Name: the preparation of electrohydrodynamic bridges from polar dielectric liquids
Uploaded: 2014-09-30T14:00:00.000+00:00
Duration: 10 min 3 s
Description: Watch this Scientific Journal Video about The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids at JoVE.com

在Wetsus，卓越中心，为可持续水技术（www.wetsus.nl）的TTIW，合作框架进行这项工作。 Wetsus是由经济事务，欧盟区域发展基金，Fryslân的省，市吕伐登和"Samenwerkingsverband北 - 荷兰的EZ /罗盘计划"的荷兰教育部资助。作者要感谢的研究主题为"应用物理学水"与会者的富有成果的讨论，并提供财政支持。

1，一般建议<ol><li>整个设置了实验，以防止污染由手汗或者油戴一次性，无粉手套。 </li><li>清洗所有玻璃，电极和接触液体正在研究中，要特别注意防止污染物可以在液相中溶解的任何其他部分。 </li><li>采用电导仪，测量将在实验中使用，并确认它是≤1μS/ cm的液体的导电率。 </li></ol> 2，实验装置<ol><li>卧式桥系统（ 图1a） <ol><li>放置在水平的非导电表面上对可调节高度的平台。修正了一个平台到位并安装其他平台上的电动线性平移的阶段，具有25毫米的最小行程。 </li><li>安全绝缘板（ 图1a，部分j）至TH可调节的平台ê顶面。用绝缘板是过大的，使得它们突出在平台通过至少为10mm四面八方。使用普通的材料如聚四氟乙烯，丙烯酸树脂，或用窗玻璃。选择，以防止在该计划中的最大电压击穿的厚度。 </li><li>根据制造商的指示连接的高压电源（ 图1a，部分米）。 </li><li>焊料鳄鱼夹，以对高电压和接地线的末端。 </li><li>钳从刚性绝缘材料构成到环的支撑臂的一端与支架水平在绝缘平台突出的绝缘杆。 </li><li>安装在地面和高压电线用绝缘胶带，尼龙扎线带，或其它适当的手段的任一数涡卷支撑臂使弹簧夹向下伸出上述绝缘平台。 </li><li>片断中的铂电极（ 图1a，部K）成每两个鳄鱼夹。 </li><li>定位在支撑臂，以使高压电线是固定的平台上和接地线是上述活动平台。 </li></ol></li><li>垂直桥系统（ 图1b） <ol><li>附加的非导电夹到一个线性平移台，使得夹子可行驶的最小值为25毫米。使用该夹具保持容器（ 图1b，第I部分），其将被连接到地线。 </li><li>该组件安装在垂直的刚性支撑结构。 </li><li>附上一个类似的非导电夹在线路和下面的线性平移平台的支持。使用该夹具以容纳将被连接到所述高电压线的船只。 </li></ol></li><li>做一个"死棒"（参见图1c作说明） <ol><li>获得一块非导电刚性材料制成，例如玻璃或塑料棒30-40厘米长（ 图与＃160; 1C，部分P）。 </li><li>附加一块导电性金属10-15厘米长（ 图1c，部分Q）的使用在交错的方式或其它固定材料施加电带（ 图1c，部分R）的几个包裹的杆的一端。 </li><li>使用"死棒"弥合高压电极和接地电极与该金属端的电源被关断之后，以确保该电路之前处理设备排出。 </li></ol></li></ol> 3，操作液桥<ol><li>卧式液桥<ol><li>填写每艘船（ 图1a，第一部分）有足够的液体，使表面内1-5毫米的烧杯嘴或轮辋。在本演示中使用的容器（60mm直径），使用67克液对水74克二甲基亚砜，或84.4克甘油。 </li><li>放置2容器上的绝缘性平台，使得它们物理ically彼此接触，在单个位置上，如管口，但直壁缘也将起作用。 </li><li>调整平台的高度，以使液体将只接触铂电极和未鳄鱼夹或金属丝。注意垂直取向，以使所得的桥是水平的水平。 </li><li>将铂电极定位到液体填充容器，使它们至少从接触位置所在的桥将形成15mm以下。注意:通常在电极被放置在容器的中心，并从其中的两个容器进行接触最远的壁上之间。 </li></ol></li><li>立式液桥<ol><li>用两个干净的，封闭的容器与一个液体端口， 如图1b所示 ，第一部分。 </li><li>每个容器中填充所研究的液体，使得没有气泡。 </li><li>插入电极（ 图1b，部分K）为每艘船舶，并关闭的CAP保存的液体中发生。 </li><li>安装在两个封闭的容器进入非导电夹子（见2.2），使得所述开口指向彼此。 </li><li>添加几滴液体到下管的开口部，使弯曲的液面突出几毫米以上的玻璃边缘。 </li><li>把上容器，从而使其刚好接触中较低者形成了一个小的毛细管桥。 </li><li>连接电源的高电压输出（ 图1b，部分米）到下部容器（静止）的电极端子和接地到上（翻译）容器中。 </li></ol></li><li>高压操作<ol><li>一般注意事项<ol><li>在进一步继续之前确认所有的表面是干燥的，没有液体池，膜，或微滴存在于绝缘平台。 </li><li>在此之前通电的实验证实，有没有短路，而且没有理由pATHS本这可能导致人员或设备进入与带电表面接触。务必遵循所有程序，并观察了高压电源制造商发出警告。如有疑问咨询有资格的电气安全人员。 </li><li>设置电源的极性（如果选择）之前接通电源。通常情况下，使用正电压极性，因为这提供了更稳定的桥。注:负极也可以使用，但往往产生明显的空间电荷效应可以显著同时影响介电液体48的物理性能，并影响在实验区的局部电荷密度由于功能上的差异在下沉，而不是采购电子在高电势作为剩余电荷可以被喷洒到周围的绝缘支撑结构。 </li><li>在电源开启电流限制，以提供不超过5-6毫安的电流。 </li></ol> &lt;/ LI&gt; <li>选择的，可以应用这两个电压分布1 - 斜坡或步骤。 <ol><li>使用一个电压斜坡，当第一次启动和液体的性能特性还不清楚。 <ol><li>调低电压限制在电源提供0千伏。 </li><li>使在电源的输出和慢慢开始在大约250伏/秒的速率增加的电压的限制。 </li><li>观察在其桥发生点火的电压，这是近似的点火阈值电压（V t）的 。 </li></ol></li><li>使用一个电压阶跃快速应用电压到系统。 <ol><li>置的电源电压限制到上面的点火阈值所需的值，该值是通过使用一个电压斜坡为所研究的液体系统（见3.3.2.1.3）测定。 </li><li>使在电源的输出端。注意:一个电压步骤可能导致电弧放电和墨滴的喷射，并且可能需要数本身前一个稳定的桥梁形式conds。电弧放电会产生臭氧和过氧化导致增加的液体的电导率，如果允许持续超过几秒钟。建议更换新鲜材料的液体，如果电弧是一个问题。 </li></ol></li></ol></li><li>稳定下点火的桥梁。 <ol><li>通过观察这两个容器之间的液体源源不断确认大桥点燃。注意:这将发生通常8-10千伏之间的，并会伴随着电流传导250-500μA之间根据所使用的液体上。 </li><li>调通过增加电压至10-15千伏电流消耗〜1,000μA桥为扩展名。注:实际值取决于所用的液体上。 </li><li>扩展桥约1mm每1千伏的距离施加电压， 例如 15毫米，15千伏。如果必要，可以调整电桥还取决于实验的要求。注:一个稳定的桥CA许多小时Ñ存在。 </li></ol></li></ol></li><li>关机程序<ol><li>通过禁止在高电压电源的输出熄灭的桥梁。等待几秒钟，电源电容器放电，电压读数降至零。 </li><li>使用"死棒"在1.3节构造短前处理任何先前带电部件的电极夹。 </li></ol></li></ol> 4，影像学<ol><li>条纹投影<ol><li>通过印刷黑色条纹上的透明薄膜准备一个二进制边缘板贴上此乳白色漫射屏幕。对于这个例子，使用A4纸（ 即 297毫米x 210毫米）条纹板。 </li><li>放置条纹板的背光源的前面，以使条纹投影到整个实验装置。 </li><li>记录或者静止图像或使用任何数目的数码相机的条纹图案的电影。 </li><li>跟踪更改ìn中的液体表面，以及通过分析记录在4.1.3的图像变化的级联液体的光路长度。通过使用各种软件包附带的评估进行，如免费提供的IDEA项目49定量的观察到的变化分析:注意。具体的细节和边缘分析考虑在其他地方49-51覆盖。 </li></ol></li><li>热成像<ol><li>设置热成像摄像机的动态范围，根据制造商的说明进行操作。注意:通常两点校准其中包括期望的温度范围内是足够的，以提供良好的热解析。流动性最强的桥梁，在工作温度范围20-50℃。 </li><li>通过成像的液体的所研究的容积的开口表面的温度适宜为实验进行的发射率校正和温度校正。 <ol><li>填写相同的容器即使用在所研究的实验装置与液体在室温下。 </li><li>测量使用浸没测温器中的液体的温度，例如K型热电偶。 </li><li>记录在红外线的液体的一个图像。 </li><li>提高了液体的温度的温度预计在使用加热板或微波的桥梁。注意:这是典型地不高于10℃以下的液体的沸点（ 例如 ，90℃的水）。 </li><li>重复步骤4.2.2.2 4.2.2.3，并在高温下液体。 </li></ol></li><li>定位相机略高于水平的桥梁和水平与垂直的桥梁，从而最大限度地记录表面积。注:由于中期的强吸收和长波大多数极性液体的红外辐射，只是表面的温度分布是可见的。 </li><li>桥系统开始记录红外线使输出的PO之前WER供应和持续，直到实验结束或相机缓冲区已满。 </li></ol></li></ol>

