Name: generation and control of electrohydrodynamic flows in aqueous electrolyte solutions
Uploaded: 2018-09-07T14:00:00.000+00:00
Duration: 8 min 41 s
Description: Watch this Scientific Journal Video about Generation and Control of Electrohydrodynamic Flows in Aqueous Electrolyte Solutions at JoVE.com

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1. 整流离子输送引起的 EHD 流量
<ol><li>一种用于整流离子输送通路的流道装置的研制
	<ol>
<li>制作一层聚四氟乙烯模具:<ol>
<li>使用铣削机从聚四氟乙烯 (PTFE) 块中切割 13 x 30 x 10 mm3模具 (见图 2)。或者, 购买定制产品。</li>
			<li>在 PTFE 模具两端的 15 x 18 x 1 毫米3的丙烯酸板与一个塑料胶粘剂, 这将使裂缝在水库解决偏置电极。这些零件可以从一个大盘子里剪下来或购买。</li>
			<li>将 13 x 30 x 1 毫米3的丙烯酸板材粘在聚四氟乙烯模具的顶部和底部表面, 用塑料粘合剂使平面表面清晰地观察。</li>
		</ol>
</li>
		<li>将硅胶弹性体底座和固化剂混合在50毫升管中的比例为 10:1, 并用手摇动管子。</li>
		<li>将液体在真空容器中, 用旋转泵加气。</li>
		<li>把管子从船上取下。将其倒入 40 x 50 x 24 毫米3塑料容器中, 以塑造储层的外层形状, 并将储层模 (见步骤 1.1.1) 放入其中。</li>
		<li>在80摄氏度的热板上烘烤液体的整个身体, 大约4小时。</li>
		<li>烘烤后, 用手将其从 PTFE 模具和外容器中分离出来。用一把手术刀在水库的中心缝上。这将被用来把阴离子交换膜的边缘 (在步骤1.1.16 中准备) 使用镊子。 注: 在以后的电解质溶液中填充了该聚合物, 如图 2所示。</li>
		<li>获得玻璃板 (由特殊顺序) 与圆形18毫米直径或在正方形与18毫米边缘。</li>
		<li>用丙酮、乙醇和纯净水 (按顺序) 在超声波浴中浸泡15分钟, 清洗玻璃板材。</li>
		<li>用气枪将任何残留液体吹走, 或将玻璃板加热5分钟, 约 473 K。</li>
		<li>使用射频溅射, 将镀铬或 Ti 暴露在 Ar 等离子体上的玻璃表面涂上1分钟, 并连续 75 w, 在 75 w 处沉积金薄膜5分钟, 将厚度设置为大约 100 nm。 注: 在用靶金属涂装玻璃表面之前, 样品被设置在真空室中, 用旋转泵和分子扩散泵进行疏散, 直到压力降到 1 x 10−2宾夕法尼亚州。</li>
		<li>用烙铁在金电极表面焊铅。 注: 金电极的形状可能被正方形和螺旋线所取代, 维持足够大的表面积以产生离子电流。</li>
		<li>用镊子, 在储层两端设置涂有金薄膜的玻璃板。这些是偏置电极。</li>
		<li>用剪刀将阴离子交换膜切成 20 x 18 毫米2的长方形。表面面积为13毫米, 高度为10毫米, 暴露于液体中。在这里, 一个箱子刀或手术刀也可以用来切割膜。</li>
		<li>切出一个长方形的 3 x 5.5 毫米2从一个边缘的膜与剪刀。 注: 阴离子膜的厚度为220µm。该膜易于切割与剪刀或框刀。膜的边缘部分固定在腔内的狭缝上。</li>
		<li>用 1 x 1 mm2横截面的不锈钢棒凝固一个1.1.4 块, 其方法与步骤中的1.1.5 相同, 以创建渗透膜的流通道。一夜之间离开建筑, 然后将不锈钢棒拉出外推块。</li>
		<li>用一把手术刀把一个方形的流道切割成 3 x 6 x 4.5 毫米片 (见图 2)。沿外边缘做狭缝, 然后将其附着在矩形切口内的膜上。 注意: 通道的顶面必须水平设置, 以便通过透明壁对流道中的颗粒进行清晰的观察。</li>
	</ol></li>
	<li>实验的制备及预处理方法
	<ol>
<li>在 1 x 10−1、1 x 10−2和 1 x 10−3摩尔/升的浓度下, 通过稀释库存溶液制备氢氧化钠水溶液。</li>
		<li>通过将浓度设置为 4.2 x 10−3体积%, 在步骤1.2.1 中制备的每种氢氧化钠溶液中, 分散2.93 µm 的聚苯乙烯颗粒的平均直径。 注意: 可以适当改变示踪粒子的大小, 以改善可观测性。</li>
		<li>Ultrasonicate 格式的阴离子交换膜 20 x 18 毫米2与一狭缝 3 x 5.5 毫米2 2x 为10分钟在纯净的水中以 100 W 的力量。</li>
		<li>用镊子, 将阴离子交换膜与聚硅烷的流动通道结合到了聚硅烷储层。用微填充4毫升的氢氧化钠溶液。 注: 膜表面和流道浸入溶液中, 所暴露于溶液中的膜表面至少比流道的横断面大100x。</li>
		<li>利用直流电源在2小时的前后向方向应用 2.2 V 的电势, 以提高膜在观测前的电导率。</li>
		<li>用镊子拔出金电极。使用微从储层中取出溶液。</li>
		<li>用镊子在储层中设置新的金电极。用微填充4毫升的氢氧化钠溶液。在解决方案平衡时开始观察。 注意: 它可能需要几分钟的等待时间, 直到自然对流定居下来, 这可以通过观察跟踪粒子的行为来判断。</li>
