作者非常感谢协助DOSY核磁共振马尔科纽文豪生。

<img alt="计划1" src="/files/ftp_upload/3975/3975scheme1.jpg" /> 计划1。自组装成球形团聚体直径约为5 nm，显示在毫摩尔浓度的积木柠檬酸缓冲液中的排屑discotics。增加的加入氯化钠结果形成一个直径约3 nm和长度大于25纳米的细长杆的离子强度。 <a href="http://www.jove.com/files/ftp_upload/3975/3975scheme1large.jpg" target="_blank">点击这里查看大图</a> 。 1。准备1 BTA的钆（Ⅲ）胺解CD光谱和温度相关的CD光谱测量NaCl浓度的功能<ol><li>准备一个100毫米的柠檬酸缓冲液（pH值6.0）。 </li><li>准备用2 M氯化钠100毫米柠檬酸缓冲液（pH值6.0）。 </li><li> BTA-GD（三）DTPA 100毫米柠檬酸缓冲，在10毫升（兆瓦=3184克•摩尔-1）ţ溶解0.254毫克ARGET浓度8•10 BTA-GD（三）胺 -3毫米。 </li><li>超声5分钟的解决方案。 </li><li>填写与解决方案1厘米的紫外线cuvet和衡量一个从230到350纳米的CD谱和强度最高的CD带在CD冷却曲线（如λ= 269 nm处）363 - 283在1 K的分率ķ - 1。 </li><li>加入相同体积的2 M氯化钠缓冲溶液中的柠檬酸缓冲BTA-GD（三）胺的解决方案，以增加离子强度的1 M氯化钠，稀释的discotics一半的浓度，靶浓度4•10-3 BTA-GD（三）胺毫米。 </li><li>涡的解决方案与离子强度增加5分钟。 </li><li>重新测量，从230到350 nm和CD冷却曲线在最高强度从363 CD带的CD谱- 1 K的分-1的速度在283 K表。 </li></ol> 2。装修依赖的T-CD数据的T-依赖模型耳鼻喉科自组装<ol><li>原始CD数据导出到8.5起源和规范化。这是实现定义的CD效果等于0，测得的最高温度和最低测量温度等于1的CD效果。由于CD效应的大小是8聚集程度成正比的，规范化的CD-曲线是聚集的程度成正比。 </li><li>使用非线性曲线，OriginPro 8.5合适的选项，使用范德Schoot 8,9派生的T-依赖的自组装模型的规范化的数据进行拟合。在这种模式下，核和伸长率制度有区别的。首先聚集在的伸长制度（T &lt;T E）的程度被安装，使用下列公式: </li></ol><img alt="式（1）" src="/files/ftp_upload/3975/3975eq1.jpg" /> 包含上述方程（变温，T，程度AGGRegation，Φn）的三个参数， 即伸长H E，伸长温度 T E（自组装开始时的温度）和参数Φ 税务总局介绍，这是确保ΦN /Φ 总局焓不超过团结，从约束，聚集度不能超过团结如下。 拟合呈现伸长H E（焦耳/摩尔）和延伸温度 T E（K）的特点在一定浓度的分子自组装焓。装修时，应服从，这是只有在温度低于T E聚集度应安装，因为方程2.1是仅在延伸制度的有效约束。 接下来，实验发现聚集程度核制度，可以安装，使用下列公式: <img alt="公式（2）" src="/files/ftp_upload/3975/3975eq2.jpg" /> 包含上述方程（变量T和Φ 列印 ），其中4人已经有四分之三与方程2.1确定参数; 即H E伸长，伸长温度 T e和参数Φ焓坐在旁边。唯一的未知参数是 K 值 ，描述的阶段，这是发现核温度高于T E拟合实验发现聚集程度的协同。 3。准备通过低温透射电镜BTA的钆（Ⅲ）超分子聚合物的透射电子显微镜和可视化的胺解<ol><li>准备两个缓冲区:100毫米柠檬酸缓冲液（pH值6.0）和100毫米柠檬酸缓冲液（pH值6.0）W第i 5 M氯化钠。 </li><li>溶解0.318毫克BTA-GD（三）胺 （兆瓦=3184克•摩尔-1）准备的缓冲区，每年在0.1毫升，目标浓度为1毫米BTA-GD（三）胺 。 </li><li>低温透射电镜的样品玻璃化进行了使用自动玻璃化机器人（费Vitrobot马克III）。电网CryoTEM（R / 2 Quantifoil耶拿格Quantifoil微型工具有限公司）是表面等离子体处理前的玻璃化冷冻程序，使用5毫安，40秒1 Cressington 208碳涂布作业。对自动化费Vitrobot的玻璃化冷冻过程中对电网的水溶液，然后应用。这涉及到对电网的示例应用程序，多余的液体的印迹，以创建一个随后很快浸在液态乙烷电网对电网和玻璃化溶液的薄膜。玻璃化冷冻后的样品在液氮中保存，手动自动加载机磁带传输，也库尔D用液氮。然后插入盒式磁带自动加载机的TEM。这一切都是手工完成。 </li><li>恩/ E cryoTITAN（费），（ <a href="http://www.cryotem.nl" target="_blank">www.cryotem.nl</a> ） cryoTEM实验。杜叶锡恩/écryoTITAN的配备了300千伏场发射枪（FEG的）经营。使用一个2K x 2K的加坦CCD相机配备后列，加坦能源过滤器（GIF）图像记录。 </li></ol> 1 H的DOSY核磁共振测量球形自组装排屑-GD（三）胺在低离子强度4。 <ol><li>准备了50毫米D 6，琥珀酸在D 2 O的缓冲液（pH值6.0）;溶解在D 2 D 6琥珀酸缓冲区准备，通过调节pH至6.0，使用1米ND 4外径D 2澳终浓度为50毫米琥珀调整与额外的D 2 O。 </li><li>由于钆（Ⅲ）是高度顺和1 H信号，从而大大拓宽，钆（Ⅲ）Y（三）被替换下场。 </li><li>溶解2.98毫克BTA - Y（Ⅲ）胺 （兆瓦=2979克•摩尔-1）D 6琥珀酸，目标集中在D 2 O的 （pH值6.0）的缓冲，在1毫升50毫米1毫米排屑Ÿ（三）胺 。 </li><li> 1 H的DOSY核磁共振测量进行了瓦里安的统一INOVA的500配备了一个5毫米的ID-PFG探头从瓦里安谱仪。 DOSY实验进行了使用的DOSY一杆（Doneshot，瓦里安）脉冲序列。 90度脉冲UND混合时间进行相应的调整。化学位移参考使用化学位移的3 - （三甲基硅基）丙酸-2，2,3,3 -研究[D]磺酸钠（第三届会议）。 </li><li>自我的HDO扩散被用于校准测量，它是从文学，在298 K的HDO在D 2 O的自我扩散是19.0×10-9米2 </suP&gt;·S -1。作为参考，在D 2的HDO自我扩散O的在瓦里安2赫兹D 2 O标准样品测量和校准的标准值。用于计算流体力学半径R 的 H聚集模型是球形粒子的扩散斯托克斯-爱因斯坦的关系。 </li></ol> 5。代表结果 1 H核磁共振DOSY和BTA - M（Ⅲ）-DTPA射线散射测量:柠檬酸缓冲液中的球状物体周边钆（Ⅲ）配合离子特性介绍盘状单体聚合成细长的棒状聚合物，其核心的一维增长的挫折。吸引和排斥的相互作用之间的平衡，控制总量（ 计划2）的大小和形状。 <img alt="方案2" src="/files/ftp_upload/3975/3975scheme2.jpg" /> 计划2。 一个强大的技术，以确定在溶液中的粒子的大小和形状是同步辐射光源的小角度X射线散射（SAXS）。 BTA-GD（Ⅲ）-DTPA在柠檬酸缓冲溶液溶解和SAXS研究概况进行了记录和安装在该地区的0.01 &lt;Q &lt;0.1 -1。斜坡接近零的低 Q（Q &lt;0.06 -1）表示缺乏总的形状各向异性，这意味着球状物体的存在（ 图1）。使用3.2 nm的均匀的单分散球形外形，导致计算的半径R，在不同浓度的测量数据进行拟合。单体盘状排屑-GD（Ⅲ）-DTPA计算几何半径为3.0 nm，这表明存在总量与长宽比接近1。 <img alt="图1" src="/files/ftp_upload/3975/3975fig1.jpg" /> 图1。SAXS研究概况（三）BTA-GD-DTPA的柠檬酸缓冲液（100毫米，pH值6）在0.5和1.0毫米（上）。 DOSY核磁共振的BTA - Y（三）-DTPA在50毫米D 6，琥珀酸为1.0毫米（下）的缓冲区。 <a href="http://www.jove.com/files/ftp_upload/3975/3975fig1large.jpg" target="_blank">点击这里查看大图</a> 。 为了提供进一步的证据和自组装的对象为球形纳米大小，我们进行的1 H扩散下令核磁共振光谱（1 H核磁共振DOSY）（ 图1）。 DOSY核磁共振允许的集合体，可以计算流体力学半径（ 高 ）的扩散系数测定。由于钆（Ⅲ）是高顺和1 H信号，从而大大拓宽，我们改变了钆（Ⅲ），Y（Ⅲ）为抗磁性。聚合抗磁盘状两亲在氘琥珀酸缓冲的扩散系数（50毫米，pH为6，C = 1毫米）被确定为0.69x10-10米2 S -1。通过斯托克斯-爱因斯坦的关系，我们计算出液力半径为2.9 nm的R H球大小的离散对象（ 见表1）。与BTA-GD（Ⅲ）-DTPA的SAXS研究数据获得的价值，这个规模是非常吻合。 <table border="1"><tbody><tr><td> BTA - M（Ⅲ）-DTPA [MM] </td><td> ðT A [10 -10米2秒-1] </td><td> R Hà [NM] </td><td> R B [NM] </td></tr><tr><td> 1 </td><td> 0.69 </td><td> 2.9 </td><td> 3.2 </td></tr></tbody></table>从DOSY A，B从SAXS研究散射和BTA - M（Ⅲ）-DTPA DOSY测量结果见表1。 排屑-GD的Cryo-TEM（Ⅲ）-DTPA:从球状物体拉长棒堆栈长度超过一维的成功控制，得到了进一步的证据，从低温的TEM照片。