The authors Dr. M&#243;nica L&#243;pez S&#225;enz and Dr. Oliver Schreer are employees of IRCAM GmbH that produces instruments used in this Article. The remaining authors declare that they have no competing financial interests.

成功组建稳定和强大的EHD液桥需要注意支付给某些简单而重要的细节。至关重要的是，该解决方案的离子电导率可低至实用（ 例如 1-5微秒/厘米）。要知道，水的污染可能会导致某些极性液体（ 如甘油）增加导电性。清洗所有玻璃器皿以及注意仔细清洗，只用玻璃器皿不受表面污染或电弧引起的烧伤痕迹。总的来说这是很好的做法，戴手套时操作任何设备，以防止皮肤的油和盐污染的实验。电极应该在所研究的溶剂中进行超声处理几分钟，所以建议这些都是"加热"由30-45分钟，在高电流值运行的未伸出的桥（ 例如 ，3-5毫安）来降低次级侧电极反应。高纯度（ 例如 ，&gt; 99.9％）贵金属工作最好作为电极材料，并应具有足够的表面面积，以保持10 A /平方米量级的低电流密度，从而减少局部加热。 在具有稳定性差或难以启动它桥的情况下，建议第一确认电导率为〜1μS/ cm的并有液体没有多余的池，可以让一个备用电流通路。一般而言，建议将所有的表面是尽可能干燥，要特别注意薄膜可血管和绝缘板之间形成。如果发生电弧中断电源，降低电压值，然后重新接通电源的电弧持续将导致受影响地区可降低桥梁的稳定性和防止桥点火在一起的"炭化"。如果电源被施加到系统上的阈值电压和无桥形式的绝缘玻璃棒可以用来向上画出液体朝第两艘船之间的电子邮件联系点（ 如烧杯嘴）。如果系统继续行为处于不稳定的方式清洁设备并用新鲜液体重新开始。如果做不到这一点，建议采取周围的清单作为大型金属物体，在支持的静电荷，或者强烈的气流可破坏桥和/或电场，它支持它的材料。 该实验系统很容易地修改，以适应大多数实验室常用的材料。液体容器可以从几乎任何相容的材料和特殊应注意在容器或液相的情况下电弧的可燃性;例如，燃烧时特氟龙会产生有害气体。电极形状，位置和材料也可以改变以适应给定的设置的限制。由箔制成通常的平面电极被使用，但是金属丝也可以使用，只要电流密度准则<html>被考虑在内。所施加的电场可以是纯直流，纯交流，或直流偏置的交流。所有将产生随频率而变的响应范围内的液体桥，在电介质（EWOD）在文献中描述的电润湿液体和介电电泳（DEP）9，它在20赫兹和高达20千赫为中等电压定义的响应的频率范围。较高的频率范围内也可以生成桥虽然这些没有被明确地检测和一些工人已报道在AC垂直桥的下限为50赫兹42。方向与重力也容易，只要系统可以被设计成提供自由液体表面是稳定的，没有施加电场改性。实验已经在没有重力41的这表明，这些桥梁对重力的保持力在液体桥的微妙平衡的稳定作用的依赖已经进行。 ENT"&gt; EHD液桥是可以被添加到许多自然科学的应用剧目的新工具，它们允许的体积和表面力与外加电场相互作用的探索，他们打开了机会研究的新途径混合不同的液体37;改变化学反应动力学52;质子运输44,45;和检查生物系统的条件53的反应除了这些桥允许直接访问的液面没有它已经产生了新的任何物理级联结构。在液体水28的动力学和光谱信息提示不仅在电控状态开关的存在，由此新的整体性质出现31而在电位通过一个全新的方法来检查液-液相转变54。的广泛的工业应用EHD进程（ 如 </eM&gt;，静电26日 ，和电32,33方法）肯定可以从这些密切联系的现象的进一步研究中受益。

An erratum was issued for <a href="http://www.jove.com/video/51819/the-preparation-electrohydrodynamic-bridges-from-polar-dielectric">The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids</a>. Figure 3 was updated because it had an incorrect representation of the power used in an operating bridge.
Figure 3 has been updated from:
<img alt="Figure 3" src="/files/ftp_upload/5806/51819fig3old.jpg" /> 
Figure 3.&#160;Characteristic curves for a liquid water bridge. The current-voltage relationship for liquid water bridges at 0, 5, 10, 15 mm separation distance is plotted. A lower threshold below which no liquid bridge will form (see inset photo at lower left), and an upper threshold above which bridges are unstable (inset photos 1-4) bound the region of stability. For most bridges with some measureable extension (i.e. &#8805; 5 mm) the total power dissipation lies between 10 and 20 watts. The rupture of a bridge beyond the upper threshold will often follow a sequence of events progressing from normal operation (inset 1), to leaking (inset 2), sagging (inset 3), and finally rupture (inset 4).
to:
<img alt="Figure 3" src="/files/ftp_upload/5806/51819fig3new.jpg" /> 
Figure 3.&#160;Characteristic curves for a liquid water bridge. The current-voltage relationship for liquid water bridges at 0, 5, 10, 15 mm separation distance is plotted. A lower threshold below which no liquid bridge will form (see inset photo at lower left), and an upper threshold above which bridges are unstable (inset photos 1-4) bound the region of stability.&#160; Power dissipation is a tunable parameter where longer bridges have a more narrow tuning range than shorter bridges. The rupture of a bridge beyond the upper threshold will often follow a sequence of events progressing from normal operation (inset 1), to leaking (inset 2), sagging (inset 3), and finally rupture (inset 4).