	</ol></li>
	<li>实验设置和测量系统
	<ol>
<li>将高速互补金属氧化物半导体 (CMOS) 相机的帧速率和曝光时间分别设置为 500 fps 和1毫秒。 注: 如图 1所示, 实验装置设置在与高速 CMOS 相机相连接的显微镜阶段, 以记录粒子运动。该视图在显示器上放大 15, 100X 透镜。</li>
		<li>在应用电势之前, 将微的尖端插入通道端, 将其从通道中移除, 以推动或拉出。</li>
		<li>外部应用电位为 2.2 V 的 Au 偏置电极。使用恒电位仪或直流电源与数字万用表同时监测电气响应。 注: 电压值确定为上限, 避免在溶液中产生 O2和 H2气泡的水电解。</li>
		<li>记录跟踪粒子在计算机上的行为。</li>
		<li>用 Au 探针电极和数字万用表测量流道两端的电位差, 以确认离子浓度梯度触发 EHD 流38,39。</li>
		<li>确定笛卡尔坐标系在通道中心的原点。 注: x轴沿流通道的纵向方向, y轴和z坐标轴分别位于通道横断面的水平和垂直方向, 如图 2所示。透明的双通道允许液体流沿x轴可视化。通过控制焦点的深度, 视图聚焦在z = 0 的xy平面上。流数据独立于测试部分中的x , 但仅在通道的入口和出口附近, 观测点设置在大约0.75 毫米从原点下游, 例如x = 0.75、 y = 0 和z= 0 毫米。</li>
		<li>在一次测量 (十五年代) 以后, 短路电极通过连接他们互相以铅20分钟, 直到解答是平衡的。</li>
		<li>接下来, 将解决方案的整体移动到另一条船上 (例如, 一个10毫升的样品瓶), 并用微搅拌。</li>
		<li>迭代执行实验时, 再次使用微将搅拌溶液倒入腔室。 注: 观察后, 利用粒子图像测速 (PIV) 方法39对 EHD 流速进行评价, 可以利用相应的软件对粒子的位移进行跟踪, 并对速度进行数值计算。在这里省略了 piv 方法的详细说明以及如何使用它们, 因为 piv 分析已被广泛使用, 计算过程取决于所使用的软件和操作系统。</li>
	</ol></li>
</ol>2. 阳离子诱导 EHD 流的观察
<ol><li>
实验装置的研制
	<ol>
<li>根据类似于步骤 1.1.5 1.1.7 中描述的程序, 在底部玻璃板上形成 26 x 10 毫米2表面的 Au 偏置电极。</li>
		<li>使用射频溅射, 将镀铬或 Ti 的玻璃表面涂上2分钟, 在 75 w 处, 将金薄膜沉积在 75 w 的5分钟。 注: 这种电极形状是为了在最窄的通道区域内高度集中电场而确定的。电极表面的比率, 10 x 10 毫米2被暴露对液体, 到渠道的横断面是理想地 100:1;预计这一比例将足以使该通道的电势下降16。</li>
		<li>用烙铁在电极的边缘焊一条引线。</li>
		<li>从大型硅橡胶板, 切出2室, 每一个由 1 x 1 x 1 毫米3流通道放置在两个 10 x 10 x 1 毫米3水库之间, 使用一把外科刀 (见图 3)。这些部件可能会被采用。</li>
		<li>用盒刀或手术刀切割出一个平均厚度为127µm 到 20 x 30 毫米的阳离子交换膜, 如图 3所示。</li>
		<li>通过应用 100 W, 在纯净水中 Ultrasonicate 每部分15分钟。</li>
		<li>用镊子在腔间插入阳离子交换膜, 如图 3所示。这将分离2种不同浓度的电解质溶液。</li>
		<li>按下和密封的分庭和阳离子交换膜的玻璃板, 其尺寸是26毫米的宽度和38毫米长。</li>
	</ol>
</li>
	<li>
解决方案的准备
	<ol>
<li>在 1 x 10−2摩尔/升三 (羟甲基) 氨基甲烷乙二胺 (三 EDTA) 缓冲液中制备平均直径为1.01 µm 的聚苯乙烯微粒的分散体, 其中体积比调整为 1 x 10−2体积%。</li>
		<li>准备1摩尔/升的氯化钾和 1 x 10−2摩尔/升的三 EDTA 混合物。</li>
		<li>将三 edta/聚苯乙烯颗粒和三 edta/氯化钾溶液分别注入下部和上部的腔内,通过从腔体的侧壁插入注射器针。 注: 每室注入的溶液的数量约为210µL。</li>
		<li>等待大约18小时, 直到溶液被平衡, 因为离子的扩散使上层和下层之间的离子浓度差得以放松。 注: 在扩散过程中, 在上部溶液中的 K+和在膜中的 H+将首先穿透膜, 而 Cl−有望跟随它们。</li>
	</ol>
</li>
	<li>
实验设置和测量系统
	<ol>
<li>将在步骤2.1 中开发的实验装置用手放在倒置显微镜的舞台上, 如图 3所示。将显微镜连接到高速 CMOS 相机上, 监测粒子运动的轨迹, 并在计算机上记录观测数据。</li>
		<li>使用函数发生器作为电源, 在两个电极之间应用电位差为6秒的2伏。</li>
		<li>为了证实 EHD 流动是由离子传输引起的, 使用电流表40同时测量离子电流。</li>
		<li>用粒子跟踪测速仪 (PTV) 法分析了粒子的记录轨迹39。 注: 观察后, 用 PTV 法对 EHD 流速进行了评价, 利用适当的软件, 可以对颗粒的位移进行跟踪, 并对速度进行数值计算。这里省略了 PTV 方法的详细说明以及如何使用它们, 因为 PTV 分析已被广泛使用, 计算过程取决于所使用的软件和操作系统。</li>
	</ol>
</li>
</ol>

