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To understand the in-plane elastic character of ultrasonic waves in the skull, longitudinal wave velocities were studied in the MHz range using a conventional pulse technique. Taking advantage of the thickness of swine skulls, anisotropic in-plane wave velocity changes in the outer and diploe layers were experimentally investigated using structural information measured by X-ray computer tomography (CT). The velocities in the thin inner layer were difficult to measure. The main trabecular alignment (MTA) in the thick swine diploe layer was almost perpendicular to the thickness direction and changed with position inside the skull. The degree of anisotropy of in-plane longitudinal wave velocity ranged 1.07-1.33 in both outer and diploe layers, depending on position and swine sample. The angle of the fastest velocity in the outer layer was different from that in most parts of the diploe layer. Anisotropic character in the diploe layer gradually changed with position in the thickness direction.

This study investigated a method to control neurite outgrowth direction using ultrasound vibration. An ultrasound cell culture dish comprising a glass-bottom culture surface and a glass disc with an ultrasound transducer was fabricated, and undifferentiated neuron-like PC12 cells were grown on the dish as an adherent culture. The 78 kHz resonant concentric flexural vibration mode of the dish was used to quantitatively evaluate the neurite outgrowth direction and length. Time-lapse imaging of cells was performed for 72 h under ultrasound excitation. Unsonicated neurites grew in random directions, whereas neurite outgrowth was circumferentially oriented during ultrasonication in a power-dependent manner. The neurite orientation correlated with the spatial gradient of the ultrasound vibration, implying that neurites tend to grow in directions along which the vibrational amplitude does not change. Ultrasonication with 30 Vpp for 72 h increased the neurite length by 99.7% compared with that observed in unsonicated cells.

Although ultrasonically controlled liquid crystal lens may play in important role in future optical systems, many optical properties in the liquid crystal layer are still unclear. Moreover, most of the previously conducted studies control the liquid crystal molecular orientation by an applied electric field using transparent electrodes. In this study, using multichannel piezoelectric transducer, standing wave and traveling wave actuation mechanism were applied to the liquid crystal lens and further reported about its optical characteristics using a Shack-Hartmann wavefront sensor. The surface data obtained from the sensor was analyzed and the optical aberrations measured. Traveling wave actuation showed small optical aberrations when compared to the standing wave.

New technologies for adaptive optics are becoming increasingly important for miniature devices such as cell-phone cameras. In particular, motion-free autofocusing and optical image stabilization require sophisticated approaches for alternative lens architectures, materials, and processing to replace multiple solid elements. We discuss a new method, to the best of our knowledge, that provides image stabilization via an annular piezoelectric ceramic that uses ultrasound to drive a liquid crystal layer sandwiched between two circular glass substrates. The piezoelectric ceramic is divided into four quadrants that are independently driven with sinusoidal voltages at the resonant frequency of the lens. The technique is based on ultrasound vibrations with a suitable driving scheme. The lens configuration was modeled via finite-element analysis. Various combinations of the four-channel ultrasound transducer can be used to define the focal point of the liquid crystal lens. Clear optical images could be obtained with the lens. By using two-dimensional fast Fourier transforms, the focal point position was defined and shifted in the radial direction.

As biotechnology develops, techniques for manipulating and separating small particles such as cells and DNA are required in the life sciences. This paper investigates on-chip manipulation of microparticles in small channels by using ultrasonic vibration. The chip consists of a rectangular glass substrate with a cross-shaped channel (cross-section: 2.0×2.0mm2) and four lead zirconate titanate transducers attached to the substrate's four corners. To efficiently generate the flexural vibration mode on the chip, we used finite element analysis to optimize the configurations of the glass substrate and transducers. Silicon carbide microparticles with an average diameter of 50μm were immersed in the channels, which were filled with ethanol. By applying an in-phase input voltage of 75V at 225kHz to the four transducers, a flexural vibration mode with a wavelength of 13mm was excited on the glass substrate, and this flexural vibration generated an acoustic standing wave in the channel. The particles could be trapped at the nodal lines of the standing wave. By controlling the driving phase difference between the two pairs of transducers, the vibrational distribution of the substrate could be moved along the channels so that the acoustic standing wave moved in the same direction. The trapped particles could be manipulated by the two-phase drive, and the transport direction could be switched at the junction of the channels orthogonally by changing the combination of the driving condition to four transducers.

