Invited Speakers

University of Oxford

Turn Up the Heat or Pop the Bubble? Clinical Translation of Ultrasound-Enhanced Drug Delivery to Solid Tumours

Over the past 5 years, both thermally-triggered and cavitation-mediated ultrasound-enhanced drug delivery approaches have been translated into early-phase clinical trials for the treatment of solid tumours, demonstrating their potential for significant enhancements in drug delivery, distribution and therapeutic efficacy in solid tumours. The challenges and opportunities presented in clinically translating both of these approaches from bench to bedside will be discussed, with particular reference to the need for scalable thermometry methods, rapid patient-specific modelling of ultrasound propagation based on standard clinically available imaging, and the further development and refinement of methods for mapping and quantifying cavitation activity in patients.
University of Maryland (Neurosurgery)

MRI-guided, acoustic emissions-informed, microbubble-enhanced ultrasound for controlled blood-brain barrier opening

Dr. Woodworth’s clinical research team is leading the first-in-human US clinical trials studying MRI-guided focused ultrasound-mediated blood brain barrier disruption (MRgFUS-BBBD) in brain tumor patients. These studies are designed to evaluate the safety and feasibility of MRgFUS BBBD, with the eventual goal of using this technology to improve therapeutic delivery to and effects against intrinsic brain tumors.
Washington University in St. Louis

Sonobiopsy for noninvasive and spatiotemporally controlled brain tumor liquid biopsies

Brain tumors severely threaten human health due to their fast development and poor prognosis. The current standard of care relies on MRI to identify suspicious tumor lesions, followed by surgical resection or stereotactic biopsy for histological confirmation. However, invasive brain tumor biopsy carries a 5–7% risk of major morbidity. It may not be possible at all to perform this procedure on medically inoperable patients or patients with tumors in surgically inaccessible locations. Repeated tissue biopsies to assess treatment response and recurrence are often not feasible given the increased risk for complications and morbidity. These challenges limit the timely diagnosis and selection of treatment options, hinder a better understanding of the disease, and impair the development of effective treatment approaches. Blood-based liquid biopsy provides a noninvasive strategy for tumor diagnosis, but its application in brain tumors has remained challenging. This is partially due to the blood-brain barrier (BBB), which is a physical obstacle preventing the transfer of brain tumor biomarkers into the peripheral circulation, resulting in extremely low concentrations of circulating biomarkers. To address this challenge, we developed a technique called sonobiopsy, which used focused ultrasound (FUS) to disrupt the BBB and release tumor biomarkers into the blood circulating, enabling molecular characterization of the brain tumor without surgery. Sonogiopbys provides a promising technique for noninvasive and spatiotemporal controlled molecular diagnosis of brain tumors. It has the potential to radically advance the diagnosis, monitoring, and understanding of brain tumors by precisely, rapidly, and safely identifying tumor molecular signatures.
University of Brescia

Energy Harvesting and Passive Resonators with Contactless Interrogation for Stand-Alone Sensors based on Piezoelectric Films

One of the main trends in sensors for both research and industrial applications is to increasingly aim at freestanding sensor units with wireless signal transmission, often across a short range. Eliminating cables requires means to make energy available in the sensor unit for power supply. On-board energy sources, such as batteries, are still the primary choice, yet they suffer limitations in terms of depletion and need for recharge/replacement, which makes them unsuitable in many applications and ultimately demands for new solutions in the long run. In order to develop stand-alone sensor units, two attractive options, each with specific features, are either energy harvesting to power sensors from the surroundings, thereby making them energetically-autonomous nodes, or passive sensors with energy supplied on demand from an external interrogation module. Both options can be enabled by piezoelectric film elements embedded in miniaturized devices. In particular, the piezoelectric effect as a cross-field transduction mechanism between the electrical and mechanical domains can be exploited in either energy harvesting from mechanical inputs or in electromechanical microresonators working as passive sensors coupled to specific external electronics to obtain short-range contactless readout. The talk will offer an overview of energy harvesters from vibration and motion and of resonant sensors with contactless interrogation based on piezoelectric films and present examples of stand-alone sensors.
University of Cambridge

