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Particles and cells can be patterned and moved (i.e., manipulated) precisely using acoustically driven techniques. To date, application of acoustic particle manipulation has been limited to plain surfaces. There is much potential for applying acoustic manipulation techniques to surfaces with microfabricated structures for high-throughput sensing. But adding thin film structures could alter manipulation characteristics compared to a plain surface. Using a two-chip setup that allows the wave generating device to be reused, we study the feasibility of acoustofluidic micro-manipulation on a surface-micromachined silicon (SMS) chip. The SMS chip is a complex superstrate with generic thin-film structures fabricated by patterning and etching multiple layers of thin films, with properties meant to represent a broad range of microfabricated devices. We report notable alterations in the particle separation distances on the SMS chip compared to a bare silicon superstrate, which we attribute to a change in wave type through a comparison of different superstrates prepared. We demonstrate a high cell viability after acoustic manipulation of live cells on the SMS chip. The results herein demonstrate the possibility of integrating a suite of microfabricated sensors on a chip with acoustically driven manipulation capabilities for multiplexed sensing and analysis for bio-applications.

This work describes a two-chip acoustofluidic platform for two-dimensional (2D) manipulation of microparticles in a closed microchamber on a reusable surface acoustic wave (SAW) device. This platform comprises two microfabricated chips: (1) a detachable silicon superstrate enclosed by a PDMS microfluidic chamber and (2) a reusable SAW device for generating standing SAW (SSAW), which is typically an expensive component. Critical to such a two-chip acoustofluidic platform is the selection of a suitable coupling agent at the interface of the SAW device and superstrate. To this end, we applied a polymer thin film as a coupling agent that balances between acoustic coupling efficiency, stability over time, and reusability. Recycling of the SAW device lowers the cost-barrier for acoustofluidic particle manipulation. The SSAW is transmitted into the silicon superstrate via the coupling agent to form a standing Lamb wave (SLW) to trap and move microparticles. The reported two-chip strategy enables the single-use microfluidic superstrates to avoid chemical and biological contaminations, while maintaining the merits of acoustofluidic manipulation of being noncontact and label-free and applicable to a wide range of microparticles with different shapes, density, polarity, and electrical properties.

We demonstrate the boosting of quality factor (Q) of a aligned Aluminum Nitride (AlN) on Silicon (Si) laterally vibrating resonator (LVR) by using wide acoustic bandgap (ABG) phononic crystal (PnC) anchors. To date, Q-boosting strategies have been studied predominantly for the common orientation. Given the anisotropy of Si, changing orientation could notably affect the effectiveness of Q-boosting strategies. We show experimentally that Qs of aligned LVRs more than doubled to 10000 with the PnC anchors. To further corroborate the effectiveness of the PnCs, we also incorporated the PnCs into delay lines with wave propagation along the axis, showing that the PnCs provide large acoustic attenuation of 45 dB.

Acoustofluidic platforms for cell manipulation benefit from being contactless and label-free at potentially low cost. Particle concentration in a droplet relies on augmenting spatial asymmetry in the acoustic field, which is difficult to reproduce reliably. Etching periodic patterns into a chip to create acoustic band gaps is an attractive approach to spatially modify the acoustic field. However, the sensitivity of acoustic band structures to geometrical tolerances requires the use of costly microfabrication processes. In this work, we demonstrate particle concentration across a range of periodic structure patterns fabricated with a laser-cutting tool, suitable for low-cost and low-volume rapid prototyping. The relaxation on precision is underscored by experimental results of equally efficient particle concentration outside band gaps and even in their absence, allowing operation over a range of frequencies independent of acoustic band gaps. These results are significant by indicating the potential of extending the proposed method from the microscale (e.g. tumor cells) to the nanoscale (e.g. bacteria) by scaling up the frequency without being limited by fabrication capabilities. We demonstrate the device's high degree of biocompatibility to illustrate the method's applicability in the biomedical field for applications such as basic biochemical analysis and in vitro diagnosis.

Phononic crystals (PnC) can help shape acoustic fields to enhance microfluidic functions in acoustofluidic devices. But operating within the defined phononic band gap (PBG) limits the scope for optimizing microfluidic functions. We show, for the first-time, efficient droplet centrifugation that works outside the range of the PBG. Instead of using deep reactive ion etching (DRIE) to create the PnC, we here use laser machining with the aim to demonstrate low cost and rapid prototyping of complex superstrates that can enhance particle concentration greatly. The results of this work are significant given that the center frequency of a PBG is tied to the size of the PnC. In the case of particle concentration, the efficiency increases with frequency. As such, working in the confines of a PBG requires a high level of precision in fabrication. The ability to work outside PBGs removes such restrictions, opening a range of possibilities. Besides, the results are based on a two-chip approach that yields a low-cost solution for disposable single-use acoustofluidics.

We report the first demonstration of two-dimensional (2D) patterning of microparticles on a silicon superstrate via a plug-and-play reusable acoustofluidic setup. The proposed integrated device comprises two independent parts: (1) a silicon superstrate enclosed in a PDMS microfluidic chamber (containing the particles) and (2) a reusable lithium niobate (LN) piezoelectric substrate for generating standing surface acoustic waves (SSAW). The proposed method enables patterning of particles on a silicon superstrate with the aim of ultimately enabling 2D patterning of particles or cells on functional silicon micromechanical chips. Such a capability would enable functional applications such as diagnostics and biosensing. This contactless, label-free, low-cost technique would be widely employed in biological application regardless of shape, size, charge or polarity of samples.

