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Lithium (Li) has long been known to be the best anode material for rechargeable batteries, however, lithium metal batteries (LMB) have never been commercialized due to dendrite formation, resulting in thermal runaway and fire or explosion. During charging, Li ions deposit onto Li anode from the cathode via electrolyte. However, the deposition is not uniform due to the inhomogeneous ion distribution in the electrolyte from a thick Li ion depletion layer, typically >400 μm. Our objective is to reduce the diffusion layer from 400 μm to only 1 μm by using surface acoustic wave (SAW)-driven mixing flow of the electrolyte during charging and to prevent dendrite formation.

Surface acoustic wave (SAW) generation on 128° YX acoustic superlattice has been investigated by considering the finite-depth of the domain created by the UV direct-domain writing. We found that bound and localized SAW will be generated when the domain depth of the ASL structure, underlying the transducer, is smaller and bigger than the lattice period, respectively. Efficient bound SAW can be achieved, provided the domain depth is 30% of the lattice period.

Surface acoustic wave (SAW) atomization has been found to be a rapid and efficient way for generating micron or submicron aerosols within a controllable fashion. The SAW atomizer is small and light-weighted, attractive for many applications, especially for pulmonary drug delivery and biomicrofluidics. Control the sizes of the aerosols generated by SAW is crucial for successful applications. Unlike the theory applied and published in many SAW atomization works—the size of the aerosol can be tuned by manipulating the driving frequency; —we however found the aerosol size is irrelevant to the driving frequency, but governed by the capillary vibration frequency given by the balance between the acoustic forcing and capillary stress. The self-pumping effect of SAW, on the other hand, leads to the design of a disposable pump-free liquid supply system, which is able to deliver liquids to atomizer automatically for continuous atomization.

The microfluidic applications of a ZnO/Sapphire based layered surface acoustic wave structure are being investigated. Properties of the ZnO/Sapphire layered SAW device including surface wave velocity and propagation loss were measured and correlated to the fluidic behavior of micro droplets. Acoustic streaming was observed in the form of two vortices. Micro particles were also observed to concentrate in the vortices within 4 seconds of device activations.

We present a surface acoustic wave (SAW) actuated rotating micro motor. The rotors are 1 millimeter metal spheres which are placed on the surface of a Lead Zirconate Titanate (PZT) substrate with IDTs designed to generate SAW with ∼ 700 µm wavelength. A Laser Doppler Vibrometer (LDV) was used to visualize the travelling SAW and the result was compared with the rotation of the rotor. The motor transient responses are presented, along with its torque-speed curve. The maximum rotational speed and torque reported were ∼1000 rpm and ∼14 µN.mm, respectively. Arbitrary motions have also been demonstrated utilizing a magnetic pre-load and multiple IDTs activation.

We demonstrate complex nonlinear pattern formation dynamics associated with standing wave vibrations induced along a piezoelectric substrate on which a small drop of colloidal suspension is placed. Interfacial colloidal islands which self-assemble due to surface acceleration and capillarity are subsequently erased once fluid streaming becomes significant at higher powers. Due to a peculiar instability, the system cycles between colloidal island assembly when streaming ceases and erasure when streaming resumes.

Surface acoustic wave atomization is promising in various kinds of industrial and pharmaceutical processes. In order to properly apply this technology for a wide range of applications, controlling the aerosol size distribution is crucial. It is widely believed that the aerosol size can be controlled by the driving frequency, our experimental results, show a rather weak frequency dependence, especially when the driving frequency is above 10 MHz. Fundamental studies were therefore carried out to determine the underlying mechanism associated with the destabilization of the liquid interface leading towards atomization with the objective of elucidating this apparent contradiction. Our investigation supports the notion that the droplet sizes appear to be governed by the capillary vibration frequency given by a balance between the capillary stress and viscous forcing, not the driving frequency as previously claimed. Furthermore, the aerosol size can be altered by controlling the surface tension and viscosity. For this case, we employ the laser diffraction to obtain the size distributions of octanol aerosol and water aerosol generated by SAWatomization. The experimental results matches our theocratical prediction that water, with higher surface tension and lower viscosity, generates relatively larger aerosols than octanol.

We investigate uniform fluid and mixing flows with linear speeds up to 1–10 mm/s, actuated by surface acoustic waves. Under strong acoustic excitation, transition from uniform to oscillatory mixing flow occurs when the width of the channel increases beyond one acoustic wavelength of sound in the fluid λ f . In this high velocity regime, particles of one micrometer in diameter suspended in aqueous solution are observed to follow the streamlines. Under weak acoustic excitation, particles aligning into equally-spaced lines (with a separation of λ f /2) due to the presence of acoustic standing waves across the channel and move slowly in the reverse direction due to the slow streaming. We developed a numerical model of the system that accounts for the acoustic streaming in the fluid with treatment of viscous and solid-fluid coupling effects, and the results qualitatively support the observed phenomena in the experiments.

