Name: a method to manipulate surface tension of a liquid metal via surface oxidation and reduction
Uploaded: 2016-01-26T19:00:00.000+00:00
Duration: 9 min 20 s
Description: Watch this Scientific Journal Video about A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction at JoVE.com

The authors acknowledge support from Samsung, the NC State Chancellors Innovation Funds, NSF (CAREER CMMI-0954321 and Triangle MRSEC DMR-1121107), and Air Force Research Labs.

1.操纵液态金属在电解液的界面张力<ol><li>氧化<ol><li>倾的含水电解质（酸性或碱性）到培养皿。以确保该氧化物完全除去，可使用的酸或碱与浓度大于0.1M的24（如1 M氢氧化钠或1M的HCl）。使用体积，将填补菜到大约1-3毫米的深度。避免与这些解决方案的皮肤接触。 </li><li>用注射器放置在该电解质的镓基合金的下降（最佳之间10-500微升）。实例包括共晶镓铟（EGAIN）或镓铟锡（Galinstan）。如果纯镓时，暖电解质到至少30℃，以防止冻结。 </li><li>放置一个铜线到液体金属建立工作电极。使用铜线的直径小于所述下降，以及使用根据数字万用表制造商的说明步骤ensure该导线具有的&lt;1Ω的电阻。在酸或碱，液体金属将润湿铜，从而形成良好的电接触。 </li><li>放置一个导电对电极（如铜，石墨，铂等 ）在溶液中，但不与金属液接触。如果反电极具有&lt;1Ω的电阻，它的尺寸是不相关的。 </li><li>的电线连接到一个电压源和施加正电位加到液态金属。对于小的形状变形，应用正电压&lt;1 V.对于较大的形状的变形（和液体金属朝向反电极的移动），申请&gt; 1 V 注意:溶液的浓度，并从反电极下降的距离决定以诱导改变界面张力以来的电化学表面氧化的速率竞争与氧化物溶解的电解质的速率所需的电压。 </li></ol></l我&gt; <li>减少<ol><li>分配液体金属的压降（10-500微升）从注射器到一个空的皮氏培养皿。 </li><li>倾的中性水电解质放入培养皿（例如1M的氟化钠（NaF）或1M氯化钠（NaCl）中），以该浸没金属的水平。 注意:使用酸性（pH值&lt;3）或碱性溶液（pH&gt; 10）将导致氧化物自发地溶解。 </li><li>放置一个铜线到液体金属作为工作电极，和一导线（例如，铜）到电解质作为反电极。 </li><li>的电线连接到一个电压源和施加负电位加到液态金属。应用大约-1V时，除去表面氧化膜，导致金属从基材dewet。金属应dewet上最接近一边对电极。 </li><li>施加更大的负电位（&lt;-1Ⅴ）完全去除氧化物层。避免将excessively大的负电压，以防止氢气泡从出现在液态金属由于还原电解质。 </li></ol></li></ol>通过固着液滴2.表面张力测量<ol><li>使用激光切割机或铣削刀具，切割距离市中心的直接路径一块聚甲基丙烯酸甲酯（约1毫米厚）的边缘，不要一路过关斩将的PMMA的厚度切的路径。只有削减约一半。这一块将作为底物的液体金属。其它平面和电绝缘材料，如玻璃，陶瓷，或聚合物也可以作为基材。 </li><li>使用相同的工具，切断通过聚甲基丙烯酸甲酯的中心的1毫米2孔。 </li><li>利用路径作为引导，只有暴露在聚甲基丙烯酸甲酯的中心的前端运行绝缘铜线。定位导线，以便它突出在PMMA表面。密封线到位了防漏胶。切导线只是聚甲基丙烯酸甲酯的表面上方，但不让它延伸太远（超出〜100微米），或者它会扰乱滴的形状。 </li><li>磁带上的​​聚甲基丙烯酸甲酯片分解成通过其能够获得清晰的图像的透明容器。填充容器用1M的NaOH，然后将液态金属的25-50微升滴在突出铜线。此线将作为工作电极和将润湿液滴。 </li><li>放置一个铂网状反电极和饱和银/氯化银（银/氯化银）参考电极，在溶液中。连接所有的电极，以恒电位。 </li><li>放置在容器中的接触角测角仪，使液滴的表面轮廓清晰可见。使用恒电位仪来控制电压相对于参考电极，并使用测角器来测量的形状和下降，从而界面张力。确保测角仪能够测量座滴界面tensi的上;但也可以使用从一个水平安装的照相机25拍摄的图像降定制轴对称形状分析。 </li></ol> 3.毛细管注入<ol><li>填充的1M氢氧化钠的溶液的玻璃毛细管。毛细管直径应为约1毫米。 </li><li>放置针对一滴液态金属的毛细平齐的一端。对准毛细管，使得它与表（即，垂直于重力）的表面平行。避免液态金属下跌，电解质填充毛细管之间的空气间隙。使用擦拭，轻拍掉任何多余的电解液可能在装配过程中已经泄漏。 </li><li>放置一个铜线（工作电极）的液态金属，和导电对电极（例如铜线）在毛细管的开口端，使得它接触溶液。 </li><li>的电线连接到一个电压源和施加正电位加到液态金属。液态金属应该开始填写的Capillary（避免出现大的潜力，这将导致在反电极过量泡沫的形成）。 </li></ol> 4.毛细管提款<ol><li>利用软光刻26和复制成型技术制造聚二甲基硅氧烷（PDMS）组成的微流体通道。制作渠道是约100至1000微米宽，100微米高，而25至65毫米长。 注:通道尺寸1000微米宽，100微米高，65毫米长的通道产生一致的结果，但其他人也可以正常工作。另外，使用玻璃毛细管（例如，1毫米直径，硼硅玻璃）代替PDMS微通道。 </li><li>注入液态金属手动或使用注射泵，以完全填充通道任一（即，6.5毫米3为1000微米宽，100微米高，和65毫米长的信道）。 </li><li>使用已经浸渍在1M的NaOH或1M的HCl棉签，除去里的过量从通道的所述入口（和，如果需要的话，出口）嚼食金属，使得金属保持与PDMS的顶面齐平。 </li><li>淹没在电解液（如，1M NaCl）中的通道的一端，并放置在阳极（例如，铜，铂，或钨的金属丝），使得其接触电解质而不是金属。 </li><li>在通道的另一端，与一个单独的电极（例如，铜导线）在金属表面上，使液体金属本身作为阴极。 </li><li>连接这些电线（即，阳极和阴极），以一电压源或恒电位，并完成电路。用于三电极系统中，放置基准电极，使得它几乎没有浸没入电解液的下降。 </li><li>之前进行还原电压，安装在三脚架上，或在显微镜摄像机记录实验。使用自动对焦模式，以获得一切的焦点。利用手动对焦有一个更好的控制景深，白平衡，及ISO的。根据需要，使用较高的光圈值（ 即 11或更高版本），1/100快门，自动白平衡和自动ISO。 </li><li>开始录制的实验。应用大约-1 V到从微通道撤出液体金属。转电压关闭，以使金属以停止移动的中性电解质。 </li></ol>

