, migration and many cellular markers are stimulated by LIPUS at frequencies of 1.0 – 1.5 MHz, even down to 45 kHz [1]. However, most trials did not control or measure the acoustic field, so the dose experienced by the cells across such studies cannot be compared. An in vitro ultrasound exposure method was developed to maintain control of the acoustic field. Murine osteoblasts (MC3T3-E1) were exposed to 20-minute LIPUS fields at the frequencies 1 MHz and 45 kHz and Mechanical Index from 0 (control) to 0.2. Cell proliferation was assessed by counting viable cells immediately before and twenty hours after LIPUS exposure in the centre of a custom-designed cell culture vessel. Initial results indicate that LIPUS fields increase cell proliferation at 1 MHz, 0.1 MI and more significantly at 45 kHz, 0.2 MI compared to controls, but has a detrimental or no effect otherwise. Future work will involve further repeats to acquire larger data sets, along with cell counts in other areas of the cell growth surface to increase data obtained from a single repeat. The study demonstrates the efficacy of the method for quantitative in vitro investigation of LPUS mechanisms and will be used in future work to find optimum LIPUS field characteristics, in terms of frequency, Mechanical Index, and pulse characteristics such as pulse repetition rate and pulse width.

An ultrasonic orthopaedic surgical device is presented, where the ultrasonic actuation relies on a modification of the classical cymbal transducer. All current devices consist of a Langevin ultrasonic transducer with a tuned cutting blade attached, where resonance is required to provide sufficient vibrational amplitude to cut bone. However, this requirement restricts the geometry and offers little opportunity to propose miniaturised devices or complex blades. The class V flextensional cymbal transducer is proposed here as the basis for a new design, where the cymbal delivers the required vibrational amplitude, and the design of the attached cutting insert can be tailored for the required cut. Consequently, the device can be optimised to deliver an accurate and precise cutting capability. A prototype device is presented, based on the cymbal configuration and designed to operate at 25.5kHz with a displacement amplitude of 30μm at 300V. Measurements of vibrational and impedance responses elucidate the mechanical and electrical characteristics of the device. Subsequent cutting tests on rat femur demonstrate device performance consistent with a commercial Langevin-based ultrasonic device and show that cutting is achieved using less electrical power and a lower piezoceramic volume. Histological analysis exhibits a higher proportion of live cells in the region around the cut site for the cymbal device than for a powered sagittal or a manual saw, demonstrating the potential for the ultrasonic device to result in faster healing.

The Badger Explorer is a rig-less oil and gas exploration tool which drills into the subsea environment to collect geological data. Drill spoil is transported from the front end of the system to the rear, where the material is compacted. Motivated by the need to develop a highly efficient compaction system, an ultrasonic compactor for application with granular geological materials encountered in subsea environments is designed and fabricated as part of this study. The finite element method is used to design a compactor configuration suitable for subsea exploration, consisting of a vibrating ultrasonic horn called a resonant compactor head, which operates in a longitudinal mode at 20 kHz, driven by a Langevin piezoelectric transducer. A simplified version of the compactor is also designed, due to its ease of incorporating in a lab-based experimental rig, in order to demonstrate enhanced compaction using ultrasonics. Numerical analysis of this simplified compactor system is supported with experimental characterisation using laser Doppler vibrometry. Compaction testing is then conducted on granular geological material, showing that compaction can be enhanced through the use of an ultrasonic compactor.

The class V transducer has found popularity in a diverse range of applications such as surgical and underwater projection systems, where high vibration amplitude for relatively low piezoceramic volume is generated. The class IV transducer offers the potential to attain even higher performance per volume than the class V. In this research, a miniaturized class IV power ultrasonic flextensional transducer is proposed. Simulations were performed using PZFlex finite element analysis, and electrical impedance analysis and experimental modal analysis were conducted for validation, where a high correlation between simulation and experiment has been demonstrated.

