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The ability of ultrasound to produce highly controlled erosion phenomenon was investigated and various erosion models have been compared by considering various parameters. In cleaning industry, Vibro Cleaner (VC) has been used to remove contaminations from the surface of metal components. This process is most preferable to out of reach or critical surface of the objects. The novelty of this research is to compare various erosion models and to identify appropriate model for ultrasonic cleaning application to get meaningful results of metal removal rate. The computational model of Vibro Cleaner has been developed using pressure acoustic transient in COMSOL Multiphysics software. Acoustic and Computational Fluid Dynamics (CFD) modules have been coupled together to investigate erosion rate. In acoustic approach, acoustic pressure and sound pressure level have been studied by means of piezoelectric transducer through tank wall transience. In CFD approach, Bubbly fluid flow has been applied to get turbulence in acoustic streaming. Also, particle tracing has been coupled to understand the particle trajectories and motion of fluid flow. Erosion terms are also introduced at a surface of metal parts which need to be clean. The Erosion rate has been evaluated by using cavitation erosion phenomenon in which cavitation bubbles strike and implode over the metal surface and clean the dirt, dust, oil and other contaminations. Various Erosion models like Finnie, E/CRC, Oka and Det Norske Veritas (DNV) have been studied and results have been compared to identify appropriate erosion model towards the ultrasonic cleaning application by considering 28 kHz frequency and PZT-4 piezoelectric transducer. Comparative study leads to conclude that the Finnie erosion model have given stringent results as compare to other erosion model.

Arc plasma shape under pulsed and continuous ultrasound field was studied in this research using a self-developed welding device which combines arc and ultrasound field coaxially. The results show that, compared with the arc of conventional tungsten inert gas welding, the shape of arc under pulsed power ultrasound field relates to the pulse frequency. From 1 to 20 Hz, the arc plasma expands and contracts periodically in one pulse. When more than 20 Hz, the arc plasma contracts as the pulse frequency increases. During high-pulse frequency, the arc shape becomes steady and similar to those in the continuous ultrasound field. When at 500 Hz, the contraction ratio of arc projected area under pulsed power ultrasound field reaches 38 %, compared with 30 % of the same power continuous ultrasound field; i.e., in high-frequency, low-power pulsed power ultrasound can obtain arc control effect similar to high power continuous ultrasound, raising usage efficiency of ultrasound energy. The mechanism of ultrasonic influence on arc is analyzed based on sound pressure and acoustic streaming.

Large-scale cell suspension culture technology opens up opportunities for numerous medical and bioengineering applications. For these purposes, scale-up of the culture system is paramount. For initial small-scale culture, a simple static suspension culture (SSC) is generally employed. However, cell sedimentation due to the lack of agitation limits the culture volume feasible for SSC. Thus, when scaling up, cell suspensions must be manually transferred from the culture flask to another vessel suitable for agitation, which increases the risk of contamination and human error. Ideally, the number of culture transfer steps should be kept to a minimum. The present study describes the fabrication of an ultrasonic suspension culture system that stirs cell suspensions with the use of acoustic streaming generated by ultrasound irradiation at a MHz frequency. This system was applied to 100-mL suspension cultures of Chinese hamster ovary cells-a volume ten-fold larger than that generally used. The cell proliferation rate in this system was 1.88/day when applying an input voltage of 40 V to the ultrasonic transducer, while that of the SSC was 1.14/day. Hence, the proposed method can extend the volume limit of static cell suspension cultures, thereby reducing the number of cell culture transfer steps.

Background: Arthritis pain is primarily managed by nonsteroidal anti-inflammatory drugs (NSAIDs), such as diclofenac. Topical diclofenac gel is limited in efficacy due to its limited penetration through the skin. This study investigates the use of a multihour, wearable, localized, sonophoresis transdermal drug delivery device for the penetration enhancement of diclofenac through the skin. Materials & methods: A commercially available, sustained acoustic medicine (sam®) ultrasound device providing 4 h, 1.3 W, 132 mW/cm2, 3 MHz ultrasound treatment was evaluated for increasing the drug delivery of diclofenac gel through a human skin model and was compared with standard of care topical control diclofenac gel. Results: Sonophoresis of the diclofenac gel for 4 h increases diclofenac delivery by 3.8× (p

Optical imaging with nanoscale resolution and a large field of view is highly desirable in many research areas. Unfortunately, it is challenging to achieve these two features simultaneously while using a conventional microscope. An objective lens with a low numerical aperture (NA) has a large field of view but poor resolution. In contrast, a high NA objective lens will have a higher resolution but reduced field of view. In an effort to close the gap between these trade-offs, we introduce an acoustofluidic scanning nanoscope (AS-nanoscope) that can simultaneously achieve high resolution with a large field of view. The AS-nanoscope relies on acoustofluidic-assisted scanning of multiple microsized particles. A scanned 2D image is then compiled by processing the microparticle images using an automated big-data image algorithm. The AS-nanoscope has the potential to be integrated into a conventional microscope or could serve as a stand-alone instrument for a wide range of applications where both high resolution and large field of view are required.

In the field of endodontics, lasers have been used for a long time for the optimization of Endodontic irrigation in particular. The laser-activated irrigation (LAI) technique is based on the photomechanical effects of the lasers at low settings. They create specific cavitation phenomena and acoustic streaming in intracanal fluids. More recently, a new technique with a Er:YAG laser has been used with sub-ablative energy (20 mJ, 15 Hz) and ultra-short pulses (50 µs). This leads to intracanal cavitation and shockwaves as a result of photoacoustic and photomechanical effects. This phenomenon is called photon-induced photoacoustic streaming (PIPS). PIPS and Laser activated irrigation are described in the literature as a revolutionary and powerful method to activate the irrigant; however, systematic literature on this topic is missing. This review compares the literature on Er:YAG LAI and PIPS on endodontic irrigation with other irrigation methods. An article search was performed on the PubMed database using a series of keywords related to endodontic irrigation, including Er:YAG LAI and PIPS; 59 articles were selected for the review according to the inclusion and exclusion criteria. No in vivo study was found. The Er:YAG LAI and PIPS outperformed other methods in 33 of the 59 articles. There was a great variety in the study designs including bacterial incubation time, laser parameters, irrigation protocols, and irrigating solution used. The evidence suggests that the Er:YAG LAI and PIPS are promising in canal disinfection as well as debris and smear layer removal. However, the large variety in the study methods makes the results less significant. Further studies are needed to better evaluate the efficiency of these techniques, especially in vivo studies.

