Ultrafast Acoustofluidic Exfoliation of Stratified Crystals

While the remarkable properties of 2D crystalline materials offer tremendous opportunities for their use in optics, electronics, energy systems, biotechnology, and catalysis, their practical implementation largely depends critically on the ability to exfoliate them from a 3D stratified bulk state. This goal nevertheless remains elusive, particularly in terms of a rapid processing method that facilitates high yield and dimension control. An ultrafast multiscale exfoliation method is reported which exploits the piezoelectricity of stratified materials that are noncentrosymmetric in nature to trigger electrically‐induced mechanical failure across weak grain boundaries associated with their crystal domain planes. In particular, it is demonstrated that microfluidic nebulization using high frequency acoustic waves exposes bulk 3D piezoelectric crystals such as molybdenum disulphide (MoS₂) and tungsten disulphide (WS₂) to a combination of extraordinarily large mechanical acceleration (≈10⁸ m s^?2) and electric field (≈10⁷ V m^?1). This results in the layered bulk material being rapidly cleaved into pristine quasi‐2D‐nanosheets that predominantly comprise single layers, thus constituting a rapid and high throughput chip‐scale method that opens new possibilities for scalable production and spray coating deposition.     

Miniaturized Lab-on-a-Disc (miniLOAD)

A miniaturized centrifugal microfluidic platform for lab-on-a-chip applications is presented. Unlike its macroscopic Lab-on-a-CD counterpart, the miniature Lab-on-a-Disc (miniLOAD) device does not require moving parts to drive rotation of the disc, is inexpensive, disposable, and significantly smaller, comprising a 10-mm-diameter SU-8 disc fabricated through two-step photolithography. The disc is driven to rotate using surface acoustic wave irradiation incident upon a fluid coupling layer from a pair of offset, opposing single-phase unidirectional transducers patterned on a lithium niobate substrate. The irradiation causes azimuthally oriented acoustic streaming with sufficient intensity to rotate the disc at several thousand revolutions per minute. In this first proof-of-concept, the capability of the miniLOAD platform to drive capillary-based valving and mixing in microfluidic structures on a disc similar to much larger Lab-on-a-CD devices is shown. In addition, the ability to concentrate aqueous particle suspensions at radial positions in a channel in the disc dependent on the particles' size is demonstrated. To the best of our knowledge, the miniLOAD concept is the first centrifugal microfluidic platform small enough to be self-contained in a handheld device.     

局域共振型五模超构材料的低频声波调控方法

五模超构材料是一类具有固体结构与"流体"特性的人工微结构,由于较好的压缩波与剪切波的解耦合能力、 较低的填充率、丰富的晶格构型及可调参数较多等特点,在声波/弹性波隐身衣、声学波导、声学超构表面等声波调控领域具有潜在应用.由单质材料组成的五模超构材料可以被看作是布拉格散射型的声子晶体,其工作频率在高频波段,而目前针对低频...     

UV Direct Write Metal Enhanced Redox (MER) Domain Engineering for Realization of Surface Acoustic Devices on Lithium Niobate

A new and highly versatile domain patterning method—ultraviolet direct write metal enhanced redox (UV direct write MER)—achieves deep domains with practically no thermally‐induced damage on the surface of lithium niobate crystals. In UV direct write MER, after coating with a thin layer of chromium, the domain inversion is generated by a redox process induced in the crystal by illumination with high intensity UV in an ambient dry nitrogen atmosphere. This new technique enables the fabrication of practical piezoelectric acoustic superlattice structures on 128° YX‐cut LiNbO₃, the most widely used crystal cut for surface acoustic wave applications. For example, UV direct write MER was used to form an acoustic superlattice 128° YX structure that in turn enabled the generation of surface acoustic waves of sufficient strength to develop fluid flow within a droplet of water, demonstrating its potential in practical microfluidic manipulation. This is the first demonstration of a UV direct write surface acoustic wave transducer reported to date, made possible only due to the unique qualities of the MER domain engineering process.     

Precise Manipulation and Patterning of Protein Crystals for Macromolecular Crystallography Using Surface Acoustic Waves

Advances in modern X‐ray sources and detector technology have made it possible for crystallographers to collect usable data on crystals of only a few micrometers or less in size. Despite these developments, sample handling techniques have significantly lagged behind and often prevent the full realization of current beamline capabilities. In order to address this shortcoming, a surface acoustic wave‐based method for manipulating and patterning crystals is developed. This method, which does not damage the fragile protein crystals, can precisely manipulate and pattern micrometer and submicrometer‐sized crystals for data collection and screening. The technique is robust, inexpensive, and easy to implement. This method not only promises to significantly increase efficiency and throughput of both conventional and serial crystallography experiments, but will also make it possible to collect data on samples that were previously intractable.     