由于水溶液的玻璃化冷冻透射电镜保留的自组装聚合物结构形态和避免干燥的影响与传统的TEM样品制备。 图2（左）表明，BTA-GD（Ⅲ）-DTPA产生预期的球形物体直径1毫米的浓度，从而证实了小角X射线散射和DOSY测量的结果接近6纳米。根据这些发现，我们已经能够获得自组装的离散对象，可以考虑树枝状大分子的超分子相当于10。 <img alt="图2" src="/files/ftp_upload/3975/3975fig2.jpg" /> 图2的Cryo-TEM图像排屑-GD（三）胺（左）1毫米，在298度（100毫米，pH值6）在柠檬酸缓冲玻璃化，比例尺代表50纳米;柠檬酸缓冲液（100毫米，pH值6）在298 K和整体NaCl浓度5中号玻璃化（右）1毫米，比例尺代表50纳米。 到目前为止，我们只工作在低离子强度缓冲的解决方案。但是，如果周边的静电排斥力收取BTA-GD-DTPA的（三）在沮丧的一维增长的来源是米（III）-DTPA的复合物，我们预期，增加离子强度缓冲环境，使用高度水合反惰性1:1盐，应减少静电相互作用，因此不同类型的自组装对象应形成。在柠檬酸缓冲由5 M氯化钠效果确实观察（ 图2右 ）。形成棒状超分子聚合物的高宽比在低温TEM照片清晰地观察到，在高离子强度。静电屏蔽是最可能的解释这一发现。从SPHE的形状变化rical总额约6纳米直径6纳米，长度可达几百纳米的细长杆的直径。 BTA-GD（Ⅲ）-DTPA的CD测量:开关的合作自组装，离子强度增加圆二色谱（CD）光谱测量吸收的左手和右手的圆偏振光之间的差异。当螺旋对象首选螺旋感，左，右手将圆偏振光吸收不同程度的影响，因此上升到CD效果。由于分子间氢键之间连续BTA的钆（Ⅲ）-DTPA内聚集，形成列队在一个螺旋的方式，在L-苯丙氨酸基的手性中心，有利于在其他螺旋感，我们期待一个明确的CD BTA-GD（三）基于聚合胺11,12谱。此外，随温度变化的CD光谱是一个功能强大工具，以评估的BTA-GD的自组装机制（III）-DTPA的聚合和允许派生形成总量13稳定的结论。 作为一个例子，室温CD光谱的BTA-GD（三）DTPA随盐浓度（0 M氯化钠1.0 M氯化钠）（8×10 -3毫米或100毫米柠檬酸缓冲4X10 -3毫米） 图3A。虽然显着低浓度的CD测量应用，明确Cotton效应表示完整总量的存在，甚至在微摩尔浓度。 CD谱的变化增加盐的浓度，这是一个很好的迹象减少外围栈和更好地discotics包装相互作用后的形状。此外，相同的解决方案（363 - 283 K时，在λ= 269或278纳米）的CD冷却曲线显示在形状明显的差异（ 图3B）。美联社父T E温度聚集开始转移到较高的温度较高的盐浓度和越来越多的合作机制，在CD效果更突然增加的特点，变得很明显。而最好由等键的自组装过程中所述的冷却曲线在0 M氯化钠，1.0 M氯化钠的冷却曲线是典型的合作自组装过程14。在前者情况下，所有关联的常量被认为是平等的，而在后一种情况下的自组装，至少在两个不同的阶段发生。在第一步中，形成一个"核"的需要，是大力非常不利。一个关键的聚合温度下冷却后，超分子聚合物的分子量高的伸长率和成指数增长。使用的合作模式自我组装的BTA-GD（Ⅲ）-DTPA在0和1 M氯化钠热力学参数的量化，清楚地揭示了在 K减少&lt;分A，这是量纲激活常数8。 K 的较低值表示在自组装过程中的协同程度越高，表示这是在低温TEM观察的高度拉长的超分子聚合物的形成。 <table border="1"><tbody><tr><td> BTA-GD（Ⅲ）-DTPA </td><td> Ç 氯化钠 </td><td> K 一 </td></tr><tr><td> 8×10 -3毫米</td><td> 0 M </td><td> 10 10 -2 </td></tr><tr><td> 4×10 -3毫米</td><td> 1米</td><td> 1 10-4 </td></tr></tbody></table> 表2。 由 K表示协同度的温度依赖自我组装的BTA-GD（Ⅲ）-DTPA的NaCl浓度（ 氯化钠 ）的功能。 <img alt="图3" src="/files/ftp_upload/3975/3975fig3.jpg" /> 排屑-G的图3。D（III）-DTPA在100毫米柠檬酸缓冲液（C = 8 X10在低离子强度和4×10 -3毫米-3毫米高离子强度）] CD光谱在293 K记录作为离子强度的函数氯化钠 Ç= 0米- 1.0米，摩尔椭圆Δε的计算公式如下:Δε= CD效果/（CXL），其中 c是单位为mol·L-1浓度的BTA 和 l厘米的光学路径长度，B相应的CD冷却测量曲线在λ= 269 nm表示0 M氯化钠和278纳米为1米的NaCl溶液的聚集Φ 列印程度为NaCl浓度的函数c 盐 = 0米- 1.0米，Φ n是计算除以被测影响最大的CD-CD效果。

