All work performed under the support of the National Institute of Standards and Technology. Certain commercial equipment, instruments, or materials are identified to foster understanding of this protocol. Such identification does not imply recommendation or endorsement by the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified are necessarily the best available for the purpose.

注意:请咨询实验前所有相关的安全程序。在本协议中描述的所有实验程序符合NIST的激光安全程序以及其他适用的规定执行。请一定要选择穿合适的个人防护装备（PPE），如激光防护眼镜专为特定的波长和功率。干燥处理纳米/微粒可能需要额外的呼吸保护。 1.设计与PZT持有人的制作和样品柜<ol><li> 设计一个PZT架和样品柜 注:特殊设计值取决于PZT的选择而变化。 <ol><li>打开电脑辅助设计（CAD）软件。绘制一个夹持器的两维（2D）草图对于一个给定的PZT尺寸。开发2D草图使用拉伸/拉伸切割的组合体积的特点。 </li><li>点击素描，绘制一个矩形，将其挤出，使一个矩形立方体。 </li><li>绘制立方体的顶部表面上的盘以限定圆凹功能覆盖并保持在环型的PZT。 </li><li>限定中心孔具有用于既实时成像和俘获的光接入。 </li><li>限定沿所述中心孔的周缘的圆形导向以插入一个扁平的金属（铜）环集中朝向中心区域中的超声波功率， 如图2。 </li><li>创建用于对PZT保持器M6螺丝安装两个钻孔与底板（购，4mm厚的底部铝板与在中心的孔）进行组装， 如图2c和2d。 </li><li>以类似的方式，设计样品外壳的矩形框架。点击草图，并绘制一个矩形，拉伸矩形，使其一个矩形框。 </li><li>绘制矩形，顶部表面上的较小矩形R型箱体和挤压切矩形，使其作为一个矩形管。 </li><li>借鉴管挤出切的侧壁上的小矩形将其改造成样品密封盒的框架。 </li><li>转换这些三维（3D）模型到立体光刻（STL）文件格式用于3D打印处理（ 图2b）。 </li></ol></li><li> 设计对象的3D打印 <ol><li>打开从3D打印机的操作软件设计文件（"-.STL"）。莱平的对象0 /。而中心的目标（0，0，0）通过单击对象来选择它，并使用对齐功能:"移动"，"关于平台"和"中心"。定向PZT持有人朝上眉清目秀。凹陷表面将朝上。 </li><li>在菜单进入"设置"和"质"选项卡。设置在印刷值以下，腾空:100％，贝壳数:2和层高度:0.2毫米。 </li><li>预览对象检查总打印时间，并确保根据需要分层的对象将被打印出来。导出3D打印文件在".x3g"的格式并保存在3D打印机使用。 </li><li>开启3D打印机，直到挤压喷嘴的温度达到工作温度变暖，230°C。从存储卡或网络驱动器加载的设计文件。 </li><li>在热身，将构建平台，蓝色画家的磁带，以帮助对象坚持安全。作为用于打印作业的热塑性材料，可使用两个对象的聚乳酸（PLA）长丝。 </li><li>打印设计的对象。一旦打印作业完成后，冷却下来后，关闭打印机。 </li><li>从分离用凿子平台打印的对象。清理整顿印刷对象。如果该方向是适当地选择，PZT的保持器，可以直接使用无需进一步后处理。 </li><li>佛R中的样本外壳，准备一对氧化铟锡（ITO）涂层盖玻片和三个盖玻片的覆盖框架。使用金刚石切割器对盖玻片装配到外壳。 </li><li>线材采用快干银粉漆两个平行导电板跨两个板的电源电压。这些胶五个窗口上使用即时粘接胶样品外壳。 注意:一对ITO镀膜盖玻片安装在平行样品外壳（彼此面对的），以提供均匀的电场并产生沿电场的自然带电粒子的弹道运动。这三个传统的盖玻片的样品外壳表面（顶部，另外两侧），其余为保护被困粒子从空气外流</li></ol></li></ol>为选定的微粒2.光阱加载<ol><li> 样品制备 <ol><li>存储在一个微粒抽空干燥器以减少实验前与水分接触在空气中。 </li><li>倾出微粒的一小部分到载玻片并立即把制造的瓶放回干燥器。 </li><li>拿起一些用玻璃毛细管的微粒。通过在毛细管轻轻拍打而保持在盖玻片毛细管分散在基板上的颗粒。 </li><li>验证使用暗视野显微镜在基板上的数量，并存放颗粒的分布。 注意:在样品制备步骤中，颗粒只是分散在盖玻片并与PZT和PZT保持器之间的光学显微镜将它们插入之前验证整体结构（有散微粒的盖玻片）成像。由于表面粘附足够强以保持在基片上个别微粒，附着粒子被牢固地固定，除非被施加显著外力。 </li></o升&gt; </li><li> 压电发射器组件 <ol><li>获得压电发射器的所有的组成部分:平底板，绝缘膜，PZT的，玻璃盖玻片，铜环，PZT的夹持器，两个M6螺栓，和样品的外壳。 </li><li>在底板应用的薄膜（或带），以绝缘的PZT。