International audience; Microbubbles have potential for applications as drug and gene delivery systems in which the release of a substance is triggered by an ultrasonic pulse. In this paper, we discuss the adsorption and desorption of a film of phospholipid on the surface of a single microbubble under ultrasound irradiation. Our optical observation system consisted of a high-speed camera, a laser Doppler vibrometer, and an ultrasound cell; 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) was used as the surfactant. The adsorption of the DMPC molecules onto the surface of the bubble was evaluated by measuring the contact angle between the bubble and a glass plate. A decrease of the contact angle of the bubble indicates desorption of the DMPC molecules from the bubble surface into the surrounding aqueous solution. The amount of DMPC molecules adsorbed on the bubble’s surface is shown to decrease over time after bubble generation. The type and intensity of the pulsed ultrasound waves were varied so as mimic ultrasound triggered drug release. Increasing the number of cycles and the amplitude of the sound pressure of the pulsed ultrasound yielded a greater increase of the contact angle. We also measured the radial vibrations of the microbubbles in the ultrasound field. The vibrational characteristics of the microbubbles and the desorption characteristics of the DMPC molecules showed the same variation; namely, a greater sound pressure amplitude induced greater vibrational displacement and a larger amount of molecular desorption under resonance conditions. These results support the possibility of controlling drug release with pulsed ultrasound in a microbubble-based drug delivery system.

The experimental investigation of an optical fiber Bragg grating (FBG) sensor for biomedical application is described. The FBG sensor can be used to measure sound pressure and temperature rise simultaneously in biological tissues exposed to ultrasound. The theoretical maximum values that can be measured with the FBG sensor are 73.0 MPa and 30 °C. In this study, measurement of sound pressure up to 5 MPa was performed at an ultrasound frequency of 2 MHz. A maximum temperature change of 6 °C was measured in a tissue-mimicking material. Values yielded by the FBG sensor agreed with those measured using a thermocouple and a hydrophone. Since this sensor is used to monitor the sound pressure and temperature simultaneously, it can also be used for industrial applications, such as ultrasonic cleaning of semiconductors under controlled temperatures.

This paper investigated a cell patterning technique using ultrasound vibration. The ultrasound cell culture dish consisted of a culture dish with a glass bottom and a glass disc with an ultrasound transducer that generated a resonance flexural vibration mode on the bottom of the dish. HeLa cells were used as adhesives cells, and the growth of cells on the dish was observed under ultrasound excitation for 24 hours. The vibration amplitude was largest at the center of the dish, and the axisymmetric resonance flexural vibration mode with three concentric nodal circles and no nodal line was generated on the bottom of the dish. Large vibrations inhibited the cell growth. The distributions of the sound pressure amplitude and the acoustic radiation force in the culture medium were calculated with finite element analysis and it was found that the cell growth depended strongly on both the acoustic field in the culture medium and the vibration distribution of the dish. The ultrasound vibrations did not affect the viability of the cells, and the cell growth could be controlled by the flexural vibration of the cultured dish.This paper investigated a cell patterning technique using ultrasound vibration. The ultrasound cell culture dish consisted of a culture dish with a glass bottom and a glass disc with an ultrasound transducer that generated a resonance flexural vibration mode on the bottom of the dish. HeLa cells were used as adhesives cells, and the growth of cells on the dish was observed under ultrasound excitation for 24 hours. The vibration amplitude was largest at the center of the dish, and the axisymmetric resonance flexural vibration mode with three concentric nodal circles and no nodal line was generated on the bottom of the dish. Large vibrations inhibited the cell growth. The distributions of the sound pressure amplitude and the acoustic radiation force in the culture medium were calculated with finite element analysis and it was found that the cell growth depended strongly on both the acoustic field in the culture medium and the vibration distribution of the dish. The ultrasound vibrations did not affect the v...

Contact manipulation using a micropipette is widely used for cell culture and evaluation. However, the operation efficiency and the damage on the cells depend on the individual skills. A technique for manipulating a micro biological material with high accuracy and selectivity is required. Our group has been investigating noncontact ultrasonic manipulation techniques using acoustic standing wave. In this report, ultrasonic manipulation, separation, and evaluation of HeLa cells in a microchannel are discussed.

The direct finite-difference fluid simulation of acoustic streaming on a fine-meshed three-dimensional model using a graphics processing unit (GPU)-based calculation array is discussed. Airflows are induced by an acoustic traveling wave when an intense sound field is generated in a gap between a bending transducer and a reflector. The calculation results showed good agreement with measurements in a pressure distribution. Several flow vortices were observed near the boundary layer of the reflector and the transducer, which have often been observed near the boundary of acoustic tubes, but have not been observed in previous calculations for this type of ultrasonic air pump.

We developed a plate-shaped non-contact transporter based on ultrasonic vibration, exploiting a phenomenon that a plate can be statically levitated at the place where its gravity and the acoustic radiation force are balanced. In the experiment, four piezoelectric zirconate titanate elements were attached to aluminum plates, on which lattice flexural vibration was excited at 22.3 kHz. The vibrating plates were connected to a loading plate via flexible posts that can minimize the influence of the flexure induced by heavy loads. The distribution of the vibration displacement on the plate was predicted through finite-element analysis to find the appropriate positions of the posts. The maximum levitation height of this transporter was 256 μm with no load. When two vibrating plates were connected to a loading plate, the maximum transportable load was 4.0 kgf.