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.

This study reports a seesaw-structured triboelectric nanogenerator (S-TENG) for efficiently harvesting electrical energy from rotational motion of mechanical systems. The designed S-TENG with two arms is comprised four contact-pair units with distinctly different triboelectric polarity materials. The generated electric power from the unique structure based on the seesaw system was double at every machine rotation cycle. A magnetically coupled contact mechanism was also utilized to reduce the wear of the polymer material. It was experimentally confirmed that the proposed design significantly improved the reliability and long-term stability in comparison with currently available TENG systems based on the sliding mechanism. In addition, micro-pyramid patterns were formed on the polymer surface to enhance the surface charge density. Through systematic experiments with a variety of operational conditions, an instantaneous maximum output power density of 13.86 W/m 2 was achieved at a rotation speed of 200 rpm under a constant magnetic field strength of 0.2 T. The S-TENG has been demonstrated as a direct power source to drive small electronic devices such as commercial LED arrays and to charge an energy storage unit. This study further expanded the potential applications of the S-TENG to realize the self-powered wireless sensor nodes such as structural health and condition monitoring system.

Previous works have demonstrated the use of acoustic waves to manipulate microparticles and biological samples on bare glass and silicon superstrates. Traditionally, the surface acoustic wave (SAW) is converted into a Lamb wave propagating within a bare silicon superstrate via a thin coupling agent. The potential impact of acoustically driven microfluidics could be further augmented if applied to superstrates integrated with sensing structures that would allow sequential analysis after sample treatment. In this work, we demonstrate the applicability of acoustically-driven micro-centrifugation on a superstrate with multiple thin film layers to mimic sensing structures on a chip, and characterize the underlying performance. We propose an integrated plug-and-play platform comprised of a reusable SAW device interfaced to a disposable surface-micromachined silicon (SMS) superstrate processed with five layers of thin films. To address the shortcomings of existing coupling agents, we examine and compare the transmission efficiency and long-term stability of four kinds of coupling agents with the aim to enable disposable acoustofluidics applications. To investigate the effect of different superstrates on the performance of droplet centrifugation, we characterize and compare centrifugation on different superstrates. High-performance concentration was realized on the SMS superstrate under different conditions, such as input power, temperature, droplet volume, and particle size and density. In terms of more advanced fluidic handling functionality on a multi-layered SMS superstrate, we demonstrate ultrasonic isopycnic separation between microbeads differentiated by density on the SMS superstrate. The results herein lay the groundwork for realizing particle concentration on complex superstrates processed with multilayer films that represent a range of microfabricated sensors towards a broader goal of integrating acoustically driven concentration capabilities and sensing for applications in diagnostics and fundamental analysis.

This paper describes a magnetically-driven rotating triboelectric generator (M-TEG) as a direct power source for wireless sensors. Four M-TEGs are symmetrically placed on the wheel hub of a vehicle. Permanent magnets mounted on the brake caliper provide a non-contact magnetic force to generate a seesaw-like swing motion of the M-TEG in the tire. The unique advantage of the seesaw structure eliminates the influence of a large centrifugal force at a high rotating speed. High electrical output has been achieved in the wide ranges of rotation speed. The M-TEG at the rotation speed of 100 rpm can deliver a maximal output voltage of 316 V and power of 22.3 mW under a constant magnetic field strength of 0.2 T. There is no obvious decrease in the output voltage of the M-TEG after continuous working for more than 12 h. The power generated by the TEG is stored in a capacitor and the stored energy is used to drive MEMS pressure sensor. The M-TEG has also demonstrated to power a commercial wireless sensor for sending the real-time temperature information to a receiver and displaying on a monitor.

Based on gearless continuously variable transmission technology, a cascaded wind power generation system with Variable Speed Constant Frequency (VSCF) is presented in this paper. The system has combined the advantages of doubly-fed and direct-drive wind power generation system. The raising-speed gear box has been done away with, and the system reliability has been improved. Reducing the power capacity of the aspects of the variable frequency speed regulation, the function of grid-connected electricity generation can be achieved with less cost. Synchronous generator directly connects to grid, which helps to optimize power quality. The topological structure of system is discussed in this paper, and its operating principle is analyzed, revealing its characteristics and engineering application prospects.

This article focuses on the topics of cascaded wind power generation system with Variable Speed Constant Frequency (VSCF). It consists of four key components, including the wind turbine, dual-rotor motors, low-speed synchronous motor and inverter. This paper summarizes and compares multiple topology form of cascade wind power system, and through the study of the relevant working mechanism, structure and layout of the form, the applicable conditions and scope of the new system are expounded in detail. In particular, as the superiority of cascade system, it makes a synthesis of variable speed and constant speed power generation into reality, thereby the cascaded systems comprehensive operational efficiency are improved.

This paper is related to the vibration analysis of transmission line fitting vibration damper (TLFVD) using commercial ANSYS program. According to the basic structure of the TLFVD, the three dimensional model with different parameters including diameter and length of strand is established. Through the modal analysis of the TLFVD using ANSYS WORKBENCH, the first four-order natural frequencies and mode shapes is obtained. Comparing the simulation data of vibration characteristics, the effects of model parameters on the natural frequency are summarized. Finally, the optimized model has been selected from various models established, and the resonant frequency of the TLFVD was verified by the harmonic response analysis. As a result, the optimized model structure of the TLFVD is presented.