Surface acoustic waves have been known to be able to drive fluid jetting phenomena, though the underlying physical mechanism has remained unclear. In a setup designed to reliably jet small fluid droplets, a pair of focused single-phase unidirectional transducers were placed facing each other along the x-axis of a 128°Y-X lithium niobate substrate. Driving both transducers at the same time, the laterally focused acoustic energy appears beneath a drop placed on the surface, refracting into the drop and causing destabilization of the drop's free surface. Above a critical Weber number We, an elongated jet forms for drops with dimensions greater than the fluid sound wavelength. Further increases in We leads to single droplet pinch-off and subsequent axisymmetric break-up to form multiple droplets. Derivation of a simple relationship based on the acoustics and fluid physics predicts the jetting behavior across a wide range of Newtonian fluids, droplet sizes, and input powers.

To improve on current methods of minimally invasive surgery, research is being carried out on systems that will permit procedures to be conducted on the micro-scale using remotely operated micro-robots. One of the major stumbling blocks to meeting this need has been the absence of a practical micromotor with a volume of less than 1 mm3 with which to drive these devices. To rectify this, we present a piezoelectric ultrasonic resonant micromotor with a volume of approximately 0.75 mm3. The motor uses a novel helically cut stator that matches axial and torsional resonant frequencies, excited by a lead zirconate titanate element 0.03 mm3 in volume. An earlier motor using the same stator design, but a larger overall volume, achieved a start-up torque of 47 nNm and no load angular velocity of 830 rad/s. This performance is on the order necessary to propel a swimming microbot in small human veins.

The body's stress response to surgery has been cited as a primary cause of post-operative morbidity and has prompted growth in minimally invasive surgical techniques. The future of such techniques lies in the use of in vivo procedures, but is currently limited by the availability of motors with a volume of less than 1 mm3.In response to this we present a piezoelectric ultrasonic resonant micromotor with a volume of approximately 0.75 mm3. The motor has a novel helically cut stator that couples axial and torsional resonant frequencies, excited by a lead zirconate titanate element 0.03 mm3 in volume. The motor performance reaches a start-up torque of 47 nNm and no load angular velocity of 830 rad/s. This gives the motor a power density of 18.4 kW/m3. This performance is on the order necessary to propel a swimming microbot in small human arteries.

Nanoparticle patterning on a vibrating solid surface according to the vibration modes of the solid is the result of extremely high solid surface acceleration and persistent flow beyond the steady boundary layer. The solid surface acceleration magnitude increased proportionally to the square of vibration angular frequency. The tens-of-megahertz frequency cause the surface acceleration to reach to an order of 107 m/s2, and thus providing a substantial impact force when a nanoparticle fall on the solid surface. On the other hand, the acoustic radiation pressure and acoustic streaming drag due to the persistent flow beyond the steady boundary layer transport lifted nanoparticles to an adjacent region where the adhesion force overcomes the impact force.

The concentration and indeed mixing of particle suspensions are important procedures in microfluidic processes. Relying on diffusion for mixing leads to unreasonably long mixing times, and enhancing or avoiding it by promoting chaotic mixing typically relies on complex geometries. Concentric circular and elliptical single-phase unidirectional transducers (SPUDTs) were used to focus the SAW, with a straight SPUDT as a benchmark for comparison. Due to the increased wave intensity and asymmetry of the wave, we found both circular and elliptical SPUDTs concentrate particles in under one second, one order of magnitude faster than the straight SPUDT and several orders of magnitude faster than conventional microscale devices. The concentric circular SPUDT was found to be most effective at a given input power since it generated the largest azimuthal velocity gradient within the fluid to drive particle shear migration. On the other hand, the concentric elliptical SPUDT generated the highest micromixing intensity due to the more narrowly focused SAW radiation that substantially enhances acoustic streaming in the fluid.

This work demonstrates the use of surface acoustic wave (SAW) atomization together with a nonuniform evaporation and nucleation process to give sub-50-nm diameter monodisperse nanoparticles. SAW atomization is a straightforward and energy efficient technique to generate relatively homogeneous particle size distributions that can be carried out on a chip-scale microdevice for portable drug delivery applications or scaled up for industrial production. It employs technology originally developed for the entirely different purpose of signal filtering and multiplexing, and provides direct control over the size of the particles through adjustment of the operating frequency of the ultrasonic vibration.