Nematic liquid crystal is widely used in optical devices such as liquid crystal displays and controlled by electric fields through the liquid crystal layer. Our group has proposed a control technique of liquid crystal molecular orientation using ultrasound vibration without indium tin oxide electrodes [1]. In this study, using ultrasound and nematic liquid crystal, we realized a variable focus liquid crystal lens. The liquid crystal lens has no transparent electrodes and consists of a simple structure; a nematic liquid crystal layer with a thickness of 50 μm is formed between two circular grass plates. An annular PZT ultrasonic transducer was bonded on the glass plate. By exciting the transducer at the resonance frequencies (28 kHz), the flexural vibration modes were generated. The acoustic radiation force from the vibration changed the molecular orientation of the liquid crystals, which induced the distribution of the execution refractive indices. The liquid crystal layer then worked as a lens. The focal...

A liquid lens is proposed that uses acoustic radiation force with no mechanical moving parts. It consists of a cylindrical acrylic cell filled with two immiscible liquids (degassed water and silicone oil) and a concave ultrasound transducer. The focal point of the transducer is located on the oil-water interface, which functions as a lens. The acoustic radiation force is generated when there is a difference in the acoustic energy densities of different media. An acoustic standing wave was generated in the axial direction of the lens and the variation of the shape of the oil-water interface was observed by optical coherence tomography (OCT). The lens profile can be rapidly changed by varying the acoustic radiation force from the transducer. The kinematic viscosity of silicone oil was optimized to minimize the response times of the lens. Response times of 40 and 80 ms when switching ultrasonic radiation on and off were obtained with a kinematic viscosity of 200 cSt. The path of a laser beam transmitted through the lens was calculated by ray-tracing simulations based on the experimental results obtained by OCT. The transmitted laser beam could be focused by applying an input voltage. The liquid lens could be operated as a variable-focus lens by varying the input voltage.

A compact, high-speed variable-focus liquid lens using acoustic radiation force is proposed. The lens consists of an annular piezoelectric ultrasound transducer and an aluminum cell (height: 3 mm; diameter: 6 mm) filled with degassed water and silicone oil. The profile of the oil-water interface can be rapidly varied by applying acoustic radiation force from the transducer, allowing the liquid lens to be operated as a variable-focus lens. A theoretical model based on a spring-mass-dashpot model is proposed for the vibration of the lens. The sound pressure distribution in the lens was calculated by finite element analysis and it suggests that an acoustic standing wave is generated in the lens. The fastest response time of 6.7 ms was obtained with silicone oil with a kinematic viscosity of 100 cSt.

Nematic liquid crystals are widely used in optical devices such as liquid crystal displays and controlled by electric fields through the liquid crystal layer. The authors have proposed a technique to control the orientation of liquid crystal molecules using ultrasound vibration without indium tin oxide electrodes. An ultrasound liquid crystal cell was fabricated; it consists of a liquid crystal layer sandwiched by two glass plates having two ultrasound PZT transducers. When exciting the transducers at the resonance frequencies, the flexural vibration modes were generated on the cell and the acoustic radiation force acted to the liquid crystal molecules so that the orientation direction can be changed. The relationship between the molecular orientation and the vibration distribution of the cell was investigated from the transmitted light distribution of the liquid crystal cell under the crossed Nicol condition. In addition, the orientation of liquid crystal molecules was evaluated as ultrasonic wave velocity in the GHz range by the Brillouin scattering method. The ultrasonic wave velocity in the long axis direction of the liquid crystal molecules was higher than that in the short axis direction, which indicates the uniaxial anisotropy of the liquid crystal molecules.

A variable-focus lens using a combination of liquid crystals and ultrasound is discussed. The lens uses a technique based on ultrasound vibration to control the molecular orientation of the liquid crystal. The lens structure is simple, with no mechanical moving parts and no transparent electrodes, which is helpful for device downsizing; the structure consists of a liquid crystal layer sandwiched between two glass substrates with a piezoelectric ring. The tens-of-kHz ultrasonic resonance flexural vibration used to excite the lens generates an acoustic radiation force on the liquid crystal layer to induce changes in the molecular orientation of the liquid crystal. The orientations of the liquid crystal molecules and the optical characteristics of the lens were investigated under ultrasound excitation. Clear optical images were observed through the lens, and the focal point could be controlled using the input voltage to the piezoelectric ring to give the lens its variable-focus action.

