这项工作由新加坡教育部学术研究基金 (AcRF) 1 层 (RG171/15) 主办。

1. 微流控通道的制备
<ol><li>混合甲基 () 与弹性体基础的比例为10:1。</li>
	<li>将混合物放入真空烤箱中, 将其倒在硅晶片上, 上面有一个负色调的光刻胶图案。</li>
	<li>再次德加的图案硅晶片, 并加热它在70°c 3 小时, 在一个孵化器凝固。</li>
</ol>2. 叉指变换器的制作
<ol><li>在吴林波3晶片上沉积 20 nm 铬和 400 nm 的铝;图案20条, 宽度为150µm, 在塑料面罩上的光圈为2厘米, 通过将正光刻胶沉积在基板上进行光刻。</li>
	<li>用丙酮去除未暴露区域的 Cr 铝层。</li>
	<li>用氧等离子体 (氮气和氧比为 2:1) 将其表面处理为六十年代的 30 W 的功率。</li>
	<li>将该微通道对准, 并将其与吴林波3基板结合, 用拇指按压几秒钟。</li>
	<li>将集成设备放置在加热室中, 温度为60摄氏度, 为3小时。</li>
</ol>3. 双频励磁
<ol><li>同时应用两个频率分量 (f1 和f3, 其基本频率及其三次谐波分别) 与相差φ之间的 IDTs 对对, 使所生产的锯子可表示如下。 <img alt="Equation 1" src="/files/ftp_upload/58085/58085eq1.jpg"> 这里 <img alt="Equation 2" src="/files/ftp_upload/58085/58085eq2.jpg">和<img alt="Equation 3" src="/files/ftp_upload/58085/58085eq3.jpg"> = 声学压力。</li>
	<li>利用 ArbExpress 应用软件的方程编辑器在100毫秒/秒的采样频率上合成双频波形, 然后将其存储到函数发生器中, 作为任意输入的 SAW 励磁实验通过USB 电缆。</li>
	<li>改变基本频率的力量到总发射的力量<img alt="Equation 4" src="/files/ftp_upload/58085/58085eq4.jpg">从 100% (励磁在纯粹基本的频率) 到 0% (励磁在纯粹第三谐波);为了一个好的比较, 改变, 但保持总功率相同。</li>
	<li>将双频励磁的相位差改变为360°。</li>
</ol>4. 数值模拟
<ol><li>描述低雷诺 (即 Re 0.55) 和马赫数的不可压缩层流流的运动, 如下所示35。 <img alt="Equation 5" src="/files/ftp_upload/58085/58085eq5.jpg"> <img alt="Equation 6" src="/files/ftp_upload/58085/58085eq6.jpg"> 这里 <img alt="Equation 7" src="/files/ftp_upload/58085/58085eq7.jpg">= 流体速度, <img alt="Equation 8" src="/files/ftp_upload/58085/58085eq8.jpg">= 动态粘度, <img alt="Equation 9" src="/files/ftp_upload/58085/58085eq9.jpg">= 流体密度, <img alt="Equation 10" src="/files/ftp_upload/58085/58085eq10.jpg">= 流体的压力, <img alt="Equation 11" src="/files/ftp_upload/58085/58085eq11.jpg">= 标识矩阵和 <img alt="Equation 12" src="/files/ftp_upload/58085/58085eq12.jpg">= 外力。</li>
	<li>描述在物体上产生的斯托克城拖曳力, 如下所示36。 <img alt="Equation 13" src="/files/ftp_upload/58085/58085eq13.jpg"> 这里 <img alt="Equation 14" src="/files/ftp_upload/58085/58085eq14.jpg">= 微粒的半径, <img alt="Equation 15" src="/files/ftp_upload/58085/58085eq15.jpg">= 流体的速度和 <img alt="Equation 16" src="/files/ftp_upload/58085/58085eq16.jpg">= 微粒的速度。</li>
	<li>在x轴 (横跨微通道宽度) 的微通道中, 根据16的频率推导出适用于所述微粒的声辐射力。 <img alt="Equation 17" src="/files/ftp_upload/58085/58085eq17.jpg"> 这里 <img alt="Equation 18" src="/files/ftp_upload/58085/58085eq18.jpg">= 微粒的容量, <img alt="Equation 19" src="/files/ftp_upload/58085/58085eq19.jpg">= 微粒的密度, <img alt="Equation 20" src="/files/ftp_upload/58085/58085eq20.jpg">= 介质的密度, <img alt="Equation 21" src="/files/ftp_upload/58085/58085eq21.jpg">= 微粒的压缩性, 和 <img alt="Equation 22" src="/files/ftp_upload/58085/58085eq22.jpg">= 介质的压缩性。</li>
	<li>推导了双频励磁产生的声辐射力如下。 <img alt="Equation 23" src="/files/ftp_upload/58085/58085eq23.jpg">
</li>
	<li>在声波辐射力和由牛顿第二定律所控制的斯托克斯拖曳力的情况下, 在通道宽度 (沿y轴) 上表达横向运动, 如下所示。 <img alt="Equation 24" src="/files/ftp_upload/58085/58085eq24.jpg">
</li>
	<li>在个人计算机上使用第四阶的朗格-库塔方法求解上述常微分方程。分别将时间步长和总工期设置为1µs 和二十年代。</li>
</ol>5. 实验观察
<ol><li>旋转溶液集中 5.9 x 107与4µm 绿色荧光聚苯乙烯珠每1毫升的漩涡约 2-3 分钟, 然后浸泡在超声波 sonicator 10 分钟, 以扰乱任何团聚之前, 每次测试。</li>
	<li>将混合物装入3毫升注射器, 然后用注射器泵驱动, 流速为 3-5 µL/分钟。</li>
	<li>驱动与双频信号从一个功能发生器后跟功率放大器。</li>
	<li>在40X 放大的光镜下观察下游微通道中的稳定微粒, 并用数码相机记录图像。</li>
	<li>用 ImageJ 和建立的尺度测量捕获数字图像中累积微粒的位置, 然后用规范化的荧光亮度定量测定累积微粒的浓度。每个压力节点。</li>
</ol>