Ultrasonic disinfection involves the application of low-frequency acoustic energy in a water body to induce cavitation. The implosion of cavitation bubbles generates high speed microjets >1 km/s, intense shock wave >1 GPa, localized hot spots >1000 K, and free-radicals, resulting in cell rupture and death of micro-organisms and pathogens. Treatment of marine ballast water using power ultrasonics is an energy-intensive process. Compared with other physical treatment methods such as ultraviolet disinfection, ultrasonic disinfection require 2 to 3 orders of magnitude more energy to achieve similar rate of micro-organism mortality. Current technology limits the amount of acoustic energy that can be transferred per unit volume of fluid and presents challenges when it comes to high-flow applications. Significant advancements in ultrasonic processing technology are needed before ultrasound can be recognized as a viable alternative disinfection method. The ultrasonic resonator has been identified as one of the areas of improvement that can potentially contribute to the overall performance of an ultrasonic disinfection system. The present study focuses on the design of multiple-orifice resonators (MOR) for generating a well-distributed cavitation field. Results show that the MOR resonator offers significantly larger vibrational surface area to mass ratio. In addition, acoustic pressure measurements indicate that the MOR resonators are able to distribute the acoustic energy across a larger surface area, while generating 2-4 times higher pressures than existing ultrasonic probes.

Ultrasonic-percussive drills are a leading technology for small rock drilling applications where power and weight-on-bit are at a premium. The concept uses ultrasonic vibrations to excite an oscillatory motion in a free-mass, which then delivers impulsive blows to a drilling-bit. This is a relatively complex dynamic problem involving the transducer, the free-mass, the drilling-bit and, to a certain extent, the rock surface itself. This paper examines the performance of a full-wavelength transducer compared to a half-wavelength system, which may be more attractive due to mass and dimensional drivers. To compare the two approaches, three-dimensional finite element models of the ultrasonic-percussive stacks using full and half wavelength ultrasonic transducers are created to assess delivered impulse at similar power settings. In addition, impact-induced stress levels are evaluated to optimize the design of drill tools at a range of internal spring rates before, finally, experimental drilling is conducted. The results suggest that full-wavelength systems will yield much more effective impulse but, interestingly, their actual drilling performance was only marginally better than half-wavelength equivalents.

Previous research by the authors has demonstrated the efficacy of an ultrasonic bone biopsy device that operates in a longitudinal (L)mode. Ultrasonic longitudinal-torsional (L-T)coupled vibration has proven successful in several applications including ultrasonic surgical devices. In this work, an L-mode ultrasonic bone biopsy device was geometrically modified by introducing helical slits to degenerate the longitudinal vibration into a composite L-T motion. The performance of the L-T biopsy needle device was then compared with the L-mode needle device based on their ability to penetrate animal bone samples. Finite element analysis was used to design the L-T needle. The depth and pitch of the helical slits were systematically modified in the FEA model with the aim of maximizing the achievable torsional displacement while ensuring sufficient frequency spacing between the L-T mode and the neighboring flexural modes. Experimental modal analysis (EMA)of the fabricated ultrasonic device was used to identify the modal parameters and validate the FEA model. Comparative penetration tests showed that to achieve penetration with the L-mode device, the operator was required to apply a slow backward and forward rotation as well as the small forward force, to maintain a forward motion and avoid imprinting of the needle tip. The resulting hole was slightly conical with some micro-damage on the hole surface. The L-T mode device, however, could penetrate the same animal bone sample only applying a small forward force, hence simplifying the procedure, increasing precision and resulting in a cylindrical, less damaged hole surface.

In this paper, we report both experimental and computational studies of hydrodynamic cavitation generated by accelerating liquid through a series of constrictions. The detailed process of cavitation generation is visualized using a high-speed photography. The cavitation is initiated when a gas bubble moves towards the constrictions. The gas bubble initially accelerates, expands and then splits into smaller bubbles when it moves along the constriction. As these bubbles migrate into a large liquid compartment, they collapse violently to form a bubble cloud, owing to a sudden jump in liquid pressure in the compartment. The experimental observation is further confirmed using computational fluid dynamics (CFD) simulations. We also present experimental evidence showing a significant reduction in gram-negative Escherichia coli concentration after it passes through the constrictions.

The Ultrasonic Planetary Core Drill (UPCD) project sought to develop and conduct a field trial, in an analogous Martian environment, of a space-compatible regolith-sampling tool. The project implemented a number of key technologies to achieve this aim; a drilling control loop based on ultrasonic power feedback, a bayonet interface system to allow a drillstring to be built up in-situ then disassembled after use, a coring design which captured the cores drilled out, and a mechanism for caching the core samples in sealable containers. The system was demonstrated in the laboratory with results indicating low power, low weight on bit, achievement of the targeted depth, and the retrieval of still-frozen core samples. The routines to allow the system to become fully autonomous were also demonstrated. The drill was deployed to Coal Nunatak on Alexander Island, Antarctica, for analogue trials. The drill was demonstrated to work, as was the caching and drill assembly/disassembly system, but the target depth was not achieved. A review of drill depth is provided along with a laboratory solution to the problems encountered in the field. Further work using the UPCD is also discussed.