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The authors have nothing to disclose.

<html>此方法控制使用小电压来驱动的表面氧化物的沉积和去除镓基液体金属的表面张力。尽管该方法只适用于在电解质溶液，它简单，和工作在多种不同的条件，但也有微妙之处值得​​留意。在无电势的，酸性和碱性溶液蚀刻掉氧化物27。的氧化电势的应用驱动表面氧化物在所有水电解液，包括酸性和碱性溶液的形成。然而，该氧化物在酸性或碱性溶液溶解竞争与氧化物的沉积，以防止过多的堆积氧化物层。一个厚的氧化层的形成抑制了流动，想必由于氧化提供了机械屏障的移动。这种抑制可以扩展期间是有害的，而且还提供了一种方法，以稳定该金属的形状。 e_content"&gt;界面张力作为电位的函数是连续变化的，表面张力是在最大去除表面氧化物的潜力。电位那些更还原性（更负）将略微降低表面张力由于经典电毛细管（参， 图1B）。这一减少继续作为电位直到法拉第过程 （如氢形成）出现在表面上的功能。 与此相反，在表面张力在电位下降显著其中氧化物第一形式（参见图1B）。增加（正）电位继续降低的表面张力，这可能是由于更好的覆盖表面的氧化物的。超出一个"临界势"，下降​​将使开始扩频无限制，形成分形状图案并朝向反电极迁移。这种运动继续直到电压被移除，或直到降打破CON圆通与工作电极。形成在区域上方的关键潜在的形状仍在调查，但都归结为表面张力是接近零。细节可在文献1中找到。 金属的界面张力是在电压的小变化敏感。因此重要的是具有优异的与金属和控制施加到液体金属的电位电接触。此外，酸或碱中的电解质的存在下通过溶解氧化物层竞争与电化学氧化。此竞争过程增加了复杂性的水平;了解发生在界面上的复杂的过程将是推进这一方法的关键。 氧化和还原处理可以被组合以提供超过金属的进出毛细管的流量控制。例如，有可能使用氧化电位的金属进入capillar注入IES（通过降低领先弯月面的界面张力， 如图2），然后用还原电位以引起金属从毛细管撤退（通过增加主导弯月面的界面张力， 如图3） 28,29。这种方法的限制和能力是尚未完全确定，虽然注射似乎比戒断慢。使用氧化注​​入金属包括三个关键步骤。首先，毛细管应预充有电解质，我们相信这产生水的金属和毛细管作为金属的壁之间的薄"滑移层"。其次，注入金属到毛细管要求金属的珠与毛细管的端部之间的平齐接触， 如图3，该紧密接触可确保电位降发生在电解质/金属界面，并且防止途径电荷绕过这个INTerface。 也可以使用任何双电极或三电极系统，以控制所述金属的表面张力。双电极系统是最简单的，只需要一个工作电极，对电极和电压源。尽管两电极系统适用于示范，反电极的电位可以漂移。敏感电化学测量受益于三电极系统的稳定性（即，参比电极和一个电位）。该系统允许更好地控制的电压，并提供当前的精确读数。 来控制使用适度的电压界面张力的能力是一种很有前途的方法，用于控制形状，流量和金属结构中的亚毫米尺度的位置。我们相信，这一技术可用于创建改变形状上的需求，这可能会发现形状reconfigura应用中的金属结构有用竹叶提取电子，可调天线，开关，微流体组件，​​optofluidics，和形状转移元材料。