In recent years, ultrasonic technology has been extensively applied in numerous manufacturing processes to improve the process performance and part quality. This review paper presents a broad overview on the recent progress in ultrasonic vibration-assisted (UV-A) manufacturing processes reported in the literature. Based on the ultrasonic energy propagation through solid or liquid phases, UV-A manufacturing processes can be divided into mechanical manufacturing processes (including conventional machining, densification, forming, and consolidation) and thermal manufacturing processes (including thermal non-traditional machining, casting, fusion welding, laser cladding, and direct laser deposition). The results from a great number of published investigations have strongly evidenced the significant influences of ultrasonic vibration during the material processing. In UV-A mechanical manufacturing processes, ultrasonic vibration can reduce the machining force through intermittent cutting between machine tools and the workpiece, decrease the load in both densification and forming processes due to the reduced friction, and increase the bond at the workpiece interface by breaking oxide layers in ultrasonic consolidation. In UV-A thermal manufacturing processes, on the other hand, ultrasonic vibration can exert nonlinear effects (acoustic streaming and cavitation) on the solidification behavior of liquid melting materials. The precision and quality of parts fabricated by thermal manufacturing will be thus improved through various phenomena such as element homogenization, material degassing, crack reduction, microstructure refinement, etc. This literature review aims to provide a comprehensive overview on ultrasonic vibration influences in different UV-A manufacturing processes and guide the future development of ultrasonic vibration assisted technologies.

In this study, we demonstrate an acoustofluidic device that enables single-file focusing of submicron particles and bacteria using a two-dimensional (2D) acoustic standing wave. The device consists of a 100 µm ✕ 100 µm square channel that supports 2D particle focusing in the channel center at an actuation frequency of 7.39 MHz. This higher actuation frequency compared with conventional bulk acoustic systems enables radiation-force-dominant motion of submicron particles and overcome the classical size limitation (≈ 2 µm) of acoustic focusing. We present acoustic radiation force-based focusing of particles with diameters less than 0.5 µm at a flow rate of 12 µL min-1, and 1.33 µm particles at flow rates up to 80 µL min-1. The device focused 0.25 µm particles by the 2D acoustic radiation force while undergoing a channel cross-section centered, single-vortex acoustic streaming. A suspension of bacteria was also investigated to evaluate the biological relevance of the device, which demonstrated the alignment of bacteria in the channel at a flow rate of up to 20 µL min-1. The developed acoustofluidic device can align submicron particles within a narrow flow stream in a highly robust manner, validating its use as a flow-through focusing chamber to perform high-throughput and accurate flow cytometry of submicron objects.

Micro-/nanorobots are miniaturized devices that convert energy stored in the environment into motion and are envisioned to revolutionize applications of biomedicine, environmental remediation, sensing, and micro-manufacturing. Among the various ways to power micro-/nanorobots, ultrasound is particularly advantageous because of its biocompatibility and thus wide adoption in hospitals and clinics. In this chapter, we review the recent development of ultrasound-powered micro-/nanorobots, highlighting their usefulness in biomedical applications as well as challenges ahead. We begin with a brief introduction to the operating principles of acoustic radiation forces and acoustic streaming, two concepts critical for ultrasonic propulsion. This is followed by a thorough description of four major types of ultrasound micro-/nanomotors, namely, microrod streamers, bubble streamers, flagella streamers, and acoustic jets. Their future prospects in biomedical applications are discussed in the last section. This book chapter is particularly useful for readers interested in biomedical applications but new to the field of micro-/nanorobots. It is also useful for experienced readers looking for expanding their toolbox or improving their understanding of operating mechanisms.

We 3D print micro-robotic swimmers with the size of animal cells using a Nanoscribe. The micro-swimmers are powered by the microstreaming flows induced by the oscillating air bubbles entrapped within the micro-robotic swimmers. Previously, micro-swimmers propelled by acoustic streaming require the use of a magnetic field or an additional ultrasound transducer to steer their direction. Here, we show a two-bubble based micro-swimmer that can be propelled and steered entirely using one ultrasound transducer. The swimmer displays boundary following traits similar to those biological swimmers that are known to be important for performing robust biological functions. The micro-robotic swimmer has the potential to advance the current technology in targeted drug delivery and remote microsurgery.

Microrobotics have emerged as a fascinating field with great potential for drug delivery, non-invasive microsurgery, and precise materials assembly. Acoustic devices have been exploited as effective strategies for developing underwater microrobotics. This work presents an integrated wirelessly powered microelectromechanical swimming robot driven by Lamb Wave Resonators (LWRs). Improvements have been made to the structure of LWR driver. The asymmetric distribution of reflectors and leakage hole of the LWR leads to the difference of acoustic wave transmission. Unidirectional drive was realized with the asymmetric acoustic streaming effect. Aided by programming the energy distribution of the LWRs, flexible 2-D motions can be realized, demonstrating an artificial acoustic compartment for tiny swimmers.

Acoustic Streaming is a flow phenomenon with many applications in the field of microfluidics, such as micro mixing[1, 2] and particle manipulation[3]. With the manufacturing techniques evolves, more complicated geometries can be designed for microfluidic device and 3-D acoustic streaming patterns may occurs. In this study, 3-D trajectories of particle induced by acoustic streaming around an inclined triangular obstruction in a microchannel were visualized by a volumetric tracking method using Digital Inline Holographic Microscopy (DIHM)[4-6]. The triangular obstruction has a tip angle of 20° and an inclined angle of 30°. The acoustic streaming is created under 12 kHz oscillation of a piezo plate driven by 20V voltage. Illuminated by a 450nm continuous laser, the magnified hologram of the motion of 1.79μm tracer particles was recorded by a low-cost 10X industrial microscope with a machine vision camera of 10 fps (frames per second). Using RayleighSommerfeld back-propagation method[7], particle locations was reconstructed frame by frame and 3-D tracking of individual particles was performed afterwards. The trajectories of each particle were reconstructed to reveal the vortical structure of the acoustic streaming flow. For the current system setup, the measurable range was estimated to be 550×685×840 μm3. The 3-D location reconstruction accuracy was verified with a calibration target and the location sensitivity was found to be linear throughout the measurable range. Reconstruction at different depth locations show that the dick-shaped calibration dots and the spherical polystyrene particles have different intensity profiles. The calibration dots show local minimum of intensity at the correct depth location, while polystyrene particles show local maximum of intensity instead. Resolved particle trajectories show that the acoustic streaming flows cause particles to move with 3-D spiral shaped motions near the side of the triangular obstruction, while particles away from the obstruction shows planar motions.