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B., Hann, J., Renaud, P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+the+surface+charge+on+ion+transport+through+nanoslits.">Effect of the surface charge on ion transport through nanoslits.</a> Physics of Fluids. 17, 100604 (2005).</li><li>Ross, D., Johnson, T. J., Locascio, L. E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Imaging+of+electroosmotic+flow+in+plastic+microchannels.">Imaging of electroosmotic flow in plastic microchannels.</a> Analytical Chemistry. 73, 2509-2515 (2001).</li><li>Hsieh, S. -. S., Lin, H. -. C., Lin, C. -. Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electroosmotic+flow+velocity+measurements+in+a+square+microchannel.">Electroosmotic flow velocity measurements in a square microchannel.</a> Colloid and Polymer Science. 284, 1275-1286 (2006).</li><li>Rubinstein, I., Zaltzman, B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electro-osmotically+induced+convection+at+a+permselective+membrane.">Electro-osmotically induced convection at a permselective membrane.</a> Physical Review E. 62, 2238-2251 (2000).</li><li>Bard, A. J., Faulkner, L. R. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Electrochemical methods, 2nd ed. , 362-363 (2001).</li><li>Brask, A., Goranovi&#263;, G., Jensen, M. 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G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Fabrication+and+characterization+of+electroosmotic+micropumps.">Fabrication and characterization of electroosmotic micropumps.</a> Sensors and Actuators B: Chemical. 79, 107-114 (2001).</li><li>Bhaumik, S. K., Roy, R., Chakraborty, S., DasGupta, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Low-voltage+electrohydrodynamic+micropumping+of+emulsions.">Low-voltage electrohydrodynamic micropumping of emulsions.</a> Sensors and Actuators B: Chemical. 193, 288-293 (2014).</li><li>El Moctar, A. O., Aubry, N., Batton, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electro-hydrodynamic+micro-fluidic+mixer.">Electro-hydrodynamic micro-fluidic mixer.</a> Lab on a Chip. 3, 273-280 (2003).</li><li>Bart, S. F., Tavrow, L. S., Mehregany, M., Lang, J. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfabricated+electrohydrodynamic+pumps.">Microfabricated electrohydrodynamic pumps.</a> Sensors and Actuators A: Physical. 21, 193-197 (1990).</li><li>Ashikhmin, I. A., Stishkov, Y. K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Effect+of+insulating+walls+on+the+structure+of+electrodynamic+flows+in+a+channel.">Effect of insulating walls on the structure of electrodynamic flows in a channel.</a> Technical Physics. 57, 1181-1187 (2012).</li><li>Yano, A., Doi, K., Kawano, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Observation+of+electrohydrodynamic+flow+through+a+pore+in+ion-exchange+membrane.">Observation of electrohydrodynamic flow through a pore in ion-exchange membrane.</a> International Journal of Chemical Engineering and Applications. 6, 254-257 (2015).</li><li>Doi, K., Yano, A., Kawano, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Electrohydrodynamic+flow+through+a+1+mm2+cross-section+pore+placed+in+an+ion-exchange+membrane.">Electrohydrodynamic flow through a 1 mm2 cross-section pore placed in an ion-exchange membrane.</a> The Journal of Physical Chemistry B. 119, 228-237 (2015).</li><li>Yano, A., Shirai, H., Imoto, M., Doi, K., Kawano, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concentration+dependence+of+cation-induced+electrohydrodynamic+flow+passing+through+an+anion+exchange+membrane.">Concentration dependence of cation-induced electrohydrodynamic flow passing through an anion exchange membrane.</a> Japanese Journal of Applied Physics. 56, 097201 (2017).</li><li>Nagura, R., Doi, K., Kawano, S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterisation+of+microparticle+transport+driven+by+ionic+current+conditions+in+electrically+polarized+aqueous+solutions.">Characterisation of microparticle transport driven by ionic current conditions in electrically polarized aqueous solutions.</a> Micro &amp; Nano Letters. 12, 526-531 (2017).</li><li>Doi, K., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Nonequilibrium+ionic+response+of+biased+mechanically+controllable+break+junction+(MCBJ)+electrodes.">Nonequilibrium ionic response of biased mechanically controllable break junction (MCBJ) electrodes.</a> The Journal of Physical Chemistry C. 118, 3758-3765 (2014).</li></ol>