<span style="font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; color: rgb(58, 58, 58); font-family: Arimo, &quot;Helvetica Neue&quot;, Helvetica, Arial, sans-serif; font-size: 14px; line-height: 28px; background-color: rgb(255, 255, 255);">An erratum was issued for&#160;<i style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: 12.8px; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);">The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids<span style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: 12.8px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; display: inline !important; float: none; background-color: rgb(255, 255, 255);">. Figure 3 was updated because it had an&#160;<span style="color: rgb(34, 34, 34); font-family: arial, sans-serif; font-size: 12.8px; font-style: normal; font-variant: normal; font-weight: normal; letter-spacing: normal; line-height: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: 1; word-spacing: 0px; -webkit-text-stroke-width: 0px; background-color: rgb(255, 255, 255);">incorrect representation of the power used in an operating bridge.

Erratum: The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

电场和液体物质导致了一些势力的材料本体中不断发展之间的互动。在实际液体电介质的系统中，不可忽视的场梯度和对称破几何形状导致一些看似奇特的效果。赫兹是第一个要注意在液体-固体绝缘系统1的旋转运动中的一个。 Quincke观察到两种流体之间的界面张力不仅由外部电场的施加，但是，这种变化导致了力对流体体的消耗及可用于诱发旋转运动2。阿姆斯特朗发现了漂浮水桥于1893年3这仍然是一个谜一般的方招，直到最近，当Fuchs和同事研究的质量和电荷传输机制4,5和重新严肃的科学调查由这些桥梁形成机制。电场有ability以对抗地心引力的Pellat对平行板电极间的电介质液体崛起工作解除液体显示6。这提升作用显示的频率依赖性，最终可以通过麦克斯韦应力张量7描述。考虑到与高压直流电（EHD）液桥相关的液面上升的交流条件下也表现出频率依赖性8类似电润湿电介质（EWOD）和介电电泳（DEP）的质量流量9时，这是非常重要的。此外，高电位的电场的应用是控制液体喷射分手重要和电场与液体的相互作用对于理解电雾化10,11的工业上重要的过程是必不可少的。 外部电场不仅影响表面能。由于偏振和剪切应力的作用下，流模式可以被建立。一个例子是液体在非均匀电场的存在下进行循环。特此electroconvective电流建立在液体散货剪切应力驱动。洲本证明，可以使用含有任一种极性液体或金属棒浸渍在非极性介质浴中，并置于一个非均匀电场12内的玻璃转子构建的流体马达。由冈野以后分析使用一种均匀的场近似13来解决旋转问题，只能定性匹配的实验结果和所需的电介质液体的响应为单数的质量。关于这个问题的其他研究人员忽略了一点完全是因为他们错误地报道，并探讨了洲本效力的液面回应Pellat 17率先电场工作的上涨14-16。表面对称性破缺本地化充电的过程中的重要性，并产生剪切STRESS 18必须掌握的液体EHD桥梁的研究。梅切尔公司在连续19机电论文提供了一种治疗散装液体完整的理论基础，并简化了均匀各向同性的范围内自由表面。表面的重要性仍然清晰甚至从连续的角度看为对称的结果中的剪切应力，能够生成整体运动的损失。取入的离散移动的流体体积可被极化，并有可能在方法的表面所产生的反作用力的一般情况下，电场的相互作用可以被取代成两个纳维-斯托克斯20和伯努利7,21,22关系来形容众多的EHD流现象，包括液体桥梁。液桥的进一步研究，可以提高许多基于EHD技术，如喷墨印刷23-25 ​​微米和纳米材料的处理26-28，药物输送2930，生物医学应用31,32，和海水淡化33。 这里描述的方法提供了访问而被发现在极性液体，其分子具有永久偶极矩的形成EHD液桥。在实行非均匀电场导致偶极子群的部分极化产生的介电常数的局部变化从而进一步增强磁场梯度18,34,35。这个偏振引起的位移力而根据所施加的场的相对强度将产生许多不同的液体的反应（参见图4-7），最终导致了桥的形成。液体还将开发泰勒流22,36沿着电极表面尤其是在情况下，有在电极上锋利的边缘存在。电荷注入的锋利边缘的可能性也是存在的，并且与该一致的形成能产生electroconvective电流在液体散货22从而连接液桥系统与洲本影响12混杂电荷层。桥梁理事EHD关系被广泛报道别处的水和其它极性液体22,36-38。这些理论方法蒙受应该接近实验数据时，应考虑一定的局限性。麦克斯韦应力张量治疗36是不敏感的场不均匀性，以及非均匀的液桥。纯EHD方法37提供了electrogravitational数和其给桥长宽比的关系的稳定状态的定义;然而，在流体动力学和重要的瞬变现象（ 例如 ，桥建立）未预测。在分析桥梁的稳定性，并在此推导先前公布的马林和洛斯37三无量纲数是有用的</s起来&gt;。的电毛细管数（CA E）是被定义为电和毛细作用力之间的比<img alt="式（1）" fo:content-width="2in" src="/files/ftp_upload/51819/51819eq1.jpg" width="200" />其中，ε0是真空介电常数，εr为液体的相对介电常数，E t是电场过桥，γ是表面张力，D s和d 升是这样的直径的垂直和水平投影得到的平均直径D 微米 。债券数量（博）描述重力和毛细管力之间的平衡: <img alt="式（2）" fo:content-width="1.5in" src="/files/ftp_upload/51819/51819eq2.jpg" width="150" />其中，g是重力加速度，l是自由桥的长度，而V是桥体积。之间的关系重力，毛细管，和电力可以表现在electrogravitational多少G 电子方面: <img alt="式（3）" fo:content-width="2in" src="/files/ftp_upload/51819/51819eq3.jpg" width="200" />桥的最大扩展性是关系到所施加的电压而流过电桥的电流与横截面面积，从而直径。这些关系耦合，确定桥体积，并且因此限定为任何给定的工作液体桥稳定性的区域。用于水桥的特性曲线在图3中，显示较低的阈值，低于该外加磁场太弱，以克服表面张力和上阈值，高于该电桥的质量过大导致漏水给出其进一步扰乱该字段和结果在桥断裂。 更普遍的治疗液桥在极性溶剂19,22换货提供了与桥经营预测理事流体动力学在修改后的伯努利方程增加了压力任期电位移计算的背景下，力合压力条件。此外离子稳定性24昂萨格关系纳入协议与实验观察的平衡抽水方向和热辐射。 一些极性液体已探索包括水，低级脂族醇（ 如甲醇），聚醇（ 如甘油），二甲基亚砜（DMSO）等极性有机物（ 例如 ，二甲基甲酰胺）。非极性液体介质（ 如正己烷）没有表现出桥形成。能够支撑桥梁的液体介质迄今研究8,22,37谎言一个定义良好的集团内树立了良好的起点FO物理参数范围内ř进一步的实验:低导电率（σ&lt;5μS/ cm）的，适度的静态相对介电常数（ε= 20-80），中度到高表面张力（γ= 21-72 MN / M）。有趣的是大范围的粘度（η= 0.3-987毫帕·秒）的工作在这样的桥梁。在液体中具有足够高的粘度，如甘油，可以直接从液体散货（ 见图5）拉桥，是介电电泳力和液桥之间的重要纽带。离子溶液（ 例如 ，氯化钠（水溶液））是高破坏性桥接的形成和在以前的研究中有40个已经被证明能增加桥的温度，减少的长度所加的电压比，并减少可扩展性。这种行为在很大程度上归因于溶解的离子的电荷屏蔽效应，以及更高的电流传导而降低了流体的体积元和电场之间的耦合。 &lt;P舱="jove_content"&gt;在连续级别的EHD现象的出现是因为必要的压力条件而伴随着电致伸缩只发现在液界面21。此外，存在的EHD液体桥的稳定性和在系统中的接口的稳定性之间的关系。在低重力实验41扩大表面积结果，其中除了眼泪桥力的情况下。同样，如果表面过于狭窄或级联的接触面积小的桥将有可能发展的不稳定性。这可以在桥这是由管道或在其中一个电极被向上从表面拉出垂直桥的情况下，供给进行说明 - 将得到的桥是在长期运行稳定性较差，因为它们缺乏在该情形中发现的特征的流体动力学这两个水库有大量免费的表面积。桥，其连接至所述流体储存器内的管路节目i的局限ncreased热积累和下降的表面张力。这是典型的空中接口将自发管内形成。该条件限制两者最大扩展以及用于密闭液体桥桥的平均寿命。开口表面水桥可以扩展到35毫米的长度，在35千伏，而没有桥将继续存在于这样的加速电压在限制作为液体优先地转换成电喷雾模式。同样地自由表面水桥有稳定的寿命接近受控条件下10小时，而在管供给系统的生命周期通常小于2小时。 EHD现象通常被认为仅在连续的水平。的液体桥的分子基础上研究有限数量已经进行。拉曼研究42利用垂直交流电桥研究了分子间的OH拉伸带相比，散水。在SC的一些变化应用电场后attering剖面示为具有结构原点。在一个浮动的水桥43的振动HDO分子中所含的HDO的OH伸缩振动的一生用超快的中红外泵浦探测光谱:D 2 O水桥被认为是较短的（630±50 FSEC）比HDO分子散装HDO:D 2 O（740±40 FSEC），而与此相反，下面的振动弛豫的热化动力学慢得多（1500±400 FSEC）比散装HDO:D 2 O（250±90 FSEC）。这些差异在能量弛豫动力学强烈表明，在分子尺度的水桥和散水不同。此外，在一个浮动水桥的红外线发射的研究揭示了这可能是由于从激发态到质子传导带44的地面状态的变化的非热特性。另一种较新的激光拉曼光谱研究reporteð在直流水桥中有其表示在桥45的芯和外壳之间的局部pH值的相对差的光谱的径向分布。的EHD液桥内的物理特性的径向分布是由无弹性的紫外线散射实验46，它给出了矛盾的径向分布中的温度和密度分布，并可以解释或者通过在分子自由度的梯度或第二相的存在下进一步支持纳米气泡。而受阻旋转的概念（ 即 librations）由红外线发射光谱44支持的存货概念是不支持的小角X射线散射研究47。在EHD液桥的优先流方向产生于变化自动解离动力学。与翁萨格的工作协议这一发现有希望用于连接分子和连续的现象级&lt;SUP&gt; 22。用于分子基础EHD现象进一步证据是在观察发现，由电介质液滴热发射响应于增加的电场局部降低并达到最小刚刚之前的桥梁的发病（参见图7）。 EHD液桥提供一个机会，以检查在多个尺度的力量之间的相互作用，这是这项工作的具体目标是生产这类桥梁的一些液体的方向相对任何提供一个标准化的方法来重支持出现的全套特有现象先前所讨论的。