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作者没有什么可透露的。

本文研究了双频激励下的螺旋埋弧焊微通道中的微粒运动, 并对双频励磁信号进行了有效的可调谐图形技术的开发和测试。这种波形的产生很容易由大多数函数发生器实现, 调整方法非常方便。12和 s 的11频率响应的捏造 IDTs 说明了几个共振模式34。测量的基本频率为6.1 兆赫和17.8 兆赫的第三次谐波接近那些被设计的价值 (6.2 和18.6 兆赫) 以相似的传输系数,-8.34 </...

在生物、化学、生物物理学和医学过程中, 中控技术将一个或多个功能集成在微芯片上。通量允许实验室设置的规模小于亚毫米, 快速反应速度, 短响应时间, 高过程控制, 低容量消耗 (减少浪费, 较低的试剂成本, 和较少的样品量), 高吞吐量由于并行化, 在未来大规模生产和经济高效的一次性耗材的低成本, 化学, 放射性, 或生物研究的高安全性, 以及紧凑和便携设备1,2的优势。精确的细胞操作 (即积累和分离) 在基于控制的分析和诊断3,4中是至关重要的。然而, 微粒操纵的准确性和重现性有各种各样的挑战。许多技术, 如电渗透5, 介电泳 (DEP)6, magnetophoresis7, thermophoresis8,9, 光学方法10, 光电方法11, 开发了水动力方法12和 acoustophoresis13、14、15。相比之下, 声学方法是适用于一个应用, 因为理论上, 许多类型的微粒/细胞可以有效地操纵和无创性与足够高的对比度 (密度和压缩性) 比较周围的液体。因此, 与它们的对应物相比, 声学方法天生符合大多数微粒和生物物体的条件, 不管它们的光学、电学和磁性特性16。
根据斯内尔定律17, IDTs 的表面声波 (锯) 主要传播在压电基底的表面, 在几个波长的厚度上, 然后在瑞利角向微通道中的流体泄漏. 18,19,20,21,22。由于其能量的定位, 在高频率下具有很好的设计灵活性, 具有良好的微流控通道和小型化的系统集成, 使其在表面上具有高能量效率的技术优势。微电子-机械系统 (MEMS) 技术, 具有很高的大批量生产潜力23。在这个协议中, 锯是由一对相同的 IDTs 产生的, 并以相反的方向传播, 在微通道中产生驻波, 或螺旋弧, 悬浮微粒被推到压力节点, 主要由应用的声学辐射力24。这种合力的振幅由激发频率、微粒大小和声学对比系数22、25决定。
这样的 acoustophoresis 限制了预先设定的操作模式, 而这些方式不易调整。IDTs 的激发频率由它们的周期距离决定, 因此带宽相当有限。为了提高调谐和操纵能力, 开发了一些策略。在微通道的不同部位应用的声驻波的第一和第二模态, 可以根据不同的运动速度将微粒更有效地分离到节点线26。这两种模式也可应用于微通道的整个部分, 并交替切换27、28、29。然而, 为此, 需要大量的设备 (即三个函数发生器、两个阻抗匹配单元和一个电磁继电器), 由于不同的实验装置的成本和控制复杂性的增加,电阻抗在压电陶瓷板的基本频率和第三次谐波30。此外, 倾斜手指叉指变换器 (SFITs) 可以用来调整细胞和微粒模式的刺激一段时间的倾斜手指为某一共振20,31。然而, 带宽与倾斜的手指的数量成反比。与传统的螺旋型磁粉分离器的单节线相比, 多压力节线具有较高的分离效率和灵敏度。另外, 压力节点的位置也可以通过调整在设计32,33中应用到两个 IDTs 的相位差来改变。
IDTs 的基本频率和第三次谐波具有相似的频率响应, 使它们能够同时激发, 为微粒操作34提供了更多的调谐。与传统的单频励磁相比, 调整双频励磁的声压和两者之间的相位提供了技术的唯一性, 例如高达2倍的缩短运动时间到压力节点线或中心的微通道, 不同数量和位置的压力节点线, 和微粒浓度。