This method provides a simple way to control the surface tension of liquid metals containing gallium. The method uses modest voltages (~1 V) applied directly to the liquid metal (relative to a counter electrode in the presence of electrolyte) to achieve enormous and reversible changes to the surface tension of the metal1. 
Surface tension is a dominant force for liquids at small length scales and is important for a number of capillary phenomena including wetting, spreading, and surface-tension driven flow. Consequently, the ability to control surface tension is a sensible way to manipulate the shape, position, and flow of liquids at sub-mm length scales. The most common way to alter surface tension between two fluids is to use a surfactant, which is a molecule that spans the interface between the fluids. Surfactants lower surface tension, but in a way that is not easy to reverse since it is difficult to remove surfactants from the interface. Surface tension can also be altered using a variety of techniques, including temperature gradients2,3, light4, surface chemistry5-7,and voltage8. But most of these methods result in modest changes to surface tension, particularly for liquid metals, which have notably large surface tensions.
The ability to control the surface tension of liquid metal could enable new opportunities for creating shape reconfigurable structures with metallic properties for electronic, thermal, and optical applications9-14. The most common liquid metal is Hg, which is noted for its toxicity. The methods described here are relevant for liquid metals based on gallium. These metals have low viscosity, large surface tension, low volatility (low vapor pressure), and low toxicity15. Importantly, these metals form surface oxides composed of gallium oxide that are a few nm thick in air16. This oxide layer creates a physical skin that historically has been a nuisance for electrochemical and fluid dynamic applications17. The method here utilizes the oxide in new ways to control surface tension.
The most common way to manipulate liquid metals in electrolyte is to apply a potential to the metal relative to a counter electrode18. Oppositely charged ions from the electrolyte match the charges on the metal, causing the interfacial tension to drop. This phenomenon-termed electrocapillarity-has been known since the 1870s as described by Lippman19and has been utilized for alloys of gallium20. Typically, electrocapillarity achieves modest changes to surface tension, since undesirable electrochemical reactions limit the range of voltages applied to the metal. In contrast, the method described here utilizes the surface oxidation of the metal (or conversely, the reduction of the surface oxide) as a way to achieve enormous changes in surface tension above and beyond changes resulting from electrocapillarity. The leading explanation for this phenomenon is that the oxide is asymmetric; that is, the outer surface of the oxide terminates with hydroxyl groups (making a low interfacial tension interface with the aqueous electrolyte), and the interior surface of the oxide terminates with gallium atoms (making a low interfacial tension interface with the metal). In contrast, the removal of the oxide via electrochemical reduction results in a bare metal-electrolyte interface, which returns the metal back to a state of high surface tension. We characterize the interfacial tension of the metal by analyzing the shape of sessile droplets as a function of voltage while assuming that gravity and surface tension are the dominant forces that define the curvature of its surface. 
The advantage of this technique relative to classic electrocapillarity is that it can reversibly tune the tension of low toxicity liquid metals over enormous ranges (from ~500 mN/m to near zero). This delta change in surface tension may be the largest ever reported in literature for any fluid and it can be accomplished in a tunable and reversible manner. These large changes in surface tension are useful for manipulating the capillary behavior of metals; for example, it can induce the metal to spread on a surface, withdraw the metal from microchannels, fill microchannels with metal, and overcome the Rayleigh instabilities to form liquid metal fibers1,21. 
A drawback of this technique is that it requires electrolyte. It works best in acidic or basic conditions, because these electrolytes remove excess surface oxide that would otherwise contaminate the surface of the metal and mechanically restrict the movement of the metal. The simultaneous removal and deposition of the oxide layer complicates the analysis of the interfacial phenomena and it is our hope the methods described in this paper empowers additional analysis. Another disadvantage is that the electrochemical reactions at the surface of the metal must be matched by complimentary half-reactions at the counter electrode22,23. This can lead to hydrogen bubbles forming at the counter electrode.