<table><tbody><tr><td>Borosilicate Crystallization Dishes</td><td>VWR</td><td>216-0064</td><td></td></tr><tr><td>Double walled roundbottom flask with GL14 and GL8 openings along with 6 mm spherical joint port</td><td>LGS</td><td>SP757102a</td><td>Custom glassware with minimum two openings one for electrode, one for bridge spout.</td></tr><tr><td>Adjustable Platforms</td><td>Rudolf Grauer AG</td><td>Swiss Boy 115</td><td></td></tr><tr><td>Motion Translation Stage</td><td>Thorlabs</td><td>MTS25/M-Z8E</td><td>Complete motorized stage, controller, and power supply</td></tr><tr><td>Insulating Plates</td><td></td><td></td><td>Should be appropriate for resisting the intended voltages without breakdown</td></tr><tr><td>Pt Electrodes</td><td>Alfa-Aesar</td><td>000261</td><td>Wash and then sonicate in 18.2 M&amp;Omega; water prior to use</td></tr><tr><td>HVPS</td><td>FUG GmbH</td><td>HCP 350-65000</td><td>65 kV DC at 5 mA maximum output</td></tr><tr><td>Fiber Optic Temperature Probe System</td><td>OpSens</td><td>OTG-F Sensor/ XXX-XXX Control Unit</td><td>Readout speed 1 kHz, accuracy 0.01 K, probe size 120 &amp;#956;m</td></tr><tr><td>Long Wave Infrared Camera</td><td>IRCAM GmBH</td><td>Taurus 110K L</td><td>168 FPS 384 x 288 Sensitivity &amp;lt; 30 mK</td></tr><tr><td>Long Wave Infrared Camera</td><td>FLIR</td><td>FLIR 620</td><td>30 FPS 640 x 480 pixel Sensitivity to &amp;lt; 45 mK</td></tr><tr><td>Dual Band Mid- and Long-Wave Infrared Camera</td><td>IRCAM GmBH</td><td>Geminis 110k ML</td><td></td></tr><tr><td>Digital Camera</td><td>Canon</td><td>550D</td><td>Used for both video and still frames</td></tr><tr><td>Tripod</td><td>Manfrotto</td><td>475B/405</td><td></td></tr><tr><td>18.2 M&amp;Omega; Water</td><td>Milli-Q</td><td>Advantage</td><td>Allow 24 hr to equilibrate after dispensing into clear borosilicate bottles</td></tr><tr><td>Methanol dehydrated with less than 0.0050% water AnalaR NORMAPUR</td><td>VWR-BDH</td><td>20856.296</td><td>Keep dry until needed</td></tr><tr><td>Glycerol anhydrous for synthesis</td><td>VWR - Merck Millipore</td><td>8.18709.1000</td><td>Keep dry until needed</td></tr><tr><td>Dimethylsulfoxide, ACS Grade</td><td>VWR-BDH</td><td>BDH1115-1LP</td><td>Keep dry until needed</td></tr></tbody></table>

the preparation of electrohydrodynamic bridges from polar dielectric liquids

水平和垂直的液体桥是探索高强度的电场（8-20千伏/厘米）和极性液体介质的相互作用简单而强大的工具。这些桥梁都是从他们表现出超过几毫米扩展毛细管桥独特的，具有复杂的双向传质模式，并发出非普朗克红外辐射。一些常用的溶剂，可以形成这样的桥梁和低电导率溶液和胶体悬浮液。宏观行为是由电流体管，并提供学习流体流动现象没有刚性壁的存在的手段。在此之前的液体桥的几个重要现象的发生，可观察到包括促进半月板高度（电润湿），散装流体循环（在洲本的效果），和带电液滴（电）的喷射。表面极化和位移力之间的相互作用，可以直接审查改变施加电压和桥梁的长度。在电场作用下，由于重力的协助下，对稳定瑞利高原不稳定液桥。结构基本装置用于沿与操作实例，包括热成像图像，三种液体（ 如 ，水，DMSO和甘油）中，提出了垂直和水平方向。