圆台型自聚焦超声压电换能器研究

对圆台型自聚焦超声压电换能器辐射声场分布进行了数值计算,分析了圆台换能器几何参数小端半径b、大端半径a以及高度h对轴向声场以及焦平面声场分布的影响。结果表明:圆台型自聚焦超声换能器轴向声场为振荡分布,声强平均值较高,存在一组最佳参数对应于最佳的聚焦效果,而径向声场分布比较均匀,焦平面有效半径小,受参数影响较小。     

Continuous nanoparticles production through a combination of a micro electro mechanical system and an electromagnetic resonator cavity

In the present work, a reliable, rapid, and controllable method is developed for the continuous generation of pharmaceutical curcumin and loratadine nanoparticles (NPs). Micro droplets of curcumin and loratadine were generated by atomization of their corresponding solutions by a combination of a micro electro mechanical system and an electromagnetic resonator cavity. After evaporation of the solvent of micro droplets by electromagnetic waves, the NPs were collected by a polytetrafluoroethylene (PTFE) filter. NPs were characterized by scanning electron microscopy. Results showed that this method can be an effective way to produce amorphous NPs with narrow particle size distribution, where particle size can be easily controlled by solution concentration. Particles size varies from 152 to 446?nm and from 116 to 719?nm for loratadine and curcumin, respectively.     

水下压电/弹性材料复合层球壳声波反射的数值研究

采用有限单元计算软件ANSYS对无限水域中压电/弹性材料复合层球壳的声波反射进行了数值研究.研究表明,在压电层中加载适当的电压可以在一个圆锥形的流体区域内有效地减小壳体对于外来声波的反射,并且有可能完全消除任意选定空间点上的反射.     

可调声表面波滤波器的研究进展

随着移动通信产业的迅猛发展,作为通信系统关键器件之一的声表面波滤波器(SAWF)迎来了新的研究热潮.可调SAWF(TSF)因其体积小巧、性能卓越,越来越受到重视.简述了SAWF的原理,介绍了几种主要TSF的结构、性能和特点,展望了其今后的发展趋势.     

爆炸物检测SAW传感器膜材料研究进展

爆炸物检测SAW传感器的膜材料是国外目前研究的热点之一,综述了近几年这方面的研究状况.依据膜材料在检测中的作用,从3个方面进行了系统的阐述,包括膜材料的选择、制膜方法以及膜的表征;列举了大量国内外有关的最新工艺和研究进展,简要地分析了今后爆炸物检测SAW传感器膜材料的发展趋势和前景.     

压电水声换能器的声学特性分析

压电水声换能器是一种既能作为驱动器又能作为传感器工作的水下探测装置。准确预测其在嘈杂水下环境中的声学特性对设计出坚固耐用的换能器是十分重要的。有限元方法对分析换能器在不同环境中的各种性能十分有效和实用。建立了一种Tonpilz型换能器的二维轴对称有限元模型,设计了基于有限元方法的程序,对其进行了动力学分析,包括模态分析和谐响应分析等,获得了一些声学特性。该程序分析的结果与ANSYS软件分析的结果显示出较好的吻合性。     

声表面波谐振器型振荡器的研制

本文介绍了金属条射栅双端对声表面波谐振器型的原理和结构特点，给出了一种采用声表面波谐振器稳频的低噪声，高稳定性的振荡器电路设计方案。对影响振荡器频率稳定度的因素进行了分析讨论，并探讨改善声表面波振荡器频率稳定性的方法。该声表面波谐振器的中心频率为１２０ＭＨｚ，无载Ｑｖ，大于２０，０００，插入损耗小于６．０ｄＢ，经测试，秒级频率稳定度为１０＾－１０数量级，在自由室温下的日平均波动为１０＾－６／ｄ数量     

“水鸣天梯”声景观成因分析

基于周期台阶表面声阻抗理论,解释了"水鸣天梯"声景观的物理机制。首先在低频准平面波近似的情况下,利用阻抗转移公式得到了周期台阶单元表面声阻抗。数值解表明,在低频段台阶表面的声阻抗呈现纯容抗性,证实了表面波的存在。有限元软件仿真的结果与理论分析保持一致。应用表面波的性质,设计并进行了现场试验。试验数据分析表明:在台阶底部脚踏石阶或者发射脉冲声波,声波经过台阶表面作用,到达台阶顶部时只有低频部分的声能量得到了较大保留,与理论分析和模拟结果相一致,最终确定了正是周期台阶的表面波滤波效应使得脚踏声转变为悦耳的水滴声。