<table><tbody><tr><td>Eutectic Gallium Indium</td><td>Indium Corporation</td><td></td><td></td></tr><tr><td>Sodium Hydroxide</td><td>Fisher Scientific</td><td>2318-3</td><td></td></tr><tr><td>Hydrochloric Acid</td><td>Fisher Scientific</td><td>A481-212</td><td></td></tr><tr><td>Sodium Fluoride</td><td>Sigma-Aldrich</td><td>201154</td><td></td></tr><tr><td>Optical Adhesive</td><td>Norland</td><td>NOA81</td><td></td></tr><tr><td>Polydimethylsiloxane (Sylgard-184)</td><td>Dow Corning</td><td></td><td>Silicone Elastomer Kit</td></tr><tr><td>Borosilicate Glass Capillaries</td><td>Friedrich and Dimmoch</td><td>B41972</td><td></td></tr><tr><td>Ag/AgCl Reference Electrode</td><td>Microelectrodes Inc.</td><td>MI-401F</td><td></td></tr><tr><td>Voltage Source</td><td>Keithley</td><td>3390</td><td></td></tr><tr><td>Potentiostat</td><td>Gamry</td><td>Ref 600</td><td></td></tr><tr><td>Laser Cutter</td><td>Universal Laser Systems</td><td>VLS 3.50</td><td></td></tr></tbody></table>

a method to manipulate surface tension of a liquid metal via surface oxidation and reduction

控制界面张力是一种有效的方法，用于操纵在亚毫米尺度，其中界面张力是一个主导力的形状，位置和流量的流体。有多种方法存在用于控制这种规模的含水和有机液体的界面张力;然而，这些技术具有有限的效用的液态金属，由于其大的界面张力。 液态金属可以形成在电子和电磁设备的软的，可拉伸和形状重构组件。虽然是可能的操纵通过机械方法 （例如，泵送）这些流体，电的方法是比较容易的小型化，控制和执行。然而，大多数电气技术有自己的约束:电式电介质需要大量的（千伏）潜力适度的驱动，电毛细管会影响界面张力相对较小的变化，而不断ELEctrowetting仅限于液态金属在毛细管的插头。 这里，我们提出用于通过电化学表面反应致动镓和镓基液体金属合金的方法。控制液体金属在电解质迅速的表面上的电化学势和可逆地变化的界面张力数量级超过两个数量（̴50020mN / m至接近零）。此外，这种方法只需要一个非常温和的电位（&lt;1 V）的施加相对于反电极。在张力所得变化主要是由于表面氧化层，其作为表面活性剂的电化学沉积;除去氧化的增加的界面张力，且反之亦然。这种技术可以在各种电解质被应用，是独立于所依靠的基板。