Phononic frequency combs in microelectromechanical systems

Phononic frequency combs are the mechanical analogue of optical frequency combs These frequency combs (response features evidenced as a series of equispaced discrete spectral lines) have been experimentally observed in a multitude of microelectromechanical devices confirming theoretical predictions of such phenomena in FPU chains. The formation of phononic frequency combs is mediated by nonlinear mode coupling and mixing, where comb-like spectra in the RF can be generated by driving a microelectromechanical device via a single-tone drive signal. The first systematic experimental observations were made in a system comprising two coupled modes in a single resonator device, and this has been recently followed by observations of the same phenomena in micromechanical systems comprising three coupled modes, and in coupled devices where multiple comb regimes can co-exist, with comb features defined by the system and drive parameters. While the engineering of optical frequency combs has significantly impacted the fields of time and frequency metrology and molecular spectroscopy, phononic frequency combs similarly have the potential to enable new applications such as stable resonance tracking in physical sensors, broadband vibration energy harvesting, and as component technologies for wireless communication systems and quantum information processing.
Creatis Laboratory, University of Lyon

How will echocardiography benefit from deep learning?

For several years now, deep learning techniques have been successfully applied to medical imaging in general, and echocardiography in particular. Far from being the promised panacea, these methods have allowed major advances in many specific areas such as echocardiogram analysis, view classification, recognition and segmentation of anatomical structures, user guidance or even automatic report generation. Moreover, the combination of these different techniques allows the deployment of complete and fully automated processing chains, making it possible to increase the reliability of clinical measurements and facilitate the use of ultrasound scanners outside of hospitals. In my talk, I will describe proven deep learning techniques, why they have led to significant improvements in many cardio-vascular applications, their limitations, and the innovations needed to keep the echocardiographic imaging revolution moving forward.
The Institute of Cancer Research London

The combination of focused ultrasound and immunotherapy for pancreatic cancer therapy

Abstract to come
University of Rochester

Elastographic imaging of tumor microenvironment

Pancreatic ductal adenocarcinoma (PDAC) has a 5-year survival rate of less than 10%. Surgical resection is the most effective therapy, but only 15-20% of pancreatic cancer patients have resectable disease at diagnosis. For a subset of patients with borderline resectable tumors, neoadjuvant therapies can downstage the tumor and enable surgical resection. However, the tumor microenvironment (TME) limits the ability of neoadjuvant therapies to do so. X-ray computed tomography provides information about major blood vessels and soft tissue geometry, but it does not provide information about tumor microenvironmental changes. In this talk, I will report the results of our preclinical studies that demonstrate that elastography is a good surrogate imaging biomarker for assessing changes in pancreatic cancer’s tumor microenvironment during different neoadjuvant therapies.
University of California Davis

Commercialization of PMUT-based Ultrasonic Time-of-Flight Range Sensors

Ultrasonic sensors based on bulk piezoelectric ceramics are widely used in range-finding applications today. In 2019, we introduced a new type of ultrasonic sensor based on a piezoelectric micromachined ultrasonic transducer (PMUT) combined with a custom application specific integrated circuit (ASIC) in a 3.5 x 3.5 x 1.25 mm3 package. Originally conceived in a university research project, we started a company, Chirp Microsystems (acquired in 2018 by TDK Inc.), to bring these sensors into mass production. The sensor’s signal processing ASIC incorporates a programmable microprocessor, enabling the sensor to perform various application-specific algorithms, from basic time-of-flight range-finding to human presence detection. Relative to competing range sensors based on infrared time-of-flight, PMUT-based ultrasonic ToF sensors have numerous advantages, including much lower supply current (10 µA from a 1.8V supply), the ability to operate in direct sunlight, and the ability to detect transparent or black targets. We will present data on two ultrasonic sensors, the first targeted at short-range, high-sample rate applications, such as robotics, and a second targeted a longer-range applications, such as human presence detection.
University of Michigan

Histotripsy for Brain Applications

Histotripsy uses microsecond-length ultrasound pulses to generate focal cavitation to liquefy the target tissue into acellular homogenate. Applied through excised human skulls, histotripsy has been shown to treat locations from the skull base to 5 mm from the inner skull surface as well as volume targets. By using a very low duty cycle (<0.1%), overheating to the skull can be prevented. This allows transcranial histotripsy to overcome the treatment location and volume limitations of transcranial focused ultrasound thermal ablation. This talk presents the latest results on the development of transcranial histotripsy systems, in vivo data on using transcranial MR-guided histotripsy in the porcine brain through an excised human skull, and in vivo data on transcranial histotripsy in murine brain tumor models.