A combined top-down/bottom-up microfluidic assembly system is demonstrated in which microspheres undergo directed assembly within microchannels. The approach is adapted from macroscale templated assembly by selective removal (TASR), in which high-frequency acoustic excitations drive selective assembly into shape- and size-matched wells patterned in a planar surface. A PDMS layer patterned with microchannels is bonded to a PDMS layer molded to define assembly wells. A suspension of 10 $\mu \text{m}$ diameter polystyrene microspheres is flowed into the microchannels, and an external, high-frequency ultrasonic transducer circulates the microspheres within the channels and removes them from everywhere except the size-matched wells. Microspheres are successfully assembled in wells inside the microchannels with yields of up to 90%. Smaller channel dimensions reduce assembly yield in part because smaller internal channel volumes reduce the availability of microspheres relative to assembly wells. In addition, reducing channel width below about $500~\mu \text{m}$ is shown to be an independent predictor of low assembly yields; this is attributed to the physics of acoustic streaming flow under the acoustic excitation. Assembly yield is largely independent of the location of the assembly wells within the microchannels, and selectivity is confirmed by low assembly yield of $6~\mu \text{m}$ diameter microspheres into the larger wells. [2020-0072]

The acoustic streaming which can facilitate the heat and mass transfer inside liquids is of great importance in ultrasonic processing. Most of previous investigations were mainly focused on the acoustic streaming induced by one dimensional (1D) ultrasound. In this paper, the flow field generated by 1D, 2D and 3D ultrasounds in a cubic box filled with water was investigated by numerical simulations. It is found that the jet flow emitted from the sound source is in the form of cylinder, vortex and wave, for 1D, 2D and 3D ultrasounds, respectively. When the ultrasonic dimension is increased, the flow becomes much stronger in the vicinity of the sound source but little weaker at the box center. By comparing the patterns of the flow generated by the ultrasounds of different dimensions, we demonstrate that 3D ultrasounds not only enhance the overall flow strength, but also effectively promote the uniformity of the flow and enlarge the size of vortices.

Bacterial biofilms are a cause of contamination in a wide range of medical and biological areas. Ultrasound is a mechanical energy that can remove these biofilms using cavitation and acoustic streaming, which generate shear forces to disrupt biofilm from a surface. The aim of this narrative review is to investigate the literature on the mechanical removal of biofilm using acoustic cavitation to identify the different operating parameters affecting its removal using this method. The properties of the liquid and the properties of the ultrasound have a large impact on the type of cavitation generated. These include gas content, temperature, surface tension, frequency of ultrasound and acoustic pressure. For many of these parameters, more research is required to understand their mechanisms in the area of ultrasonic biofilm removal, and further research will help to optimise this method for effective removal of biofilms from different surfaces.

A number of acoustic and fluid-dynamic phenomena appear in ultrasonic cleaning baths and contribute to physical cleaning of immersed surfaces. Propagation and repeated reflection of ultrasound within cleaning baths build standing-wave-like acoustic fields; when an ultrasound intensity gradient appears in the acoustic fields, it can in principle induce steady streaming flow. When the ultrasound intensity is sufficiently large, cavitation occurs and oscillating cavitation bubbles are either trapped in the acoustic fields or advected in the flow. These phenomena are believed to produce mechanical action to remove contaminant particles attached at material surfaces. Recent studies suggest that the mechanical action of cavitation bubbles is the dominant factor of particle removal in ultrasonic cleaning, but the bubble collapse resulting from high-intensity ultrasound may be violent enough to give rise to surface erosion. In this paper, we aim to carefully examine the role of cavitation bubbles from ultrasonic cleaning tests with varying dissolved gas concentration in water. In our cleaning tests using 28-kHz ultrasound, oxygen-supersaturated water is produced by oxygen-microbubble aeration and used as a cleaning solution, and glass slides spin-coated with silica particles of micron/submicron sizes are used to define cleaning efficiency. High-speed camera recordings and Particle Image Velocimetry analysis with a pressure oscillation amplitude of 1.4 atm at the pressure antinode show that the population of cavitation bubbles increases and streaming flow inside the bath is promoted, as the dissolved oxygen supersaturation increases. The particle removal is found to be achieved mainly by the action of cavitation bubbles, but there exists optimal gas supersaturation to maximize the removal efficiency. Our finding suggests that low-intensity ultrasound irradiation under the optimal gas supersaturation in cleaning solutions allows for having mild bubble dynamics without violent collapse and thus cleaning surfaces without cavitation erosion. Finally, observations of individual bubble dynamics and the resulting particle removal are reported to further support the role of cavitation bubbles as cleaning agents.

Ultrasound is an effective method to intensify gas-liquid processes as the oscillation energy is easily focused at the gas-liquid interface, which can induce strong interface oscillation and acoustic streaming. The combination of ultrasound and microreactor provides ideal control over the ultrasound field, making the energy efficiently utilized. In this study, characteristics of chemical absorption of C2H4 from the mixture of C2H6/C2H4 into AgNO3 solutions under Taylor flow are investigated in a high-power ultrasonic microreactor. The effect of ultrasound on the bubble size reduction, absorption and mass transfer coefficient is presented and discussed. It is demonstrated that very large mass transfer coefficient with kLa and kL in the range of 7–42 s−1 and 0.00169–0.0225 m s−1 respectively are obtained, presenting significant intensification compared to absorption without ultrasound in the same reactor.