高压直流电桥的液体从毛细管液相桥梁不同的三个特性:1）流量，2）可扩展性，3）热辐射;比较示于图2。之前施加电压小的毛细管桥常常观察到的两个容器之间时液面是即使在水平配置的嘴。这是不可避免的，在垂直配置时的分离距离小于几毫米。 电压可以应用无论是在斜坡（见3.4.2.1协议）或步骤（见协议3.4.2.2）。低于该阈值（V t）的不会产生EHD桥，但能引发其它几种现象如液体体积膨胀的电压（ 图4）中，液体的电极接触线的向上移动（ 图5）的液体的，旋转和循环体积（ 图6），ELEctrospraying和射流形成（ 图7）。 V吨是所研究的介电液体的性质，浓度和成分的本类型，以及在保护气氛中使用。点火阈值也是容器分离的功能。而桥的点火可能与许多毫米的分离所施加的电压必须更高和更长的休止期间可以用更猛烈电喷雾可以观察到形成了稳定的液体连接之前。例如，以水填充储层相隔5mm时，V吨增加至17-20千伏或更高。 一旦V吨已超过电弧和喷涂标记点火的组合（ 图8a，9a）中紧跟一个薄桥&lt;1mm直径的形成。一旦桥被建立电流将流随后肿胀的桥（ 图8B，9B），以3-5毫米直径取决于条件。在许多液体的迄今研究的时间从桥点火到肿胀是10-500毫秒之间以及在很大程度上是所施加的电压，分离距离，并且液体的粘度8,22,37的功能。 在水平桥的流动方向是依赖于特定液体的条件。通常净流量运行从朝向阴极的阳极时的高电压的极性是正的。在延伸部（ 图8c）的直径会波动通常在低频率1-10赫兹之间。更高频率的振荡也发生，是因为面波可见。旋光密度波在桥体时可见背照用二进制条纹图案。该系统的特定响应函数取决于两者的液体系统以及电源特性。 垂直桥在许多方面与H相似orizo​​ntal的人;然而，这些并没有显示强的质量流的证据，并且通常有一个夸张双耳罐状。增加的驱动电压导致液体和延伸性（ 图9c）的更圆柱形柱比在 ​​水平桥（ 例如 ，1.25毫米/千伏为水）更好一些。像水平桥垂直桥可以形成没有事先向电压的液体之间的直接接触。在这种情况下，泰勒锥被观察到形成在上部下垂液滴。这种喷雾将向下延伸形成了一个稳定的喷射后，与较低的无柄液滴的接触会快速膨胀。 不像electrosprays，在极性液体电介质的EHD桥在两个热的形式以及非热红外（IR）辐射44消散的能量。液桥（ 图7-10）的热成像记录是研究地表径流动态变化以及对曲有用的工具antifying能量在operando红外活性分布。热发射是由于在很大程度上通电加热，因此是稳定的离子敏感的措施为不同的液体偏热的不同给予相同的功耗。例如水桥（ 图9c）之间在35-50℃下一般操作，并且醇桥运行在兼顾低蒸汽压以及差异冷却器中的离子稳定性39几度。这种链接行为另一图示在非质子DMSO其具有低的蒸气压并形成在相反的方向上大多数其它极性液体迁移负离子找到。二甲基亚砜桥梁往往在温度接近100℃（ 图10a）进行操作。粘度和热容量也起到能量如何热耗散在系统中的显著作用可通过局部加热可以看出在甘油桥实测值（ 图10b）。 图8D，9D），直到一个临界值达到与高原瑞利不稳定性破坏配体样桥（ 图8E，9E），其中将在迁移液滴串电场。桥中断的另一个模式中，通常仅在水平配置的发现，发生在桥的直径变得过大从而导致高的质量和水向下喷射。这种行为可以导致电桥产生"摇摆"的效果，可能导致桥再次破坏成小滴的振荡。大直径的大鸟GES可发生在一个容器中，由于单向流动，这导致上溢条件过量静水头压力的结果;或者增加电压到高的数值，只有少量的分离会产生一个很宽的桥或"水高速公路"。这些大直径桥梁也可以通过折叠成一个大的液滴的落下向下重力作用下失效。 <img alt="图1" fo:content-width="5in" src="/files/ftp_upload/51819/51819fig1highres.jpg" width="500" /> 图1:基本设备EHD液桥实验。典型的水平（ 一）和垂直（B）实验系统的建立EHD液桥的示意图。一些机械细节，如固定带和电极载体是为清楚起见省略。的基本成分是液体容器（i）中，绝缘平台或莫UNTS（j）中，电极（K），以及一个高压电源（米）。线性平移阶段，建议一次的桥梁，建立了两艘船只的安全间隔。在面板（c）所示的死棒子是从一块不导电的硬质材料（P），导电金属杆（Q）组装，并在纵横交错的方式或其他固定材料（R）应用于电工胶带缠绕数。金属端所使用的实验结束后，形成一个短的两个电极之间，以保证电路的前处理设备排出。 <a href="https://www.jove.com/files/ftp_upload/51819/51819fig1highres.jpg" target="_blank">请点击这里查看该图的放大版本。</a> <img alt="图2" fo:content-width="5in" src="/files/ftp_upload/51819/51819fig2highres.jpg" width="500" /> 图毛细管和枳椇水桥2比较。的水平毛细管桥只能跨越小的差距为1.5毫米（A），而在三个不同电压4 kV的（B），6千伏（C），8千伏（D）水平的EHD桥梁轻松过关的差距。需要注意的是EHD桥流过嘴，而毛细管桥出水口之间的暂停。同样地，垂直毛细管桥（五）具有更窄腰（约1.5毫米直径），并且只能延长〜3.3毫米不像它是可扩展的垂直EHD桥。在4千伏（f）所示 ，6千伏（g）和8千伏（H）以相同的间隔距离为毛细管桥驱动的三个EHD桥示。较高的电压增大桥的束腰直径，流速和增加加热为在桥中增加的功率耗散的结果。在形成气泡的增加，也观察到在更高的电压作为随温度升高气体的溶解度降低。比例条在所有的帧是1毫米。 <a href="https://www.jove.com/files/ftp_upload/51819/51819fig2highres.jpg" target="_blank">请点击这里查看该图的放大版本。</a> <img alt="图3" fo:content-width="5in" src="/files/ftp_upload/51819/51819fig3highres.jpg" width="500" /> 图3的特性曲线为液体水桥。为液体水桥，在0得到的电流-电压关系，5，10，15毫米分离距离作图。较低的阈值，低于该没有液体桥将形成（见插图的照片在左下角），和上阈值，高于该桥梁是不稳定的（插图照片1-4）结合的稳定性的区域。对于大多数桥梁用一些可测量的延伸部分（ 即 ≥5mm）的总功耗介于10和20瓦。超出上限的桥梁断裂往往会跟着活动正常OPERAT进展的顺序离子（插图1），渗出（插图2），下垂（小图3），最后破裂（小图4）。 <a href="https://www.jove.com/files/ftp_upload/51819/51819fig3highres.jpg" target="_blank">请点击这里查看该图的放大版本。</a> <img alt="图4" fo:content-width="5in" src="/files/ftp_upload/51819/51819fig4highres.jpg" width="500" /> 图4体积膨胀。的两个容器的整个液体表面可以看出上升响应于所施加的电场与投影二进制条纹图案的帮助。两个聚四氟乙烯烧杯盛满水是在两个不同的外加电压的 ）0千伏和b）15千伏成像与投影的条纹图案。在投影边缘（图C）的变化是用IDEA 33软件，该软件使用了过滤傅立叶变换的变化转换中的边缘调制频率为分析相对高度上升。非均匀性检测的转变是由于投影条纹和文物的低空间频率，由于离散余弦变换的相位展开方法， <a href="https://www.jove.com/files/ftp_upload/51819/51819fig4highres.jpg" target="_blank">请点击这里查看该图的放大版本。</a> <img alt="图5" fo:content-width="5in" src="/files/ftp_upload/51819/51819fig5highres.jpg" width="500" /> 图5介电泳和电润湿。甘油的高电位的电场的机电响应。两个铂电极在0千伏（一）浸在无水甘油，和19千伏（b）示出了如何将液体强烈向上驱动。在Pellat的实验的变形例的举起量完全从级联储层产生一个EHD甘油BRIDG除去在两个电极之间举行E（C）。同样地，在杆形电极（d）该接触线前进与应用15千伏（e）该电极提高了电极拉动液体向上，以形成截头圆锥体（F）示出了由强产生增强润湿性的情况下领域。比例尺是为5mm。从补充视频S1（AC）和S2（DF）拍摄剧照。 <a href="https://www.jove.com/files/ftp_upload/51819/51819fig5highres.jpg" target="_blank">请点击这里查看该图的放大版本。</a> <img alt="图6" fo:content-width="5in" src="/files/ftp_upload/51819/51819fig6highres.jpg" width="500" /> 用一个简单的点面电极提供图6洲本效果可视化的红外，甘油单船在不均匀电场红外图像序列在面板的可见光显示系统（ 一）。电源（19千伏直流）在t = 0秒时施加。当地面冷却，就会发生这个局部冷却散布在表面上，并开发非均质性，的旋转力的产生而直接开始是小的，并且需要大约75秒，成为可见的表面上的点电极（T = 15秒）下方。帧之间的时间间隔为15秒。比例尺为10毫米。从补充视频S3的剧照。 <a href="https://www.jove.com/files/ftp_upload/51819/51819fig6highres.jpg" target="_blank">请点击这里查看该图的放大版本。</a> <img alt="图7" fo:content-width="5in" src="/files/ftp_upload/51819/51819fig7highres.jpg" width="500" /> 图7预点火冷却垂直桥梁系统10 mm的间距。上泰勒锥和一个垂直水桥的低座滴设置-U<html> p的显示在过程中的电压斜坡的特写。该图像是在长波红外和代表的面辐射。从图像中有两个液体的表面上的稳定的冷却和伸长率（ 广告 ），作为施加电压的增加都达到1-2℃以下，初始（ 一 ）之前，为了喷射的喷射（E）的最低温度从上面的泰勒锥。下液滴反冲提前收取喷射，但很快加入以下联系（EF），排放迅速上升为一种稳定的EHD液桥成立（G）。使用光纤的热探头温度降低证实。下部固着液滴是〜2℃，比上侧锥体由于操作预先温暖;通常在高压容器将达到稍高的温度。剧照补充视频S4（顶锥）和S5（下滴）。上传/ 51819 / 51819fig7highres.jpg"目标="_ blank将"&gt;请点击这里查看该图的放大版本。 <img alt="图8" fo:content-width="5in" src="/files/ftp_upload/51819/51819fig8highres.jpg" width="500" /> 卧式水桥图8热成像火灭绝。代表系列复合中波（3.7-5.0微米）和长波（8.0-9.4微米）的红外图像的特征显示为横向液桥的运行阶段水:（1）点火，（二）扩大，（三）扩展，（四）稳定，（五）分手。在这个图像序列的桥梁被扑灭通过删除系统电源。剧照补充视频S6。 <a href="https://www.jove.com/files/ftp_upload/51819/51819fig8highres.jpg" target="_blank">请点击这里查看</a>更大的版本这个数字。 <img alt="图9" fo:content-width="5in" src="/files/ftp_upload/51819/51819fig9highres.jpg" width="500" /> 。垂直水桥图9热成像火灭绝的代表系列的长波红外（7.5-9.0微米）的图像表征为立式液桥梁运营阶段所示的水:（1）点火，（二）扩大，（C）降低的电压，（D）配位体的形成，（E）分裂成的瑞利-平台的不稳定性的影响下，微滴。经过时间显示在毫秒。背景对比度的过去的帧，以改善液滴的可视化。从补充视频S7的剧照。 <a href="https://www.jove.com/files/ftp_upload/51819/51819fig9highres.jpg" target="_blank">请点击这里查看大图版本</a>锡安这个数字。 <img alt="图10" fo:content-width="5in" src="/files/ftp_upload/51819/51819fig10highres.jpg" width="500" /> 图10热成像在DMSO和甘油水平的桥梁。二甲基亚砜（DMSO）（A）和甘油（ 二）中波（3.7-5.0微米）和长波红外的复合桥排放（8.0-9.4微米）。从补充视频S8（DMSO）和S9（甘油）剧照。 <a href="https://www.jove.com/files/ftp_upload/51819/51819fig10highres.jpg" target="_blank">请点击这里查看该图的放大版本。</a>