作者没有什么可透露的。

本研究的目的是将阳离子和阴离子与水溶液中的空间分布和传输数分开。使用阴离子交换膜, 阴离子和阳离子的传输可以在膜和渗透膜的流动通道中得到矫正。二者择一地, 分离高和低浓度解决方案的阳离子交换膜工作, 在相当长的等待时间后产生电极化溶液。因此, 整流离子电流成功地降低了应用电压, 以诱导离子拖动 EHD 流。
在这里提出的方法是适用于低应用电压的水溶液, ...

近年来, 液体流量控制技术引起了人们的广泛关注, 因为它对微 nanofluidic 器件的应用有很大的兴趣1、2、3、4、5、6,7,8,9,10,11,12,13,14,15. 在极性溶液中, 如水溶液和离子液体, 离子和带电粒子通常会在液体流动中产生电荷。这种极化粒子的传输提供了各种应用的扩展, 如单分子操作6、10、11、13、14,15,16,17、离子二极管器件12、18、液体流量控制19、20、21、22。EHD 流是 Stuetzer 1 以来液体流量控制系统的一个适用现象,2发明了离子拖动泵。Melcher 和泰勒3发表了一篇重要文章, 其中 EHD 流的理论框架进行了很好的回顾和一些突出的实验也证明。萨维尔4和他的工友23,24贡献了 EHD 技术的以下扩展在液体。然而, 有一些限制, 以诱导液体流驱动的电力, 因为有数以万计的 kV 必须应用在液体中注入电荷的非极性溶液, 如油, 极化他们1,2,3. 这是水溶液的一个缺点, 因为电位高于 1.23 V 的电电解会改变溶液的特性, 使溶液不稳定。
在微和 nanofluidic 通道中, 通道壁的表面电荷导致 counterions 在外部应用电场25、26、27 下有效诱导渗流 (EOFs) 的浓度. ,28,29。使用 EOFs, 一些液体泵浦技术已应用于水溶液中, 降低了电压30,31,32。另一方面, EOFs 被限制在微观和 nanospaces 中产生, 而表面区域比液体体积更具优势。此外, 由于高度集中离子的传输非常接近壁面, 如在电双层, 滑移边界只导致液体流动, 这可能不足以使压力梯度7,8,22,26,27. 用于 EOF 的应用需要微调, 如通道尺寸和盐浓度。相比之下, 如果可以降低应用电压, 以避免降解溶剂, 则由身体力量驱动的 EHD 流似乎可以用于运输质量和能量。最近, 一些研究人员提出了低电压33、34、35、36EHD 流的应用。虽然这些技术尚未实施, 但预计边界将会扩大。
在以前的研究中, 我们还对水溶液37、38、39、40中的 EHD 流进行了实验和理论研究。在电场作用下, 离子传输通路的校正是产生带电的溶液的有效方法。通过使用离子交换膜和通过膜的流动通道, 我们能够矫正离子电流。在应用阴离子交换膜时, 离子集中在流道上, 将溶剂拖走, 形成了 EHD 流37、38、39。离子和阴离子电流分离的一个重要的因素是在不同类型的阳离子和阴离子的流动。离子交换膜由于离子选择性而有效地调节了流动性。从41应用电场影响的离子电流密度的角度研究了离子传输现象。这些研究为发展单一分子的操作技术, 即微粒子和纳米微粒, 产生了丰硕的成果, 其运动受到热涨落11、16、17 的强烈影响..EOFs 和 EHD 流量预计将扩大精确流量控制方法和压力梯度的各种。
在本研究中, 我们演示了两种在水溶液中驱动 EHD 流的方法。首先, 氢氧化钠溶液用于工作流体驱动 EHD 流37,38,39。阴离子交换膜将液体分离成两部分。一个烷的流通道, 其截面为 1 x 1 毫米, 长度为3毫米, 穿透膜。利用 2.2 V 的电势, 沿电场诱导 Na+、H+和 OH−离子的电泳传输。阴离子交换膜和流道有效地分离出离子传输通路, 在那里, 阴离子主要通过膜和阳离子集中在流道中, 虽然两种通常在相反方向移动,维护 electroneutrality。因此, 这种情况不会造成液体流动的驱动力。这种结构对于产生一个 EHD 流, 其流速达到1毫米/秒在通道中的顺序是至关重要的, 因为由外部电场加速的高浓度阳离子会拖累溶剂分子。EHD 流是通过显微镜和高速相机观察和记录的, 如图 1所示。第二, 由离子交换膜分离的两个液相之间的浓度差导致了通过离子交换膜40产生的电极化条件。在这项研究中, 我们发现了相当长的等待时间的重要性, 平衡离子分布和相应的电势, 这会导致更好的条件适用于身体的力量在液体中。通过离子交换膜, 实现了弱极化条件。在这种情况下, 外部应用电场诱导定向离子传输, 在液体中产生体力, 因此, 从离子到溶剂的动量转移发展出 EHD 流。
如上所述, 目前的装置成功地大幅度降低了应用电压差到几个伏特, 因此这种方法可以用于水溶液, 虽然传统的电荷注入方法需要数伏和仅限于非水溶液的应用。