玻璃盖玻片隔离堆栈的顶部。 </li><li>通过围绕平板现在绝缘用胶带的顶部PZT，随后盖玻片，铜环和PZT保持器组装叠层。螺杆堆栈一起保持PZT的定心以避免短路的PZT在支架如果保持器在图2c和2d进行如图所示。铜圈提供了堆栈塑料PZT持有人在一个均匀分布的机械预紧力。 </li><li>最后，胶水样品外壳压入堆栈，并在显微镜安装在一个XYZ平移阶段装配。 </li></ol></li><li> PZT的发射器配置 注:驾驶PZT具有高电压信号都有潜在的触电危险。请与实验前安全人员咨询。所有的电连接应实验前被固定。关闭放大器并断开PZT导致只要有可能。 <ol><li>连接PZT导致电压放大器和函数发生器连接到电压放大器的输入端口。 </li><li>打开函数发生器和配置它来生成连续方波1 V的输出电压不产生电压信号，直到所有的连接进行验证和保护。 </li><li>开启电压放大器和通过使输出产生的方波输出电压为1V的。 </li><li>放大器的监视输出端口（输出电压200伏）连接到示波器。配置放大器转动到具有200 V / V的增益获得前面板旋钮。验证由示波器测量的监测输出电压具有的1伏的幅度。 </li><li>一旦函数发生器和所述放大器配置，通过扫描驱动信号的调制频率，而实时视频显微镜图像附着粒子找到PZT发射器的共振频率。重复扫描直到微粒运动是一个最大值。使用这个频率（64千赫这里）释放的颗粒。 注:调制频率是手动改变（扫描）从零到150千赫找到谐振频率。 </li><li>配置函数发生器，以产生一个方波，在突发模式的周期的指定数目。按下面板上的"突发"按钮，然后选择"N循环脉冲串"。 </li><li>按"＃循环"软键选择脉冲数和数量设置为10或20。 </li><li>配置方波产生与电压信号600伏的幅度在已经从以前的步骤中发现64千赫的共振频率（用于连续激励的电压的三倍）。验证脉冲信号释放，确保颗粒，每个脉冲之后移动以重复的方式目标粒子。 </li></ol></li><li> 选择性光阱装载 注:PZT发射器组件被安装在一个手动线性平移的xy阶段。颗粒可以相对于所述固定波束焦点通过移动平移阶段被翻译。 <ol><li>去掉激光线滤波器通过旋转显微镜转台（ 图3a），以确定该俘获光束的焦点。垂直移动机动聚焦块来回周围的可见图像的最佳聚焦，以优化聚焦。 </li><li>一旦焦点位置被验证时，将过滤器回得到澄清的实时视频而不脱离俘获光束干涉。 </li><li>翻译的样品为p在捕集激光的聚焦位置花边选定粒子。集中在粒子图像的选定颗粒，其中约一半半径则以低于粒子中心标称捕获位置，同时使粒子上方的悬浮位置的中心。 </li><li>调整连接到所述电光调制器（EOM）驱动程序来设置光阱功率电源。最佳功率取决于颗粒尺寸和材料。光功率通过反复试验发现，以确定足以悬浮颗粒，而不从梁弹出它的力量。这里，使用140毫瓦的光功率在物镜套住20微米直径的聚苯乙烯（PS）粒子的后焦平面。 </li><li>所选颗粒中心对准后，致动与多个脉冲压电启动器。从静态聚焦图像到运动模糊图像的颗粒图像的变化指示成功加载到利itation位置。 </li><li>竖直平移悬浮颗粒对由移动物镜，以防止可能的表面相互作用的基片上方一毫米。然后降低光功率转变的悬浮颗粒（ 图3b）成标称捕获位置（ 图3c），这是更稳定。 注:捕集激光的光功率可以通过电光调制器（EOM）进行调制。该EOM调节输出功率，通过数字电源提供的偏置电压。人们可以观察到通过CCD捕获位置而缓慢地降低了光功率从悬浮的过渡。 </li><li>用于位置测量，如在图3c到3D所描述的，仔细地移动至PZT保持器的中心光轴，然后移动至物镜上（垂直地）到粒子转化为样品的外壳的中间（9毫米的位置的SUBSTR吃），其中边缘电场最小化。 </li><li>执行如下所述在测量后，通过移动物镜向下直到颗粒接触基板放置在基板上的颗粒。由于大部分的颗粒被邻近的角施加时，捕获微粒可以容易地识别和重新捕获时，它被放置在中心区域。这使得可逆陷阱负荷以测量诸如颗粒和基板的接触相互作用发生超出单个俘获事件的变化。 </li></ol></li></ol> 3.数据采集<ol><li>对准聚光和聚焦透镜以最大化QPD"SUM"信号随着陷阱的颗粒。 </li><li>对准的聚焦透镜以在名义上归零QPD的X和Y通道， 如图4c中 。 </li><li>重复该冷凝器的调整和聚焦透镜，直到经傅立叶变换的位置信号（或功率谱密度<html>在X的（PSD）地块）和Y通道叠加显示平衡的敏感性。正确对准QPD信号（X和Y）显示几乎相同的行为， 如图4b所示 。 </li><li>一旦QPD对准验证，连接电压放大器的两个ITO板。放大器的电压监视输出信号连接到数据采集系统以记录步骤激励信号和感应颗粒轨道同步。 </li><li>提供一个连续的方波的400伏到产生电场（ 图4d），该由约500nm（ 图4e）横向移动粒子的光轴。测量使用QPD被困颗粒的步骤的响应。 </li><li>平均多个周期作为必要减少布朗运动的影响。诱导运动可以用于在更宽范围比热波动的运动来测量光力。 12，EF"&gt; 17 图4D和4E表示平均外加电压和过一步激发的50次迭代引起的颗粒运动轨迹的信号。 </li></ol>