图 1A示出了用于氧化和还原的简单的两电极技术的一个例子。在这种情况下，液态金属的70微升滴置于1 M氢氧化钠溶液接触的铜线，以建立电连接。的1 M氢氧化钠去除表面氧化物从金属和能使金属水珠，由于其界面张力。施加降和铂网状反电极之间一个2.5伏电势使液滴的表面氧化并在迁移朝向反电极（图1Aⅱ）油滴扩散。施加-1的电势到液体金属去除氧化物（除去除氧化的NaOH），使金属对珠粒起来，并产生氢气泡的下拉由于还原电位 （ 图 1 艾）。氢气泡在铂反电极由于免费电化学半反应是大概降低质子在溶液中形成。 一个电毛细管曲线 （ 图 1B）示出了在该氧化物层形成时有效的表面张力的急剧下降。使用饱和的Ag / AgCl参比电极，这些数据被送往在1M NaOH中。在这种情况下，开路电位约为-1.5 V，相对于银/氯化银，和氧化物层附近形成-1.3 V，相对于银/氯化银（由虚线指示）。用1 M盐酸导致类似现象的行为，但气泡的金属的表面上的形成，甚至在氧化电位，使视觉分析困难。 在没有氧化物（它是由1 M氢氧化钠除去，例如）的，裸金属液是高表面张力的流体，并采用球形所示Figu重新[2] A。一滴液态金属在于相邻的毛细管充满1 M氢氧化钠。甲擦拭除去多余的电解质从熔滴的底部，如图图 2B。甲铜线接触液滴，以形成阳极和另一电极（即，阴极;在图 2中未示出）靠在电解质填充毛细管内部。在毛细管的电解质完成两个电极之间的电路， 如图 2℃。施加+ 1V降低处于领先界面的表面张力，使液体金属以填充毛细管，如图2 D。该实验中效果最好，如果所述金属是与管的端部齐平。 相反，减少偏差去除氧化皮并返回箱TAL的表面张力大的状态。一个这样的例子示于图 3A。氧化皮稳定液态金属的熔池浸没在中性电解质（图3 艾）的形状。一个减少偏差应用去除氧化皮，允许金属对珠粒上，如图3所述的 （II-III）。我们称这种技术"recapillarity"，因为它使用的还原电势诱导毛细血管的行为21。这个词的另一个含义是，毛细现象或关闭多次被打开。例如，EGAIN可以从PDMS微流体通道通过减少否则稳定在通道中的金属（如在4.1节）的氧化物撤回。 图 3B -D示出了一种这样的试验序列。 我们插入注射器针头在毛细管的一端，并且慢慢推针筒柱塞迫使从注射器的金属进入毛细管。我们将填充毛细管上的聚甲基丙烯酸甲酯构成的定制支架。保持件有两个水库，两个凹槽，以确保在毛细管，两个孔把电线，并且也可以选择到磁带尺子，如图3 中的B。电解质（例如钠水溶液氟化物）注入金属后添加到储存器的阳极连接到毛细管的末端， 如图 3℃。内的管接触反电极上的毛细管的另一端的金属以完成电路。施加1V减少偏差导致金属撤回和移离阳极， 如图 3天。后来，我们通过比较断定测量撤军速度金属离子相对于时间。一个这样的速度曲线图显示在图3] E。速度衰减作为金属远离阳极。这个速度衰减是由于增加在所述阳极和所述液体金属21之间的电阻。 <img alt="图1" src="/files/ftp_upload/53567/53567fig1.jpg" /> 图 1.（A）降EGAIN的浸没在1M NaOH中，用附接到降和铂对电极啮合在溶液中的铜线。 ⅰ）施加到降A-1V电位导致金属对珠粒和产生氢气的金属的表面上。二）应用到降的2.5 V的潜力引起传播。 （ 二）在1M氢氧化钠的EGAIN降的电毛细管曲线。还原侧（下面-1.4 V，相对于银/氯化银的电压）表示传统的电毛细管的行为，而氧化侧面说明了从参考文献1（版权所有2014年，美国国家科学院，美国）采用了表面张力。 图1B一显著下降。 <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/53567/53567fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图2" src="/files/ftp_upload/53567/53567fig2.jpg" /> 图 2. 毛细注射用氧化偏液态金属。（A）一滴液态金属接触开口毛细管充满电解液。 （B）中的管被对准并推着的下降。一擦拭去除多余的电解液量。 （三）一个标记这个实验装置的图像。的1 V（D）中的应用到金属降低了金属的通过表面氧化氮的表面张力通货膨胀，并导致流动。 <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/53567/53567fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图3" src="/files/ftp_upload/53567/53567fig3.jpg" /> 图 3.（A）在1M氟化钠溶液将一滴液态金属。 i）本氧化物允许一个稳定的，非球形水坑中的溶液中。 II-III）应用一个-1的电势使金属水珠。 （B）一个定制的丙烯酸树脂基材有两个水库插入电极。 A 70毫米长，1个毫米内径的玻璃毛细管充满EGAIN跨越两个水库。该基片具有两个凹槽以牢固地适合这种毛细管。 （C）将一滴电解质加入到一个贮，另一个贮存器保持原样。有时气泡的形式，这可以通过使用细尖的针被最小化。 （ <stro纳克&gt;一减少偏差D）的应用去除氧化物，并且使金属撤出。 （E）退出毛细管作为时间的函数的液态金属的速度。 <a href="https://www-jove-com.bdigitaluss.remotexs.co/files/ftp_upload/53567/53567fig3large.jpg" target="_blank">请点击此处查看该图的放大版本。</a>

Watch this Scientific Journal Video about A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction at JoVE.com

A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction

方法通过表面氧化还原操纵液态金属的表面张力

We present a method to control the interfacial energy of a liquid metal in an electrolyte via electrochemical deposition (or removal) of a surface oxide layer. This simple method can control the capillary behavior of gallium-based liquid metals by tuning the interfacial energy rapidly, significantly, and reversibly using modest voltages.

Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where ...

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15.2K 次观看.  North Carolina State University. We present a method to control the interfacial energy of a liquid metal in an electrolyte via electrochemical deposition (or removal) of a surface oxide layer. This simple method can control the capillary behavior of gallium-based liquid metals by tuning the interfacial energy rapidly, significantly, and reversibly using modest voltages.

视频: A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction

Taking Advantage of Reduced Droplet-surface Interaction to Optimize Transport of Bioanalytes in Digital Microfluidics

Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of &#8220;lab-on-a-chip&#8221; platforms. Often, droplet motion relies on the wetting of a surface, directly associated with the application of an electric field; surface interactions, however, make motion dependent on droplet contents, limiting the breadth of applications of the technique.
Some alternatives have been presented to minimize this dependence. However, they rely on the addition of extra chemical species to the droplet or its surroundings, which could potentially interact with droplet moieties. Addressing this challenge, our group recently developed Field-DW devices to allow the transport of cells and proteins in DMF, without extra additives.
Here, the protocol for device fabrication and operation is provided, including the electronic interface for motion control. We also continue the studies with the devices, showing that multicellular, relatively large, model organisms can also be transported, arguably unaffected by the electric fields required for device operation.