<table><tbody><tr><td>Sylgard 184</td><td>Dow Corning Corp.</td><td>3097366-0516, 3097358-1004</td><td>PDMS</td></tr><tr><td>Acetone</td><td>Wako Pure Chemical Industries, Ltd.</td><td>012-00343</td><td></td></tr><tr><td>Ethanol</td><td>Wako Pure Chemical Industries, Ltd.</td><td>054-00461</td><td></td></tr><tr><td>0.1 mol/L Sodium Hydroxide Solution</td><td>Wako Pure Chemical Industries, Ltd.</td><td>196-02195</td><td></td></tr><tr><td>Pottasium Chloride</td><td>Wako Pure Chemical Industries, Ltd.</td><td>163-03545</td><td></td></tr><tr><td>Tris-EDTA buffer 100x concentrate</td><td>Sigma-Aldrich Co. LLC.</td><td>T9285-10014L</td><td></td></tr><tr><td>2.93 &amp;mu;m polystyrene particle</td><td>Merck KGaA</td><td>L300 Rouge</td><td>Tracer particle</td></tr><tr><td>1.01 &amp;mu;m polystyrene particle</td><td>Merck KGaA</td><td>K100(23716)</td><td>Tracer particle</td></tr><tr><td>Anion exchange membrane</td><td>ASTOM Corp.</td><td>Neosepta AHA</td><td></td></tr><tr><td>Gold (Au)</td><td>Furuuchi Chemical Corp.</td><td>AUT-13301X</td><td>Sputtering target metal</td></tr><tr><td>Titanium</td><td>Furuuchi Chemical Corp.</td><td>TIT-72301X</td><td>Sputtering target metal</td></tr><tr><td>Chromium</td><td>Furuuchi Chemical Corp.</td><td>CRT-24301X</td><td>Sputtering target metal</td></tr><tr><td>Hight-speed CMOS camera</td><td>Keyence Corp.</td><td>VW-600M</td><td></td></tr><tr><td>Microscope</td><td>Keyence Corp.</td><td>VW-9000</td><td></td></tr><tr><td>Data logger</td><td>Keyence Corp.</td><td>NR-500, NR-HA08</td><td></td></tr><tr><td>Laser displacement meter</td><td>Keyence Corp.</td><td>LK-G5000, LK-H008W</td><td></td></tr><tr><td>PIV and PTV software</td><td>DITECT Co. Ltd.</td><td>Flownizer 2D</td><td></td></tr><tr><td>Potentiostat</td><td>AMTEK Inc.&amp;nbsp;</td><td>VersaSTAT4</td><td></td></tr><tr><td>Inverted microscope</td><td>Olympus Corp.</td><td>IX73</td><td></td></tr><tr><td>High-speed CMOS camera</td><td>Andor Technology Ltd.</td><td>Zyla 5.5 sCMOS</td><td></td></tr><tr><td>Function generator</td><td>NF Corp.&amp;nbsp;</td><td>WF1945B</td><td></td></tr><tr><td>Function generator</td><td>NF Corp.&amp;nbsp;</td><td>WF1973</td><td></td></tr><tr><td>Ultrasonic cleaner</td><td>AS ONE Corp.</td><td>AS22GTU</td><td></td></tr><tr><td>Rotary pump</td><td>ULVAC, Inc.</td><td>G-100S</td><td>Degas liquid PDMS</td></tr><tr><td>Rotary pump</td><td>ULVAC, Inc.</td><td>GLD-201A</td><td>Sputtering&amp;nbsp;</td></tr><tr><td>Molecular diffusion pump</td><td>ULVAC, Inc.</td><td>VPC-400</td><td>Sputtering</td></tr></tbody></table>

generation and control of electrohydrodynamic flows in aqueous electrolyte solutions