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Soc. 130, 606-611 (2008).</li><li>Jonkheijm, P., van der Schoot, P., Schenning, A. P. H. J., Meijer, E. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Probing+the+solvent-assisted+nucleation+pathway+in+chemical+self-assembly.">Probing the solvent-assisted nucleation pathway in chemical self-assembly.</a> Science. 313, 80-83 (2006).</li><li>Bosman, A. W., Janssen, H. M., Meijer, E. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=About+dendrimers:+structure,+physical+properties,+and+applications.">About dendrimers: structure, physical properties, and applications.</a> Chem. Rev. 99, 1665-1688 (1999).</li><li>Veld, M. A. J., Haveman, D., Palmans, A. R. A., Meijer, E. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sterically+demanding+benzene-1,3,5-tricarboxamides:+tuning+the+mechanisms+of+supramolecular+polymerization+and+chiral+amplification.">Sterically demanding benzene-1,3,5-tricarboxamides: tuning the mechanisms of supramolecular polymerization and chiral amplification.</a> Soft Matter. 7, 524-531 (2011).</li><li>Stals, P. J. M., Smulders, M. M. J., Mart&#237;n-Rap&#237;n, R., Palmans, A. R. A., Meijer, E. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Asymmetrically+substituted+benzene-1,3,5-tricarboxamides:+self-assembly+and+odd-even+effects+in+the+solid+state+and+in+dilute+solution.">Asymmetrically substituted benzene-1,3,5-tricarboxamides: self-assembly and odd-even effects in the solid state and in dilute solution.</a> Chem. Eur. J. 15, 2071-2080 (2009).</li><li>De Greef, T. F. A., Smulders, M. M. J., Wolffs, M., Schenning, A. P. H. J., Sijbesma, R. P., Meijer, E. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Supramolecular+polymerization.">Supramolecular polymerization.</a> Chem. Rev. 109, 5687-5754 (2009).</li><li>Smulders, M. M. J., Nieuwenhuizen, M. M. L., de Greef, T. F. A., Schoot, P. v. a. n. d. e. r., Schenning, A. P. H. J., Meijer, E. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=How+to+distinguish+isodesmic+from+cooperative+supramolecular+polymerization?+Chem.">How to distinguish isodesmic from cooperative supramolecular polymerization? Chem.</a> Eur. J. 16, 362-367 (2010).</li><li>Besenius, P., Heynens, J. L. M., Straathof, R., Nieuwenhuizen, M. M. L., Bomans, P. H. H., Terreno, E., Aime, S., Strijkers, G. J., Nicolay, K., Meijer, E. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Paramagnetic+self-assembled+nanoparticles+as+supramolecular+MRI+contrast+agents.">Paramagnetic self-assembled nanoparticles as supramolecular MRI contrast agents.</a> Contrast Media Mol. Imaging. , (2012).</li></ol>