The protocol for fabrication and operation of field dewetting devices (Field-DW) is described, as well as the preliminary studies of the effects of electric fields on droplet contents.

以减少液滴表面的相互作用来优化Bioanalytes运输中的数字微流体

Digital microfluidics (DMF), a technique for manipulation of droplets, is a promising alternative for the development of &#8220;lab-on-a-chip&#8221; ...

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Ultrasound Velocity Measurement in a Liquid Metal Electrode

A growing number of electrochemical technologies depend on fluid flow, and often that fluid is opaque. Measuring the flow of an opaque fluid is inherently more difficult than measuring the flow of a transparent fluid, since optical methods are not applicable. Ultrasound can be used to measure the velocity of an opaque fluid, not only at isolated points, but at hundreds or thousands of points arrayed along lines, with good temporal resolution. When applied to a liquid metal electrode, ultrasound velocimetry involves additional challenges: high temperature, chemical activity, and electrical conductivity. Here we describe the experimental apparatus and methods that overcome these challenges and allow the measurement of flow in a liquid metal electrode, as it conducts current, at operating temperature. Temperature is regulated within &#177;2 &#176;C using a Proportional-Integral-Derivative (PID) controller that powers a custom-built furnace. Chemical activity is managed by choosing vessel materials carefully and enclosing the experimental setup in an argon-filled glovebox. Finally, unintended electrical paths are carefully prevented. An automated system logs control settings and experimental measurements, using hardware trigger signals to synchronize devices. This apparatus and these methods can produce measurements that are impossible with other techniques, and allow optimization and control of electrochemical technologies like liquid metal batteries.

Ultrasound velocimetry is used to study mixing by fluid flow in liquid metal electrodes. The focus of this manuscript is to illustrate the methods used for making precise, spatially-resolved ultrasound measurements while limiting oxidation and controlling and monitoring temperature, applied current, and the heater power being supplied.

超声速度测量的液态金属电极

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Selective Area Modification of Silicon Surface Wettability by Pulsed UV Laser Irradiation in Liquid Environment

The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of biosensing devices. We report on a protocol of using KrF and ArF lasers irradiating Si (001) samples immersed in a liquid environment with low number of pulses and operating at moderately low pulse fluences to induce Si wettability modification. Wafers immersed for up to 4 hr in a 0.01% H2O2/H2O solution did not show measurable change in their initial contact angle (CA) ~75&#176;. However, the 500-pulse KrF and ArF lasers irradiation of such wafers in a microchamber filled with 0.01% H2O2/H2O solution at 250 and 65 mJ/cm2, respectively, has decreased the CA to near 15&#176;, indicating the formation of a superhydrophilic surface. The formation of OH-terminated Si (001), with no measurable change of the wafer&#8217;s surface morphology, has been confirmed by X-ray photoelectron spectroscopy and atomic force microscopy measurements. The selective area irradiated samples were then immersed in a biotin-conjugated fluorescein-stained nanospheres solution for 2 hr, resulting in a successful immobilization of the nanospheres in the non-irradiated area. This illustrates the potential of&#160;the method for selective area biofunctionalization and fabrication of advanced Si-based biosensing architectures. We also describe a similar protocol of irradiation of wafers immersed in methanol (CH3OH) using ArF laser operating at pulse fluence of 65 mJ/cm2 and in situ formation of a strongly hydrophobic surface of Si (001) with the CA of 103&#176;. The XPS results indicate ArF laser induced formation of Si&#8211;(OCH3)x compounds responsible for the observed hydrophobicity. However, no such compounds were found by XPS on the Si surface irradiated by KrF laser in methanol, demonstrating the inability of the KrF laser to photodissociate methanol and create -OCH3 radicals.

We report on a process of in situ alteration of HF treated Si (001) surface into a hydrophilic or hydrophobic state by irradiating samples in microfluidic chambers filled with&#160;H2O2/H2O solution (0.01%-0.5%) or methanol solutions using pulsed UV laser of a relative low pulse fluence.

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The wettability of silicon (Si) is one of the important parameters in the technology of surface functionalization of this material and fabrication of ...

Determining the Chemical Composition of Corrosion Inhibitor/Metal Interfaces with XPS: Minimizing Post Immersion Oxidation

An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, the focus is on metallic substrates immersed in acidic solutions containing organic corrosion inhibitors, as these systems can be particularly sensitive to oxidation following removal from solution. To minimize the likelihood of such degradation, samples are removed from solution within a glove box purged with inert gas, either N2 or Ar. The glove box is directly attached to the load-lock of the ultra-high vacuum X-ray photoelectron spectroscopy instrument, avoiding any exposure to the ambient laboratory atmosphere, and thus reducing the possibility of post immersion substrate oxidation. On this basis, one can be more certain that the X-ray photoelectron spectroscopy features observed are likely to be representative of the in situ submerged scenario, e.g. the oxidation state of the metal is not modified.