<table><tbody><tr><td>poly-dimethylsiloxane</td><td>Dow Corning</td><td>Sylgard 184</td><td></td></tr><tr><td>poly-dimethylsiloxane elastomer base</td><td>Dow Corning</td><td>Sylgard 184</td><td></td></tr><tr><td>silicon wafer</td><td>Bonda Technology</td><td>SI8PSPD</td><td></td></tr><tr><td>negative tone photoresist</td><td>Microchem</td><td>SU-8</td><td></td></tr><tr><td>double-side polished LiNbO&lt;sub&gt;3&lt;/sub&gt; wafer</td><td>University Wafer</td><td>Y-128&amp;deg;</td><td></td></tr><tr><td>positive photoresist</td><td>Nicolaus-Otto-Stra&amp;szlig;e</td><td>AZ 9260</td><td></td></tr><tr><td>oxygen plasma</td><td>Harrick Plasma</td><td></td><td></td></tr><tr><td>plastic mask</td><td>Infinite Graphics</td><td></td><td></td></tr></tbody></table>

microparticle manipulation by standing surface acoustic waves with dual-frequency excitations

本文演示了一种提高驻面声波 (螺旋埋弧) 在单片机系统中微粒操作的调谐能力的方法。同时激发的基本频率和它的第三次谐波, 这被称为双频励磁, 对一对交叉传感器 (IDTs) 可以产生一种新的类型的驻声波在微流控通道。改变双频励磁信号中的功率和相位, 可重构应用于微通道内微粒的声辐射力 (例如, 压力节点的数量和位置, 以及在相应的压力节点上的微粒浓度)。本文表明, 微粒子的运动时间只有一个压力节点可以减少2倍的功率比的基本频率大于90%。相比之下, 微通道中有三个压力节点, 如果小于这个阈值。此外, 调整基本频率与第三次谐波之间的初始相位, 会导致三个螺旋埋弧压力节点的不同运动速率, 以及微通道中每个压力节点的微粒百分比。实验观测与数值预测有很好的一致性。这种新颖的励磁方法能够很容易地、无创性地集成到系统中, 具有广泛的可维持, 对实验装置的改动也只有少数。

在双频励磁 (6.2 和18.6 兆赫) 下, 螺旋埋弧焊的声压和声辐射力分布在图 1中。在这里, 双频励磁发生在聚苯乙烯微粒 (直径4µm) 在微通道, 宽度为300µm 在一个声学功率146兆瓦。在P1 > 90% 的情况下, 产生的声学压力总是处于阶段, 因此只有一个压力节点存在于y = 150 µm。相比之下, 三压力节点存在于y = 75, 150, 225 µm 在p1</s...