没有利益冲突的声明。

含钆（Ⅲ）-DTPA复杂的贡献在此讨论的自组装的盘状双亲目前正在调查15因此，他们的自我细节作为一种新的磁共振成像（MRI）代理相结合的高对比度可调的排泄时间。装配在不同条件下的行为和他们的稳定是至关重要的。结合光谱（CD和NMR），散射（SAXS）和显微镜（低温TEM）技术允许可视化所形成的结构和热力学参数的量化。这种技术的结合是普遍适用于自组装分子只要在所研究的系统作为一个优惠螺旋感允许的左手和右手的圆偏振光的吸收不同。

<table border="1"><tbody><tr><td> 试剂/设备名称 </td><td> 公司 </td><td> 目录编号 </td><td> 评论 </td></tr><tr><td> BTA-GD（Ⅲ）-DTPA </td><td></td><td></td><td>取得内部</td></tr><tr><td> BTA - Y（Ⅲ）-DTPA </td><td></td><td></td><td>取得内部</td></tr><tr><td> CD光谱</td><td> JASCO </td><td> JASCO J-815 spectropolarimeter </td><td></td></tr><tr><td>核磁共振</td><td>瓦里安</td><td>瓦里安统一INOVA的500谱仪</td><td> 5毫米的ID-PFG探头瓦里安</td></tr><tr><td>低温TEM </td><td>费</td><td> cryoTITAN透射电镜</td><td></td></tr><tr><td> SAXS研究</td><td>荷兰和比利时的光束线在欧洲Synchotron的辐射装置（ESRF）（BM26B）在法国格勒诺布尔</td><td></td><td&gt; </td></tr></tbody></table>

controlling the size, shape and stability of supramolecular polymers in water

对于水基的超分子聚合物，形状，大小和稳定性的同时控制超过是非常困难的。同时，这样做的能力在功能软物质中的应用，包括电子，生物医学工程和传感器的数量是非常重要的。在过去，成功的策略，以控制超分子聚合物的大小和形状，通常集中使用模板2,3，4月底封盖机或选择性溶剂技巧5。 在这里，我们披露基于自组装的盘状双亲的策略，导致有序，手性柱状总量超过栈的长度和形状的控制。由平衡亲水RIM和内聚合积木的疏水核心吸引力的非共价势力的静电排斥作用，我们设法建立小的和离散的球状物体6,7。 increa唱的盐浓度筛选收费引起球杆过渡。有趣的是，这种转变表现在随温度变化的自组装机制的协同增加，并得到更稳定的聚合。 对于我们的研究中，我们选择苯,3,5-tricarboxamide（BTA）的核心，连接通过疏水性，氟化基于L-苯丙氨酸的垫片（ 计划1）亲水性金属螯合。所选的金属螯合是一个GD（Ⅲ）-DTPA的复杂，它包含两个大局其余的复杂和必然两个反离子的收费。的一维的增长，总导演由π-π堆积和分子间氢​​键。然而，静电排斥力的Gd（Ⅲ）-DTPA的复杂开始限制一维的的排屑基于盘状增长达到一定规模后，收费的过程中出现。在毫摩尔浓度的形成总有一个SPHErical形状和一个直径约5纳米的1 H-NMR光谱，小角X射线散射，低温透射电子显微镜（冷冻TEM）推断。盐缓冲溶液浓度增加，可减少分子间的静电排斥作用的力量。这种检查收费，导致一个球形聚合成一个长度大于25纳米的细长杆的过渡。冷冻透射电镜允许可视化的形状和大小的变化。此外，CD光谱允许派生盐除了之前和之后的自组装过程中的机械细节。重要的协同，一个关键的功能，显着，经筛选的静电相互作用产生的超分子聚合物，增加的物理性质，化学性质，决定了。这种增加在水中形成的超分子聚合物的分子量在显着增加的协同结果。