Ultrasonic surgical devices are currently used in various soft and hard tissue surgeries. This study focuses on investigating how modifications of the device driving signal can affect the needle penetration speed. The penetration speed, and therefore time for extraction of a biopsy, should be comparable with a conventional trephine biopsy needle. The ultrasonic bone biopsy device was designed using finite element analysis (FEA) and tuned to operate in a longitudinal mode at 25 kHz. The device was manufactured and experimental modal analysis (EMA) was used to validate the FEA model and measure the modal parameters. A series of tests were carried out, based on the time to perform a 5mm penetration of the needle into a polyurethane foam which acts as a substitute trabecular bone material. During each penetration the temperature and time were recorded. Following this, the study focused on investigating power modulation techniques, as have been widely adopted for phacoemulsification where power modulation in cataract surgery delivers less ultrasound energy to the eye and hence improves visual rehabilitation. It is shown how modifications to the signal shape and power modulation techniques when driving the ultrasonic bone biopsy device effect the penetration speed of an ultrasonic needle device.

In this study, we introduce a new prototype ultrasonic cutting device for bone surgery based on a class V flextensional cymbal transducer, configured for use in power ultrasonics applications, which removes many of the geometrical restrictions on the cutting tip of Langevin-based transducers. The benefit of incorporating a cymbal transducer is that since the cutting blade itselfdoes not have to be tuned, blade design can focus more closely on delivering the best interaction with bone to provide a highly accurate cut. Small variations to the geometry of the blade do not affect the final resonance frequency. Also the ultrasonic device can be miniaturised to allow the design of devices for delicate orthopaedic procedures involving minimal-access surgery. Theresults show how the cymbal transducer, driven by a single piezoceramic disc, can excite sufficiently high vibration displacement amplitudes at lower driving voltages. This is achieved by adapting the configuration of the cymbal to remove the problem of epoxy layer debonding, and by optimising the cymbal end-cap and geometry through finite element modelling supported withexperimental vibration characterisation. Preliminary characterisations of the resulting prototype ultrasonic bone cutting device, which operates at around 25 kHz, illustrate the success of this novel device design.

Ultrasonic water treatment is based on the ability of an ultrasonic device to induce cavitation in the liquid, generating physical and chemical effects that can be exploited to produce effective treatment. This require the device be capable of generating high amplitude pressure waves in a relatively large volume of water and biological inactivation within a realistic exposure period for the application. Most conventional ultrasonic devices fulfill only the first requirement, rendering such devices highly unsuitable for use in high-volume, high-flow liquid processes. In this report, the multiple orifice radial (MOR) resonator is proposed to overcome the said limitations by offering both high vibrational amplitude and large radiating area in a relatively compact assembly. This paper discusses the approach to the MOR resonator design and follow on with experimental measurements to characterize their dynamic characteristics. Results show that the vibrational amplitudes at the radiating surfaces of the radial resonators are comparable with conventional high-output ultrasonic probes. This demonstrates the high acoustic power capability of the MOR devices proposed.

Some industrial processes like particle agglomeration or food dehydration among others can be enhanced by the use of power ultrasonic technologies. These technologies are based on an airborne power ultrasonic transducer (APUT) constituted by a pre-stressed Langevin-type transducer, a mechanical amplifier and an extensive plate radiator. In order to produce the desired effects in industrial processing, the transducer has to vibrate in an extensional mode driving an extensive radiator in the desired flexural mode with high amplitude displacements. Due to the generation of these high amplitude displacements in the radiator surfaces, non-linear effects like frequency shifts, hysteresis or modal interactions, among others, may be produced in the transducer behavior. When any nonlinear effect appears, when applying power, the stability and efficiency of this ultrasonic technology decreases, and the transducer may be damaged depending on the excitation power level and the nature of the nonlinearity. In this paper, an APUT with flat rectangular radiator is presented, as the active part of an innovative system with stepped reflectors. The nonlinear behavior of the APUT has been characterized numerically and experimentally in case of the modal analysis and experimentally in the case of dynamic analysis. According to the results obtained after the experiments, no modal interactions are expected, nor do other nonlinear effects.