While the low-intensity pulsed ultrasound technique has proved useful for healing of bone fractures, the ultrasound healing mechanism is not yet understood. To understand the initial physical effects of the ultrasound irradiation process on bone, we have studied the anisotropic piezoelectric properties of bone in the MHz range. Bone is known to be composed of collagen and hydroxyapatite (HAp) and shows strong elastic anisotropy. In this study, the effects of HAp on the piezoelectricity were investigated experimentally. To remove the HAp crystallites from the bovine cortical bone, demineralization was performed using ethylene diamine tetra-acetic acid (EDTA) solutions. To investigate the piezoelectricity, we have fabricated ultrasound transducers using the cortical bone or demineralized cortical bone. The induced electrical potentials due to the piezoelectricity were observed as the output of these transducers under pulsed ultrasound irradiation in the MHz range. The cortical bone transducer (before mineralization) showed anisotropic piezoelectric behavior. When the ultrasound irradiation was applied normal to the transducer surface, the observed induced electrical potentials had minimum values. The potential increased under off-axis ultrasound irradiation with changes in polarization. In the demineralized bone transducer case, however, the anisotropic behavior was not observed in the induced electrical potentials. These results therefore indicate that the HAp crystallites affect the piezoelectric characteristics of bone.

Ultrasonic manipulation of small particles, including liquid droplets, over long distances is discussed. We used an experimental setup consisting of a 605-mm-long duralumin bending vibrating plate and a reflector. Two bolt-clamped Langevin transducers with horns were attached to both sides of the vibrating plate to generate flexural vibrations along the plate. A plane reflector with the same dimensions as the vibrating plate was installed parallel to the plate at a distance of approximately 17 mm to generate an ultrasonic standing wave between them and trap the small particles at the nodal lines. The acoustic field and acoustic radiation force between the vibrator and reflector were calculated by finite element analysis to predict the positions of the trapped particles. The sound pressure distribution was measured experimentally using a scanning laser Doppler vibrometer. The flexural wave was excited along the vibrator at 22.5 kHz. A lattice standing wave with a wavelength of 35 mm in the length direction could be excited between the vibrator and the reflector, and polystyrene spheres with diameters of several millimeters could be trapped at the nodal lines of the standing wave. The experimental and calculated results showed good agreement for the relationship between the driving phase difference and the positions of the trapped particle. Noncontact transportation of the trapped particles over long distances could be achieved by changing the driving phase difference. The position of the trapped particles could be controlled to an accuracy of 0.046 mm/deg. An ethanol droplet could also be trapped and moved.

In this paper, we propose a configuration for the two dimensional array of multi-degree-of-freedom (MDOF) ultrasonic actuators suitable for two-dimensionally moving table. The MDOF motions of a ball rotor are achieved by the combination of two bending and one longitudinal vibrations excited on columns fixed on a substrate. A 2 x 2 array of MDOF column actuator is fabricated for two-dimensional movement of a plate placed on the array. Only one piezoelectric element is used for one column instead of a stack of different types of PZT elements to drive the vibrations. First, we describe the configuration of the actuator, an excitation method of each vibration, and the operating principle of the stage motion. Then, moving table operation was demonstrated and evaluated.

Purification of wastewater is indispensable to civil engineering construction. Since natural sedimentation requires much time, coagulants are used to increase the sedimentation rate. However, this may cause environment disruption. In this study, we investigated an ultrasonic agglomeration method which needs no coagulants as a possible solution to this problem. This method is based on phenomena that suspended particles are trapped at the nodal lines of a standing ultrasonic field due to acoustic radiation forces and then agglomerate. Our experimental setup had a water channel between a piezoelectric plate transducer designed to resonate at 1 MHz and a reflector. In the experiments, the suspended particles moved to and were trapped at the nodal lines and agglomerated both with and without water flow. By tilting the transducer, the position of trapping was varied and the agglomerated clusters settled out more easily. We obtained a maximum purification rate of 0.09 L/min with electrical power of 40 W.

Characteristics of an ultrasonic suction pump that uses a vibrating piston surface and a pipe are numerically simulated and compared with experimental results. Fluid analysis based on the finite-difference time-domain (FDTD) routine is performed, where the nonlinear term and the moving fluid-surface boundary condition are considered. As a result, the suction mechanism of the pump is found to be similar to that of a check valve, where the gap is open during the inflow phase, and it is nearly closed during the outflow phase. The effects of Reynolds number, vibration amplitude and gap thickness on the pump performance are analyzed. The calculated result is in good agreement with the previously measured results.

With development of biotechnology, manipulation and separation techniques of small particles such as cells and DNA are required in the field of life sciences. This report investigates on-chip manipulation of micro-particles in channels using ultrasound. The chip consists of a rectangular glass substrate having a cross-shaped channel and four PZT transducers attached to four corners on the glass substrate. The configuration of the glass substrate and the transducers were determined by the finite element analysis to generate the flexural vibration mode on the chip efficiently. The channel is filled with ethanol, and silicon carbide micro-particles with an average diameter 50 µm were immersed in the channel. By applying the in-phase input voltages of 75 V pp at 225 kHz to the four transducers, the flexural vibration mode with the wavelength of 13.0 mm was excited on the glass substrate, and the particles can be trapped at the nodal lines of a standing wave in the channel generated by the flexural vibration. By controlling the driving phase difference between two pairs of the transducers, the vibrational distribution of the chip can be changed and the trapped particles can be manipulated.