Watch this Scientific Journal Video about The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids at JoVE.com

The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

水平和垂直电水液桥是探索高强度的电场和极性液体介质的相互作用简单而强大的工具。基本的设备和操作实例，包括热成像图像，三个液体（ 如水 ，DMSO和甘油）提出的建设。

高压直流电桥从极地介电液的制备

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and ...

the-preparation-electrohydrodynamic-bridges-from-polar-dielectric

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Unit 1

Flow over Immersed Bodies

SCIENTISTS IN ACTION

26.2K 次观看.  Wetsus - Centre of Excellence for Sustainable Water Technology. 水平和垂直电水液桥是探索高强度的电场和极性液体介质的相互作用简单而强大的工具。基本的设备和操作实例，包括热成像图像，三个液体（ 如水 ，DMSO和甘油）提出的建设。 

视频: The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

Separating Beads and Cells in Multi-channel Microfluidic Devices Using Dielectrophoresis and Laminar Flow

Microfluidic devices have advanced cell studies by providing a dynamic fluidic environment on the scale of the cell for studying, manipulating, sorting and counting cells. However, manipulating the cell within the fluidic domain remains a challenge and requires complicated fabrication protocols for forming valves and electrodes, or demands specialty equipment like optical tweezers. Here, we demonstrate that conventional printed circuit boards (PCB) can be used for the non-contact manipulation of cells by employing dielectrophoresis (DEP) for bead and cell manipulation in laminar flow fields for bioactuation, and for cell and bead separation in multichannel microfluidic devices. First, we present the protocol for assembling the DEP electrodes and microfluidic devices, and preparing the cells for DEP. Then, we characterize the DEP operation with polystyrene beads. Lastly, we show representative results of bead and cell separation in a multichannel microfluidic device. In summary, DEP is an effective method for manipulating particles (beads or cells) within microfluidic devices.

Dielectrophoresis (DEP) is an effective method to manipulate cells. Printed circuit boards (PCB) can provide inexpensive, reusable and effective electrodes for contact-free cell manipulation within microfluidic devices. By combining PDMS-based microfluidic channels with coverslips on PCBs, we demonstrate bead and cell manipulation and separation within multichannel microfluidic devices.

使用介电泳分离珠和多通道微流控芯片细胞和层流

Microfluidic devices have advanced cell studies by providing a dynamic fluidic environment on the scale of the cell for studying, manipulating, sorting ...