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The authors declare no competing financial interest.

压电发射器被设计为优化选择PZT的动态性能。 PZT材料和超声波振动管理的正确选择是关键步骤，以产生一个成功的实验。 PZTs具有取决于换能器的类型（散装或层叠）不同的特性和成分的材料（硬或软）。由硬质的压电材料的一个大容量类型的PZT被选择的原因如下。首先，硬的压电材料具有较低的介电损耗，比软质材料更高的机械品质因数。其次，大容量型的PZT代表低级电负载和更容易以驱动在?...

Ashkin报道在1970年1他的小说成就的加速和辐射压力微粒捕集促进了光学捕获技术的发展为物理和生物物理学基础研究的主要工具。 2，3，4，5迄今为止，光学捕获的应用已主要集中在液体环境中，并且被用于研究非常广泛的系统中，从胶体到单个生物分子的力学性能的行为。 6，7，光学捕获的气态介质8中的应用，但是，需要解决几个新的技术问题。 最近，在空气/真空光学捕获已被越来越多地在基础研究应用。由于光学列维塔季翁潜在提供了一种系统的几乎完全的隔离从周围的环境中，光学悬浮粒子成为在小物体研究量子接地状态，4个测量高频引力波，9和搜索分数电荷的理想的实验室。 10此外，空气/真空的低粘度允许人们使用惯性测量布朗粒子11的瞬时速度和在很宽的范围之外的线性弹簧状制度运动的创建弹道运动。 12因此，详细的技术信息，并在气体介质光学陷阱的做法已成为更广泛的研究团体更有价值。 新的实验技术是必需的纳米/微粒装入在气体介质的光学陷阱。压电换能器（PZT），即转换ELECTR设备集成电路能量转换成机械性的声能，已用于小颗粒递送到空气/真空5,12光学陷阱由于光悬浮的第一示范。 1此后，几个加载技术已经被提出来加载使用由商业喷雾器13或声波发生器产生的挥发性气溶胶更小的颗粒。 14固体夹杂物（颗粒）浮动气溶胶随机经过靠近的重点和偶然被困住。一旦该气溶胶被捕获，溶剂蒸发出来和颗粒残留在光阱。然而，这些方法不能很好适合于从样品中识别所需的颗粒，装载所选粒子，如果从阱释放来跟踪其变化。该协议的目的是提供对在空气中选择性光阱装载，包括实验细节新从业人设置，与颗粒运动的同时在频域和时域分析相关联的PZT保持架和样品的外壳，陷阱装载，和数据采集的制造。对于在液体培养基中捕获的协议也已出版。 15,16 整个实验装置在商业倒置光学显微镜的发展。 图1示出了用于证明选择性光阱装载的步骤设置的示意图:释放休息微粒，用聚焦束提起选择粒子，测量其运动，并再次将其放置到衬底上。首先，平移阶段（横向和纵向）被用来使选定的微粒在基片上，以由物镜聚焦的捕集激光（波长1064纳米）的焦点（近红外校正长工作距离物镜:NA 0.4，放大倍数20X，工作ðistance20毫米）通过透明衬底。然后，压电发射器（一个机械预加载环型PZT）产生超声波振动，打破微粒和基材之间的粘合。因此，任何释放颗粒可以通过单束梯度激光陷阱聚焦在选定的粒子上抬起。一旦粒子被捕获，它被转换到包含用于静电激励两个平行的导电板样品外壳的中心。最后，一个数据采集系统（DAQ）同时记录了粒子的运动，由一个象限小区光检测器（QPD）捕获，并且所施加的电场。在结束测量之后，粒子被可控放置到衬底，以便它可以再次以可逆的方式被捕获。这整个过程可以重复数百次，而不颗粒损失来衡量的变化，如接触带电发生在几个俘获循环。请参考我们近期的F条或细节。 12