Significance A revolutionary microfluidic pump is demonstrated; it has no moving parts and no electrical contacts. It consists of a quartz plate implanted by Au particles where every point on the plate can function as a micropump. The pump is driven by a laser beam and is based on the discovered principle of photoacoustic laser streaming. When a pulsed laser hits the plate, it is absorbed by Au nanoparticles that generate an ultrasound wave, which then drives the fluid via acoustic streaming. Because laser beams can be arbitrarily patterned and timed, the fluid can be controlled by laser in a fashion similar to musical water fountains. Such a laser-driven photoacoustic micropump will find wide applications in microfluidics and optofluidics., Enabled initially by the development of microelectromechanical systems, current microfluidic pumps still require advanced microfabrication techniques to create a variety of fluid-driving mechanisms. Here we report a generation of micropumps that involve no moving parts and microstructures. This micropump is based on a principle of photoacoustic laser streaming and is simply made of an Au-implanted plasmonic quartz plate. Under a pulsed laser excitation, any point on the plate can generate a directional long-lasting ultrasound wave which drives the fluid via acoustic streaming. Manipulating and programming laser beams can easily create a single pump, a moving pump, and multiple pumps. The underlying pumping mechanism of photoacoustic streaming is verified by high-speed imaging of the fluid motion after a single laser pulse. As many light-absorbing materials have been identified for efficient photoacoustic generation, photoacoustic micropumps can have diversity in their implementation. These laser-driven fabrication-free micropumps open up a generation of pumping technology and opportunities for easy integration and versatile microfluidic applications.

This paper explores to use graphene as transparent interdigital transducer (IDT) electrode for a fully transparent surface acoustic wave (SAW) device due to its extraordinary electrical, physical and mechanical properties. The number of graphene atomic layers was firstly optimized for its best performance as the SAW electrode, and a 4-layered graphene IDT electrode, with aluminum doped zinc oxide, AZO, as the bus bar and wire bonding pad, was selected to fabricate fully transparent ZnO/glass SAW devices. The SAW resonators exhibited obvious resonant response at different wavelengths, and resonance signals with amplitude up to 20 dB were obtained with the transparency above 80%. The graphene-based transparent SAW sensor has been used for differ-ent sensing applications. Temperature sensing tests showed that the frequencies increase linearly with the increase of temperature, which has an opposite trend compared to that obtained from a conventional LiNbO3 SAW device. The humidity sensing and human breathing detection have been demonstrated, and discontinuous respiration measurement can be used to distinguish the human respiration at the normal state or the state after exercise. Strong acoustic streaming and particle concentration using the transparent SAW devices have been achieved, which are suitable for microfluidic and lab-on-chip applications.

Monodisperse droplet has been widely used as a versatile tool in different disciplines including biosensing. Existing methods still struggle to balance the droplet generation performance with system simplicity. Here we introduce a novel droplet generation scheme based on the acoustic streaming generated from a vibrating sharp-tip capillary. The unique fluid pattern enables efficient droplet generation without any external pressure sources. This method achieved real-time modulation of droplet size over an ultra-wide range (6.77-661 μm), high throughput (up to 5000 droplets/s), and good monodispersity (4%) with a power consumption below 60 mW. This method has enabled a multi-volume digital PCR with a dynamic range of ~6 orders of magnitude and multiplexing capability. It has also enabled a simple protocol to produce cell-laden alginate microcapsules in variable sizes with excellent biocompatibility. Overall, the present method combines high performance with small footprint and portability, which will be especially valuable for droplet applications requiring variable droplet size and performed in resource-limited settings.

Smartphone-enabled microfluidic chemiluminescence immunoassay is a promising portable system for point-of-care (POC) biosensing applications. However, due to the rather faint emitted light in such a limited sample volume, it is still difficult to reach the clinically accepted range when the smartphone serves as a standalone detector. Besides, the multiple separation and washing steps during sample preparation hinder the immunoassay's applications for POC usage. Herein, we proposed a novel acoustic streaming tweezers-enabled microfluidic immunoassay, where the probe particles' purification, reaction, and sensing were simply achieved on the same chip at continuous-flow conditions. The dedicatedly designed high-speed microscale vortexes not only enable dynamic trapping and washing of the probe particles on-demand but also enhance the capture efficiency of the heterogeneous particle-based immunoassay through active mixing during trapping. The enriched probe particles and enhanced biomarker capture capability increase the local chemiluminescent light intensity and enable direct capture of the immunobinding signal by a regular smartphone camera. The system was tested for prostate-specific antigen (PSA) sensing both in buffer and serum, where a limit of detection of 0.2 ng/mL and a large dynamic response range from 0.3 to 10 ng/mL using only 10 μL of sample were achieved in a total assay time of less than 15 min. With the advantages of on-chip integration of sample preparation and detection and high sensing performance, the developed POC platform could be applied for many on-site diagnosis applications.

In this chapter, the development of acoustofluidics as well as state-of-the-art acoustofluidic devices for cell mechanical characterization is presented. The idea of acoustofluidics, the integration of acoustics and fluids, dates to two centuries ago. The development of this technique started around the 1990s with early applications based on three versatile working principles: acoustic radiation force, acoustic streaming, and acoustic sensing. The advancement of microfabrication by the end of the 20th century further spurred the development of acoustofluidics into a well-established microfluidic discipline, with SAW most commonly integrated. The versatility and biocompatibility of modern acoustofluidics provide a powerful tool for cell mechanical characterization.

Simple and low-cost solutions are becoming extremely important for the evolving necessities of biomedical applications. Even though, on-chip sample processing and analysis has been rapidly developing for a wide range of screening and diagnostic protocols, efficient and reliable fluid manipulation in microfluidic platforms still require further developments to be considered portable and accessible for low-resource settings. In this work, we present an extremely simple microfluidic pumping device based on three-dimensional (3D) printing and acoustofluidics. The fabrication of the device only requires 3D-printed adaptors, rectangular glass capillaries, epoxy and a piezoelectric transducer. The pumping mechanism relies on the flexibility and complexity of the acoustic streaming patterns generated inside the capillary. Characterization of the device yields controllable and continuous flow rates suitable for on-chip sample processing and analysis. Overall, a maximum flow rate of ~ 12 μL/min and the control of pumping direction by frequency tuning is achieved. With its versatility and simplicity, this microfluidic pumping device offers a promising solution for portable, affordable and reliable fluid manipulation for on-chip applications. Supplementary Information The online version contains supplementary material available at 10.1007/s10404-020-02411-w.