科研

生物工程

Solid-state Graft Copolymer Electrolytes for Lithium Battery Applications

Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (&lt;80 &deg;C), flammable, and volatile organic electrolytes. These organic based electrolyte systems are viable at ambient temperatures, but require a cooling system to ensure that temperatures do not exceed 80 &deg;C. These cooling systems tend to increase battery costs and can malfunction which can lead to battery malfunction and explosions, thus endangering human life. Increases in petroleum prices lead to a huge demand for safe, electric hybrid vehicles that are more economically viable to operate as oil prices continue to rise. Existing organic based electrolytes used in lithium ion batteries are not applicable to high temperature automotive applications. A safer alternative to organic electrolytes is solid polymer electrolytes. This work will highlight the synthesis for a graft copolymer electrolyte (GCE) poly(oxyethylene) methacrylate (POEM) to a block with a lower glass transition temperature (Tg) poly(oxyethylene) acrylate (POEA). The conduction mechanism has been discussed and it has been demonstrated the relationship between polymer segmental motion and ionic conductivity indeed has a Vogel-Tammann-Fulcher (VTF) dependence. Batteries containing commercially available LP30 organic (LiPF6 in ethylene carbonate (EC):dimethyl carbonate (DMC) at a 1:1 ratio) and GCE were cycled at ambient temperature. It was found that at ambient temperature, the batteries containing GCE showed a greater overpotential when compared to LP30 electrolyte. However at temperatures greater than 60 &deg;C, the GCE cell exhibited much lower overpotential due to fast polymer electrolyte conductivity and nearly the full theoretical specific capacity of 170 mAh/g was accessed.

Lithium ion batteries employ flammable and volatile organic electrolytes that are suitable for ambient temperature applications. A safer alternative to organic electrolytes are solid polymer batteries. Solid polymer batteries operate safely at high temperatures (&gt;120 &deg;C), thus making them applicable to high temperature applications such as deep oil drilling and hybrid electric vehicles. This paper will discuss (a) the polymer synthesis, (b) the polymer conduction mechanism, and (c) provide temperature cycling for both solid polymer and organic electrolytes.

接枝共聚物固态电解质的锂离子电池的应用

Battery safety has been a very important research area over the past decade. Commercially available lithium ion batteries employ low flash point (&lt;80 ...

工程学

Fabrication and Visualization of Capillary Bridges in Slit Pore Geometry

A procedure for creating and imaging capillary bridges in slit-pore geometry is presented. High aspect ratio hydrophobic pillars are fabricated and functionalized to render their top surfaces hydrophilic. The combination of a physical feature (the pillar) with a chemical boundary (the hydrophilic film on the top of the pillar) provides both a physical and chemical heterogeneity that pins the triple contact line, a necessary feature to create stable long but narrow capillary bridges. The substrates with the pillars are attached to glass slides and secured into custom holders. The holders are then mounted onto four axis microstages and positioned such that the pillars are parallel and facing each other. The capillary bridges are formed by introducing a fluid in the gap between the two substrates once the separation between the facing pillars has been reduced to a few hundred micrometers. The custom microstage is then employed to vary the height of the capillary bridge. A CCD camera is positioned to image either the length or the width of the capillary bridge to characterize the morphology of the fluid interface. Pillars with widths down to 250 &#181;m and lengths up to 70 mm were fabricated with this method, leading to capillary bridges with aspect ratios (length/width) of over 1001.

A procedure for creating and imaging capillary bridges in slit-pore geometry is presented. The creation of capillary bridges relies on the formation of pillars to provide a directional physical and chemical heterogeneity to pin the fluid. Capillary bridges are formed and manipulated using microstages and visualized using a CCD camera.

狭缝孔几何中毛细金香桥的制造和可视化

A procedure for creating and imaging capillary bridges in slit-pore geometry is presented. High aspect ratio hydrophobic pillars are fabricated and ...

Development of a 3D Graphene Electrode Dielectrophoretic Device

The design and fabrication of a novel 3D electrode microdevice using 50 &#181;m thick graphene paper and 100 &#181;m double sided tape is described. The protocol details the procedures to construct a versatile, reusable, multiple layer, laminated dielectrophoresis chamber. Specifically, six layers of 50 &#181;m x&#160;0.7 cm x&#160;2 cm graphene paper and five layers of double sided tape were alternately stacked together, then clamped to a glass slide. Then a 700 &#956;m diameter micro-well was drilled through the laminated structure using a computer-controlled micro drilling machine. Insulating properties of the tape layer between adjacent graphene layers were assured by resistance tests. Silver conductive epoxy connected alternate layers of graphene paper and formed stable connections between the graphene paper and external copper wire electrodes. The finished device was then clamped and sealed to a glass slide. The electric field gradient was modeled within the multi-layer device. Dielectrophoretic behaviors of 6 &#956;m polystyrene beads were demonstrated in the 1 mm deep micro-well, with medium conductivities ranging from 0.0001 S/m to 1.3 S/m, and applied signal frequencies from 100 Hz to 10 MHz. Negative dielectrophoretic responses were observed in three dimensions over most of the conductivity-frequency space and cross-over frequency values are consistent with previously reported literature values. The device did not prevent AC electroosmosis and electrothermal flows, which occurred in the low and high frequency regions, respectively. The graphene paper utilized in this device is versatile and could subsequently function as a biosensor after dielectrophoretic characterizations are complete.

A microdevice with high throughput potential is used to demonstrate three-dimensional (3D) dielectrophoresis (DEP) with novel materials. Graphene nanoplatelet paper and double sided tape were alternately stacked; a 700 &#956;m micro-well was drilled transverse to the layers. DEP behavior of polystyrene beads was demonstrated in the micro-well.

三维石墨电极介电泳装置的研制

The design and fabrication of a novel 3D electrode microdevice using 50 &#181;m thick graphene paper and 100 &#181;m double sided tape is described. The ...

Creating Sub-50 Nm Nanofluidic Junctions in PDMS Microfluidic Chip via Self-Assembly Process of Colloidal Particles

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its transparency. Due to the softness of the PDMS material, however, it is challenging to use PDMS for building nanochannels. The channels tend to collapse easily during plasma bonding. In this paper, we present an evaporation-driven self-assembly method of silica colloidal nanoparticles to create nanofluidic junctions with sub-50 nm pores between two microchannels. The pore size as well as the surface charge of the nanofluidic junction is tunable simply by changing the colloidal silica bead size and surface functionalization outside of the assembled microfluidic device in a vial before the self-assembly process. Using the self-assembly of nanoparticles with a bead size of 300 nm, 500 nm, and 900 nm, it was possible to fabricate a porous membrane with a pore size of ~45 nm, ~75 nm and ~135 nm, respectively. Under electrical potential, this nanoporous membrane initiated ion concentration polarization (ICP) acting as a cation-selective membrane to concentrate DNA by ~1,700 times within 15 min. This non-lithographic nanofabrication process opens up a new opportunity to build a tunable nanofluidic junction for the study of nanoscale transport processes of ions and molecules inside a PDMS microfluidic chip.

We propose a simple self-assembly technique of silica colloidal nanoparticles to create a nanofluidic junction between two microchannels in polydimethylsiloxane (PDMS). Using this technique, a nanoporous bead membrane with a pore size down to ~45 nm was built inside a microchannel and applied to electrokinetic preconcentration of DNA samples.

通过胶体粒子自组装过程创建在PDMS微流控芯片分50纳米的纳米流体结

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its ...