<table><tbody><tr><td>ScotchBlue Painter&#039;s Tape Original</td><td>3M</td><td>3M2090</td><td></td></tr><tr><td>Scotch 810 Magic Tape</td><td>3M</td><td>3M810</td><td></td></tr><tr><td>Function/Arbitrary Waveform generator</td><td>Agilent</td><td>HP33250A</td><td></td></tr><tr><td>Power supply/Digital voltage supplier</td><td>Agilent</td><td>E3634A</td><td></td></tr><tr><td>Ring-type piezoelectric transducer</td><td>American Piezo Company</td><td>item91</td><td></td></tr><tr><td>Electro-optic modulator</td><td>Con-Optics</td><td>350&amp;minus;80-LA</td><td></td></tr><tr><td>Amplifier for Electro-optic modulator</td><td>Con-Optics</td><td>302RM</td><td></td></tr><tr><td>Mitutoyo NIR infinity Corrected Objective</td><td>Edmund optics</td><td>46-404</td><td>Manufactured by Mitutoyo and Distributed by Edmund optics</td></tr><tr><td>LOCTITE SUPER GLUE LONGNECK BOTTLE</td><td>Loctite</td><td>230992</td><td></td></tr><tr><td>3D printer</td><td>MakerBot</td><td>Replicator 2</td><td></td></tr><tr><td>Polylactic acid (PLA) filament</td><td>MakerBot</td><td>True Red PLA Small Spool</td><td></td></tr><tr><td>Data Acquisition system</td><td>National Instruments</td><td>780114-01</td><td></td></tr><tr><td>Quadrant-cell photodetector</td><td>Newport</td><td>2031</td><td></td></tr><tr><td>Translational stage</td><td>Newport</td><td>562-XYZ</td><td></td></tr><tr><td>Inverted optical microscope</td><td>Nikon Instruments</td><td>EclipsTE2000</td><td></td></tr><tr><td>Fluorescence filter (green)</td><td>Nikon Instruments</td><td>G-2B</td><td></td></tr><tr><td>Flea3/CCD camera</td><td>Point Grey</td><td>FL3-U3-13S2M-CS</td><td>Trapping laser</td></tr><tr><td>Diode pumped neodymium yttrium vanadate(Nd:YVO&lt;sub&gt;4&lt;/sub&gt;)</td><td>Spectra Physics</td><td>J20I-8S-12K/ BL-106C</td><td></td></tr><tr><td>Indium tin oxide (ITO) Coated coverslips</td><td>SPI supplies</td><td>06463B-AB</td><td>Polystyrene microparticles</td></tr><tr><td>Fast Drying Silver Paint</td><td>Tedpella</td><td>16040-30</td><td></td></tr><tr><td>Dri-Cal size standards</td><td>Thermo Scientific</td><td>DC-20</td><td></td></tr><tr><td>Optical Fiber</td><td>Thorlabs</td><td>P1&amp;minus;1064PM-FC-5</td><td>bottom plate</td></tr><tr><td>Aluminium plate&amp;nbsp;</td><td>Thorlabs</td><td>CP4S</td><td></td></tr><tr><td>High voltage power amplifier</td><td>TREK</td><td>PZD700A M/S</td><td></td></tr></tbody></table>

optical trap loading of dielectric microparticles in air

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly scattered dielectric microparticles adhered to a glass substrate are momentarily detached using ultrasonic vibrations generated by a piezoelectric transducer (PZT). Then, the optical beam focused on a selected particle lifts it up to the optical trap while the vibrationally excited microparticles fall back to the substrate. A particle may be trapped at the nominal focus of the trapping beam or at a position above the focus (referred to here as the levitation position) where gravity provides the restoring force. After the measurement, the trapped particle can be placed at a desired position on the substrate in a controlled manner. 
In this protocol, an experimental procedure for selective optical trap loading in air is outlined. First, the experimental setup is briefly introduced. Second, the design and fabrication of a PZT holder and a sample enclosure are illustrated in detail. The optical trap loading of a selected microparticle is then demonstrated with step-by-step instructions including sample preparation, launching into the trap, and use of electrostatic force to excite particle motion in the trap and measure charge. Finally, we present recorded particle trajectories of Brownian and ballistic motions of a trapped microparticle in air. These trajectories can be used to measure stiffness or to verify optical alignment through time domain and frequency domain analysis. Selective trap loading enables optical tweezers to track a particle and its changes over repeated trap loadings in a reversible manner, thereby enabling studies of particle-surface interaction.

PZT的发射是使用CAD软件程序包设计的。在这里，我们使用一个简单的夹层结构的预压（的PZT夹紧与两个板），如示于图2的压电陶瓷保持架和样品的外壳可以从各种材料和方法来制造。对于一个快速演示，我们选择如图所示的二维与三维热塑性塑料印刷。根据所制造的组件，光学阱装载示于图3。用于选择性加载，反射捕?...

Watch this Scientific Journal Video about Optical Trap Loading of Dielectric Microparticles In Air at JoVE.com

Optical Trap Loading of Dielectric Microparticles In Air

A protocol for launching and stably trapping selected dielectric microparticles in air is presented.

介电微粒的光阱装载在空气中

We demonstrate a method to trap a selected dielectric microparticle in air using radiation pressure from a single-beam gradient optical trap. Randomly ...

optical-trap-loading-of-dielectric-microparticles-in-air

Universidad San Sebastian

Research

JoVE Journal

Engineering

9.0K 次观看.  National Institute of Standards and Technology. A protocol for launching and stably trapping selected dielectric microparticles in air is presented.