Methods for controlling the periodic molecular orientation of liquid crystals using ultrasound vibrations and estimating the orientational direction are proposed. An ultrasonic liquid crystal cell was used, consisting of a liquid crystal layer sandwiched by two glass plates fitted with piezoelectric ultrasound transducers. The transmitted light intensity distribution through the cell was measured by changing the polarization direction to investigate the orientation direction of the liquid crystal molecules. The transmitted light distributions changed periodically owing to the flexural vibration of the cell at resonance frequencies of 43.9 and 70.7 kHz. The orientational direction of the liquid crystal molecules correlated with the vibrational distribution of the glass substrates, and the molecular orientation was changed periodically by the acoustic radiation force. The interval and intensity of the transmitted light could be controlled by the driving frequency and voltage amplitude, respectively.

A junction for noncontact ultrasonic transportation paths in which small objects can be manipulated is proposed. The junction consists of a vibrating disc and a reflector. The reflector is installed parallel to the vibrator to generate an acoustic standing wave in the cavity between the vibrating disc and the reflector. The resonance modes of the acoustic field in the disc cavity between the two plates are calculated theoretically. The distributions of the sound pressure amplitude and the acoustic radiation force in air are calculated using finite element analysis. The flexural vibration modes with one nodal circle and four nodal lines at 45.4 kHz and two nodal circles and three nodal lines at 58.1 kHz are used to trap and eject small objects, respectively. The transportation velocity and the thrust force in the radial direction for a polystyrene particle with a diameter of 2 mm and a weight of 0.3 mg are 812 mm/s and 24 μN, respectively. The ejection direction of the trapped object can be controlled by the driving condition of the vibrating disc.

Nematic liquid crystals used in optical devices such as liquid crystal displays are controlled by the electric fields. Although indium tin oxide (ITO) is generally employed as the transparent electrode material to apply the electric field, it includes the rare metal indium and needs complicated processes such as sputtering deposition method. Our group has been investigating control techniques of molecular orientation of liquid crystals using ultrasound. In this study, we have applied these techniques to optical variable-focus lenses and the optical characteristics were examined. The ultrasonic liquid crystal cell has a simple structure with no transparent electrodes; it consists of has an annular ultrasound PZT transducer (inner diameter: 30 mm; thickness: 2 mm) and a liquid crystal cell in which a nematic liquid crystal layer (thickness: 25 μm) was formed between two glass substrates (thickness: 0.7 mm) and orientational films. The concentric flexural vibration modes could be generated on the cell at the...

We propose a technique to control the orientation of nematic liquid crystals using ultrasound and investigate the optical characteristics of the oriented samples. An ultrasonic liquid crystal cell with a thickness of 5–25 μm and two ultrasonic lead zirconate titanate transducers was fabricated. By exciting the ultrasonic transducers, the flexural vibration modes were generated on the cell. An acoustic radiation force to the liquid crystal layer was generated, changing the molecular orientation and thus the light transmission. By modulating the ultrasonic driving frequency and voltage, the spatial distribution of the molecular orientation of the liquid crystals could be controlled. The distribution of the transmitted light intensity depends on the thickness of the liquid crystal layer because the acoustic field in the liquid crystal layer is changed by the orientational film.

An optical lens array whose focal length and lens pitch can be varied by acoustic radiation force was investigated. It has no mechanical moving parts and a simple structure that consists of a glass plate, four ultrasound transducers, and a viscoelastic film. A lens array can be formed by generating acoustic radiation force through flexural vibrations of the glass plate. Its focal length can be controlled by varying the voltage applied to the transducers and the lens pitch can be altered by changing the driving frequency.

Varifocal imaging using an optical lens that employs acoustic radiation force and a viscoelastic material and that has no mechanical moving parts is investigated. The lens has a simple and thin structure that consists of an annular ultrasonic transducer and silicone gel. An axially symmetric acoustic standing wave can be generated in the gel by exciting a vibration mode in the radial direction on the transducer. The lens profile can be altered by varying the acoustic radiation force of the transducer. The focal length can be controlled by varying the transducer input voltage so that the lens functions as a variable-focus lens.

We estimated the dependences of Brillouin frequency shift (BFS) on temperature and strain in poly(methyl methacrylate)-based polymer optical fibers using ultrasonic pulse-echo technique at ~10 MHz. The estimated BFS dependence on temperature was linear with a coefficient of approximately -17 MHz/K at 650 nm pump, which was -34 times larger than that of silica fibers at 650 nm pump. In contrast, its strain dependence was found to be nonlinear, probably originating from the elastic-to-plastic transition. © (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.