5G: Revolution or Evolution?

5G has been hailed by many in the industry as the advent of mm-wave technology becoming mainstream in mobile device communication. However, over the last several years, the focus of what is indeed being implemented and rolled out has shifted away significantly from the mm-wave domain. And there are good reasons for this. This paper will discuss the underlying physical principles, of propagation loss, diffraction, materials penetration, power efficiency and battery lifetime. Based on these underpinnings, we will take a look at the dynamics of the 5G roll-out over the next few years. Furthermore, the impact on RF front-end module architecture will be discussed. The conclusions will be broken down into consequences for the individual technologies involved, and the technological and architectural challenges that could potentially arise. Finally, the three pillars of mobile technology development – performance, size, and cost – will be re-evaluated under the boundary conditions derived from above.
University of Illinois Urbana-Champaign

Lithium Niobate-based RF Microsystems: Advances and Prospects

This talk will review the recent advances made in leveraging Lithium Niobate (LN) thin films to engineer RF microsystems, including resonators, filters, delay lines, circulators, and oscillators. The discussion will first give an overview of the material properties of LN and the film transfer techniques that are foundational to enabling various configurations of thin-film LN on a carrier. Next, These configurations and their benefits for realizing different vibrational modes will be offered. Multiple microsystems are then shown to exemplify how material-level advances can translate to device-level breakthroughs. Finally, prospects hold by LN-based RF microsystems will be discussed in the hope of charting a path to successful commercialization.
The Fifth Medical Center of Chinese PLA General Hospital

Improving B-mode ultrasound diagnostic performance for focal liver lesions using deep learning

The liver is the largest digestive gland in the body and there are dozens of types of focal liver lesions (FLLs) including benign, malignant and non-neoplastic lesions. It is important to precisely identify the characteristics of FLLs for it is the basis of providing reasonable treatment guidance for patients. Ultrasound (US), as the most widely used imaging modality in work-up of FLLs, its diagnosis of FLLs is often subjective process requiring substantial experience and expertise of radiologists. Therefore, diagnosis of FLLs has led to increasingly use the time and cost-consuming MRI/CT and even invasive biopsy in clinical practice. It is necessary for the development of methods that serve as an instrument that identify the dominant US features to accurately classify FLLs and narrow the gap between the radiologists with different experience level. Deep convolutional neural network, as a newly emerging technique, provides new opportunity for FLLs diagnosis by US image. It can provide automated quantification of large amounts of image features from medical images, which has the potential to uncover disease characteristics that fail to be appreciated by naked eyes. In this presentation, we will demonstrate a deep convolutional neural network model for classifying of malignant from benign FLLs. Our study indicates that the diagnosis capability of our model was comparable to contrast enhanced CT and superior to skilled radiologists with 15-year experience in FLLs diagnosis performance. The high performance of deep learning model may fuel the time-consuming and relatively expensive contrast enhanced imaging to concentrate on uncertain or complex cases in order to filtrate highly benign or non-urgent cases for clinicians. In addition, it can also maximize healthcare resources and assist less-experienced radiologists from low-volume hospitals to improve their diagnostic accuracy of liver cancer, similar to the level of CECT and rich-experienced radiologists. Furthermore, it has a high potential to contribute to narrow the gap between the radiologists with different experience level and reduce the barriers for rural and community hospitals with relatively scarce of medical resources to improve the FLL diagnosis.
Polish Academy of Sciences