High Throughput Microfluidic Rapid and Low Cost Prototyping Packaging Methods

In this work, 3 different packaging and assembly techniques are presented. They can be classified into two categories: one-time use and reusable packaging techniques.
The one-time use packaging technique employs UV-based and temperature curing epoxies to connect microtubes to access holes, wire-bonding for integrated circuit connections, and silver epoxy for electrical connections. This method is based on a robust assembly technique that can support relatively high pressure close to 1 psi and does not need any support to strengthen the microfluidic architecture.
Reusable packaging techniques consist of PDMS-based microtube interconnectors and anisotropic adhesive films for electrical connections. These devices are more sensitive and fragile. Consequently, Plexiglas support is added to the microfluidic structure to improve the electrical contact when anisotropic adhesive films are used, and also to strengthen the microfluidic architecture. In addition, a micromanipulator is needed to maintain tubes while using a thin PDMS layer to connect them to the access holes. Different PDMS layer thicknesses, ranging from 0.45-3 mm, are tested to compare the best adherence versus injection rates. Applied injection rates are varied from 50-300 &#956;l/hr for 0.45-3 mm PDMS layers, respectively. These techniques are mainly applicable for low-pressure applications. However, they can be extended for high-pressure ones through plasma-oxygen process to permanently seal the PDMS to glass substrates. The main advantage of this technique, besides the fact that it is reusable, consists of keeping the device observable when the microchannel length is very short (in the range of 3 mm or lower).

In this article we describe different techniques for microfluidic rapid prototyping platforms. The proposed techniques are based on ultraviolet (UV) sensitive and temperature curing epoxies, polydimethylsiloxane (PDMS) based tubing, wire-bonding, and anisotropic adhesive films. The assembling procedures presented are developed for both one-time use devices as well as reusable microfluidic systems.

In this work, 3 different packaging and assembly techniques are presented. They can be classified into two categories: one-time use and reusable packaging ...

Preparation of Artificial Bilayers for Electrophysiology Experiments

Planar lipid bilayers, also called artificial lipid bilayers, allow you to study ion-conducting channels in a well-defined environment. These bilayers can be used for many different studies, such as the characterization of membrane-active peptides, the reconstitution of ion channels or investigations on how changes in lipid bilayer properties alter the function of bilayer-spanning channels.  Here, we show how to form a planar bilayer and how to isolate small patches from the bilayer, and in a second video  will also demonstrate a procedure for using gramicidin channels to determine changes in lipid bilayer elastic properties.   We also demonstrate the individual steps needed to prepare the bilayer chamber, the electrodes and how to test that the bilayer is suitable for single-channel measurements.

Planar lipid bilayers, also called artificial lipid bilayers, allow you to study ion-conducting channels in a well-defined environment. Here, we demonstrate the individual steps needed to prepare the bilayer chamber, the electrodes and how to test that the bilayer is suitable for single-channel measurements.

电生理实验人工双层膜的制备

Planar lipid bilayers, also called artificial lipid bilayers, allow you to study ion-conducting channels in a well-defined environment. These bilayers can ...

生物学

Microscale Vortex-assisted Electroporator for Sequential Molecular Delivery

Electroporation has received increasing attention in the past years, because it is a very powerful technique for physically introducing non-permeant exogenous molecular probes into cells. This work reports a microfluidic electroporation platform capable of performing multiple molecule delivery to mammalian cells with precise and molecular-dependent parameter control. The system&#8217;s ability to isolate cells with uniform size distribution allows for less variation in electroporation efficiency per given electric field strength; hence enhanced sample viability. Moreover, its process visualization feature allows for observation of the fluorescent molecular uptake process in real-time, which permits prompt molecular delivery parameter adjustments in situ for efficiency enhancement. To show the vast capabilities of the reported platform, macromolecules with different sizes and electrical charges (e.g., Dextran with MW of 3,000 and 70,000 Da) were delivered to metastatic breast cancer cells with high delivery efficiencies (&#62;70%) for all tested molecules. The developed platform has proven its potential for use in the expansion of research fields where on-chip electroporation techniques can be beneficial.

A microfluidic vortex assisted electroporation platform was developed for sequential delivery of multiple molecules into identical cell populations with precise and independent dosage control. The system&#8217;s size based target cell purification step preceding electroporation aided to enhance molecular delivery efficiency and processed cell viability.

微型涡辅助电穿孔的顺序传递分子

Electroporation has received increasing attention in the past years, because it is a very powerful technique for physically introducing non-permeant ...

Generation and Control of Electrohydrodynamic Flows in Aqueous Electrolyte Solutions

To drive electrohydrodynamic (EHD) flows in aqueous solutions, the separation of cation and anion transport pathways is essential because a directed electric body force has to be induced by ionic motions in liquid. On the other hand, positive and negative charges attract each other, and electroneutrality is maintained everywhere in equilibrium conditions. Furthermore, an increase in an applied voltage has to be suppressed to avoid water electrolysis, which causes the solutions to become unstable. Usually, EHD flows can be induced in non-aqueous solutions by applying extremely high voltages, such as tens of kV, to inject electrical charges. In this study, two methods are introduced to generate EHD flows induced by electrical charge separations in aqueous solutions, where two liquid phases are separated by an ion-exchange membrane. Due to a difference in the ionic mobility in the membrane, ion concentration polarization is induced between both sides of the membrane. In this study, we demonstrate two methods. (i) The relaxation of ion concentration gradients occurs via a flow channel that penetrates an ion-exchange membrane, where the transport of the slower species in the membrane selectively becomes dominant in the flow channel. This is a driving force to generate an EHD flow in the liquid. (ii) A long waiting time for the diffusion of ions passing through the ion-exchange membrane enables the generation of an ion-dragged flow by externally applying an electric field. Ions concentrated in a flow channel of a 1 x 1 mm2 cross-section determine the direction of the liquid flow, corresponding to the electrophoretic transport pathways. In both methods, the electric voltage difference required for an EHD flow generation is drastically reduced to near 2 V by rectifying the ion transport pathways.

The rectification of ion transport pathways is an effective method to generate one-directional ion-dragged electrohydrodynamic flows. By setting an ion-exchange membrane in a flow channel, an electrically polarized condition is generated and causes a liquid flow to be driven when an electric field is externally applied.

水电解质溶液中 Electrohydrodynamic 流的产生与控制

To drive electrohydrodynamic (EHD) flows in aqueous solutions, the separation of cation and anion transport pathways is essential because a directed ...

Automated Lipid Bilayer Membrane Formation Using a Polydimethylsiloxane Thin Film

An artificial lipid bilayer, or black lipid membrane (BLM), is a powerful tool for studying ion channels and protein interactions, as well as for biosensor applications. However, conventional BLM formation techniques have several drawbacks and they often require specific expertise and laborious processes. In particular, conventional BLMs suffer from low formation success rates and inconsistent membrane formation time. Here, we demonstrate a storable and transportable BLM formation system with controlled thinning-out time and enhanced BLM formation rate by replacing conventionally used films (polytetrafluoroethylene, polyoxymethylene, polystyrene) to polydimethylsiloxane (PDMS). In this experiment, a porous-structured polymer such as PDMS thin film is used. In addition, as opposed to conventionally used solvents with low viscosity, the use of squalene permitted a controlled thinning-out time via slow solvent absorption by PDMS, prolonging membrane lifetime. In addition, by using a mixture of squalene and hexadecane, the freezing point of the lipid solution was increased (~16 &#176;C), in addition, membrane precursors were produced that can be indefinitely stored and readily transported. These membrane precursors have reduced BLM formation time of &#60; 1 hr and achieved a BLM formation rate of ~80%. Moreover, ion channel experiments with gramicidin A demonstrated the feasibility of the membrane system.

We demonstrate a storable, transportable lipid bilayer formation system. A lipid bilayer membrane can be formed within 1 hr with over 80% success rate when a frozen membrane precursor is brought to ambient temperature. This system will reduce laborious processes and expertise associated with ion channels.