Watch this Scientific Journal Video about Controlling the Size, Shape and Stability of Supramolecular Polymers in Water at JoVE.com

Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

这个实验的目的是确定和控制的大小，形状和在水中自组装的盘状双亲的稳定。为水基超分子聚合物的控制水平是非常困难的。我们申请的策略，同时使用排斥力和吸引力的互动。实验技术应用到这个系统的特征是广泛的适用性。

控制的大小，形状和稳定性超分子聚合物在水

For aqueous based supramolecular polymers, the simultaneous control over shape, size and stability is very difficult1. At the same time, the ability to do ...

controlling-size-shape-stability-supramolecular-polymers

Research

JoVE Journal

Engineering

18.5K 次观看.  Westfälische Wilhelms-Universität Münster. 这个实验的目的是确定和控制的大小，形状和在水中自组装的盘状双亲的稳定。为水基超分子聚合物的控制水平是非常困难的。我们申请的策略，同时使用排斥力和吸引力的互动。实验技术应用到这个系统的特征是广泛的适用性。

视频: Controlling the Size, Shape and Stability of Supramolecular Polymers in Water

Fine-tuning the Size and Minimizing the Noise of Solid-state Nanopores

Solid-state nanopores have emerged as a versatile tool for the characterization of single biomolecules such as nucleic acids and proteins1. However, the creation of a nanopore in a thin insulating membrane remains challenging. Fabrication methods involving specialized focused electron beam systems can produce well-defined nanopores, but yield of reliable and low-noise nanopores in commercially available membranes remains low2,3 and size control is nontrivial4,5. Here, the application of high electric fields to fine-tune the size of the nanopore while ensuring optimal low-noise performance is demonstrated. These short pulses of high electric field are used to produce a pristine electrical signal and allow for enlarging of nanopores with subnanometer precision upon prolonged exposure. This method is performed in situ in an aqueous environment using standard laboratory equipment, improving the yield and reproducibility of solid-state nanopore fabrication.

A methodology for preparing solid-state nanopores in solution for biomolecular translocation experiments is presented. By applying short pulses of high electric fields, the nanopore diameter can be controllably enlarged with subnanometer precision and its electrical noise characteristics significantly improved. This procedure is performed in situ using standard laboratory equipment under experimental conditions.

微调尺寸和最小化固态纳米孔的噪音

Solid-state nanopores have emerged as a versatile tool for the characterization of single biomolecules such as nucleic acids and proteins1. However, the ...

科研

工程学

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 ...

Experimental Methods for Investigation of Shape Memory Based Elastocaloric Cooling Processes and Model Validation

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor compression based cooling process. Nickel-Titanium (Ni-Ti) based alloy systems, especially, show large elastocaloric effects. Furthermore, exhibit large latent heats which is a necessary material property for the development of an efficient solid-state based cooling process. A scientific test rig has been designed to investigate these processes and the elastocaloric effects in SMAs. The realized test rig enables independent control of an SMA&#39;s mechanical loading and unloading cycles, as well as conductive heat transfer between SMA cooling elements and a heat source/sink. The test rig is equipped with a comprehensive monitoring system capable of synchronized measurements of mechanical and thermal parameters. In addition to determining the process-dependent mechanical work, the system also enables measurement of thermal caloric aspects of the elastocaloric cooling effect through use of a high-performance infrared camera. This combination is of particular interest, because it allows illustrations of localization and rate effects &#8212; both important for efficient heat transfer from the medium to be cooled.
The work presented describes an experimental method to identify elastocaloric material properties in different materials and sample geometries. Furthermore, the test rig is used to investigate different cooling process variations. The introduced analysis methods enable a differentiated consideration of material, process and related boundary condition influences on the process efficiency. The comparison of the experimental data with the simulation results (of a thermomechanically coupled finite element model) allows for better understanding of the underlying physics of the elastocaloric effect. In addition, the experimental results, as well as the findings based on the simulation results, are used to improve the material properties.

Experimental methods for investigation of solid state cooling processes and characterization of elastocaloric material properties of Shape Memory Alloys (SMA) are presented. A custom-built test rig has been designed for controlling and comprehensive monitoring of elastocaloric cooling processes. Furthermore, it provides a validation platform for thermomechanically coupled modeling approaches.

基于形状记忆调查Elastocaloric冷却过程和模型验证实验方法

Shape Memory Alloys (SMA) using elastocaloric cooling processes have the potential to be an environmentally friendly alternative to the conventional vapor ...