New Fascinating Properties and Potential Applications of Love Surface Waves

Love surface waves are elastic waves propagating in waveguides composed of a surface layer deposited on a semi-infinite substrate. The mechanical displacement of Love waves decreases rapidly, as a function of depth, therefore the energy of the Love wave can attain very high densities in the vicinity of the waveguide surface. This fact was crucial in development of Love wave sensors that are strongly affected by the parameters of the surrounding viscoelastic liquid. On the other hand, Love surface waves have many unique features that differentiate them from other types of surface waves, such Rayleigh, Lamb or Stoneley waves. For example, Love surface waves: have only one shear horizontal (SH) component of vibration (mechanical displacement) have mathematical model with a moderate complexity have an exact analogue in electromagnetism (TM and TE modes in planar dielectric waveguides) have a direct analogy in quantum mechanics (quantum particles in potential wells). Love surface waves were predicted theoretically in 1911 by the prominent British scientist A. E. H. Love, who analyzed seismic data registered in wake of Earthquakes. In fact, Love surface waves are most destructive of all seismic waves, since they may generate huge shear forces that can literally cut-off foundations of most civil engineering structures. On the other hand, Love surface waves revealed their benign face by the end of the twentieth century with the advent of Love wave bio, chemo and physico-sensors with parameters superior to those achievable with other types of acoustic sensors. Despite their centennial history Love surface waves do not cease to surprise us by unveiling their new unexpected properties and possibilities for novel applications. Indeed, in recent two years the author of this presentation discovered a number of new original phenomena that occur in lossy Love wave waveguides loaded with a viscoelastic liquid that were entirely unexpected and are to some extent completely counterintuitive. As an example we can mention the occurrence of abrupt changes in phase velocity v_p and attenuation α, as a function of viscosity η_0 of the loading Newtonian liquid resonant-like maxima in attenuation, as a function of thickness “”h”” of a lossy surface layer and frequency f maximum in attenuation α as a function of viscosity η_0 of the loading Newtonian liquid minimum in phase velocity v_p as a function of viscosity η_0 of the loading Newtonian liquid In fact, the phase velocity v_p and attenuation α of the Love wave can abruptly change not only their values but also their qualitative character, e.g., from aperiodic to oscillatory and vice-versa, for a certain value of viscosity of the loading Newtonian liquid. The above phenomena can occur only in multilayer Love wave waveguides with a number of surface layers N≥2. These phenomena may be attributed to a sudden repartition of Love wave energy from one surface layer to another. The author intends to cover in this presentation the following topics: 1. basic properties of Love surface waves 2. applications of Love waves in seismology and sensor technology 3. mathematical models (direct Sturm-Liouville problems) of Love surface waves 4. analogies in electromagnetism and quantum mechanics 5. power flow in Love wave waveguides (Poynting vector) 6. new counter intuitively phenomena discovered in Love wave waveguides: a) minimum of the phase velocity as a function of viscosity of the loading Newtonian liquid b) maximum of the attenuation as a function of viscosity of the loading Newtonian liquid 7. new unexpected phenomena in Love wave waveguides: a) sudden qualitative changes in phase velocity and attenuation as a function of waveguide parameters b) resonant-like attenuation of Love waves, etc. 8. new mathematical tools applied in analyze of Love wave waveguides a) Inverse Sturm-Liouville Problem that may revolutionize Love wave sensors b) modified Auld’s perturbation formula expressed entirely in term of the complex power flow in Love wave waveguides 9. new potential applications of Love surface waves in sensors and signal processing.
University of Michigan Medical School

Immunotherapeutic implications of histotripsy focused ultrasound ablation

In this presentation, we will review recent observations made regarding the ability of histotripsy to incite local pro-inflammatory immunogenic cell death and systemic anti-tumor immune responses. Possible underlying mechanisms for these observations and their potential clinical application will be explored.
Shanghai Tenth People’s Hospital

Towards a tumor-free world: when ultrasound meets immunotherapy

Combined checkpoint blockade (e.g., PD1/PD-L1) with traditional clinical therapies can be hampered by side effects and low tumour-therapeutic outcome, hindering broad clinical translation. Here we report a combined tumour-therapeutic modality based on integrating nanosonosensitizers-augmented noninvasive sonodynamic therapy (SDT) with checkpointblockade immunotherapy. All components of the nanosonosensitizers (HMME/[email protected]) are clinically approved, wherein liposomes act as carriers to co-encapsulate sonosensitizers (hematoporphyrin monomethyl ether (HMME)) and immune adjuvant (imiquimod (R837)). Using multiple tumour models, we demonstrate that combining nanosonosensitizersaugmented SDT with anti-PD-L1 induces an anti-tumour response, which not only arrests primary tumour progression, but also prevents lung metastasis. Furthermore, the combined treatment strategy offers a long-term immunological memory function, which can protect against tumour rechallenge after elimination of the initial tumours. Therefore, this work represents a proof-of-concept combinatorial tumour therapeutics based on noninvasive tumours-therapeutic modality with immunotherapy.
Erasmus MC