An efficient numerical technique for modeling biological tissues using the radiative transfer equation is presented. Time dependence of the transient radiative transfer equation is approximated using Laguerre expansion. Azimuthal angle is discretized using the discrete ordinates method and the resulting set of ordinary differential equations is solved using the Runge-Kutta-Felhberg method.

This report presents a new design and its performance test for a non-contact sliding table by ultrasonic levitation. A slider is levitated by an acoustic radiation force emitted from two vibrating guide rails, and a flexural traveling wave propagated along the guide rails allows a non-contact transportation of the slider. The reduction of the abrasion and dust generation, high cost performance and simple structure are expected. The profile of the sliding table was designed using the finite element method (FEM) for high levitation and transportation efficiency. The prototype sliding table made of alumina ceramics for obtaining higher machining accuracy and rigidity. A structure consists of a pair of 152-mm-long beams with a triangle cross-section, two bolt-clamped Langevin transducers (BLT) with the diameter of 11 mm and cross-shaped vibration direction converters to permit low height of 11 mm. A slider with the length of 40 mm was designed to fit the two rail guides. The flexural mode standing wave was observed along the guide rail at the resonance frequencies of 89.4 kHz, and the levitation of the slider could be confirmed even if the levitation distance is less than 10 µm. The levitation distance of the slider was measured with increasing the slider's weight, and the levitation force, the levitation rigidity and the displacement amplitude of the levitating slider in the vertical direction were measured to be 4.8 kN/m 2 , 2.5 kN/µm/m 2 and under ±1 µm, respectively, in the case of the levitation distance of 2.2 µm. The non-contact transporting of the slider was achieved with the phased drive of two transducers. By controlling the phase difference, the slider transportation direction could be switched. The maximum thrust and the transportation speed were 1.3 mN and 34.6 mm/s, respectively, in the case of the slider's weight of 107 g.

A long period optical fiber grating is obtained by ultrasonic bending vibration propagating along the fiber. The rejection optical wavelength is tunable by the ultrasonic frequency, since it is determined by the period of refractive index modulation due to the vibration. The rejection center wavelength and the rejection ratio are experimentally investigated as functions of the frequency, intensity and length of the ultrasonic vibration excitation. The rejection ratio is changed by the ultrasonic vibration amplitude, while the rejection bandwidth depends on the fiber length where the vibration is excited. The wide tunable range of 160 nm (from 1490 to 1650 nm) was available for ultrasonic frequency range of 300 kHz. The rejection ratio of 17 dB was achieved for the vibration velocity of 0.25 m/s. A method to synthesize the rejection band shape is also discussed.

A new linear microactuator, using bulk PZT and electro-discharge-machined components, generates a sliding velocity and force of 100 mm/s and 12 mN in either direction, and a peak velocity and force of 212 mm/s and 44 mN, is an order of magnitude smaller than any other reported piezoelectric linear actuator to date at less than 4 mm/sup 3/ in volume. Using a simple combination of two slightly different fins, placed in contact with a slider, and vibrated at two different resonance frequencies, 508 and 522 kHz, by a specially-designed, axially-vibrating piezoelectric element, bidirectional linear motion was obtained. By simply reducing the length of the applied signal, the sliding distance was reduced to 90/spl plusmn/2 nm, which could be improved with a variety of control methods. The design offers not only silent operation, slider clamping upon removal of power, and all the other advantages of piezoelectric actuators, but also the potential to be further reduced in size to sub-mm/sup 3/ for microrobotics and other applications.

A torsional microactuator was developed using standard bulk lead zirconium titanate placed upon a small rectangular prism made from phosphor bronze, with a tapered conical end serving as a horn and a carefully machined interior to improve the actuator's response. The results of testing indicate torsional motion was obtained from the device, with torsional vibration velocities of 295 mm/s at 190 kHz being obtained at 27.5 V/sub RMS/ at the output, amounting to 19,320 deg/sec vibration velocity along the outer circumference of the tip.

The design, optimization, and properties of a prototype small traveling-wave ultrasonic piezoelectric linear motor design are described. A method for optimizing the geometry of the motor to maximize its mechanical output for a given electrical input is described, as is the inherent properties of the design to maximize the motors durability and utilization of the piezoelectric material. Results from testing the motor demonstrate the design and indicate a maximum speed of 2.5 cm/s with a preload of 16 g due to an applied voltage of 80 VRMS at an applied current of 15 mA.