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Low frequency sonophoresis (LFS) is a type of transdermal drug delivery method, which is useful for enhancing the permeation of hydrophobic and hydrophilic compounds across the skin. At present, the main ultrasonic effects of LFS include cavitation, microstreaming from bubbles, thermal effects, and recently bilayer sonophore effect, in which cavitation effect has been studied to interpret LFS principle since 2003. However, our experimental results show that the acoustic streaming is another factor in high-intensity acoustic input. Therefore, a calculation model is built up based on acoustic equation and turbulence k-ε model in terms of the finite element software COMSOL Multiphysics. In vitro LFS experiment consists of a Langevin-type ultrasonic transducer working at 21 kHz and a Franz diffusion system, and Calcein permeations were measured at different acoustic intensities and distance between the transducer horn and skin. Calculated and experimental results demonstrate that the velocity of acoustic streaming in the donor is another important physical effect for the improvement of LFS. When the increase of acoustic intensity can enlarge the acoustic pressure and velocities of acoustic streaming, and enhance Calcein permeation at the same time; However, when the transducer horn was away from the skin surface, the acoustic pressure decreased but the velocity of acoustic streaming increased first and then decreased, and the latter varying tendency is in accordance with Calcein permeation change. Furthermore, calculated results of the line integral along the radial velocity show that spatial synthesis effect of acoustic streaming velocity may be the key factor for the enhancement of Calcein permeation other than the maximum velocity value. Therefore, it can be recognized that the acoustic streaming resulting from the transducer horn may be another important influence factor in in vitro LFS, especially in high acoustic intensity input (>1 W/cm 2 ). [ABSTRACT FROM AUTHOR]

Piezoceramic disks with spiral interdigitated electrodes (SIDEs) on their surfaces are proposed to produce in-plane torsion. With constant electrode spiral angle (Type I) and constant pitch between adjacent electrodes (Type II), two typical types of the SIDEs are developed and studied. Working principles of the discal piezoelectric actuators are explained and their static in-plane torsional deformations are formulated. Finite element simulations are used to investigate the static and dynamic properties of the actuators. Non-ideal distributions of electric fields appear serious suppressions on the actuating abilities, even worse for Type I actuator. Due to unsymmetric piezoelectric strains in the thickness direction, bending deformations of the disks are inevitable. Prototype actuators with fixed boundary at the radius of 12 mm are fabricated and tested. With a driving voltage of 400 V p-p at 1 Hz, the maximum quasi-static in-plane torsional angles are 0.00458° for Type I actuator and 0.00605° for Type II actuator at the radius of 6 mm. With a driving voltage of 10 V p-p , the vibration amplitudes at the radius of 6 mm are 0.00105° at 86.0 kHz for Type I actuator and 0.00149° at 84.4 kHz for Type II actuator at the first in-plane torsional vibration modes. [ABSTRACT FROM AUTHOR]

Highlights: [•] A new electromagnetic structure for resonant cavity wind energy harvester was developed. [•] A tuning fork-like reed structure to reduce system losses was designed. [•] A new method of virtual resistance to achieve maximum output power was demonstrated. [•] The magnetic field was analyzed and compared. [•] The locations of the coils and magnet were optimized and tested. [Copyright &y& Elsevier]

Abstract: A novel optical scanner excited by a torsional piezoelectric fiber actuator is presented. The device consists of a piezoelectric fiber actuator generating torsional and longitudinal vibrations simultaneously and a specially designed metal frame transforming the two vibrations to orthogonal deflections of the mirror. Theoretical and experimental studies were performed on the structure. The changing trends of the vibration modes and resonant frequencies were obtained from finite element simulations. Samples with 1mm×1mm mirrors were fabricated from PZT hollow fibers with a diameter of 1mm and a stainless steel sheet with a thickness of 50μm. A horizontal scanning angle of 17.9° and a vertical scanning angle of 2.6° were achieved at 6780 and 10,330Hz under an applied voltage of 400Vp–p. [Copyright &y& Elsevier]

• A new type of fiber-based mechanomyography (MMG) sensor was developed and used as a motion on/off trigger sensor for a lower limb rehabilitation exoskeleton (LLRE). • To make a MMG sensor with better voltage signals output, the groups of different interspaces and pairs of IDT electrodes were designed and analyzed. • From physiological signals captured from the MMG sensor for the human walking with the LLRE, this new sensor had higher sensitivity compared to EMG sensors. • During the LLRE walking process, maximum signal amplitude and SNR of the MMG sensor were about ∼2.8 V and ∼25 and were 14 and 7 times compared to that of the EMG signals. In this study, a new type of fiber-based mechanomyography (MMG) sensor was developed and used as a motion on/off trigger sensor for a lower limb rehabilitation exoskeleton (LLRE). Piezoelectric material, polyvinylidene difluoride (PVDF), was applied to fabricate a MMG sensor, using the near-field electrospinning technology to electrically spin PVDF fibers to ∼5-10 μm in diameter. PVDF fibers attached on an interdigitated (IDT) electrode with different pole pairs and interspaces were packaged into a MMG sensor. This MMG sensor was stuck on the thigh muscles to detect and acquire human motion intention signal, then trigger the controller and actuate the LLRE. The LLRE multi-axis control system included a master and four slave controllers. The master controller released the command signal to control the slave controllers via controller area network (CAN). A multi-axis control system was developed to actuate the joints of hips and knees of both legs by the LLRE. In the study, commercial electromyography (EMG) sensors were also to compare with the as-made MMG sensors. Results showed that the maximum signal amplitude of the commercail EMG sensor was about ∼0.2 V, whereas the MMG sensor was about ∼2.8 V. The signal-to-noise ratio (SNR) of EMG was about ∼4, while that of MMG was about ∼25. From physiological signals captured from the MMG sensor for the human walking with the LLRE, this new sensor improved the sensitivity in driving the LLRE. [ABSTRACT FROM AUTHOR]

Highlights: [•] A piezoelectric inertia linear motor based on the harmonic bending vibration synthesis is proposed. [•] A piezoelectric bending actuator was designed by using the three modifying methods we studied. [•] A prototype resonant-type piezoelectric inertia linear motor was designed, fabricated and tested. [•] The PILM driving mechanism in one period is studied. [ABSTRACT FROM AUTHOR]

Highlights: [•] It is proved that leakage current is mainly determined by the voltage on actuator. [•] A compensation circuit for charge drive is proposed. [•] Displacement drift rate is decreased from 0.9nm/s to lower than 0.033nm/s. [Copyright &y& Elsevier]

Highlights: [•] The mechanism that a DC motor can be controlled by a SCR using AC voltage efficiently is imitated to realize high efficient mechanical motion control. [•] By minimizing the duration of transition state, a piezoelectric motor of high efficiency and low wear are proposed. [•] A prototype motor proved the effectiveness of the working principle. [ABSTRACT FROM AUTHOR]

Abstract: A new kind of piezoelectric pump utilizing centrifugal force directly is introduced in this paper. It uses a metal tube to act as both the wobbling part and the liquid channel. Several piezoelectric elements attaching to the metal tube are used as the actuators to push the metal tube to wobble at its resonant frequency. The centrifugal force generated by wobbling motion will force the liquid in the metal tube out. The dynamic characteristics of the pump are studied. A prototype pump is fabricated by four piezoelectric tubes and a steel tube with an outer diameter of 1.0mm, an inner diameter of 0.7mm and a length of 80mm. Experimental results show that the system can pump tap water at a flow rate of 7.7ml/min under a backpressure of 2.0kPa. [Copyright &y& Elsevier]