Microbubble-mediated drug delivery revealed at microsecond and micrometer resolution

Treating cardiovascular disease and cancer using ultrasound-activated vibrating microbubbles (1-10 µm in size) has shown preclinical potential to boost drug therapy and reduce side-effects because drugs are delivered locally. Recently, several clinical trials have demonstrated safety of the treatment and increased survival. Despite advances in the field, the underlying mechanism of microbubble-mediated drug delivery are poorly understood. One of the reasons for this is the huge range in time scales involved. The time scale of the microbubble vibration is 2 million times per second in a 2 MHz ultrasound field (microseconds), which is many orders of magnitude smaller than the time scale of physiological effects (milliseconds), let alone that of biological effects (seconds to minutes) and clinical relevance (days to months). To allow the investigation of the microbubble-cell-drug interaction at a microsecond and micrometer resolution, unique technology was created by coupling the Brandaris 128 ultra-high-speed camera (~25 million frames per second recordings) to a custom-built confocal microscope. In this talk, I will describe new insights gained into the microbubble-cell-drug interaction by using this technology for two different cell types: endothelial cells and bacteria. For endothelial cells the focus will be on the microbubble behavior in relation to the drug delivery pathways sonoporation and cell-cell contact opening, as well as how intracellular calcium fluctuations play a role. Novel microbubble-mediated treatments for the life-threatening disease bacterial infective endocarditis, either on native heart valves or cardiac devices such as pacemakers, are the focus for the bacteria biofilm work.
City University of New York

Exotic Sound Interactions in Acoustic Metamaterials

Metamaterials are artificial materials with properties well beyond what offered by nature, providing unprecedented opportunities to tailor and enhance the control of waves. In this talk, I discuss our recent activity in acoustics and mechanics, showing how suitably tailored meta-atoms and their arrangements open exciting venues for new technology. I will focus in particular on the opportunities offered by time modulation and switching, as well as gain, in acoustic metamaterials, which offer an interesting platform for enhanced sensing, one-way signal transport and nonlinear phenomena. These concepts are ideally suited for the new technological opportunities in the context of ultrasound technologies. Physical insights into the underlying phenomena, and new devices based on these concepts will be presented.
University of Potsdam

Soft Transducer Materials – Polymer-Based Electrets for Sensors and Actuators

Since the first report of natural electrets – pieces of amber that could attract or repel light objects or draw tiny electric sparks – more than 2500 years ago, electret science and technology underwent more and more rapid developments via the electrophorus (1760s) and wax-resin mixtures (1920s) to modern polymer-based electrets. Today, we can distinguish between space-charge electrets, electro-electrets (a.k.a. dielectric elastomers), ferro- or piezo-electrets, ferro-, pyro- and piezoelectric polymers and ceramic-polymer composites. Stress-induced movements of their internal electric charges or dipoles, and electric-field-induced displacements of the charged or poled polymer, give rise to direct and inverse electro-mechanical/piezo-electrical effects, respectively. Longitudinal and transverse transduction effects may be used in sensors (micro-energy harvesters, microphones, etc.) and in actuators (sound and ultrasound emitters, haptic-feedback devices, soft micro-actuators, etc.). A significant range of densities, as well as isotropic or anisotropic elastic properties, of the various soft materials lead to a broad range of specific acoustic impedances. Recent advances, e.g. in polymer science and technology, in rather stable high-field dielectrics, and in additive manufacturing of patterned and heterogeneous materials, promise a bright future for soft transducer materials – in particular, but not only, for sound and ultrasound applications.
The Second Affiliated Hospital of Zhejiang University