Watch this Scientific Journal Video about Microparticle Manipulation by Standing Surface Acoustic Waves with Dual-frequency Excitations at JoVE.com

Microparticle Manipulation by Standing Surface Acoustic Waves with Dual-frequency Excitations

提出了一种用双频励磁微流控通道处理微粒的协议。

双频激励下驻面声波的微粒操纵

We demonstrate a method for increasing the tuning ability of a standing surface acoustic wave (SSAW) for microparticles manipulation in a lab-on-a-chip ...

microparticle-manipulation-standing-surface-acoustic-waves-with-dual

Universidad de Cartagena UDEC

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Application of Newton's Laws of Motion

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6.9K 次观看.  Nanyang Technological University. 提出了一种用双频励磁微流控通道处理微粒的协议。

视频: Microparticle Manipulation by Standing Surface Acoustic Waves with Dual-frequency Excitations

Activating Molecules, Ions, and Solid Particles with Acoustic Cavitation

The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic cavitation: the nucleation, growth, and implosive collapse of microbubbles in liquids submitted to power ultrasound. The violent implosion of bubbles leads to the formation of chemically reactive species and to the emission of light, named sonoluminescence. In this manuscript, we describe the techniques allowing study of extreme intrabubble conditions and chemical reactivity of acoustic cavitation in solutions. The analysis of sonoluminescence spectra of water sparged with noble gases provides evidence for nonequilibrium plasma formation. The photons and the "hot" particles generated by cavitation bubbles enable to excite the non-volatile species in solutions increasing their chemical reactivity. For example the mechanism of ultrabright sonoluminescence of uranyl ions in acidic solutions varies with uranium concentration: sonophotoluminescence dominates in diluted solutions, and collisional excitation contributes at higher uranium concentration. Secondary sonochemical products may arise from chemically active species that are formed inside the bubble, but then diffuse into the liquid phase and react with solution precursors to form a variety of products. For instance, the sonochemical reduction of Pt(IV) in pure water provides an innovative synthetic route for monodispersed nanoparticles of metallic platinum without any templates or capping agents. Many studies reveal the advantages of ultrasound to activate the divided solids. In general, the mechanical effects of ultrasound strongly contribute in heterogeneous systems in addition to chemical effects. In particular, the sonolysis of PuO2 powder in pure water yields stable colloids of plutonium due to both effects.

Acoustic cavitation in liquids submitted to power ultrasound creates transient extreme conditions inside the collapsing bubbles, which are the origin of unusual chemical reactivity and light emission, known as sonoluminescence. In the presence of noble gases, nonequilibrium plasma is formed. The "hot" particles and the photons generated by collapsing bubbles are able to excite species in solution.

活化分子，离子和固体颗粒与声空化

The chemical and physical effects of ultrasound arise not from a direct interaction of molecules with sound waves, but rather from the acoustic ...

科研

化学

Fabrication, Operation and Flow Visualization in Surface-acoustic-wave-driven Acoustic-counterflow Microfluidics

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we present the fabrication protocol for a multilayered SAW acoustic counterflow device. The device is fabricated starting from a lithium niobate (LN) substrate onto which two interdigital transducers (IDTs) and appropriate markers are patterned. A polydimethylsiloxane (PDMS) channel cast on an SU8 master mold is finally bonded on the patterned substrate. Following the fabrication procedure, we show the techniques that allow the characterization and operation of the acoustic counterflow device in order to pump fluids through the PDMS channel grid. We finally present the procedure to visualize liquid flow in the channels. The protocol is used to show on-chip fluid pumping under different flow regimes such as laminar flow and more complicated dynamics characterized by vortices and particle accumulation domains.

In this video we first describe fabrication and operation procedures of a surface acoustic wave (SAW) acoustic counterflow device. We then demonstrate an experimental setup that allows for both qualitative flow visualization and quantitative analysis of complex flows within the SAW pumping device.

制造，操作和表面声波驱动声逆流微流体流动可视化

Surface acoustic waves (SAWs) can be used to drive liquids in portable microfluidic chips via the acoustic counterflow phenomenon. In this video we ...

工程学

Fabrication and Operation of Acoustofluidic Devices Supporting Bulk Acoustic Standing Waves for Sheathless Focusing of Particles

Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must be smaller than the incident wavelength of sound and the width of the fluidic channels are typically tens to hundreds of micrometers across, acoustofluidic devices typically use ultrasonic waves generated from a piezoelectric transducer pulsating at high frequencies (in the megahertz range). At characteristic frequencies that depend on the geometry of the device, it is possible to induce the formation of standing waves that can focus particles along desired fluidic streamlines within a bulk flow. Here, we describe a method for the fabrication of acoustophoretic devices from common materials and clean room equipment. We show representative results for the focusing of particles with positive or negative acoustic contrast factors, which move towards the pressure nodes or antinodes of the standing waves, respectively. These devices offer enormous practical utility for precisely positioning large numbers of microscopic entities (e.g., cells) in stationary or flowing fluids for applications ranging from cytometry to assembly.