为了驱动 electrohydrodynamic (EHD) 在水溶液中的流动, 阳离子和阴离子传输通路的分离是必不可少的, 因为在液体中离子运动必须诱导出定向的电体力。另一方面, 正负电荷相互吸引, electroneutrality 在平衡条件下处处保持。此外, 必须抑制施加电压的增加, 以避免水电解, 从而使溶液变得不稳定。通常, 在非水溶液中, EHD 流可以通过应用极高的电压 (如伏伏特) 来注入电荷来诱导。在这项研究中, 引入两种方法来产生由电荷分离引起的 EHD 流, 在水溶液中, 两个液相由离子交换膜分离。由于膜离子流动的不同, 膜的两侧产生离子浓度极化。在本研究中, 我们演示了两种方法。(i) 离子浓度梯度的松弛是通过渗透离子交换膜的流道而产生的, 在这种通道中, 膜中较慢的物种在流动通道中有选择性地成为主导。这是在液体中产生 EHD 流的驱动力。(二) 通过离子交换膜传播离子的时间长, 可以通过外部应用电场产生离子拖曳流。离子集中在流道的 1 x 1 毫米2剖面上, 确定液流方向, 对应于电泳输送通路。在这两种方法中, 通过整流离子传输通路, EHD 流产生的电压差急剧降低到接近 2 V。

图 4(视频图) 显示了 EHD 流产生的一个代表性结果, 这是由于在该协议的步骤1中, 离子传输通路和高度集中的阳离子的整流导致了通道内的液体流动。图 5显示了 PIV 分析的结果, 其中20个数据点靠近通道中心 (y = z = 0 毫米) 的平均值。在 1 x 10−1摩尔/L 氢氧化钠溶液的情况下, 当在t = 5 s 上应用 2.2 V 的电...

Watch this Scientific Journal Video about Generation and Control of Electrohydrodynamic Flows in Aqueous Electrolyte Solutions at JoVE.com

Generation and Control of Electrohydrodynamic Flows in Aqueous Electrolyte Solutions

离子传输通路的校正是产生单向离子拖曳 electrohydrodynamic 流的有效方法。通过在流道中设置离子交换膜, 产生电极化条件, 并在外部应用电场时使液体流动被驱动。

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 ...

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8.8K 次观看.  Osaka University. 离子传输通路的校正是产生单向离子拖曳 electrohydrodynamic 流的有效方法。通过在流道中设置离子交换膜, 产生电极化条件, 并在外部应用电场时使液体流动被驱动。

视频: Generation and Control of Electrohydrodynamic Flows in Aqueous Electrolyte Solutions

Waste Water Derived Electroactive Microbial Biofilms: Growth, Maintenance, and Basic Characterization

The growth of anodic electroactive microbial biofilms from waste water inocula in a fed-batch reactor is demonstrated using a three-electrode setup controlled by a potentiostat. Thereby the use of potentiostats allows an exact adjustment of the electrode potential and ensures reproducible microbial culturing conditions. During growth the current production is monitored using chronoamperometry (CA). Based on these data the maximum current density (jmax) and the coulombic efficiency (CE) are discussed as measures for characterization of the bioelectrocatalytic performance. Cyclic voltammetry (CV), a nondestructive, i.e. noninvasive, method, is used to study the extracellular electron transfer (EET) of electroactive bacteria. CV measurements are performed on anodic biofilm electrodes in the presence of the microbial substrate, i.e. turnover conditions, and in the absence of the substrate, i.e. nonturnover conditions, using different scan rates. Subsequently, data analysis is exemplified and fundamental thermodynamic parameters of the microbial EET are derived and explained: peak potential (Ep), peak current density (jp), formal potential (Ef) and peak separation (&#916;Ep). Additionally the limits of the method and the state-of the art data analysis are addressed. Thereby this video-article shall provide a guide for the basic experimental steps and the fundamental data analysis.

Chronoamperometric growth of anodic electroactive microbial biofilms in a fed-batch reactor using a three-electrode setup, controlled by a potentiostat, is demonstrated. The extracellular electron transfer is characterized using cyclic voltammetry in the presence of the electron donor and in the absence of the electron donor. Fundamental data analysis is demonstrated.

The growth of anodic electroactive microbial biofilms from waste water inocula in a fed-batch reactor is demonstrated using a three-electrode setup ...

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环境科学

The Preparation of Electrohydrodynamic Bridges from Polar Dielectric Liquids

Horizontal and vertical liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields (8-20 kV/cm) and polar dielectric liquids. These bridges are unique from capillary bridges in that they exhibit extensibility beyond a few millimeters, have complex bi-directional mass transfer patterns, and emit non-Planck infrared radiation. A number of common solvents can form such bridges as well as low conductivity solutions and colloidal suspensions. The macroscopic behavior is governed by electrohydrodynamics and provides a means of studying fluid flow phenomena without the presence of rigid walls. Prior to the onset of a liquid bridge several important phenomena can be observed including advancing meniscus height (electrowetting), bulk fluid circulation (the Sumoto effect), and the ejection of charged droplets (electrospray). The interaction between surface, polarization, and displacement forces can be directly examined by varying applied voltage and bridge length. The electric field, assisted by gravity, stabilizes the liquid bridge against Rayleigh-Plateau instabilities. Construction of basic apparatus for both vertical and horizontal orientation along with operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

Horizontal and vertical electrohydrodynamic liquid bridges are simple and powerful tools for exploring the interaction of high intensity electric fields and polar dielectric liquids. The construction of basic apparatus and operational examples, including thermographic images, for three liquids (e.g., water, DMSO, and glycerol) is presented.