Contrast Enhanced Ultrasound from diagnostics to the therapy

The emergence of CEUS has brought about a new revolution in ultrasound imaging. CEUS has been increasingly mature in diagnosing different kinds of diseases over the recent years. Meanwhile, the interaction between ultrasound and MBs can induce various acoustic effects, including thermo effect, sonoporation, and cavitation. In the recent decade, more and more researches indicated that ultrasound mediated microbubble stable cavitation (UMMC), as an anti-tumor drug delivery system, played a supplementary role in tumor therapy. In this presentation, I will provide an overview of approved and off-labeled clinical applications of CEUS, and some pre-clinical results of UMMC in tumor therapy and T2DM therapy in animal models from our group. Our studies indicated that UMMD could inhibit the growth of VX2 hepatic tumors in rabbits by irreversible destroying tumor microvessel and tumor cells. Meanwhile, UTMD GLP-1 gene therapy may be an effective approach to regenerate islet beta cells and normalize glycemic control in type 2 diabetes humans.
Shenzhen Institute of Advanced Technology

Magnetic resonance imaging-guided ultrasound brain stimulation in non-human primates

Neuromodulation is a fundamental tool in neuroscience to explore neural mechanisms from molecular to behavioral levels. Recently, ultrasound has been found to be an effective noninvasive neuromodulation tool. This cutting-edge discovery may have great potential for the therapy of many functional brain diseases. One major limitation of ultrasound neuromodulation is the accurate steering of ultrasound beams throughout the skull to the target position inside the brain. Magnetic resonance imaging (MRI) plays an important role in the precise and dynamic guidance of ultrasound neuromodulation by providing target localization, neural activity monitoring, and safety assurance. In the presentation, MRI-guided ultrasound neuromodulation techniques are reviewed, including transcranial focused ultrasound technology, localization and visualization by magnetic resonance (MR) acoustic radiation force imaging, brain activity monitoring and assessment by functional MRI, and applications of ultrasound neuromodulation. The principles of all the above-mentioned techniques are briefly introduced, and some preliminary results of our group are described. The results of our study showed that ultrasound stimulation of the primary visual cortex of rhesus monkeys activated the target area and its downstream and associated brain regions, which suggested that ultrasound stimulation is capable of exciting neuronal activities that may be transmitted to related functional regions. MRI is believed to be a powerful imaging modality for accurate ultrasound neuromodulation.
North Carolina State University

Leveraging scattering to unlock lung quantitative ultrasound

Conventional ultrasound imaging of the lung has remained elusive due to the complexity of the parenchyma. The millions of air-filled alveoli are responsible for large amounts of scattering, precluding the common assumptions underlying B-mode imaging. We propose to leverage this purported weakness. Each scattering event can be seen as an opportunity for the ultrasound wave to embed information on the architecture of lung parenchyma. By leveraging scattering, we developed new methods for the quantitative assessment of the lung. The diffusivity of ultrasound is exploited as a new source of contrast for lung tissue characterization. Lung diseases such as pulmonary edema and pulmonary fibrosis affect the micro-architecture of the parenchyma. We show how ultrasound scattering parameters can be used to quantify these changes, and ultimately be used as a biomarkers for these diseases. There is tremendous potential of such non-invasive biomarkers for monitoring and follow up of response to treatment. Finally, we will also show how these concepts can be used for ultrasound-based lung imaging to detect and localize pulmonary nodules in real time during surgery, to ensure lung nodules resection with safe margins so no cancerous tissue is left behind.
University of Virginia

Promoting the Cancer Immunity Cycle with Focused Ultrasound

In this presentation, I will provide an overview of recent studies from our group aimed at driving anti-cancer immunity using both thermal and mechanical forms of focused ultrasound energy deposition. Our research in thermal focused ultrasound centers primarily on applications for breast cancer and melanoma. Here, we employ a variety of pre-clinical approaches (e.g. flow cytometry and RNA sequencing) to understand how the immune system is modulated by focused ultrasound, as well as to design and implement new immunotherapeutic regimens that will most effectively cooperate with focused ultrasound. Ongoing clinical trials at our institution are now exploring how partial thermal ablation interacts with checkpoint inhibitors in patients with metastatic disease. Meanwhile, our research on mechanical forms of focused ultrasound primarily entails lifting immunosuppression in brain tumors via the delivery of immunotherapies across the blood-brain tumor barrier under MR image-guidance.
Hong Kong University of Science and Technology