By using a pair of bimorph transducers, we have already miniaturized a traveling-wave-based ultrasonic linear motor and achieved a diameter of < 10 mm, but its motor performances were not sufficient for practical applications. In this study, in order to improve its performances, the motor structure is optimized with the two methods: by reducing the thickness of the transmission bar, and by increasing the number of the bimorph transducers. The highest motor speed of 118 mm/s is achieved with the former, while the largest motor thrust of 0.5 N is obtained with the latter. These values are approximately 25 and 15 times as large as those in our previous experiments.

In the next generation of the pharmaceutical industry, noncontact transportation technology of liquid is highly required for higher purity production process. In this paper, we focused on transporting liquid without contact using ultrasonic levitation. An acoustic waveguide was developed to excite a highly confined travelling wave using a plate vibrator and a semicylindrical reflector. We used an aluminum plate as a vibrator and an acrylic semi-cylindrical tube as a reflector to excite travelling waves of bending vibration at 37 kHz on the vibration plate. In the waveguide between the vibration plate and the reflector, a droplet could be trapped at the position of horizontal nodal line, and experienced the horizontal thrust force due to the travelling wave. Then, the droplet would be transported without contact. We designed the waveguide using a finite element analysis to find an appropriate propagating mode for trapping droplet. We also confirmed that the vibration distributions on the plate and the sound pressure field inside the waveguide were travelling waves by using a laser Doppler vibrometer and a probe microphone. Noncontact transportation of liquid with an ethanol droplet has been demonstrated. The movement was observed with a highspeed video camera. A droplet of around 1.5 mm in diameter was successfully transported without contact between two horizontal antinodal lines of the sound pressure distribution. The transportation distance and the maximum velocity have reached 65 mm and 2.3 m/s, respectively.

We estimated the dependences of Brillouin frequency shift (BFS) on temperature and strain in poly(methyl methacrylate)-based polymer optical fibers using ultrasonic pulse–echo technique at ~10 MHz. The estimated BFS dependence on temperature was linear with a coefficient of approximately -17 MHz/K at 650 nm pump, -34 times larger than that of silica fibers at 650 nm pump. In contrast, its strain dependence was found to be nonlinear, probably originating from the elastic-to-plastic transition.

A variable-focus lens that employs acoustic radiation force and a viscoelastic material and that has no mechanical moving parts is investigated. The lens has a simple and thin structure that consists of an annular ultrasonic transducer and silicone gel. An axially symmetric acoustic standing wave can be generated in the gel by exciting a vibration mode in the radial direction on the transducer. The lens profile can be altered by varying the acoustic radiation force of the transducer. The focal length can be controlled by varying the transducer input voltage so that the lens functions as a variable-focus lens.

Switch of transport direction and junction in a noncontact ultrasonic transporter are discussed. A 0.5-mm-thick aluminum circular plate with a diameter of 30 mm was employed as a vibrating plate and a 0.5-mm-thick piezoelectric ring was attached to the vibrating plate. Two difficult vibration modes were selectively generated at 47.8 and 64.9 kHz, respectively, using divided electrodes in order to change the direction of the radiation force acting on the particle. The (1, 4) flexural mode enables noncontact trapping and transportation of a small object in the circumferential direction, and the (2, 3) mode assists the transfer through a junction. The reflecting plate was installed parallel to the vibrator with a distance of approximately 5 mm to generate an acoustic standing wave in air between them. The acoustic field between the vibrator and reflector was calculated via the finite element analysis, and the distribution of the acoustic radiation force acting to a small rigid particle was calculated to predict the trapped position of the particle and the direction of ejection. By using a prototype of the vibrating plate, polystyrene particles with the diameter of several millimeters was successfully ejected in the radial direction. The ejecting force acting on the particle in the horizontal direction was estimated to be 7.5×10−6 N from the trace of the particle movement.

Mechanical scanning probe using vibration of silica-glass fiber is developed for optical coherence elastography. High repetition rate and wide scanning angle are obtained with high frequency bending vibration of a single mode optical fiber. Deformation is generated in sample by illuminating the surface with focused MHz-ultrasonic burst waves, and then measured using optical coherence tomography (OCT) method with the depth resolution of around 10 μm. The prototype of the scanner probe is 1 mm in diameter and 20 mm in length. Strain is calculated with the cross-correlation detection using the images before and after applying the ultrasonic waves.

Direct finite difference fluid simulation of acoustic streaming on the fine-meshed threedimension model by graphics processing unit (GPU)-oriented calculation array is discussed. Airflows due to the acoustic traveling wave are induced when an intense sound field is generated in a gap between a bending transducer and a reflector. Calculation results showed good agreement with the measurements in the pressure distribution. In addition to that, several flow-vortices were observed near the boundary of the reflector and the transducer, which have been often discussed in acoustic tube near the boundary, and have not yet been observed in the calculation in the ultrasonic air pump of this type.