Introduction: Apart from manual activation methods of irrigants during final irrigation procedure, multiple irrigant activation devices have been introduced which can influence the postoperative pain. Aim: To evaluate postoperative pain after final irrigation with open and closed-ended endodontic needles and Endoactivator during root canal treatment. Materials and Methods: This randomised controlled trial was conducted in Department of Conservative Dentistry and Endodontics, Bapuji Dental College and Hospital, Davangere, from June 2018 to August 2018. Total of 75 symptomatic irreversible pulpitis patients were randomly assigned into three groups. In group EN-1, final irrigation protocol was performed with 30-gauge notched tip needle (Pac-Dent, India), group EN-2 using side-vented, closed 30-gauge needle (Max-i-Probe, Dentsply, USA) and in group EA using Endoactivator (Dentsply, USA). Pain using Visual Analog Scale (VAS) was evaluated at 8, 24 and 48 hours. Participants were prescribed Non-steroidal Anti-Inflammatory Drugs (NSAIDs) as an escape medication. Comparison between the three groups at each time interval was done using Kruskal Wallis test followed by Mann-Whitney U test as post-hoc test. Change in VAS score over different time intervals (8, 24 and 48 hours) in each group was compared using Kruskal Wallis test and Mann-Whitney U test. The p-value less than 0.05 was considered statistically significant. SPSS version 20 was used for statistical analysis. Results: Mann-Whitney U test revealed significant difference between EN-1 and EN-2 (p=0.002) and between EN-1 and EA (p

The study of neurons is fundamental for basic neuroscience research and treatment of neurological disorders. In recent years ultrasound has been increasingly recognized as a viable method to stimulate neurons. However, traditional ultrasound transducers are limited in the scope of their application by self-heating effects, limited frequency range and cavitation effects during neuromodulation. In contrast, surface acoustic wave (SAW) devices, which are producing wavemodes with increasing application in biomedical devices, generate less self-heating, are smaller and create less cavitation. SAW devices thus have the potential to address some of the drawbacks of traditional ultrasound transducers and could be implemented as miniaturized wearable or implantable devices. In this mini review, we discuss the potential mechanisms of SAW-based neuromodulation, including mechanical displacement, electromagnetic fields, thermal effects, and acoustic streaming. We also review the application of SAW actuation for neuronal stimulation, including growth and neuromodulation. Finally, we propose future directions for SAW-based neuromodulation.

Enrichment and separation of Micro/Nano-scale specimens are fundamental requirements in biomedical researches. In this paper, we demonstrated a simple and efficient microfluidic chip for the continuous enrichment and separation of nanoscale polystyrene particles using the acoustic streaming induced by gigahertz(GHz) bulk acoustic waves(BAW). The bulk acoustic resonator released ultrahigh frequency (2GHz) acoustic waves into the fluid and triggered the acoustic streaming. The nanoparticles were continuous concentrated and segregated by the combination action of the viscosity force and the acoustic radiation force. The separation of 300 and 100 nm particles was achieved with the high purity (92.4%). These data contribute proof-in-principle that acoustic streaming is a label-free strategy that can be used to enrich and separate nanoscale specimens with high efficiency.

Non-contact manipulation is of great importance in the actuation of micro-robotics. It is challenging to contactless manipulate micro-scale objects over large spatial distance in fluid. Here, we describe a novel approach for the dynamic position control of microparticles in three-dimensional (3D) space, based on high-speed acoustic streaming generated by a micro-fabricated gigahertz transducer. The hydrodynamic force generated by the streaming flow field has a vertical component against gravity and a lateral component towards the center, thus the microparticle is able to be stably trapped at a position far from the transducer surface, and to be manipulated over centimeter distance in 3D. Only the hydrodynamic force is utilized in the system for particle manipulation, making it a versatile tool regardless the material properties of the trapped particle. The system shows high reliability and manipulation velocity, revealing its potentials for the applications in robotics and automation at small scales.

Modulation of intra-cellular calcium by ultrasound offers a possible means for therapeutic applications. One such possibility is the modulation of nucleus pulposus cells as a preventive measure for inter-vertebral disc degeneration. We report a cellular stimulation device (micro-pipette ultrasound) using a glass micro-pipette as a waveguide to deliver ultrasound through the pipette tip and to elevate intra-cellular calcium in nucleus pulposus cells. The device generates two relevant stimuli at the cellular level: ultrasound propagation throughout the cell and acoustic streaming on the apical side. Ultrasound is radiated from a tip of a few microns, and its amplitude is proportional to the input voltage; acoustic streaming can be controlled by the duty factor. The novelty of the device is to impose a unique cellular loading: shear stress on cell apical surfaces combined with compressional waves propagating through the cells. G protein–coupled receptors and acid-sensing ion channel 3 were shown to play a role in calcium elevation by micro-pipette ultrasound in nucleus pulposus cells. Our results demonstrate that micro-pipette ultrasound can be an effective tool to elevate intra-cellular calcium levels in different cells, facilitating the identification of different mechanoreceptors in action.

Manipulation of fluids and particles by acoustic actuation at small scale is aiding the rapid growth of lab-on-a-chip applications. Megahertz-order surface acoustic wave (SAW) devices generate enormous accelerations on their surface, up to 108 m/s2, in turn responsible for many of the observed effects that have come to define acoustofluidics: acoustic streaming and acoustic radiation forces. These effects have been used for particle, cell, and fluid handling at the microscale-and even at the nanoscale. In this paper we explicitly demonstrate two major fabrication methods of SAW devices on lithium niobate: the details of lift-off and wet etching techniques are described step-by-step. Representative results for the electrode pattern deposited on the substrate as well as the performance of SAW generated on the surface are displayed in detail. Fabrication tricks and troubleshooting are covered as well. This procedure offers a practical protocol for high frequency SAW device fabrication and integration for future microfluidics applications.