视频: Optical Trap Loading of Dielectric Microparticles In Air

A Microfluidic-based Hydrodynamic Trap for Single Particles

The ability to confine and manipulate single particles in free solution is a key enabling technology for fundamental and applied science. Methods for particle trapping based on optical, magnetic, electrokinetic, and acoustic techniques have led to major advancements in physics and biology ranging from the molecular to cellular level. In this article, we introduce a new microfluidic-based technique for particle trapping and manipulation based solely on hydrodynamic fluid flow. Using this method, we demonstrate trapping of micro- and nano-scale particles in aqueous solutions for long time scales. The hydrodynamic trap consists of an integrated microfluidic device with a cross-slot channel geometry where two opposing laminar streams converge, thereby generating a planar extensional flow with a fluid stagnation point (zero-velocity point). In this device, particles are confined at the trap center by active control of the flow field to maintain particle position at the fluid stagnation point. In this manner, particles are effectively trapped in free solution using a feedback control algorithm implemented with a custom-built LabVIEW code. The control algorithm consists of image acquisition for a particle in the microfluidic device, followed by particle tracking, determination of particle centroid position, and active adjustment of fluid flow by regulating the pressure applied to an on-chip pneumatic valve using a pressure regulator. In this way, the on-chip dynamic metering valve functions to regulate the relative flow rates in the outlet channels, thereby enabling fine-scale control of stagnation point position and particle trapping. The microfluidic-based hydrodynamic trap exhibits several advantages as a method for particle trapping. Hydrodynamic trapping is possible for any arbitrary particle without specific requirements on the physical or chemical properties of the trapped object. In addition, hydrodynamic trapping enables confinement of a "single" target object in concentrated or crowded particle suspensions, which is difficult using alternative force field-based trapping methods. The hydrodynamic trap is user-friendly, straightforward to implement and may be added to existing microfluidic devices to facilitate trapping and long-time analysis of particles. Overall, the hydrodynamic trap is a new platform for confinement, micromanipulation, and observation of particles without surface immobilization and eliminates the need for potentially perturbative optical, magnetic, and electric fields in the free-solution trapping of small particles.

In this article, we present a microfluidic-based method for particle confinement based on hydrodynamic flow. We demonstrate stable particle trapping at a fluid stagnation point using a feedback control mechanism, thereby enabling confinement and micromanipulation of arbitrary particles in an integrated microdevice.

一个单粒子为基础的微流控液力陷阱

The ability to confine and manipulate single particles in free solution is a key enabling technology for fundamental and applied science.  Methods for ...

科研

生物工程

Optical Trapping of Nanoparticles

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping and manipulating small biological particles. Ashkin and co-workers first demonstrated optical tweezers using a single focused beam1. The single beam trap can be described accurately using the perturbative gradient force formulation in the case of small Rayleigh regime particles1. In the perturbative regime, the optical power required for trapping a particle scales as the inverse fourth power of the particle size. High optical powers can damage dielectric particles and cause heating. For instance, trapped latex spheres of 109 nm in diameter were destroyed by a 15 mW beam in 25 sec1, which has serious implications for biological matter2,3.
A self-induced back-action (SIBA) optical trapping was proposed to trap 50 nm polystyrene spheres in the non-perturbative regime4. In a non-perturbative regime, even a small particle with little permittivity contrast to the background can influence significantly the ambient electromagnetic field and induce a large optical force. As a particle enters an illuminated aperture, light transmission increases dramatically because of dielectric loading. If the particle attempts to leave the aperture, decreased transmission causes a change in momentum outwards from the hole and, by Newton's Third Law, results in a force on the particle inwards into the hole, trapping the particle. The light transmission can be monitored; hence, the trap can become a sensor. The SIBA trapping technique can be further improved by using a double-nanohole structure.
The double-nanohole structure has been shown to give a strong local field enhancement5,6. Between the two sharp tips of the double-nanohole, a small particle can cause a large change in optical transmission, thereby inducing a large optical force. As a result, smaller nanoparticles can be trapped, such as 12 nm silicate spheres7 and 3.4 nm hydrodynamic radius bovine serum albumin proteins8. In this work, the experimental configuration used for nanoparticle trapping is outlined. First, we detail the assembly of the trapping setup which is based on a Thorlabs Optical Tweezer Kit. Next, we explain the nanofabrication procedure of the double-nanohole in a metal film, the fabrication of the microfluidic chamber and the sample preparation. Finally, we detail the data acquisition procedure and provide typical results for trapping 20 nm polystyrene nanospheres.

The following setup approach details low power optical trapping of dielectric nanoparticles using a double-nanohole in metal film.

纳米粒子的光学捕获

Optical trapping is a technique for immobilizing and manipulating small objects in a gentle way using light, and it has been widely applied in trapping ...