A transportation system for small object or fluid without contact is investigated being based on ultrasonic levitation. Small objects are suspended against gravity at the nodal points in ultrasonic pressure field due to the sound radiation force generated as the gradient of the energy density of the field. In this study, the trapped object is transported in the horizontal plane by introducing the spatial shift of the standing waves by the switching the lateral modes or travelling waves. The goal of the study is to establish a technology which can provide a total system with the flexibility in composing various transportation paths. Methods for linear/rotary stepping motions and continuous linear transportation are explained in this report. All the transportation tracks are composed of a bending vibrator and a reflector. The design for these acoustic cavity/waveguide is discussed.

The acoustic velocity in a poly(methyl methacrylate) (PMMA) polymer optical fiber (POF) was measured to be 2.8×103 m/s using ultrasonic pulse-echo technique, from which its Brillouin frequency shift (BFS) was estimated to be ~13 GHz at 650 nm. The BFS was also predicted to show a negative dependence on temperature with a coefficient of approximately -17.1 MHz/K at 650 nm, -14.5 times larger than that of a silica fiber at 1.55 µm.

A compact, high-speed variable-focus liquid lens using acoustic radiation force is proposed. The lens consists of an annular piezoelectric ultrasound transducer and an aluminum cell (height: 3 mm; diameter: 6 mm) filled with degassed water and silicone oil. The profile of the oil-water interface can be rapidly varied by applying acoustic radiation force from the transducer, allowing the liquid lens to be operated as a variable-focus lens. A theoretical model based on a spring-mass-dashpot model is proposed for the vibration of the lens. The fastest response time of 6.7 ms was obtained with silicone oil with a kinematic viscosity of 100 cSt.

Small-sized ultrasonic linear motors are demanded for replacing pneumatic actuators. We propose a new structure of traveling wave ultrasonic linear motor less than 10 mm in diameter using bimorph transducers. The length of the transducer is determined to be 17 mm being based on finite element analysis for the resonance frequency of 90 kHz. A traveling wave of bending vibration is excited along the transmission bar with the electrical termination at one of the transducers. The maximum speed of 154 mm/s and the maximum thrust of 0.4 N were obtained.

An ultrasonic air pump utilizing acoustic streaming is discussed and its accurate simulation method using finite element analysis (FEA) is suggested in this paper. The pump induces air streaming in a thin air layer between a bending transducer and a reflector by exciting an intense sound field. The absolute sound pressure and streaming velocity in the air layer are calculated on the basis of full-fluid dynamics through FEA, and the calculation results are compared with experimental results for the sound pressure and flow velocity. As a result, the sound pressure is calculated in the derivation of the error of 5.9%, and the measurement and analysis results for the streaming distribution are in good agreement.

We have developed a noncontact ultrasonic technique for transporting small objects with a linear trajectory over long distances using a bending vibrating plate and a reflector. In this paper, noncontact transportation of small particles around a circular trajectory was investigated. A circular aluminum plate with a piezoelectric ring was employed as a vibrating plate. On the basis of finite element analysis (FEA) calculations, the electrodes of the piezoelectric ring were divided into 24 pieces to generate a flexural vibration mode with one nodal circle and four nodal lines at the resonance frequency of 47.8 kHz. A circular plate having the same dimensions as the vibrating plate was installed parallel to the vibrator. It was used as a reflector to generate an acoustic standing wave in the air between the two plates. The acoustic field between the vibrating plate and reflector was calculated by FEA and the distribution of the acoustic radiation force acting on a small rigid particle was calculated to predict the position of the trapped particle. Using a prototype of the vibrating plate, polystyrene particles with diameters of several millimeters could be trapped at regular intervals along the horizontal nodal line of the standing wave. The sound pressure distribution between the vibrating plate and reflector was measured by a fiber optic probe and the experimental and calculated results showed good agreement. By switching the driving conditions of the divided electrodes in the circumferential direction, the nodal lines of the vibrating plate could be rotated and the trapped particle could be manipulated with a circular trajectory in air.

Ultrasonic manipulation of small particles, including liquid droplets, over long distances is discussed. It is well known that particles can be trapped at the nodal points of an acoustic standing wave if the particles are much smaller than the wavelength of the standing wave. We used an experimental setup consisting of a 3-mm-thick, 605-mm-long duralumin bending vibrating plate and a reflector. A bolt-clamped Langevin transducer with horn was attached to each end of the vibrating plate to generate flexural vibrations along the plate. A plane reflector with the same dimensions as the vibrating plate was installed parallel to the plate at a distance of approximately 17 mm to generate an ultrasonic standing wave between them and to trap the small particles at the nodal lines. The acoustic field and acoustic radiation force between the vibrator and reflector were calculated by finite element analysis to predict the positions of the trapped particles. The sound pressure distribution was measured experimentally using a scanning laser Doppler vibrometer. By controlling the driving phase difference between the two transducers, a flexural traveling wave can be generated along the vibrating plate, and the vertical nodal lines of the standing wave and the trapped particles can be moved. The flexural wave was excited along the vibrator at 22.5 kHz. A lattice standing wave with a wavelength of 35 mm in the length direction could be excited between the vibrator and the reflector, and polystyrene spheres with diameters of several millimeters could be trapped at the nodal lines of the standing wave. The experimental and calculated results showed good agreement for the relationship between the driving phase difference and the positions of the trapped particles. Noncontact transportation of the trapped particles over long distances could be achieved by changing the driving phase difference. The position of the trapped particles could be controlled to an accuracy of 0.046 mm/deg. An ethanol droplet could also be trapped and moved.