Ice Generation and the Heat and Mass Transfer Phenomena of Introducing Water to a Cold Bath of Brine

We demonstrate a method for the study of the heat and mass transfer and of the freezing phenomena in a subcooled brine environment. Our experiment showed that, under the proper conditions, ice can be produced when water is introduced to a bath of cold brine. To make ice form, in addition to having the brine and water mix, the rate of heat transfer must bypass that of mass transfer. When water is introduced in the form of tiny droplets to the brine surface, the mode of heat and mass transfer is by diffusion. The buoyancy stops water from mixing with the brine underneath, but as the ice grows thicker, it slows down the rate of heat transfer, making ice more difficult to grow as a result. When water is introduced inside the brine in the form of a flow, a number of factors are found to influence how much ice can form. Brine temperature and concentration, which are the driving forces of heat and mass transfer, respectively, can affect the water-to-ice conversion ratio; lower bath temperatures and brine concentrations encourage more ice to form. The flow rheology, which can directly affect both the heat and mass transfer coefficients, is also a key factor. In addition, the flow rheology changes the area of contact of the flow with the bulk fluid.

Here, we present a protocol to demonstrate the generation of ice when water is introduced to a cold bath of brine, as a secondary refrigerant, at a range of temperatures well below the freezing point of water. It can be used as an alternative way of producing ice for industry.

冰生成和传热传质现象将水引入到盐水冷水浴

We demonstrate a method for the study of the heat and mass transfer and of the freezing phenomena in a subcooled brine environment. Our experiment showed ...

Detecting the Water-soluble Chloride Distribution of Cement Paste in a High-precision Way

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a high-precision chloride profile. Firstly, paste specimens are molded, cured, and exposed to cyclic wet-dry conditions. Then, powder samples at different specimen depths are grinded when the exposure age is reached. Finally, the water-soluble chloride content is detected using a silver nitrate titration method, and chloride profiles are plotted. The key to improving the accuracy of the chloride distribution along the depth is to exclude the error in the powderization, which is the most critical step for testing the distribution of chloride. Based on the above concept, the grinding method in this protocol can be used to grind powder samples automatically layer by layer from the surface inward, and it should be noted that a very thin grinding thickness (less than 0.5 mm) with a minimum error less than 0.04 mm can be obtained. The chloride profile obtained by this method better reflects the chloride distribution in specimens, which helps researchers to capture the distribution features that are often overlooked. Furthermore, this method can be applied to studies in the field of cement-based materials, which require high chloride distribution accuracy.

A protocol for obtaining a water-soluble chloride profile by using a high precision milling method is presented.

高精度水泥浆水溶氯分布的检测

To improve the accuracy of the chloride distribution along the depth of cement paste under cyclic wet-dry conditions, a new method is proposed to obtain a ...

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. ...

Near-Infrared Temperature Measurement Technique for Water Surrounding an Induction-heated Small Magnetic Sphere

A technique to measure the temperature of water and non-turbid aqueous media surrounding an induction-heated small magnetic sphere is presented. This technique utilizes wavelengths of 1150 and 1412 nm, at which the absorption coefficient of water is dependent on temperature. Water or a non-turbid aqueous gel containing a 2.0-mm- or 0.5-mm-diameter magnetic sphere is irradiated with 1150 nm or 1412 nm incident light, as selected using a narrow bandpass filter; additionally, two-dimensional absorbance images, which are the transverse projections of the absorption coefficient, are acquired via a near-infrared camera. When the three-dimensional distributions of temperature can be assumed to be spherically symmetric, they are estimated by applying inverse Abel transforms to the absorbance profiles. The temperatures were observed to consistently change according to time and the induction heating power.

A technique utilizing wavelengths of 1150 and 1412 nm to measure the temperature of water surrounding an induction-heated small magnetic sphere is presented.

感应加热小磁球周围水近红外测温技术

A technique to measure the temperature of water and non-turbid aqueous media surrounding an induction-heated small magnetic sphere is presented. This ...