工程学

Utilization of Plasmonic and Photonic Crystal Nanostructures for Enhanced Micro- and Nanoparticle Manipulation

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological research. Perhaps the most widely used physical force to achieve noninvasive manipulation of small particles has been dielectrophoresis(DEP).1 However, DEP on its own lacks the versatility and precision that are desired when manipulating cells since it is traditionally done with stationary electrodes. Optical tweezers, which utilize a three dimensional electromagnetic field gradient to exert forces on small particles, achieve this desired versatility and precision.2 However, a major drawback of this approach is the high radiation intensity required to achieve the necessary force to trap a particle which can damage biological samples.3 A solution that allows trapping and sorting with lower optical intensities are optoelectronic tweezers (OET) but OET's have limitations with fine manipulation of small particles; being DEP-based technology also puts constraint on the property of the solution.4,5
This video article will describe two methods that decrease the intensity of the radiation needed for optical manipulation of living cells and also describe a method for orientation control. The first method is plasmonic tweezers which use a random gold nanoparticle (AuNP) array as a substrate for the sample as shown in Figure 1. The AuNP array converts the incident photons into localized surface plasmons (LSP) which consist of resonant dipole moments that radiate and generate a patterned radiation field with a large gradient in the cell solution. Initial work on surface plasmon enhanced trapping by Righini et al and our own modeling have shown the fields generated by the plasmonic substrate reduce the initial intensity required by enhancing the gradient field that traps the particle.6,7,8 The plasmonic approach allows for fine orientation control of ellipsoidal particles and cells with low optical intensities because of more efficient optical energy conversion into mechanical energy and a dipole-dependent radiation field. These fields are shown in figure 2 and the low trapping intensities are detailed in figures 4 and 5. The main problems with plasmonic tweezers are that the LSP's generate a considerable amount of heat and the trapping is only two dimensional. This heat generates convective flows and thermophoresis which can be powerful enough to expel submicron particles from the trap.9,10 The second approach that we will describe is utilizing periodic dielectric nanostructures to scatter incident light very efficiently into diffraction modes, as shown in figure 6.11 Ideally, one would make this structure out of a dielectric material to avoid the same heating problems experienced with the plasmonic tweezers but in our approach an aluminum-coated diffraction grating is used as a one-dimensional periodic dielectric nanostructure. Although it is not a semiconductor, it did not experience significant heating and effectively trapped small particles with low trapping intensities, as shown in figure 7. Alignment of particles with the grating substrate conceptually validates the proposition that a 2-D photonic crystal could allow precise rotation of non-spherical micron sized particles.10 The efficiencies of these optical traps are increased due to the enhanced fields produced by the nanostructures described in this paper.

Plasmonic tweezers and photonic crystal nanostructures are shown to produce useful enhancements in the efficiency and orientation control of optically trapping micro- and nano-particles.

为增强微型和纳米操纵利用电浆和光子晶体纳米结构

A method to manipulate the position and orientation of submicron particles nondestructively would be an incredibly useful tool for basic biological ...

Fabrication and Operation of a Nano-Optical Conveyor Belt

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological and physical sciences over the past few decades. The progress made in this field invites further study of even smaller systems and at a larger scale, with tools that could be distributed more easily and made more widely available. Unfortunately, the fundamental laws of diffraction limit the minimum size of the focal spot of a laser beam, which makes particles smaller than a half-wavelength in diameter hard to trap and generally prevents an operator from discriminating between particles which are closer together than one half-wavelength. This precludes the optical manipulation of many closely-spaced nanoparticles and&#160;limits the&#160;resolution of optical-mechanical systems. Furthermore, manipulation using focused beams requires beam-forming or steering optics, which can be very bulky and expensive. To address these limitations in the system scalability of conventional optical trapping our lab has devised an alternative technique which utilizes near-field optics to move particles across a chip. Instead of focusing laser beams in the far-field, the optical near field of plasmonic resonators produces the necessary local optical intensity enhancement to overcome the restrictions of diffraction and manipulate particles at higher resolution. Closely-spaced resonators produce strong optical traps which can be addressed to mediate the hand-off of particles from one to the next in a conveyor-belt-like fashion. Here, we describe how to design and produce a conveyor belt using a gold surface patterned with plasmonic C-shaped resonators and how to operate it with polarized laser light to achieve super-resolution nanoparticle manipulation and transport. The nano-optical conveyor belt chip can be produced using lithography techniques and easily packaged and distributed.

The scalability and resolution of conventional optical manipulation techniques are limited by diffraction. We circumvent the diffraction limit and describe a method of optically transporting nanoparticles across a chip using a gold surface patterned with a path of closely spaced C-shaped plasmonic resonators.

一个纳米光输送带的制作和操作

The technique of using focused laser beams to trap and exert forces on small particles has enabled many pivotal discoveries in the nanoscale biological ...