Bone biopsy is an invasive clinical procedure, where a bone sample is recovered for analysis during the diagnosis of a medical condition. When the architecture of the bone tissue is required to be preserved, a core-needle biopsy is taken. Although this procedure is performed while the patient is under local anaesthesia, the patient can still experience significant discomfort. Additionally, large haematoma can be induced in the soft tissue surrounding the biopsy site due to the large axial and rotational forces, which are applied through the needle to penetrate bone. It is well documented that power ultrasonic surgical devices offer the advantages of low cutting force, high accuracy, and preservation of soft tissues. This paper reports a study of the design, analysis, and test of two novel power ultrasonic needles for bone biopsy that operate using different configurations to penetrate bone. The first utilizes micrometric vibrations generated at the distil tip of a full-wavelength resonant ultrasonic device, while the second utilizes an ultrasonic-sonic approach, where vibrational energy generated by a resonant ultrasonic horn is transferred to a needle via the chaotic motion of a free-mass. It is shown that the dynamic behavior of the devices identified through experimental techniques closely match the behavior calculated through numerical and finite-element analysis methods, demonstrating that they are effective design tools for these devices. Both devices were able to recover trabecular bone from the metaphysis of an ovine femur, and the biopsy samples were found to be comparable to a sample extracted using a conventional biopsy needle. Furthermore, the resonant needle device was also able to extract a cortical bone sample from the central diaphysis, which is the strongest part of the bone, and the biopsy was found to be superior to the sample recovered by a conventional bone biopsy needle.

Mill annealed Ti-6Al-4V is a commonly used material in high-power ultrasonic devices, including cutting tips for ultrasonic soft tissue surgical devices. The advantages of Ti-6Al-4V include its high elastic strain limit, low acoustic attenuation, and biocompatibility. It is known that the microstructure of Ti-6Al-4V can influence its mechanical and acoustic properties. This research focuses on how altering the Ti-6Al-4V microstructure affects the performance of ultrasonic surgical tips. Through heat treatment five distinct types of Ti-6Al-4V sample were created: mill annealed; course lamellar; widmanstatten; fully equiaxed alpha plus intergranular beta; bimodal - equiaxed plus lamellar. The mechanical and acoustic properties of the samples and their dynamic response to ultrasonic excitation were characterised. Acoustic attenuation of the samples in static state was measured using a time of flight experiment. Strong links were shown between microstructural features and material properties, with the fully l...

Ultrasonic bone cutting is known to offer advantages over more conventional techniques, however ultrasonic surgical devices for hard tissues are currently limited to small bone procedures. This study investigates the potential benefits of an ultrasonically assisted sagittal saw, and explores two designs based on incorporating planar ultrasonic transducers in sagittal saw blades. Designs were developed using finite element analysis (FEA) and were subsequently characterised using experimental modal analysis (EMA). Both blades were tuned to operate in a longitudinal mode of vibration. The dynamic response characterisations were measured and compared, using a harmonic analysis involving bi-directional frequency sweeps through the tuned longitudinal resonance at increasing excitation levels. The blades were tested in a linear loading rig, where they were drawn across a fixed piece of bone substitute material, mimicking a typical cut of a sagittal saw. Each blade was tested first with no ultrasonic excitation, and then under ultrasonic excitation. The depth of cut and the current draw of the drive actuator was recorded for comparison of performance. The results of the tests show that the current draw remained constant for control and ultrasonically excited cuts, whilst one design demonstrated a greater depth of cut for an ultrasonically excited blade.Ultrasonic bone cutting is known to offer advantages over more conventional techniques, however ultrasonic surgical devices for hard tissues are currently limited to small bone procedures. This study investigates the potential benefits of an ultrasonically assisted sagittal saw, and explores two designs based on incorporating planar ultrasonic transducers in sagittal saw blades. Designs were developed using finite element analysis (FEA) and were subsequently characterised using experimental modal analysis (EMA). Both blades were tuned to operate in a longitudinal mode of vibration. The dynamic response characterisations were measured and compared, using a harmonic analysis involving bi-directional frequency sweeps through the tuned longitudinal resonance at increasing excitation levels. The blades were tested in a linear loading rig, where they were drawn across a fixed piece of bone substitute material, mimicking a typical cut of a sagittal saw. Each blade was tested first with no ultrasonic excitation, ...