PURPOSE: The purpose of this study was to develop a new computational fluid dynamics (CFD)-based model of the complex transport and droplet drying kinetics within a laboratory-scale spray dryer, and relate CFD-predicted drying parameters to powder aerosolization metrics from a reference dry powder inhaler (DPI). METHODS: A CFD model of the Buchi Nano Spray Dryer B-90 was developed that captured spray dryer conditions from a previous experimental study producing excipient enhanced growth powders with L-leucine as a dispersion enhancer. The CFD model accounted for two-way heat and mass transfer coupling between the phases and turbulent flow created by acoustic streaming from the mesh nebulizer. CFD-based drying parameters were averaged across all droplets in each spray dryer case and included droplet time-averaged drying rate (κ(avg)), maximum instantaneous drying rate (κ(max)) and precipitation window. RESULTS: CFD results highlighted a chaotic drying environment in which time-averaged droplet drying rates (κ(avg)) for each spray dryer case had high variability with coefficients of variation in the range of 60–70%. Maximum instantaneous droplet drying rates (κ(max)) were discovered that were two orders of magnitude above time-averaged drying rates. Comparing CFD-predicted drying parameters with experimentally determined mass median aerodynamic diameters (MMAD) and emitted doses (ED) from a reference DPI produced strong linear correlations with coefficients of determination as high as R(2)=0.98. CONCLUSIONS: For the spray dryer system and conditions considered, reducing the CFD-predicted maximum drying rate experienced by droplets improved the aerosolization performance (both MMAD and ED) when the powders were aerosolized with a reference DPI.

With many emerging applications such as chemical reactions and ultrasound therapy, acoustic cavitation plays a vital role in having improved energy efficiency. For example, acoustic cavitation results in substantial enhancement in the rates of various chemical reactions. In this regard, an applied acoustic field within a medium generates acoustic streaming, where cavitation bubbles appear due to preexisting dissolved gas in the working fluid. Upon cavitation inception, bubbles can undergo subsequent growth and collapse. During the last decade, the studies on the effects of different parameters on acoustic cavitation such as applied ultrasound frequency and power have been conducted. The bubble growth and collapse mechanisms and their distribution within the medium have been classified. Yet, more research is necessary to understand the complex mechanism of multi-bubble behavior under an applied acoustic field. Various parameters affecting acoustic cavitation such as surface roughness of the acoustic generator should be investigated in more detail in this regard. In this study, single bubble lifetime, bubble size and multi-bubble dynamics were investigated by changing the applied ultrasonic field. The effect of surface roughness on bubble dynamics was presented. In the analysis, images from a high-speed camera and fast video recording techniques were used. Numerical simulations were also done to investigate the effect of acoustic field frequency on bubble dynamics. Bubble cluster behavior and required minimum bubble size to be affected by the acoustic field were obtained. Numerical results suggested that bubbles with sizes of 50 µm or more could be aligned according to the radiation potential map, whereas bubbles with sizes smaller than 10 µm were not affected by the acoustic field. Furthermore, it was empirically proven that surface roughness has a significant effect on acoustic cavitation phenomena.

Controlled nanoscale manipulation of fluids is known to be exceptionally difficult due to the dominance of surface and viscous forces. Megahertz-order surface acoustic wave (SAW) devices generate tremendous acceleration on their surface, up to 108 m/s2, in turn responsible for many of the observed effects that have come to define acoustofluidics: acoustic streaming and acoustic radiation forces. These effects have been used for particle, cell, and fluid manipulation at the microscale, although more recently SAW has been used to produce similar phenomena at the nanoscale through an entirely different set of mechanisms. Controllable nanoscale fluid manipulation offers a broad range of opportunities in ultrafast fluid pumping and biomacromolecule dynamics useful for physical and biological applications. Here, we demonstrate nanoscale-height channel fabrication via room-temperature lithium niobate (LN) bonding integrated with a SAW device. We describe the entire experimental process including nano-height channel fabrication via dry etching, plasma-activated bonding on lithium niobate, the appropriate optical setup for subsequent imaging, and SAW actuation. We show representative results for fluid capillary filling and fluid draining in a nanoscale channel induced by SAW. This procedure offers a practical protocol for nanoscale channel fabrication and integration with SAW devices useful to build upon for future nanofluidics applications.

The present study aims to develop an ultrasound acoustic streaming actuator for flow control. The driving force can be derived from the continuity equation and the Navier-Stokes equation for the viscous compressible flow. Commercially available transducers are used as an ultra sound source, and the acoustic and induced flow characteristics for a single and multiple transducer configurations are examined. The sound pressure distribution indicates the strong acoustic pressure fluctuation near the transducer. For the multiple transducer cases, the region of the strong pressure fluctuation is widened due to the superposition of the waves. The distributions of the induced velocity are evaluated using particle image velocimetry. It is revealed that the maximum flow velocity is about 0.04 m/s for the single transducer case, and the maximum velocity is observed slightly downstream of the high sound intensity region. Since the driving force is proportional to the square of the sound pressure intensity, the higher flow velocity can be achieved using more transducers. A transducer array having 100 transducers has been applied in a turbulent boundary layer. It is confirmed that the flow velocity near the wall increases in the case with the control, and turbulence intensity augments by approximately 17% compared with the case without the control.

We present a numerical model for the recently introduced simple and inexpensive micromachined aluminum devices with a polydimethylsiloxane (PDMS) cover for microparticle acoustophoresis. We validate the model experimentally for a basic design, where a microchannel is milled into the surface of an aluminum substrate, sealed with a PDMS cover, and driven at MHz frequencies by a piezoelectric lead-zirconate-titanate (PZT) transducer. Both experimentally and numerically we find that the soft PDMS cover suppresses the Rayleigh streaming rolls in the bulk. However, due to the low transverse speed of sound in PDMS, such devices are prone to exhibit acoustic streaming vortices in the corners with a relatively large velocity. We predict numerically that in devices, where the microchannel is milled all the way through the aluminum substrate and sealed with a PDMS cover on both the top and bottom, the Rayleigh streaming is suppressed in the bulk thus enabling focusing of sub-micrometer-sized particles.

This paper reports the first demonstration of acoustic tweezers to manipulate microparticles in a sessile droplet over a functional surface-micromachined silicon chip fabricated with polysilicon micromechanical sensing structures. The proposed plug-and-play setup comprises two interchangeable parts: a detachable silicon micromachined sensor chip (acting as a superstrate) and a surface acoustic wave (SAW) device substrate. The SAW device provides the off-chip acoustic source from which Rayleigh waves couple into the functional silicon chip. We demonstrate concentration of initially randomly dispersed microparticles in a water droplet loaded on the functional silicon chip by means of acoustic streaming forces using a drive power of 1 W.