Acoustofluidic devices use ultrasonic waves within microfluidic channels to manipulate, concentrate and isolate suspended micro and nanoscopic entities. This protocol describes the fabrication and operation of such a device supporting bulk acoustic standing waves to focus particles in a central streamline without the aid of sheath fluids.

制造和Acoustofluidic设备的运营支撑体声波驻波的聚焦鞘颗粒

Acoustophoresis refers to the displacement of suspended objects in response to directional forces from sound energy. Given that the suspended objects must ...

A Microfluidic Platform for Precision Small-volume Sample Processing and Its Use to Size Separate Biological Particles with an Acoustic Microdevice

A major advantage of microfluidic devices is the ability to manipulate small sample volumes, thus reducing reagent waste and preserving precious sample. However, to achieve robust sample manipulation it is necessary to address device integration with the macroscale environment. To realize repeatable, sensitive particle separation with microfluidic devices, this protocol presents a complete automated and integrated microfluidic platform that enables precise processing of 0.15&#8211;1.5 ml samples using microfluidic devices. Important aspects of this system include modular device layout and robust fixtures resulting in reliable and flexible world to chip connections, and fully-automated fluid handling which accomplishes closed-loop sample collection, system cleaning and priming steps to ensure repeatable operation. Different microfluidic devices can be used interchangeably with this architecture. Here we incorporate an acoustofluidic device, detail its characterization, performance optimization, and demonstrate its use for size-separation of biological samples. By using real-time feedback during separation experiments, sample collection is optimized to conserve and concentrate sample. Although requiring the integration of multiple pieces of equipment, advantages of this architecture include the ability to process unknown samples with no additional system optimization, ease of device replacement, and precise, robust sample processing.

This protocol describes a system architecture for performing automated small volume (0.15&#8211;1.5 ml) particle separations using a microfluidic device, and discusses methods to optimize acoustofluidic device performance and operation.

微流体平台精密小批量来样加工及它的使用尺寸分离生物颗粒的声微型

A major advantage of microfluidic devices is the ability to manipulate small sample volumes, thus reducing reagent waste and preserving precious sample. ...

生物工程

Multiplexing Focused Ultrasound Stimulation with Fluorescence Microscopy

By focusing low-intensity ultrasound pulses that penetrate soft tissues, LIPUS represents a promising biomedical technology to remotely and safely manipulate neural firing, hormonal secretion and genetically-reprogrammed cells. However, the translation of this technology for medical applications is currently hampered by a lack of biophysical mechanisms by which targeted tissues sense and respond to LIPUS. A suitable approach to identify these mechanisms would be to use optical biosensors in combination with LIPUS to determine underlying signaling pathways. However, implementing LIPUS to a fluorescence microscope may introduce undesired mechanical artefacts due to the presence of physical interfaces that reflect, absorb and refract acoustic waves. This article presents a step-by-step procedure to incorporate LIPUS to commercially-available upright epi-fluorescence microscopes while minimizing the influence of physical interfaces along the acoustic path. A simple procedure is described to operate a single-element ultrasound transducer and to bring the focal zone of the transducer into the objective focal point. The use of LIPUS is illustrated with an example of LIPUS-induced calcium transients in cultured human glioblastoma cells measured using calcium imaging.

Low-Intensity Pulsed Ultrasound Stimulation (LIPUS) is a modality for non-invasive mechanical stimulation of endogenous or engineered cells with high spatial and temporal resolution. This article describes how to implement LIPUS to an epi-fluorescence microscope and how to minimize acoustic impedance mismatch along the ultrasound path to prevent unwanted mechanical artefacts.

荧光显微镜对聚焦超声的刺激

By focusing low-intensity ultrasound pulses that penetrate soft tissues, LIPUS represents a promising biomedical technology to remotely and safely ...