Plasmonic Trapping and Release of Nanoparticles in a Monitoring Environment

Plasmonic tweezers use surface plasmon polaritons to confine polarizable nanoscale objects. Among the various designs of plasmonic tweezers, only a few can observe immobilized particles. Moreover, a limited number of studies have experimentally measured the exertable forces on the particles. The designs can be classified as the protruding nanodisk type or the suppressed nanohole type. For the latter, microscopic observation is extremely challenging. In this paper, a new plasmonic tweezer system is introduced to monitor particles, both in directions parallel and orthogonal to the symmetric axis of a plasmonic nanohole structure. This feature enables us to observe the movement of each particle near the rim of the nanohole. Furthermore, we can quantitatively estimate the maximal trapping forces using a new fluidic channel.

A microchip fabrication process that incorporates plasmonic tweezers is presented here. The microchip enables the imaging of a trapped particle to measure maximal trapping forces.

电浆捕获和纳米粒子的释放在监控环境

Plasmonic tweezers use surface plasmon polaritons to confine polarizable nanoscale objects. Among the various designs of plasmonic tweezers, only a few ...

Experimental Methods for Trapping Ions Using Microfabricated Surface Ion Traps

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due to their long coherence time and their capability to manipulate and detect individual quantum bits (qubits). In more recent years, microfabricated surface ion traps have received more attention for large-scale integrated qubit platforms. This paper presents a microfabrication methodology for ion traps using micro-electro-mechanical system (MEMS) technology, including the fabrication method for a 14 &#181;m-thick dielectric layer and metal overhang structures atop the dielectric layer. In addition, an experimental procedure for trapping ytterbium (Yb) ions of isotope 174 (174Yb+) using 369.5 nm, 399 nm, and 935 nm diode lasers is described. These methodologies and procedures involve many scientific and engineering disciplines, and this paper first presents the detailed experimental procedures. The methods discussed in this paper can easily be extended to the trapping of Yb ions of isotope 171 (171Yb+) and to the manipulation of qubits.

This paper presents a microfabrication methodology for surface ion traps, as well as a detailed experimental procedure for trapping ytterbium ions in a room-temperature environment.

利用 Microfabricated 表面离子阱捕获离子的实验方法

Ions trapped in a quadrupole Paul trap have been considered one of the strong physical candidates to implement quantum information processing. This is due ...

Use of Dual Optical Tweezers and Microfluidics for Single-Molecule Studies

Visual biochemistry is a powerful technique for observing the stochastic properties of single enzymes or enzyme complexes that are obscured in the averaging that takes place in bulk-phase studies. To achieve visualization, dual optical tweezers, where one trap is fixed and the other is mobile, are focused into one channel of a multi-stream microfluidic chamber positioned on the stage of an inverted fluorescence microscope. The optical tweezers trap single molecules of fluorescently labeled DNA and fluid flow through the chamber and past the trapped beads, stretches the DNA to B-form (under minimal force, i.e., 0 pN) with the nucleic acid being observed as a white string against a black background. DNA molecules are moved from one stream to the next, by translating the stage perpendicular to the flow to enable the initiation of reactions in a controlled manner. To achieve success, microfluidic devices with optically clear channels are mated to glass syringes held in place in a syringe pump. Optimal results use connectors permanently bonded to the flow cell, tubing that is mechanically rigid and chemically resistant, and which is connected to switching valves that eliminate bubbles that prohibit laminar flow.

Visual, single-molecule biochemistry studied through microfluidic chambers is greatly facilitated using glass barrel, gas-tight syringes, stable connections of tubing to flow cells, and elimination of bubbles by placing switching valves between the syringes and tubing. The protocol describes dual optical traps that enable visualization of DNA transactions and intermolecular interactions.

使用双光镊和微流体进行单分子研究

Visual biochemistry is a powerful technique for observing the stochastic properties of single enzymes or enzyme complexes that are obscured in the ...

生物化学

Trapping of Micro Particles in Nanoplasmonic Optical Lattice

The plasmonic optical tweezer has been developed to overcome the diffraction limits of the conventional far field optical tweezer. Plasmonic optical lattice consists of an array of nanostructures, which exhibit a variety of trapping and transport behaviors. We report the experimental procedures to trap micro-particles in a simple square nanoplasmonic optical lattice. We also describe the optical setup and the nanofabrication of a nanoplasmonic array. The optical potential is created by illuminating an array of gold nanodiscs with a Gaussian beam of 980 nm wavelength, and exciting plasmon resonance. The motion of particles is monitored by fluorescence imaging. A scheme to suppress photothermal convection is also described to increase usable optical power for optimal trapping. Suppression of convection is achieved by cooling the sample to a low temperature, and utilizing the near-zero thermal expansion coefficient of a water medium. Both single particle transport and multiple particle trapping are reported here.

We describe a procedure to optically trap micro-particles in nanoplasmonic optical lattice.

Nanoplasmonic 光学晶格中微粒子的俘获

The plasmonic optical tweezer has been developed to overcome the diffraction limits of the conventional far field optical tweezer. Plasmonic optical ...