Deep drilling using a rigid drillstring requires the assembly and disassembly of multiple drill pipes. The interfaces between these pipes provide a challenge for automation because they must transmit large drilling forces and movements while, at the same time, minimise the actions and forces that are needed to make or break the interface.\ud A geometry which can address these requirements has been suggested by the authors. This approach would use a push-and-twist bayonet system to engage drill pipes, with torque transmission through the bayonet studs. A variety of L-shaped and T-shaped bayonet paths have been proposed to ensure that separation of specific drill pipes can be achieved through a combination of clockwise and counter-clockwise rotation and single-point clamping. Sustained drills into a variety of media are used to show that percussive impulses are transmitted across the interface, whilst ensuring that the drill interface is able to withstand the shock loading associated with hammer-drilling. These tests are repeated and contrasted to control experiments using a single-piece control drillstring, which allows the performance of the interface and any degradation over time to be quantified. Results suggest that the bayonet-style connection performs well with no significant performances losses encountered or structural degradation noted.

Cymbal flextensional transducers have principally been adopted for sensing and actuation and their performance in higher power applications has only recently been investigated. Nitinol is a shape-memory alloy (SMA) with excellent strain recovery, durability, corrosion resistance, and fatigue strength. Although it has been incorporated in many applications, the implementation of nitinol, or any of the SMAs, in power ultrasonic applications is limited. Nitinol exhibits two phenomena, the first being the superelastic effect and the second being the shape-memory effect (SME). This paper assesses two cymbal transducers, one assembled with superelastic nitinol end caps and the other with shape-memory nitinol end caps. Characterization of the nitinol alloy before the design of such transducers is vital, so that they can be tuned to the desired operating frequencies. It is shown this can be achieved for shape-memory nitinol using differential scanning calorimetry (DSC); however, it is also shown that characterizing superelastic nitinol with DSC is problematic. Two transducers are assembled whose two operating frequencies can be tuned, and their dynamic behaviors are compared. Both transducers are shown to be tunable, with limitation for high-power applications largely being associated with the bond layer.

The class V cymbal is a flextensional transducer commonly used in low-power ultrasonic applications. The resonance frequency of the transducer can be tailored by the choice of end-cap and driver materials, and the dimensions of the end-caps. The cymbal transducer has one significant limitation which restricts the operational vibration amplitude of the device. This is the limit imposed by the mechanical strength of the bonding agent between the metal end-cap and the piezoceramic driver. Therefore, when there is an increase in the input power or displacement, the stresses in the bonding layer can lead to debonding, thereby rendering the cymbal transducer ineffective for high-power ultrasonic applications. In this paper, several experimental analyses have been performed, complemented by the use of Abaqus/CAE finite element analysis, in order to develop a high-power ultrasonic cutting device for bone surgery using a new configuration of cymbal transducer, which is optimised for operation at high displacement and high input power. This new transducer uses a combination of a piezoceramic disc with a metal ring as the driver, thereby improving the mechanical coupling with the metal end-cap.

Traditional rotary drilling for planetary rock sampling, in situ analysis, and sample return are challenging because the axial force and holding torque requirements are not necessarily compatible with lightweight spacecraft architectures in low-gravity environments. This paper seeks to optimize an ultrasonic percussive drill tool to achieve rock penetration with lower reacted force requirements, with a strategic view toward building an ultrasonic planetary core drill (UPCD) device. The UPCD is a descendant of the ultrasonic/sonic driller/corer technique. In these concepts, a transducer and horn (typically resonant at around 20 kHz) are used to excite a toroidal free mass that oscillates chaotically between the horn tip and drill base at lower frequencies (generally between 10 Hz and 1 kHz). This creates a series of stress pulses that is transferred through the drill bit to the rock surface, and while the stress at the drill-bit tip/rock interface exceeds the compressive strength of the rock, it causes fractures that result in fragmentation of the rock. This facilitates augering and downward progress. In order to ensure that the drill-bit tip delivers the greatest effective impulse (the time integral of the drill-bit tip/rock pressure curve exceeding the strength of the rock), parameters such as the spring rates and the mass of the free mass, the drill bit and transducer have been varied and compared in both computer simulation and practical experiment. The most interesting findings and those of particular relevance to deep drilling indicate that increasing the mass of the drill bit has a limited (or even positive) influence on the rate of effective impulse delivered.