Fabrication of Nanoheight Channels Incorporating Surface Acoustic Wave Actuation via Lithium Niobate for Acoustic Nanofluidics

Controlled nanoscale manipulation of fluids is known to be exceptionally difficult due to the dominance of surface and viscous forces. Megahertz-order surface acoustic wave (SAW) devices generate tremendous acceleration on their surface, up to 108 m/s2, in turn responsible for many of the observed effects that have come to define acoustofluidics: acoustic streaming and acoustic radiation forces. These effects have been used for particle, cell, and fluid manipulation at the microscale, although more recently SAW has been used to produce similar phenomena at the nanoscale through an entirely different set of mechanisms. Controllable nanoscale fluid manipulation offers a broad range of opportunities in ultrafast fluid pumping and biomacromolecule dynamics useful for physical and biological applications. Here, we demonstrate nanoscale-height channel fabrication via room-temperature lithium niobate (LN) bonding integrated with a SAW device. We describe the entire experimental process including nano-height channel fabrication via dry etching, plasma-activated bonding on lithium niobate, the appropriate optical setup for subsequent imaging, and SAW actuation. We show representative results for fluid capillary filling and fluid draining in a nanoscale channel induced by SAW. This procedure offers a practical protocol for nanoscale channel fabrication and integration with SAW devices useful to build upon for future nanofluidics applications.

We demonstrate fabrication of nanoheight channels with the integration of surface acoustic wave actuation devices upon lithium niobate for acoustic nanofluidics via liftoff photolithography, nano-depth reactive ion etching, and room-temperature plasma surface-activated multilayer bonding of single-crystal lithium niobate, a process similarly useful for bonding lithium niobate to oxides.

通过用于声学纳米流体的尼奥布精锂结合表面声波驱动纳米高通道的制造

Controlled nanoscale manipulation of fluids is known to be exceptionally difficult due to the dominance of surface and viscous forces. Megahertz-order ...

Fabrication of Surface Acoustic Wave Devices on Lithium Niobate

Manipulation of fluids and particles by acoustic actuation at small scale is aiding the rapid growth of lab-on-a-chip applications. Megahertz-order surface acoustic wave (SAW) devices generate enormous accelerations on their surface, up to 108 m/s2, in turn responsible for many of the observed effects that have come to define acoustofluidics: acoustic streaming and acoustic radiation forces. These effects have been used for particle, cell, and fluid handling at the microscale&#8212;and even at the nanoscale. In this paper we explicitly demonstrate two major fabrication methods of SAW devices on lithium niobate: the details of lift-off and wet etching techniques are described step-by-step. Representative results for the electrode pattern deposited on the substrate as well as the performance of SAW generated on the surface are displayed in detail. Fabrication tricks and troubleshooting are covered as well. This procedure offers a practical protocol for high frequency SAW device fabrication and integration for future microfluidics applications.

Two fabrication techniques, lift-off and wet etching, are described in producing interdigital electrode transducers upon a piezoelectric substrate, lithium niobate, widely used to generate surface acoustic waves now finding broad utility in micro to nanoscale fluidics. The as-produced electrodes are shown to efficiently induce megahertz order Rayleigh surface acoustic waves.&#160;

锂氮化锂表面声波设备的制造

Manipulation of fluids and particles by acoustic actuation at small scale is aiding the rapid growth of lab-on-a-chip applications. Megahertz-order ...

Fabrication and Characterization of Thickness Mode Piezoelectric Devices for Atomization and Acoustofluidics

We present a technique to fabricate simple thickness mode piezoelectric devices using lithium niobate (LN). Such devices have been shown to atomize liquid more efficiently, in terms of &#64258;ow rate per power input, than those that rely on Rayleigh waves and other modes of vibration in LN or lead zirconate titanate (PZT). The complete device is composed of a transducer, a transducer holder, and a &#64258;uid supply system. The fundamentals of acoustic liquid atomization are not well known, so techniques to characterize the devices and to study the phenomena are also described. Laser Doppler vibrometry (LDV) provides vibration information essential in comparing acoustic transducers and, in this case, indicates whether a device will perform well in thickness vibration. It can also be used to &#64257;nd the resonance frequency of the device, though this information is obtained more quickly via impedance analysis. Continuous &#64258;uid atomization, as an example application, requires careful &#64258;uid flow control, and we present such a method with high-speed imaging and droplet size distribution measurements via laser scattering.