Using acoustics to demonstrate topological and non-Hermitian physics

Acoustic systems are relatively simple to design, implement and characterize. As such, they are good platforms to demonstrate new physics concepts and the associated phenomena. We will use some examples to illustrate the realization of topological and non-Hermitian physics in acoustic systems. We show that an acoustic metamaterial consisting of an array of spinning cylindrical inclusions can possess many novel properties that cannot be achieved in static systems. These interesting effects include folded bulk bands and folded interface-state bands. The folding of bands inside the first Brillouin zone is generally not possible because such dispersions violate causality principles but in acoustic systems with rotation, this is made possible by a rotation-induced anti-resonance of compressibility and the rotational Doppler effect. Robust one-way transport properties can be enabled by non-degenerate interface states, but within the same band, interface states at different frequencies can have different propagation directions. If we form an interface between two acoustic crystals composing of spinning cylinders with equal but opposite spinning velocities embedded in a liquid, long-range and robust acoustic pulling can be enabled by a pair of one-way chiral surface waves supported on the interface between two counter-rotating phononic crystals. When the chiral surface mode with a relative small Bloch wave vector is excited, the particle located in the interface waveguide will scatter the excited surface mode to another chiral surface mode with a greater Bloch wave vector, and resulting in an acoustic pulling force, irrespective of the size and material of the particle. The absence of backscattering channels make the pulling force robust against local disorders, and the particle can be pulled in any trajectory as determined by the shape of the interface. This new acoustic pulling scheme overcomes some of the limitations of the traditional acoustic pulling using structured beams, such as short pulling distances, straight-line type pulling and strong dependence on the scattering properties of the particle. Acoustic systems are also good platforms to illustrate exceptional point physics. The signature of non-Hermitian systems is the existence of exceptional points. In some cases, the exceptional points can form interesting connected structures. We will see that an astroid shaped loop of exceptional points can emerge from a non-Hermitician Lieb lattice when specific hoppings are introduced. Such interesting exceptional point structure is realized in an acoustic implementation, which demonstrates that exceptional nexus with a hybrid topological invariant can be formed.
UC San Diego

Soft ultrasonic patches for continuous monitoring of deep tissues

Soft electronic devices that can acquire vital signs from the human body represent an important trend for healthcare. Combined strategies of materials design and advanced microfabrication allow the integration of a variety of components and devices on a stretchable platform, resulting in functional systems with minimal constraints on the human body. In this presentation, I will demonstrate a soft ultrasonic patch that can emit ultrasound waves to penetrate the skin and noninvasively capture dynamic events in deep tissues, such as blood pressure and blood flow waveforms in central arteries and veins. This stretchable platform holds profound implications for a wide range of applications in consumer electronics, sports medicine, defense, and clinical practices.
Beijing Institute of Technology

Controlling Elastic Wave With Solid Pentamode Metamaterials

Solid pentamode materials are degenerated elastic solids with quasi-zero shear rigidity, it can be approximately realized by genius microstructure design. Due to the flexibility in designing wave impedance, the pentamode material is potential for the control of elastic waves with broad frequency performance. In this talk, the concept and design method of pentamode materials are firstly explained, then two examples are provided to illustrate the capacity of wave manipulation by this kind of material. The first example focuses on elastic wave filtering, pentamode materials are shown to be able to support only single polarization mode (either transverse wave or longitudinal wave) depending on their microstructure design, which can hardly be possible with traditional solids. The functions of elastic wave mode splitting and sound isolation in water with this kind of metamaterials are illustrated. The second example explores broadband underwater acoustic cloak. It is shown that by carefully designing unit cells of pentamode materials and arranging them in space, a broadband underwater acoustic cloak can be designed. Both examples are validated by experiments. These findings demonstrate a great capacity of broadband mechanical wave control by solid pentamode materials.
University of Electronic Science and Technology of China

Quantum Leap in Simulation Technologies for Radio Frequency Acoustic Wave Devices Gifted by Hierarchical Cascading Technique