Controlled concentration of nanoscale materials on the surface of a smooth substrate without vibration excitation mechanism and micro channels (termed as plain substrate), and transportation of the concentrated nano material on the surface, have large potential applications in the fabrication of nano sensors and electrodes, decoration and assembly of nano materials, etc. However, implementation of these two nano manipulation functions by one single device has been a big challenge. Here we report a strategy to concentrate nanoparticles at an arbitrary location at the interface between a plain substrate and water droplet, and to transportation the concentrated nano material freely at the interface. It employs the acoustic streaming, which is generated by a micro manipulating probe (MMP) vibrating linearly above the substrate. 500 nm-diameter silicon nanoparticles (SiNPs) can be concentrated under the MMP at a desired location, forming a round spot of nano materials with a diameter up to 230 μm. The concentrated nano material can be transported through an arbitrary path at the interface by shifting the device, and has little change in size and shape during the transportation. The dependency of acoustic streaming field around the MMP on device parameters are clarified by numerical computation and verified by experiments.

This paper develops theory for bulk acoustic streaming in soft porous materials, with applications to biological tissue. The principal results of this paper are: (i) streaming equations for such porous media, which show interestingly significant differences from those that describe streaming in pure fluids; (ii) the Green functions obtained for these equations in isotropic, infinite media; and (iii) approximate evaluation of the sources in the streaming equations from acoustic wave forms often used, and the streaming velocities and particle trajectories resulting therefrom. People are now investigating acoustic enhancement of delivery of therapeutics such as drug molecules or other particulates, introduced directly into cellular tissue. A comparison of the predictions of the theory in this paper to available data is made and shown to be surprisingly good. Some macroscale effects of the ultrastructure of the tissue that are not contained in the current paper are pointed out for future studies.

Calcium ferrite (CF) is a very important binder phase in iron ore sintering processes. To improve the microstructure of CF, power ultrasound was introduced during its solidification process, and the effect of immersion depth of ultrasonic probe (IDUP) on the properties of CF was investigated in detail. The results indicated that the microstructure of CF was greatly refined; the grain size decreased from 2864 μm without ultrasonic vibration to 841 μm with ultrasonic vibration at an immersion depth of 30 mm. Without ultrasonic vibration, the density and compressive strength of CF slag were 3904 kg/m3 and 38.3 MPa, respectively. When the IDUP was increased from 10 to 30 mm, the density and compressive strength of CF increased from 4049 to 4452 kg/m3 and 52.5 to 87.3 MPa, respectively. Further, the reducibility of CF was examined. The reduction time, at the same reduction rate, decreased from 347 minutes without ultrasonic vibration to 200 minutes with ultrasonic vibration at an IDUP of 30 mm. The rate-limiting step was obviously improved, which may be attributable to the grain refinement of CF and composition segregation in the slag. In general, the properties of CF were greatly improved due to the cavitation and acoustic streaming of ultrasonic waves.

For decades, scientists have pursued the goal of performing automated reactions in a compact fluid processor with minimal human intervention. Most advanced fluidic handling technologies (e.g., microfluidic chips and micro-well plates) lack fluid rewritability, and the associated benefits of multi-path routing and re-programmability, due to surface-adsorption-induced contamination on contacting structures. This limits their processing speed and the complexity of reaction test matrices. We present a contactless droplet transport and processing technique called digital acoustofluidics which dynamically manipulates droplets with volumes from 1 nL to 100 µL along any planar axis via acoustic-streaming-induced hydrodynamic traps, all in a contamination-free (lower than 10−10% diffusion into the fluorinated carrier oil layer) and biocompatible (99.2% cell viability) manner. Hence, digital acoustofluidics can execute reactions on overlapping, non-contaminated, fluidic paths and can scale to perform massive interaction matrices within a single device., Contamination is an obstacle to the functioning of microfluidic devices. Here the authors exploit acoustic streaming to manipulate droplets which float on a layer of immiscible oil. This prevents contamination and enables rewritability by which different fluids can be used on the same substrate.

In the last few decades, new types of cell cultures have been introduced to provide better cell survival and development, with micro- and nanoenvironmental physicochemical conditions aimed at mimicking those present in vivo. However, despite the efforts made, the systems available to date are often difficult to replicate and use. Here, an easy-to-use surface-acoustic-wave (SAW)-based platform is presented for realizing dynamic cell cultures that is compatible with standard optical microscopes, incubators, and cell-culture dishes. The SAW chip is coupled to a standard Petri dish via a polydimethylsiloxane (PDMS) disc and consists of a lithium niobate (LN) substrate on which gold interdigital transducers (IDTs) are patterned to generate the SAWs and induce acoustic streaming in the dish. SAW excitation is verified and characterized by laser Doppler vibrometry, and the fluid dynamics is studied by microparticle image velocimetry (?PIV). Heating is measured by an infrared (IR) thermal camera. We finally tested this device with the U-937 monocyte cell line for viability and proliferation and cell-morphological analysis. The data demonstrate that it is possible to induce significant fluid recirculation within the Petri dish while maintaining negligible heating. Remarkably, cell proliferation in this condition was enhanced by 36 ± 12% with respect to those of standard static cultures. Finally, we show that cell death does not increase and that cell morphology is not altered in the presence of SAWs. This device is the first demonstration that SAW-induced streaming can mechanically improve cell proliferation and further supports the great versatility and biocompatibility of the SAW technology for cell manipulation.

Megasonic has obvious advantages in overcoming the limitations of electroforming process based on its low cavitation effect, high sound intensity and acoustic streaming. In this paper, megasonic was employed to achieve uniform electroformed layer in electroforming process. Impedance values, resonant frequencies were measured in order to get a high-efficiency megasonic source. Considering the directions of acoustic radiation and combining with other functional modules, an integrated megasonic electroforming equipment was designed and set up. Then, nickel was electroformed on copper substrates without megasonic wave, with single directional megasonic wave and with bidirectional alternating megasonic wave, respectively. The planeness value (PV) of electroformed layer is 15.03 μm without megasonic agitation, and the PV of electroformed layer is 15.36 μm with single directional megasonic wave radiation. Bidirectional alternating megasonic wave assisted electroforming has an outstanding performance on the uniformity of electroformed layer, which achieves the lowest planeness value (PV = 10.91 μm) of all the electroforming experiments. Besides, the bidirectional megasonic wave assisted electroforming can achieve better surface quality than other conditions too.