An ultrasonic air pump that uses a traveling wave along a small air gap between a bending vibrator and a reflector is discussed. The authors investigate ultrasonic air pumps that make use of bending vibrators and reflectors and confirm that air can be induced to flow by generating an asymmetric acoustic standing wave along an air gap. In this paper, we proposed a novel ultrasonic air pump in which a traveling wave along an air gap induces acoustic streaming and achieves one-way airflow. Two new reflector configurations, stepped and tapered, were designed and used to generate traveling waves. To predict airflow generation, sound pressure distribution in the air gap was calculated by means of finite element analysis (FEA). As a preliminary step, 2 FEA models were compared: one piezoelectric-structure-acoustic model and one piezoelectric- structure-fluid model, which included the viscosity effect of the fluid. The sound pressure distribution in the air gap, including fluid viscosity, was calculated by the FEA because it is expected to be dominant and thus have a strong effect on the sound pressure field in such a thin fluid layer. Based on the FEA results of the stepped and the tapered reflectors, it was determined that acoustic traveling waves could propagate along the gaps. Experiments were carried out with the designed bending vibrator and the reflectors. The acoustic fields in the air gap were measured via a fiber optic probe, and it was determined that the sound pressure and the phase distribution tendencies corresponded well with the results computed by FEA. Through our experiments, one-way airflow generation, in the same direction of the traveling wave and with the maximum flow velocity of 5.6 cm/s, was achieved.

In this paper, we study a new configuration of an element actuator suitable for the two-dimensional array of multi-degree-of-freedom (MDOF) ultrasonic motors. To reduce acoustic coupling between element actuators, a thin disk structure is introduced. MDOF motions are achieved by the combination of vibrations of the column for three orthogonal directions due to the vibration of the thin disk. Only one piezoelectric element is used for one column instead of a stack of different types of piezoelectric elements to drive the vibrations. First, we describe the configuration of the actuator, an excitation method of each vibration, and the operating principles of the MDOF motion. Second, resonance frequencies of excited vibrations are tuned using finite element analysis. Finally, rotation of the ball rotor is discussed.

This report presents the metal powder compaction using ultrasonic vibration for the fabrication of a three-dimensionally-shaped magnetic core. First, we describe a design of ultrasonic compaction tools using FEM. Side wall of the sample was ultrasonically excited by a radial vibration of the die, while the upper and lower punches are driven by longitudinal vibrations. Second, we present the results of compression experiment of cylindrical sample.

A high-speed variable-focus liquid optical lens using acoustic radiation force is proposed. The lens consists of a piezoelectric ring and a lens cell filled with degassed water and silicone oil. The profile of the oil-water interface can be rapidly varied by applying acoustic radiation force from the ultrasonic transducer, allowing the liquid lens to be operated as a variable-focus lens. The fastest response time of 6.7 ms was obtained with silicone oil with a kinematic viscosity of 100 cSt. The lens could scan at focal lengths of from 7.0 to 14.5 mm at 1 kHz in the axial direction.

In ultrasonic pumps, liquid is sucked into a pipe whose end is faced at an ultrasonic vibrating surface with a small gap. To simulate the pump operation, a model of the ultrasonic pump based on the squeeze film theory is presented in this paper. Nonlinear compressibility is introduced to the liquid in the gap, and the static pressure is calculated as a time average over the period of the ultrasonic vibration of the gap. We investigate the applicability of the model by comparing the simulated static pressure with the experimental pump pressure. The simulated static pressures as a function of the gap and the vibration displacement amplitude approximately agree with the experimental pump pressures if the squeeze film factor is suitably chosen.

"null", If a pipe end is faced at an ultrasonic vibrating surface with a small gap in the liquid, the liquid is sucked into the pipe. The ultrasonic pump under our investigation is based on this phenomenon. In the first part of this paper, we explore the relationships between the number of pipes and the pump characteristics. The flow rate is improved proportionally to the number of pipes if a piston-vibrating surface is used, whereas the maximum flow rate is improved by a factor of only 1.5 using two pipes if a bending vibrator is employed. Second, we research how the inner diameter of the pipe affects the flow rate. The maximum flow rate is improved by a factor of 1.9 if the inner diameter is changed from 3.5 to 5.0 mm.