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 ...

工程学

AC Electrokinetic Phenomena Generated by Microelectrode Structures

The field of AC electrokinetics is rapidly growing due to its ability to perform dynamic fluid and particle manipulation on the micro- and nano-scale, which is essential for Lab-on-a-Chip applications. AC electrokinetic phenomena use electric fields to generate forces that act on fluids or suspended particles (including those made of dielectric or biological material) and cause them to move in astonishing ways1, 2. Within a single channel, AC electrokinetics can accomplish many essential on-chip operations such as active micro-mixing, particle separation, particle positioning and micro-pattering. A single device may accomplish several of those operations by simply adjusting operating parameters such as frequency or amplitude of the applied voltage. Suitable electric fields can be readily created by micro-electrodes integrated into microchannels. It is clear from the tremendous growth in this field that AC electrokinetics will likely have a profound effect on healthcare diagnostics3-5, environmental monitoring6 and homeland security7.

In general, there are three AC Electrokinetic phenomena (AC electroosmosis, dielectrophoresis and AC electrothermal effect) each with unique dependencies on the operating parameters. A change in these operating parameters can cause one phenomena to become dominant over another, thus changing the particle or fluid behavior. 

It is difficult to predict the behavior of particles and fluids due to the complicated physics that underlie AC electrokinetics. It is the goal of this publication to explain the physics and elucidate particle and fluid behavior. Our analysis also covers how to fabricate the electrode structures that generate them, and how to interpret a wide number of experimental observations using several popular device designs. This video article will help scientists and engineers understand these phenomena and may encourage them to start using AC Electrokinetics in their research.

Manipulating fluids and suspended particles in the micro- and nano-scale is becoming more of a reality as enabling technologies, like AC electrokinetics, continue to develop. Here, we discuss the physics behind AC electrokinetics, how to fabricate these devices and how to interpret the experimental observations.

微电极结构产生的交流电动现象

The field of AC electrokinetics is rapidly growing due to its ability to perform dynamic fluid and particle manipulation on the micro- and nano-scale, ...

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 ...

生物工程

Generation of Size-controlled Poly (ethylene Glycol) Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. This paper proposes a semi-three-dimensional (semi-3D) flow-focusing microfluidic chip for droplet formation. The polydimethylsiloxane (PDMS) chip was fabricated using the multi-layer soft lithography method. Hexadecane containing surfactant was used as the continuous phase, and PEGDA with the ultraviolet (UV) photo-initiator was the dispersed phase. Surfactants allowed the local surface tension to drop and formed a more cusped tip which promoted breaking into tiny micro-droplets. As the pressure of dispersed phase was constant, the size of droplets became smaller with increasing continuous phase pressure before dispersed phase flow was broken off. As a result, droplets with size variation from 1 &#181;m to 80 &#181;m in diameter could be selectively achieved by changing the pressure ratio in two inlet channels, and the average coefficient of variation was estimated to be below 7%. Furthermore, droplets could turn into micro-beads by UV exposure for photo-polymerization. Conjugating biomolecules on such micro-beads surface have many potential applications in the fields of biology and chemistry.

Generation of Size-controlled Poly ethylene Glycol Diacrylate Droplets via Semi-3-Dimensional Flow Focusing Microfluidic Devices

Here, we present a protocol to illustrate the fabrication processes and verifying experiments of a semi-three-dimensional (semi-3D) flow-focusing microfluidic chip for droplet formation.

Semi-3-Dimensional 流聚焦微流控装置产生尺寸控制的聚乙二醇二丙烯酸酯液滴

Uniform and size-controllable poly (ethylene glycol) diacrylate (PEGDA) droplets could be produced via the flow focusing process in a microfluidic device. ...

Controlling Flow Speeds of Microtubule-Based 3D Active Fluids Using Temperature

We present a method for using temperature to tune the flow speeds of kinesin-driven, microtubule-based three-dimensional (3D) active fluids. This method allows for tuning the speeds in situ without the need to manufacture new samples to reach different desired speeds. Moreover, this method enables the dynamic control of speed. Cycling the temperature leads the fluids to flow fast and slow, periodically. This controllability is based on the Arrhenius characteristic of the kinesin-microtubule reaction, demonstrating a controlled mean flow speed range of 4&#8211;8 &#181;m/s. The presented method will open the door to the design of microfluidic devices where the flow rates in the channel are locally tunable without the need for a valve.