Fabricating Reactive Surfaces with Brush-like and Crosslinked Films of Azlactone-Functionalized Block Co-Polymers

In this paper, fabrication methods that generate novel surfaces using the azlactone-based block co-polymer, poly (glycidyl methacrylate)-block-poly (vinyl dimethyl azlactone) (PGMA-b-PVDMA), are presented. Due to the high reactivity of azlactone groups towards amine, thiol, and hydroxyl groups, PGMA-b-PVDMA surfaces can be modified with secondary molecules to create chemically or biologically functionalized interfaces for a variety of applications. Previous reports of patterned PGMA-b-PVDMA interfaces have used traditional top-down patterning techniques that generate non-uniform films and poorly controlled background chemistries. Here, we describe customized patterning techniques that enable precise deposition of highly uniform PGMA-b-PVDMA films in backgrounds that are chemically inert or that have biomolecule-repellent properties. Importantly, these methods are designed to deposit PGMA-b-PVDMA films in a manner that completely preserves azlactone functionality through each processing step. Patterned films show well-controlled thicknesses that correspond to polymer brushes (~90 nm) or to highly crosslinked structures (~1-10 &#956;m). Brush patterns are generated using either the parylene lift-off or interface directed assembly methods described and are useful for precise modulation of overall chemical surface reactivity by adjusting either the PGMA-b-PVDMA pattern density or the length of the VDMA block. In contrast, the thick, crosslinked PGMA-b-PVDMA patterns are obtained using a customized micro-contact printing technique and offer the benefit of higher loading or capture of secondary material due to higher surface area to volume ratios. Detailed experimental steps, critical film characterizations, and trouble-shooting guides for each fabrication method are discussed.

Surface fabrication methods for patterned deposition of nanometer thick brushes or micron thick, crosslinked films of an azlactone block co-polymer are reported. Critical experimental steps, representative results, and limitations of each method are discussed. These methods are useful for creating functional interfaces with tailored physical features and tunable surface reactivity.

Azlactone 功能块共聚物的刷状和交联膜制备反应表面

In this paper, fabrication methods that generate novel surfaces using the azlactone-based block co-polymer, poly (glycidyl methacrylate)-block-poly (vinyl ...

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic glasses (MGs). Despite their amorphous nature, the identification of hyperfine interactions unveils faint structural modifications. For this purpose, we have employed two techniques that utilize nuclear resonance among nuclear levels of a stable 57Fe isotope, namely M&#246;ssbauer spectrometry and nuclear forward scattering (NFS) of synchrotron radiation. The effects of heat treatment upon (Fe2.85Co1)77Mo8Cu1B14 MG are discussed using the results of ex situ and in situ experiments, respectively. As both methods are sensitive to hyperfine interactions, information on structural arrangement as well as on magnetic microstructure is readily available. M&#246;ssbauer spectrometry performed ex situ describes how the structural arrangement and magnetic microstructure appears at room temperature after the annealing under certain conditions (temperature, time), and thus this technique inspects steady states. On the other hand, NFS data are recorded in situ during dynamically changing temperature and NFS examines transient states. The use of both techniques provides complementary information. In general, they can be applied to any suitable system in which it is important to know its steady state but also transient states.

Methods of Ex Situ and In Situ Investigations of Structural Transformations: The Case of Crystallization of Metallic Glasses

Here, we present a protocol to describe ex situ and in situ investigations of structural transformations in metallic glasses. We employed nuclear-based analytical methods which inspect hyperfine interactions. We demonstrate the applicability of M&#246;ssbauer spectrometry and nuclear forward scattering of synchrotron radiation during temperature-driven experiments.

结构转换的原位和原位研究方法: 金属玻璃结晶的实例

We demonstrate the use of two nuclear-based analytical methods that can follow the modifications of microstructural arrangement of iron-based metallic ...

Design and Fabrication of an Optical Fiber Made of Water

In this report, an optical fiber of which the core is made solely of water, while the cladding is air, is designed and manufactured. In contrast with solid-cladding devices, capillary oscillations are not restricted, allowing the fiber walls to move and vibrate. The fiber is constructed by a high direct current (DC) voltage of several thousand volts (kV) between two water reservoirs that creates a floating water thread, known as a water bridge. Through the choice of micropipettes, it is possible to control the maximal diameter and length of the fiber. Optical fiber couplers, at both sides of the bridge, activate it as an optical waveguide, allowing researchers to monitor the water fiber capillary body waves through transmission modulation and, therefore, deducing changes in surface tension.
Co-confining two important wave types, capillary and electromagnetic, opens a new path of research in the interactions between light and liquid-wall devices. Water-walled microdevices are a million times softer than their solid counterparts, accordingly improving the response to minute forces.

This protocol describes the design and manufacture of a water bridge and its activation as a water fiber. The experiment demonstrates that capillary resonances of the water fiber modulate its optical transmission.

一种水上光纤的设计与制造

In this report, an optical fiber of which the core is made solely of water, while the cladding is air, is designed and manufactured. In contrast with ...