Direct Force Measurements of Subcellular Mechanics in Confinement using Optical Tweezers

During the development of a multicellular organism, a single fertilized cell divides and gives rise to multiple tissues with diverse functions. Tissue morphogenesis goes in hand with molecular and structural changes at the single cell level that result in variations of subcellular mechanical properties. As a consequence, even within the same cell, different organelles and compartments resist differently to mechanical stresses; and mechanotransduction pathways can actively regulate their mechanical properties. The ability of a cell to adapt to the microenvironment of the tissue niche thus is in part due to the ability to sense and respond to mechanical stresses. We recently proposed a new mechanosensation paradigm in which nuclear deformation and positioning enables a cell to gauge the physical 3D environment and endows the cell with a sense of proprioception to decode changes in cell shape. In this article, we describe a new method to measure the forces and material properties that shape the cell nucleus inside living cells, exemplified on adherent cells and mechanically confined cells. The measurements can be performed non-invasively with optical traps inside cells, and the forces are directly accessible through calibration-free detection of light momentum. This allows measuring the mechanics of the nucleus independently from cell surface deformations and allowing dissection of exteroceptive and interoceptive mechanotransduction pathways. Importantly, the trapping experiment can be combined with optical microscopy to investigate the cellular response and subcellular dynamics using fluorescence imaging of the cytoskeleton, calcium ions, or nuclear morphology. The presented method is straightforward to apply, compatible with commercial solutions for force measurements, and can easily be extended to investigate the mechanics of other subcellular compartments, e.g., mitochondria, stress-fibers, and endosomes.

Here, we present a protocol to investigate the intracellular mechanical properties of isolated embryonic zebrafish cells in three-dimensional confinement with direct force measurement by an optical trap.

使用光学镊子测量禁闭中的亚细胞力学的直接力

During the development of a multicellular organism, a single fertilized cell divides and gives rise to multiple tissues with diverse functions. Tissue ...

发育生物学

Optical Trapping of Plasmonic Nanoparticles for In Situ Surface-Enhanced Raman Spectroscopy Characterizations

Surface-enhanced Raman spectroscopy (SERS) enables the ultrasensitive detection of analyte molecules in various applications due to the enhanced electric field of metallic nanostructures. Salt-induced silver nanoparticle aggregation is the most popular method for generating SERS-active substrates; however, it is limited by poor reproducibility, stability, and biocompatibility. The present protocol integrates optical manipulation and SERS detection to develop an efficient analytical platform to address this. A 1064 nm trapping laser and a 532 nm Raman probe laser are combined in a microscope to assemble silver nanoparticles, which generate plasmonic hotspots for in situ SERS measurements in aqueous environments. Without aggregating agents, this dynamic plasmonic silver nanoparticle assembly enables an approximately 50-fold enhancement of the analyte molecule signal. Moreover, it provides spatial and temporal control to form the SERS-active assembly in as low as 0.05 nM analyte-coated silver nanoparticle solution, which minimizes the potential perturbation for in vivo analysis. Hence, this optical trapping-integrated SERS platform holds great potential for efficient, reproducible, and stable molecular analyses in liquids, especially in aqueous physiological environments.

Optical Trapping of Plasmonic Nanoparticles for In Situ Surface-Enhanced Raman Spectroscopy Characterizations

The present protocol describes a convenient approach to integrating optical trapping and surface-enhanced Raman spectroscopy (SERS) to manipulate plasmonic nanoparticles for sensitive molecular detection. Without aggregating agents, the trapping laser assembles plasmonic nanoparticles to enhance the SERS signals of target analytes for in situ spectroscopic measurements.

等离子体纳米颗粒的光学捕获用于 原位 表面增强拉曼光谱表征

Surface-enhanced Raman spectroscopy (SERS) enables the ultrasensitive detection of analyte molecules in various applications due to the enhanced electric ...

介电微粒的光阱装载在空气中

摘要

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此视频中的章节

一个单粒子为基础的微流控液力陷阱

纳米粒子的光学捕获

为增强微型和纳米操纵利用电浆和光子晶体纳米结构

一个纳米光输送带的制作和操作

电浆捕获和纳米粒子的释放在监控环境

利用 Microfabricated 表面离子阱捕获离子的实验方法

使用双光镊和微流体进行单分子研究

Nanoplasmonic 光学晶格中微粒子的俘获

使用光学镊子测量禁闭中的亚细胞力学的直接力

等离子体纳米颗粒的光学捕获用于原位表面增强拉曼光谱表征

介电微粒的光阱装载在空气中

摘要

探索更多视频

此视频中的章节

一个单粒子为基础的微流控液力陷阱

纳米粒子的光学捕获

为增强微型和纳米操纵利用电浆和光子晶体纳米结构

一个纳米光输送带的制作和操作

电浆捕获和纳米粒子的释放在监控环境

利用 Microfabricated 表面离子阱捕获离子的实验方法

使用双光镊和微流体进行单分子研究

Nanoplasmonic 光学晶格中微粒子的俘获

使用光学镊子测量禁闭中的亚细胞力学的直接力

等离子体纳米颗粒的光学捕获用于 原位 表面增强拉曼光谱表征

等离子体纳米颗粒的光学捕获用于原位表面增强拉曼光谱表征