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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.

Key to realizing practical resonators for liquid-phase sensing applications is efficient electromechanical transduction and reasonable ${Q}$ in liquid, which determine the motional resistance ( ${R}_{m}$ ). Both lower ${R}_{m}$ and high liquid phase ${Q}$ are important for realizing a more stable close-loop oscillator to allow a lower detection limit. But ${R}_{m}$ usually increases when scaling down resonator size, leading to weak output signals in liquid. This article describes a piezoelectrically transduced micromechanical elliptical plate resonator (EPR) targeting liquid-phase sensing applications. The proposed EPR delivers lower ${R}_{m}$ relative to other disk-based modes and has a reasonable ${Q}$ in water. These two features are critical for eventually realizing a closed-loop system to enable real-time frequency tracking for sensing applications. The low ${R}_{m}$ arises from enhanced transduction efficiency associated with the modal lateral strain profile. The EPR’s moderate liquid phase ${Q}$ stems from transducing a stiff lateral bulk mode that increases energy storage. The proposed EPR can be scaled down more efficiently compared to other disk-based modes in the limit of mode shape distortion by anchors when scaling down the resonator below a threshold. Experimental results in water are demonstrated for a $500~\mu \text{m}$ by $400~\mu \text{m}$ EPR, which delivers an ${R}_{m}$ of only 2.68 $\text{k}{\Omega }$ in water without feedthrough cancellation. Scaling down the device to $300~\mu \text{m}$ by $200~\mu \text{m}$ , we demonstrate an ${R}_{m}$ of just 5.5 $\text{k}\Omega $ and ${Q}$ of 245 in water. The proposed EPR topology boasts the lowest ${R}_{m}$ among resonators immersed in liquid after normalizing over the device area.

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.

Plug-and-play acoustofluidic devices are highly promising for dexterously aggregating microparticles owing to the advantages of being contactless, label-free, and cost-efficient. Despite the extensive progress, existing acoustofluidic devices are largely limited to addressing a single sample per device, lacking the ability to address multiple samples for high-throughput operations in a single acoustofluidic device. In this work, we report a high-throughput multi-sample acoustofluidic aggregation device that enables manipulation of up to 12 samples simultaneously using a single reusable acoustic tweezer. The key design of the multi-sample acoustofluidic device lies in the utilization of a polydimethylsiloxane frame as a selective acoustic-absorbing feature to create asymmetric acoustic waves over multiple detachable superstrates in a single device. This approach is distinct from conventional strategies which mostly have involved modifying the superstrates or tuning the settings for individual superstrates. We demonstrate that the proposed acoustofluidic device can efficiently aggregate multiple samples of various compositions ranging from non-bioactive microparticles to bioactive cells, as well as a range of object sizes spanning from 0.6 µm to 13 µm. Given its merits of simplicity, cost-efficiency and high throughput, the proposed platform could be useful for biomedical applications requiring large-scale operations, such as 3D tumor spheroids and bio-sensors.

The ability to weigh microsubstances present in low concentrations is an important tool for environmental monitoring and chemical analysis. For instance, developing a rapid analysis platform that identifies the material type of microplastics in seawater would help evaluate the potential toxicity to marine organisms. In this study, we demonstrate the integration of two different techniques that bring together the functions of sparse particle localization and miniaturized mass sensing on a microelectromechanical system (MEMS) chip for enhanced detection and minimization of negative measurements. The droplet sample for analysis is loaded onto the MEMS chip containing a resonant mass sensor. Through the coupling of a surface acoustic wave (SAW) from a SAW transducer into the chip, the initially dispersed microparticles in the droplet are localized over the detection area of the MEMS sensor, which is only 200 µm wide. The accreted mass of the particles is then calibrated against the resulting shift in resonant frequency of the sensor. The SAW device and MEMS chip are detachable after use, allowing the reuse of the SAW device part of the setup instead of the disposal of both parts. Our platform maintains the strengths of noncontact and label-free dual-chip acoustofluidic devices, demonstrating for the first time an integrated microparticle manipulation and real-time mass measurement platform useful for the analysis of sparse microsubstances.

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 typically enable only rectangular matrix-like of particle patterns in a closed microchamber actuated by a surface acoustic wave (SAW) device. More complex and unique patterns require a sophisticated and dedicated SAW transducer. As a first, we demonstrate the generation of ring-shape particle patterns on-chip actuated by a simple generic SAW transducer. The ability to reshape unique acoustic field on-chip is realized by using a bulk micromachined microelectromechanical systems (MEMS) chip. We also show for the first time the creation of a two-dimensional (2D) pattern with just a one-dimensional (1D) standing SAW (SSAW). These results pave the way toward truly plug-and-play acoustofluidics, where unique patterns are defined by a diverse range of interchangeable chips on a standard SAW transducer.

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.

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.

Tire pressure monitoring systems (TPMS) are becoming increasingly important in an effort to ensure safe and efficient use of tires in the automotive sector. There is growing interest in using energy harvesting technologies to provide power for TPMS because battery supply has serious drawbacks such as replacement difficulty, limited durability and environmental pollution. In this study, we proposed an on-vehicle magnetically triboelectric nanogenerator (V-TENG) scavenging rotating energy from tires and serves as a direct power source for tire pressure sensor. The V-TENG incorporates two different triboelectric materials with opposite polarities based on contact-electrification effect. The unique advantages of the seesaw balance structure are to overcome the influence of a large centrifugal force at high operating speed as well quadruple the efficiency contact areas of a miniaturized device. Noncontact magnets mounted on the brake calliper periodically actuate swing motion of multiple V-TENGs placed on the wheel hub. The V-TENG effectively generates electrical energy at the alarm temperature through a thermally stable polymer film. High electrical output has been achieved among the wide ranges of rotation speed and magnetic force through systematically experiments test. Meanwhile, there is no obvious decrease in the output voltage of the V-TENG after continuous working for about 12 h. Moreover, a battery-less pressure sensor was enabled by a single V-TENG device to measure barometric values of the ambient environment. The V-TENG also have been demonstrated to power a commercial wireless sensor for sending the real-time temperature data to a receiver and displaying on a monitor interface.

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.