Fabrication of piezoelectric thickness mode transducers via direct current sputtering of plate electrodes on lithium niobate is described. Additionally, reliable operation is achieved with a transducer holder and &#64258;uid supply system and characterization is demonstrated via impedance analysis, laser doppler vibrometry, high-speed imaging, and droplet size distribution using laser scattering.

用于原子化和抗波流体的厚度模式压电器件的制造和特性

We present a technique to fabricate simple thickness mode piezoelectric devices using lithium niobate (LN). Such devices have been shown to atomize liquid ...

Induction of Microstreaming by Nonspherical Bubble Oscillations in an Acoustic Levitation System

When located near biological barriers, oscillating microbubbles may increase cell membrane permeability, allowing for drug and gene internalization. Experimental observations suggest that the temporary permeabilization of these barriers may be due to shear stress that is exerted on cell tissues by cavitation microstreaming. Cavitation microstreaming is the generation of vortex flows which arise around oscillating ultrasound microbubbles. To produce such liquid flows, bubble oscillations must deviate from purely spherical oscillations and include either a translational instability or shape modes. Experimental studies of bubble-induced flows and shear stress on nearby surfaces are often restricted in their scope due to the difficulty of capturing shape deformations of microbubbles in a stable and controllable manner. We describe the design of an acoustic levitation chamber for the study of symmetry-controlled nonspherical oscillations. Such control is performed by using a coalescence technique between two approaching bubbles in a sufficiently intense ultrasound field. The control of nonspherical oscillations opens the way to a controlled cavitation microstreaming of a free surface-oscillating microbubble. High-frame rate cameras allow investigating quasi-simultaneously the nonspherical bubble dynamics at the acoustic timescale and the liquid flow at a lower timescale. It is shown that a large variety of fluid patterns may be obtained and that they are correlated to the modal content of the bubble interface. We demonstrate that even the high-order shape modes can create large-distance fluid patterns if the interface dynamics contain several modes, highlighting the potential of nonspherical oscillations for targeted and localized drug delivery.

A fast and reliable technique is proposed to control the shape oscillations of a single, trapped acoustic bubble that is based on coalescence technique between two bubbles. The steady-state, symmetry-controlled bubble shape oscillations allow analysis of the fluid flow generated in the vicinity of the bubble interface.

声学悬浮系统中非球形气泡振荡诱导微流

When located near biological barriers, oscillating microbubbles may increase cell membrane permeability, allowing for drug and gene internalization. ...

Assembly and Characterization of an External Driver for the Generation of Sub-Kilohertz Oscillatory Flow in Microchannels

Microfluidic technology has become a standard tool in chemical and biological laboratories for both analysis and synthesis. The injection of liquid samples, such as chemical reagents and cell cultures, is predominantly accomplished through steady flows that are typically driven by syringe pumps, gravity, or capillary forces. The use of complementary oscillatory flows is seldom considered in applications despite its numerous advantages as recently demonstrated in the literature. The significant technical barrier to the implementation of oscillatory flows in microchannels is likely responsible for the lack of its widespread adoption. Advanced commercial syringe pumps that can produce oscillatory flow, are often more expensive and only work for frequencies less than 1 Hz. Here, the assembly and operation of a low-cost, plug-and-play type speaker-based apparatus that generates oscillatory flow in microchannels is demonstrated. High-fidelity harmonic oscillatory flows with frequencies ranging from 10-1000 Hz can be achieved along with independent amplitude control. Amplitudes ranging from 10-600 &#181;m can be achieved throughout the entire range of operation, including amplitudes &#62; 1 mm at the resonant frequency, in a typical microchannel. Although the oscillation frequency is determined by the speaker, we illustrate that the oscillation amplitude is sensitive to fluid properties and channel geometry. Specifically, the oscillation amplitude decreases with increasing channel circuit length and liquid viscosity, and in contrast, the amplitude increases with increasing speaker tube thickness and length. Additionally, the apparatus requires no prior features to be designed on the microchannel and is easily detachable. It can be used simultaneously with a steady flow created by a syringe pump to generate pulsatile flows.

The protocol demonstrates a convenient method to produce harmonic oscillatory flow from 10-1000 Hz in microchannels. This is performed by interfacing a computer-controlled speaker diaphragm to the microchannel in a modular manner.

用于在微通道中产生亚千赫兹振荡流的外部驱动器的组装和表征

Microfluidic technology has become a standard tool in chemical and biological laboratories for both analysis and synthesis. The injection of liquid ...