This talk is aimed at introducing the hierarchical cascading technique (HCT) not only as a speed-up tool for FEM simulation but also as a versatile technique for attacking unexplored problems. In 2016, Koskela, et al., proposed HCT for fast 2D FEM simulation of SAW devices. The technique is quite powerful when the device structure under concern is mainly composed of identical cells and the number of cells N is large. This is because the time consumption is almost proportional to logN, while the required memory is almost independent of N. Now HCT-based 2D FEM is widely used in SAW device development. The author’s group applied HCT to attack various wave excitation and scattering problems including those believed to be impossible. Examples are SAW scattering at irregularity inserted in an infinitely long grating and that at IDT finger tips. The traveling wave excitation source proposed by the author’s group fits well with HCT and can be adapted efficiently in the analysis. In addition, combination of HCT with high-end GPU makes 3D FEM simulation possible for practical SAW device structures. Now we can apply periodic 2D, full 2D, periodic 3D and full 3D FEM simulations to SAW resonators. Comparison of results from these simulations enables evaluation of different loss contributions separately, and field analyses may reveal remaining loss mechanisms hidden in the structures. Once the degradation mechanism is understood, we can search possible countermeasures using the fast parameter-scan function of HCT-based FEM.

Heterogeneous material integration: from advanced substrates to acoustic resonators

The innovation of advanced substrates reflects today’s new paradigm for semiconductor technologies: key figures of merit for most advanced device technologies depend on the starting substrate material. Thin film technologies are currently being used for advanced MEMS such as acoustic filters and ultrasonic devices. Combined with single-crystalline quality of the materials, such engineered substrates enable higher device performance and better manufacturing yield. This paper reports on recent advances in material innovation and substrate technologies enabling high performance acoustic and ultrasound resonators. One example is the SAW resonators using guided acoustic modes of Piezoelectric-On-Insulator (POI) substrate combining single-crystal LiTaO3 thin film, an intermediate SiO2 layer and Silicon handle substrate. The SAW resonators fabricated using POI substrate lead to significant performance improvements compared to the conventional bulk substrates, such as very low TCF, higher coupling factor, lowest RF losses and maximum quality factor (Bode-Q). The Smart CutTM technology provides a versatile manufacturing platform for POI advanced substrates and can be adapted to different piezoelectric materials (LiTaO3, LiNbO3, etc), various crystal orientations and film thicknesses. Therefore, it enables new solutions for acoustic filter designers to overcome some of the 5G technological challenges and further explore new device concepts. This work is based on contributions of many colleagues from Soitec, frec|n|sys and collaboration projects with CEA-LETI under the Substrate Innovation Center.
Duke University

Breaking Limits in Photoacoustic Imaging: Deeper, Faster, Smaller and More colorful

By acoustically detecting the optical absorption contrast in biological tissues, photoacoustic imaging (PAI) has proven increasingly powerful for multi-scale anatomical, functional, and molecular imaging. In PAI, a short-pulsed laser beam illuminates the biological tissue to generate a small but rapid temperature rise, which leads to emission of ultrasonic waves due to thermoelastic expansion. The wideband ultrasonic waves are detected to form a high-resolution tomographic image that maps the original optical absorption in the tissue. My talk will focus on several major new fronts of PAI that have collectively enabled fast, miniaturized, deep, and high-sensitivity biomedical applications in functional neuronal imaging, drug testing, early cancer detection, and interventional therapy. First, PAI has broken the penetration limit and achieved super-deep (~10 cm) imaging by using advanced internal light delivery, extending its applications ready into internal organ imaging on large animal models. Second, by innovating novel scanning technologies, PAI has been accelerated by more than 1000 times in imaging speed with a large field of view and high spatial resolution, allowing for the monitoring of highly dynamic biological processes. Third, by adapting novel fabrication technologies in optics and acoustics, miniaturized PAI has achieved handheld, wearable and head-mounted imaging with high spatial–temporal resolutions and high throughput. Lastly, taking advantage of switchable or tunable near-infrared photoacoustic-specific probes, PAI has improved its sensitivity and specificity by more than 100 times, enabling highly sensitive detection of malignant cancer, tissue hypoxia, and neuronal activities.

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