A protocol to avoid the oxidation of metallic substrates during sample transfer from an inhibited acidic solution to an X-ray photoelectron spectrometer is presented.

确定缓蚀剂/金属界面的化学成分与XPS:最小化后浸入氧化

An approach for acquiring more reliable X-ray photoelectron spectroscopy data from corrosion inhibitor/metal interfaces is described. More specifically, ...

化学

Aerosol-assisted Chemical Vapor Deposition of Metal Oxide Structures: Zinc Oxide Rods

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, their high cost production and/or incompatibility with microfabrication technologies, due to the use of pre-deposited catalyst-seeds and/or high processing temperatures exceeding 900 &#176;C, represent a drawback for a widespread use of these methods. Here, however, we report the synthesis of ZnO rods via a non-catalyzed vapor-solid mechanism enabled by using an aerosol-assisted chemical vapor deposition (CVD) method at 400 &#176;C with zinc chloride (ZnCl2) as the precursor and ethanol as the carrier solvent. This method provides both single-step formation of ZnO rods and the possibility of their direct integration with various substrate types, including silicon, silicon-based micromachined platforms, quartz, or high heat resistant polymers. This potentially facilitates the use of this method at a large-scale, due to its compatibility with state-of-the-art microfabrication processes for device manufacture. This report also describes the properties of these structures (e.g., morphology, crystalline phase, optical band gap, chemical composition, electrical resistance) and validates its gas sensing functionality towards carbon monoxide.

Columnar zinc oxide structures in the form of rods are synthesized via aerosol-assisted chemical vapor deposition without the use of pre-deposited catalyst-seed particles. This method is scalable and compatible with various substrates based on either silicon, quartz or polymers.

金属氧化物结构的气溶胶辅助化学气相沉积: 氧化锌棒

Whilst columnar zinc oxide (ZnO) structures in the form of rods or wires have been synthesized previously by different liquid- or vapor-phase routes, ...

Preparation and High-temperature Anti-adhesion Behavior of a Slippery Surface on Stainless Steel

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A typical anti-wetting superhydrophobic surface easily fails when exposed to a high-temperature liquid. Recently, Nepenthes-inspired slippery surfaces demonstrated a new way to solve the adhesion problem. A lubricant layer on the slippery surface can act as a barrier between the repelled materials and the surface structure. However, the slippery surfaces in previous studies rarely showed high-temperature resistance. Here, we describe a protocol for the preparation of slippery surfaces with high-temperature resistance. A photolithography-assisted method was used to fabricate pillar structures on stainless steel. By functionalizing the surface with saline, a slippery surface was prepared by adding silicone oil. The prepared slippery surface maintained the anti-wetting property for water, even when the surface was heated to 300 &#176;C. Also, the slippery surface exhibited great anti-adhesion effects on soft tissues at high temperatures. This type of slippery surface on stainless steel has applications in medical devices, mechanical equipment, etc.

Slippery surfaces provide a new way to solve the adhesion problem. This protocol describes how to fabricate slippery surfaces at high temperatures. The results demonstrate that the slippery surfaces showed anti-wetting for liquids and a remarkable anti-adhesion effect on soft tissues at high temperatures.

不锈钢滑面的制备及高温抗粘接性能研究

Anti-adhesion surfaces with high-temperature resistance have a wide application potential in electrosurgical instruments, engines, and pipelines. A ...

Simultaneous Multi-surface Anodizations and Stair-like Reverse Biases Detachment of Anodic Aluminum Oxides in Sulfuric and Oxalic Acid Electrolyte

After reporting on the two-step anodization, nanoporous anodic aluminum oxides (AAOs) have been widely utilized in the versatile fields of fundamental sciences and industrial applications owing to their periodic arrangement of nanopores with relatively high aspect ratio. However, the techniques reported so far, which could be only valid for mono-surface anodization, show critical disadvantages, i.e., time-consuming as well as complicated procedures, requiring toxic chemicals, and wasting valuable natural resources. In this paper, we demonstrate a facile, efficient, and environmentally clean method to fabricate nanoporous AAOs in sulfuric and oxalic acid electrolytes, which can overcome the limitations that result from conventional AAO fabricating methods. First, plural AAOs are produced at one time through simultaneous multi-surfaces anodization (SMSA), indicating mass-producibility of the AAOs with comparable qualities. Second, those AAOs can be separated from the aluminum (Al) substrate by applying stair-like reverse biases (SRBs) in the same electrolyte used for the SMSAs, implying simplicity and green technological characteristics. Finally, a unit sequence consisting of the SMSAs sequentially combined with SRBs-based detachment can be applied repeatedly to the same Al substrate, which reinforces the advantages of this strategy and also guarantees the efficient usage of natural resources.