This study investigates combining longitudinal and torsional (L–T) vibration responses at the output face of a Langevin transducer. A mode degeneration method is adopted that converts the longitudinal response excited by the axially poled piezoceramic discs in the transducer into combined L–T vibration in the transducer front mass using geometric modifications of the wave path. The study uses three techniques; numerical, analytical, and experimental, in order to estimate and validate transducer electro-mechanical parameters for different geometric modifications, and also to evaluate transducer performance for different excitation levels in terms of the desired L–T response. A finite element (FE) analysis is used to optimise the mechanical structure of the transducer while the analytical model, which is based on an equivalent-circuit approach, is used to estimate the electrical impedance spectra and to confirm some of the FE calculations prior to fabrication. These models are then validated through an experimental characterization of the vibration response and impedance response and the results show that the operating frequency and torsionality can be tailored through modification of the transducer geometry.

Sonics and space are two topics which are not commonly considered together. However, sonic and ultrasonic models, devices and systems have space applications in both science and engineering, as well as showing promise in fields such as cleaning, healthcare and construction. This short paper describes some of these activities and appears as results start to come in from the Curiosity rover, which landed on Mars on the 6th of August, 2012, with over 20 piezoelectric and mechanically-resonant components on board.

Longitudinal-torsional vibration is used and proposed for a variety of ultrasonic applications including motors, welding, and rock-cutting. To obtain this behavior in an ultrasonic step horn one can either, (i) couple the longitudinal and torsional modes of the horn by incorporating a ring of diagonal slits in the thick base section or, (ii) place helical flutes in the thin stem section to degenerate the longitudinal mode into a modified behavior with a longitudinal-torsional motion. This paper compares the efficacy of these two design approaches using both numerical and experimental techniques.

It has been shown that the compaction of granular materials for applications such as pharmaceutical tableting and plastic moulding can be enhanced by ultrasonic vibration of the compaction die. Ultrasonic vibrations can reduce the compaction pressure and increase particle fusion, leading to higher strength products. In this paper, the potential benefits of ultrasonics in the compaction of geological granular materials in downhole applications are explored, to gain insight into the effects of ultrasonic vibrations on compaction of different materials commonly encountered in sub-sea drilling. Ultrasonic vibrations are applied, using a resonant 20kHz compactor, to the compaction of loose sand and drill waste cuttings derived from oolitic limestone, clean quartz sandstone, and slate-phyllite. For each material, a higher strain for a given compaction pressure was achieved, with higher sample density compared to that in the case of an absence of ultrasonics. The relationships between the operational parameters of ultrasonic vibration amplitude and true strain rate are explored and shown to be dependent on the physical characteristics of the compacting materials.

Finite element (FE) model of die necking process of an aluminium hollow thin cylinder has been developed. The input parameters of material properties and coefficient of friction, µ for the model have been deducted from our previous experimental study. Later the models have been validated against experimental data as reported in the previous studies. For the die necking process, the FE model has successfully to predict how much the original diameter of the aluminium hollow cylinder can be maximised necked with and without applying ultrasonic vibration. FE models showed that the application of ultrasonic vibration during the necking process has reduced buckling of the cylinder body if compared to the necking process without ultrasonic. The benefit of applying ultrasonic vibration in sheet metal forming process has been related to the reduction of interface friction between die and specimen.

Traditional rotary corers and sample retrieval mechanisms for planetary drilling suffer from a variety of technical difficulties. A heavy and rigid drillstring must be assembled on-site and deployed with considerable applied preload and torque, and these mechanical loadings are difficult to react in a low gravity environment. Furthermore the entire drillstring must often be removed to retrieve samples, unless an augering approach is taken, in which case stratigraphic sequencing is lost. Ultrasonic tools which operate by converting an ultrasonic frequency to a low impacting frequency at the tool end can resolve the mechanical problems because they require very low applied preload and no torque to operate. In developing such a tool, however, several fundamental design decisions must be taken regarding the architecture of the transducer, horn and stack. These include the choice of solid or hollow transducers and the employment of single or multiple free-masses at the ultrasonic to low frequency conversion location. This paper addresses the layout of such a system by contrasting the pros and cons of these architectural choices and concludes that a solid system with a single free-mass provides the best performance in the parameter range here discussed.