Metal organic frameworks (MOFs) are porous materials that have wide application prospects. In this study, a novel, facile, rapid, and environmentally friendly technology that uses surface acoustic waves (SAWs) as an energy source to induce the synthesis of HKUST-1 crystals in a droplet is presented. The acoustic streaming induced by SAWs has significant influence on the morphology and size of HKUST-1 crystals. By increasing the input power of SAWs, the kinetic effect of SAWs can improve the supersaturation of crystal growth units. Therefore, the HKUST-1 crystals with higher surface-energy faces and smaller sizes are generated. Moreover, we also researched the temperature trends with and without SAWs to further investigate the kinetic effect of SAWs to control the morphology and size of HKUST-1 crystals.

Cell lysis is a crucial process for the detection of intracellular secrets, which is important in various areas, such as biochemical detection, biomechanical analysis and biophysics. Typically, the acoustic method induced cell lysis relies on acoustic cavitation, which requires high acoustic power and may damage the important cell contents, such as DNA, RNA, and mRNA. We introduce herein an efficient microfluidic cell lysis approach based on nanowires collision induced by acoustic streaming using surface acoustic wave in a gentle and controllable manner. The magnetic Ag-nanowires were introduced to the cell suspension, and rotational acoustic streaming induced strong drag and the shear stress result in the collision between the cells and nanowires, leading to the cell lysis. The maximum velocity of the streaming could reach 3 mm/s Cell-lysis was obtained between 10 s, and more than 97 % lysis efficiency was achieved at just 1 W power. The experimental results show that this method has the advantage of high efficiency, very low consumption of power, ultrafast, reusability and tiny sample consumption, also Ni coated Ag-Nanowires provide reusability and highly applicable in point of care diagnostics.

The electrochemical deposition and dissolution of Cu from chloride-based electrolyte was studied employing the electrochemical quartz crystal microbalance (EQCM)-coupled ultrasound technique. The ultrasound was generated using an ultrasonic horn probe, which was positioned in the face-on configuration at a different distance (8, 15, and 22 mm) from the quartz. Small intensities of ultrasound (up to ca. 11–13 W cm−2) caused a significant enhancement of anodic, cathodic currents, as well as the amount of deposited Cu paralleled by an increase in the current efficiencies due to the enhanced mass transport caused by ultrasound acoustic streaming. A further increase in the ultrasonic intensity continuously decreased the amount of Cu deposited as well as the calculated current efficiencies where the ultrasound acoustic cavitation (favor ablation) becomes more important and overtakes the effect of acoustic streaming. The peculiarities in sonoelectrochemistry at intermediate intensities (ca. 25 W cm−2) could be explained by a competition between the two effects. In agreement with the literature, the Cu corrosion reaction is occurring in parallel to its anodic dissolution with a corrosion rate increasing with increasing the ultrasound intensity. At the horn-quartz distance of 8 mm and intensity of 76 W cm−2 limits of the EQCM application (in the ultrasound field) were reached and the Cu deposition could not take place.

Micromotors powered by megahertz ultrasound, first reported about 5 years ago, have lately been considered a promising platform for a wide range of microscale applications, yet we are only at the early stage of understanding their operating mechanisms. Through carefully designed experiments, and by comparing the results to acoustic theories, we present here an in-depth study of the behaviors of particles activated by ultrasound, especially their in-plane orbiting and spinning dynamics. Experiments suggest that metallic microrods orbit in tight circles near the resonance ultrasound frequency, likely driven by localized acoustic streaming due to slightly bent particle shapes. On the other hand, particle spins around their long axes on nodal lines, where phase-mismatched orthogonal sound waves possibly produce a viscous torque. Intriguingly, such a torque spins metal-dielectric Janus microspheres back and forth in an unusual "rocking chair" fashion. Overall, our observations and analysis provide fresh and much needed insights on the interesting particle dynamics in resonating ultrasound and could help with developing more powerful and controllable micromachines with biocompatible energy sources.

Separation of particles on the order of 100 nm with acoustophoresis has been challenging to date because of the competing natures of the acoustic radiation force and acoustic streaming on the particles. In this work, we present a surface acoustic wave (SAW)-based device that integrates a Fabry-Perot type acoustic resonator into a microfluidic channel to separate submicrometer particles. This configuration enhances the overall acoustic radiation force on the particles and thereby offers controlled manipulation of particles as small as 300 nm. Additionally, SAW-based excitation generates high-frequency acoustic waves in the system relative to bulk acoustic wave (BAW)-based actuation, which suppresses Rayleigh streaming effects on the submicrometer particles. We demonstrate a continuous-flow acoustophoretic separation of 300 and 100 nm particles in our device with a separation efficiency of 86.3%. We also present an analytical stochastic method to model the transport of submicrometer particles in the device and predict the migration trajectories as a function of acoustic and velocity potential field strengths. Our model incorporates particle diffusion, which is important for small particles, and successfully predicts the size-dependent separation modality of our system. This device can be used for several applications in microfluidics that require sorting of the submicrometer particles, and the analytical method can also be extended to predict the particle transport in other systems.

High intensity focused ultrasound (HIFU) has many applications ranging from thermal ablation of cancer to hemostasis. Although focused ultrasound can seal a bleeding site, physical mechanism of acoustic hemostasis is not fully understood yet. To understand better the interaction between different physical mechanisms involved in hemostasis a mathematical model for acoustic hemostasis is developed. This model comprises the nonlinear Westervelt equation and the bioheat equations in tissue and blood vessel. In a three dimensional domain, the nonlinear hemodynamic equations are coupled with the acoustic and thermal equations. Convective cooling and acoustic streaming effects are incorporated in the modeling study. Effect of acoustic streaming on the blood flow out of the wound has been studied for two wound shapes and different sonication angles. It was theoretically shown that if focused ultrasound beam is applied directly to the bleeding site, the flow out of the wound can be reduced due to the acoustic streaming effect. Bleeding can be completely stopped even for a big wound, if the focal point location, ultrasound power and sonication angle are appropriately chosen. The sonication angles should be chosen in the range between 45° and 90°. The temperature around 70 °C can be achieved within a second on the blood vessel wall, thus showing the theoretical possibility of sealing the bleeding site by focused ultrasound.