A protocol for fabricating nanoporous anodic aluminum oxides via simultaneous multi-surfaces anodization followed by stair-like reverse biases detachments is presented. It can be applied repeatedly to the same aluminum substrate, exhibiting a facile, high-yield, and environmentally clean strategy.

阳极氧化铝在硫酸和草酸电解质中的同时多表面 Anodizations 和阶梯式反向偏置剥离

After reporting on the two-step anodization, nanoporous anodic aluminum oxides (AAOs) have been widely utilized in the versatile fields of fundamental ...

Fabrication of Superhydrophobic Metal Surfaces for Anti-Icing Applications

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in industry. The wettability of the produced surface was analyzed by bouncing drop experiments and the topography was analyzed by confocal microscopy. In addition, we show various methodologies to measure its durability and anti-icing properties. Superhydrophobic surfaces hold a special texture that must be preserved to keep their water-repellency. To fabricate durable surfaces, we followed two strategies to incorporate a resistant texture. The first strategy is a direct incorporation of roughness to the metal substrate by acid etching. After this surface texturization, the surface energy was decreased by silanization or fluoropolymer deposition. The second strategy is the growth of a ceria layer (after surface texturization) that should enhance the surface hardness and corrosion resistance. The surface energy was decreased with a stearic acid film.
The durability of the superhydrophobic surfaces was examined by a particle impact test, mechanical wear by lateral abrasion, and UV-ozone resistance. The anti-icing properties were explored by studying the ability to repeal subcooled water, freezing delay, and ice adhesion.

We illustrate several methodologies to produce superhydrophobic metal surfaces and to explore their durability and anti-icing properties.

防结冰用超疏水性金属表面的制备

Several ways to produce superhydrophobic metal surfaces are presented in this work. Aluminum was chosen as the metal substrate due to its wide use in ...

Metal-Assisted Electrochemical Nanoimprinting of Porous and Solid Silicon Wafers

Metal-assisted electrochemical imprinting (Mac-Imprint) is a combination of metal-assisted chemical etching (MACE) and nanoimprint lithography that is capable of direct patterning 3D micro- and nanoscale features in monocrystalline group IV (e.g., Si) and III-V (e.g., GaAs) semiconductors without the need of sacrificial templates and lithographical steps. During this process, a reusable stamp coated with a noble metal catalyst is brought in contact with a Si wafer in the presence of a hydrofluoric acid (HF) and hydrogen peroxide (H2O2) mixture, which leads to the selective etching of Si at the metal-semiconductor contact interface. In this protocol, we discuss the stamp and substrate preparation methods applied in two Mac-Imprint configurations: (1) Porous Si Mac-Imprint with a solid catalyst; and (2) Solid Si Mac-Imprint with a porous catalyst. This process is high throughput and is capable of centimeter-scale parallel patterning with sub-20 nm resolution. It also provides low defect density and large area patterning in a single operation and bypasses the need for dry etching such as deep reactive ion etching (DRIE).

A protocol for metal-assisted chemical imprinting of 3D microscale features with sub-20 nm shape accuracy into solid and porous silicon wafers is presented.

金属辅助多孔硅和固体硅晶圆的电化学纳米压印

Metal-assisted electrochemical imprinting (Mac-Imprint) is a combination of metal-assisted chemical etching (MACE) and nanoimprint lithography that is ...

Metal Oxide Heterojunction for Photocatalytic Activities

There is a significant global demand for improvements in synthesis techniques and their optimal characteristics, especially for industrial-scale applications. Sol-gel-based solution combustion synthesis (SG-SCS) is a simple method to produce ordered porous materials. In this regard, Pearson&#39;s hard and soft acids and bases theory assists in selecting host-dopant reactivity to form a proper heterojunction.
The formation of a heterojunction also changes the essential properties of the materials, improving photocatalysis via charge transfer or synergistic activities. A calcination temperature of 500 &#176;C is ideal for this process based on the results of the stability assessment via a differential thermogravimetry ratio analysis (DTG).
The nanoscale dimensions of the nanoparticles (NPs) and nanocomposites (NCs) generated were validated using X-ray diffraction and high-resolution transmission electron microscopy (HRTEM). Furthermore, the scanning electron microscopy micrographs and BET analyses confirmed the porosity nature of the materials. HRTEM, X-ray photoelectron spectroscopy, and energy-dispersive X-ray investigations established the materials composition. The study found that NCs degraded the acid orange 8 (AO8) color more efficiently than bare ZnO.

The development of a heterojunction boosts the photocatalytic activities of solution combustion synthesis, which is a time-/energy-efficient process. Advanced analytical characterization techniques were used in this protocol to evaluate the materials&#39; characteristics, and nanocomposites demonstrated improved acid orange-8 dye degradation.