A composite longitudinal-torsional vibration mode has applications in ultrasonic motors, ultrasonic welding and ultrasonic drilling. There are two ways to obtain this vibration behaviour using a single transducer, namely (i) coupling of a longitudinal and a torsional mode, which is known to be difficult; and (ii) degenerating a longitudinal mode to deliver longitudinal-torsional behaviour at the horn tip. A mode-degenerating horn is achieved by incorporating helical or diagonal slits in an otherwise traditional exponential horn driven by a Langevin transducer. However, it is often difficult with this configuration to avoid coupling of unwanted bending modes, low responsiveness, and loss of ultrasonic energy due to boundaries between tuned components. Therefore, in this study the mode-degenerating characteristics are achieved by incorporating the helical slits and exponential geometry features in the front mass of the transducer itself. Finite element analysis and vibration experimental analysis show that this strategy prevents coupling of bending modes, increases responsiveness, and reduces energy losses. Most importantly the transducer delivers a very high torsionality.

This article represents the first step in an attempt to obtain an analytical model of a cymbal transducer. The structure is considered as two mechanically coupled systems (i.e. a piezoelectric disc producing radial motion and end caps amplifying under the compression caused by this radial behaviour). Therefore, an analytical model of the piezoelectric disc, core driver of the cymbal, and its dynamics under an electrical signal are presented in this article. The function describing the radial motion of the disc, distribution of the electrical potential along the thickness, and displacement along the thickness are obtained analytically. The obtained radial motion function will be used for modelling the end cap amplification as a compressive loading.

It has been reported that the application of radial ultrasonic vibration on die during wire drawing process has reduced the drawing force. The reduction of the drawing force has been related to relative oscillation motion between die and wire surface which caused the reduction of interface friction. Since the oscillatory stress has not been measured, there were conflicting interpretations of the measured data and the possible factors that reduced the drawing force. This study proposes a numerical investigation into oscillatory stress behaviour of superimposed radial ultrasonic vibration with different interface friction. A series of finite element simulation was created to model a simple compression test of aluminium. The radial ultrasonic vibration was superimposed in short interval during plastic deformation. To investigate the effect of friction in the model, the coefficient of friction between die and specimen was changed from ).l = 0 to ).l = 0.25 during static and ultrasonic compressions. The calculated static and oscillatory stress-strain can be referred to the previous experimental data. This study shows that the reduction of forming force due to radial ultrasonic vibration can be related to the reduction of the interface friction. However the use of lubricant during radial ultrasonic compression has not much reduced friction further.

The use of ultrasonic excitation of tools and dies in metal forming operations has been the subject of ongoing research for many years. However, the lack of understanding about the effects of ultrasonic vibrations on the forming process has resulted in difficulties in maximising the benefits and applications of this technology. In particular, experimental characterisations of the effects of superimposing ultrasonic oscillations have largely relied on interpretations of measurements of the mean forming load and have ignored the oscillatory forces. Previous research [1] has shown that by applying ultrasonic vibrations to the lower platen in compression tests on pure aluminium specimens, the resulting stress-strain relationship can be characterised by a temporary effective softening of the material during intervals of ultrasonic excitation. The current research investigates this effect in a series of simple forming tests using a number of different metal specimens. In this research, the forming tests are conducted using a piezoelectric force transducer to measure the oscillatory force data during ultrasonic excitation of the die. It is shown that the benefits of superimposing ultrasonic excitation of the die are highly dependent on the material being formed and that, in many cases, the maximum oscillatory force exceeds the static forming load even where the mean forming load is reduced significantly during the interval of ultrasonic excitation.

A number of architectures for a hollow Langevin ultrasonic transducer are proposed and evaluated. One of these is optimised by finite element modelling and is then manufactured and analysed experimentally. The preload on the transducer ceramics is increased and the effect on the performance is measured. At maximum preload the results of an experimental modal analysis are used to determine the natural frequency and response of both the operating longitudinal mode and unwanted bending modes. The performance of the hollow transducer is compared to a solid commercial transducer containing the same volume of piezoceramic material. The efficiency is shown to be comparable. Higher ultrasonic displacement amplitudes are achieved with the hollow transducer although a lower Q-factor is found.