The goal of this protocol is to use temperature to control the flow speeds of three-dimensional active fluids. The advantage of this method not only allows for regulating flow speeds in situ but also enables dynamic control, such as periodically tuning flow speeds up and down.

使用温度控制基于微管的3D活性流体的流速

We present a method for using temperature to tune the flow speeds of kinesin-driven, microtubule-based three-dimensional (3D) active fluids. This method ...

Aqueous Droplets Used as Enzymatic Microreactors and Their Electromagnetic Actuation

For the successful implementation of microfluidic reaction systems, such as PCR and electrophoresis, the movement of small liquid volumes is essential. In conventional lab-on-a-chip-platforms, solvents and samples are passed through defined microfluidic channels with complex flow control installations. The droplet actuation platform presented here is a promising alternative. With it, it is possible to move a liquid drop (microreactor) on a planar surface of a reaction platform (lab-in-a-drop). The actuation of microreactors on the hydrophobic surface of the platform is based on the use of magnetic forces acting on the outer shell of the liquid drops which is made of a thin layer of superhydrophobic magnetite particles. The hydrophobic surface of the platform is needed to avoid any contact between the liquid core and the surface to allow a smooth movement of the microreactor. On the platform, one or more microreactors with volumes of 10 &#181;L can be positioned and moved simultaneously. The platform itself consists of a 3 x 3 matrix of electrical double coils which accommodate either neodymium or iron cores. The magnetic field gradients are automatically controlled. By variation of the magnetic field gradients, the microreactors' magnetic hydrophobic shell can be manipulated automatically to move the microreactor or open the shell reversibly. Reactions of substrates and corresponding enzymes can be initiated by merging the microreactors or bringing them into contact with surface immobilized catalysts.

Lab-in-a-drop reaction systems allow the versatile implementation of complex reactions in a microfluidic scale. An automated actuation platform consisting of a 3 x 3 matrix of electromagnetic coils was developed and successfully used to merge two 10 &#181;L microreactors and thereby initiate an enzymatic reaction in the resulting liquid marbles.

用作酶反应器的水滴及其电磁驱动

For the successful implementation of microfluidic reaction systems, such as PCR and electrophoresis, the movement of small liquid volumes is essential. In ...

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 ...

Glass-Based Devices to Generate Drops and Emulsions

In this manuscript, three different step-by-step protocols to generate highly monodisperse emulsion drops using glass-based microfluidics are described. The first device is built for the generation of simple drops driven by gravity. The second device is designed to generate emulsion drops in a coflowing scheme. The third device is an extension of the coflowing device with the addition of a third liquid that acts as an electric ground, allowing the formation of electrified drops that subsequently discharge. In this setup, two of the three liquids have an appreciable electrical conductivity. The third liquid mediates between these two and is a dielectric. A&#160;voltage difference applied between the two conducting liquids creates an electric field that couples with hydrodynamic stresses of the coflowing liquids, affecting the jet and drop formation process. The addition of the electric field provides a path to generate smaller drops than in simple coflow devices and for generating particles and fibers with a wide range of sizes.

Here, a protocol to manufacture glass-based microfluidic devices used for generating highly monodisperse emulsions with controlled drop size is presented.

基于玻璃的设备，用于产生液滴和乳液

In this manuscript, three different step-by-step protocols to generate highly monodisperse emulsion drops using glass-based microfluidics are described. ...

Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone

The ion concentration polarization (ICP) phenomenon is one of the most prevailing methods to preconcentrate low-abundance biological samples. The ICP induces a noninvasive region for charged biomolecules (i.e., the ion depletion zone), and targets can be preconcentrated on this region boundary. Despite the high preconcentration performances with ICP, it is difficult to find the operating conditions of non-propagating ion depletion zones. To overcome this narrow operating window, we recently developed a new platform for spatiotemporally fixed preconcentration. Unlike preceding methods that only use ion depletion, this platform also uses the opposite polarity of the ICP (i.e., ion enrichment) to stop the propagation of the ion depletion zone. By confronting the enrichment zone with the depletion zone, the two zones merge together and stop. In this paper, we describe a detailed experimental protocol to build this spatiotemporally defined ICP platform and characterize the preconcentration dynamics of the new platform by comparing them with those of the conventional device. Qualitative ion concentration profiles and current-time responses successfully capture the different dynamics between the merged ICP and the stand-alone ICP. In contrast to the conventional one that can fix the preconcentration location at only ~5 V, the new platform can produce a target-condensed plug at a specific location in the broad ranges of operating conditions: voltage (0.5-100 V), ionic strength (1-100 mM), and pH (3.7-10.3).

The protocol for a novel ion concentration polarization (ICP) platform that can stop the propagation of the ICP zone, regardless of the operating conditions is described. This unique ability of the platform lies in the use of merging ion depletion and enrichment, which are two polarities of the ICP phenomenon.

并列的合并离子交换膜之间的离子浓差极化，以块极化区的传播

The ion concentration polarization (ICP) phenomenon is one of the most prevailing methods to preconcentrate low-abundance biological samples. The ICP ...