Name: prescribed 3-d direct writing of suspended micron/sub-micron scale fiber structures via a robotic dispensing system
Uploaded: 2015-06-12T13:00:00.000+00:00
Duration: 10 min 36 s
Description: Watch this Scientific Journal Video about Prescribed 3-D Direct Writing of Suspended Micron/Sub-micron Scale Fiber Structures via a Robotic Dispensing System at JoVE.com

This work is supported by the NSF-EPSCoR (grant #0814194) and the Department of Bioengineering.

<html> 1.设备安装<ol><li>组装的分配系统和阀控制器和注射器筒连接到气动源，通过一个压力调节器，用来设置所述压力为15磅，以分配从针尖的聚合物溶液以2.45微升/分钟的流速。 </li><li>插入的3轴的机器人和分送系统入热敏外壳以确保一个稳定的工作环境（ 图2）。 </li><li>安装联合机器人控制点（JR-C点）软件系统制造商提供，并通过串行通讯端口3轴机器人连接到计算机。 </li><li>安装分配阀，以3轴的机器人和安装针尖到阀。 </li><li>根据制造商的指导，以确保平整度相对于所述阀头15的高度水平，机器人阶段压板。 </li><li>组装反馈控制加热器的外壳增加环境控制。 </li></ol>内容"FO:保持together.within页="总是"&gt; <img alt="图2" src="/files/ftp_upload/52834/52834fig2.jpg" /> 图2.（A）3轴点胶机器人放置在机柜内所需的配件;和（B）关闭了连接的USB显微镜可视化分配阀的形象。 <a href="https://www.jove.com/files/ftp_upload/52834/52834fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> 2.实验材料和控制因素<ol><li>控制因素及其组合。 <ol><li>而不同进料速度为1％的速度（5毫米/秒）到100％（500毫米/秒），由JR C-点软件。 对于这种应用，使用2％的速度（10毫米/秒）来制造纤维结构提出了这项工作。 </li><li>变化的聚合物溶液的浓度，以达到特定的粘度，表面张力和波动参数所需对于所需的应用程序。 对于这种应用，使用24％聚甲基丙烯酸甲酯（PMMA）在氯苯溶液来制造在这项工作中提出的纤维结构。 </li><li>为了喷射经由气动空气解决方案有所不同控制阀分配时间为0.02秒至1秒。 对于这种应用，使用0.02秒，制作在这项工作中提出的纤维结构。 </li><li>选择精度高的针尖的计示大小来分配聚合物溶液。 对于这种应用，使用一个30 G（内径（ID）= 152.4微米）尖端制造在这项工作中提出的纤维结构。 </li><li>在隔热箱以维持聚合物样品的恒定蒸发速度之间70°F设定的工作温度范围为100°F。 对于这种应用，使用70°F的温度以制造在这项工作中提出的纤维结构。 </li></ol></li><li>制备聚合物溶液的。 <ol><li>混合聚甲基丙烯酸甲酯的聚合物的树脂（聚甲基丙烯酸甲酯0.72克）与溶剂氯苯（2.28克）的化学流罩。 </li><li>计算聚合物（PMMA）和其溶剂（氯苯），以实现聚合物在溶液中的所需浓度的重量。 对于这种应用，使用24％聚甲基丙烯酸甲酯（PMMA）在氯苯溶液来制造在这项工作中提出的纤维结构。 </li><li>放置聚合物粉末/树脂在玻璃小瓶中的所需量。 对于这种应用，使用0.72克PMMA树脂的获得的PMMA的24％的浓度。 </li><li>通过移液管，直到3克的总重量达到内小瓶转移溶剂到聚合物。 </li><li>混合瓶内，用涡旋振荡器1分钟，并用超声波处理它们5小时，以完全溶解聚合物粉末/树脂。 </li><li>检查解决方案的透明度，如果有任何混浊或不透明来样继续下超声直至澄清。 </li></ol></li><li>聚合物溶液的粘度测量。 <ol><li>经由锥和板式粘度计测量溶液的粘度（ 例如，LVDV-II +和RVDV-II +）16。 </li><li>负载0.5毫升提供的粘度计制造商校准粘度计，以尽量减少在粘度测量中的误差已知粘度的标准样品（基于甘油和水的混合物）的。制造商提供的各种标准样品的校准粘度计。使用甘油为基础的标准样品与100,000厘泊的粘度。 </li><li>连接水套到粘度计，以保持测试流体在恒定的工作温度。 </li><li>通过移动On / Off开关到ON位置以启动主轴旋转开始测试流体测量。一旦在显示面板上的转矩的值稳定后，记录的转矩，并计算使用扭矩主轴1，主轴乘数常数与速度之间的关系的最后粘度6 <img alt="式（1）" src="/files/ftp_upload/52834/52834eq1.jpg" /> 其中，是粘度，转速为固定到锥形主轴的速度，TK是转矩（0.09373为LVDV-II + 1 RVDV-II +），SMC是主轴乘数常数依赖于特定锭子粘度期间使用测量。在这项研究中，将CP-52锭子被使用，其具有9.83的主轴乘数常数。 </li></ol></li><li>聚合物溶液的表面张力的测量。 <ol><li>测量方法是指威廉米技术。14 </li><li>放置在玻璃小瓶1毫升试验溶液到高分辨率平衡（尺度分辨率= 0.001克）。浸已知直径的玻璃棒成测试溶液。 </li><li>控制杆通过一个伺服或步进控制的线性致动器的位置，以触摸表面和部分地浸入试验溶液与零接触。 </li><li>监测和天平上的记录时，在质量测量的变化从溶液表面去除杆。 </li><li>通过计算力的变化，流体杆上杆和接触角的周界表面张力。 <img alt="公式（2）" src="/files/ftp_upload/52834/52834eq2.jpg" /> 其中，被棒的浸润周界（ 升=10.05毫米直径 = 3.2 毫米 ），θ是流体的接触角在杆上，F是力变化由于表面测试流体的张力杆的尖端。 </li></ol></li><li>解决方案的传质系数的测量。 <ol><li>测量聚合物溶液通过热重分析的传质系数。14 </li><li>负载30微升24％（重量）聚甲基丙烯酸甲酯的聚合物溶液上的铂板的去皮的平衡之前。 </li><li>泄腔室，程序设备在所需的操作温度（70°F）2小时，以监测目标的解决方案的质量。 </li><li>通过改变溶液的质量计算的传质系数，面积溶液/空气界面和密度。 <img alt="公式3" src="/files/ftp_upload/52834/52834eq3.jpg" /> 其中m（t）是聚甲基丙烯酸甲酯溶液的质量，A是溶液/空气界面的面积（等于78.5毫米2为标板），mPOLYMER是在溶液中的聚合物的质量，是该溶液的密度。 </li></ol></li></ol> 3.直写实验过程<ol><li>分配系统样品装载协议。 <ol><li>负载3毫升聚合物溶液到注射器筒，将活塞推入注射器筒，以消除不一致气动压力分布。 </li><li>拧上的注射器管的入口管线的转接器，其连接到源极线的空气管。 </li><li>选择的精度针尖所需尺寸大小来执行实验。 </li><li>在分配控制面板，切换到清除状态，然后单击"循环"按钮，以填补分配阀与聚合物等等lution直到从针尖排出。 </li><li>擦拭从尖端在制备编程纤维写入过程的残留聚合物溶液。 </li></ol></li><li>直写聚合物纤维具有3轴机器人和分送系统。 <ol><li>确定机器人阶段偏移来重新定位从默认位置到规定的微/亚微米纤维结构体的引发点的分配针的尖端，以进行绘制。挂载USB显微镜（放大倍数= 200X）到分配系统阀支架，其沿Z轴平移。手动聚焦于分配器触头通过调整上的USB显微镜，其有助于精确地定位在阀头至所需位置，预制基底或设备的调焦旋钮。 </li><li>创建/设计所需的纤维结构图案（ 图3A，4A和5A）使用CAD软件程序包。输入在ROBO的空间坐标（x，Y，Z）吨JR-C的控制用于 ​​在顺序所有起始和终止点的软件相对于所述CAD程序（ 图3B，4B和5B）内产生所需的图案。15 </li><li>通过点击"发送C＆T的数据"下的JR-C软件15内的机器人菜单从计算机传送完成的纤维结构设计方案的机器人。 </li><li>负载3毫升已知浓度（24％）到注射器筒，净化阀和针的聚甲基丙烯酸甲酯溶液的样品，将所有的阀门控制器和机器人控制软件分配的参数。 </li><li>放置预制基底上的机器人阶段压板，关闭热机柜门，以防止周围空气的流动，其可以诱导聚合物溶液的不稳定蒸发。 </li><li>首先单击菜单机器人从JR-C软件，并选择写纤维在基板上"试运行"15。 </li><li>直流溅射涂层的导电性金金属层2分钟，直到2纳米厚的金层沉积在被拉伸的纤维，以允许在扫描电子显微镜将纤维的可视化。 </li><li>测量纤维的通过扫描型电子显微镜17的直径和结构。显微镜参数:高电压等级:2.00千伏;目的:InLens，工作距离（9.0毫米）。 </li></ol></li><li>根据化学流罩进行分配系统清洗程序。 <ol><li>放置在分配系统中的化学流罩来执行清洁过程。 </li><li>根据制造商的协议拆卸针阀。 </li><li>将所有的金属部件放入烧杯中，倒入丙酮放入烧杯中，直到所有部分都沉浸。 </li><li>放置烧杯在超声浴中30分钟以除去所有的聚合物残余。 </li><li>下冲洗流动DI水各个部位，然后用气枪吹他们干。 </li></ol></<html> LI&gt; </ol><img alt="图3" src="/files/ftp_upload/52834/52834fig3.jpg" /> 在一个10毫米×10毫米框架设计的"四"的网络结构图3.（A）为例，（B）连续点至点空间指令被输入到JR-C点的软件。 <a href="https://www.jove.com/files/ftp_upload/52834/52834fig3large.jpg" target="_blank">请点击此处查看更大的版本这个数字。</a> <img alt="图4" src="/files/ftp_upload/52834/52834fig4.jpg" /> 图设计的"对称的"网络结构上有10毫米×10毫米框架4（A）的实施例，（B）的顺序点对点的空间的指示将其输入到JR-C的点的软件。空白"&gt;点击此处查看该图的放大版本。 <img alt="图5" src="/files/ftp_upload/52834/52834fig5.jpg" /> 设计的"双V形"网状结构上有10毫米×10毫米框架，（B）连续点至点的空间说明图5（A）例被输入到JR-C点的软件。 <a href="https://www.jove.com/files/ftp_upload/52834/52834fig5large.jpg" target="_blank">请点击这里查看一个更大的版本这个数字。</a>

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The authors have nothing to disclose.

在尝试每个试验中，该聚合物溶液的粘度，传质系数和表面张力测试准确地测量，以便确定机器人和分送系统是否能够处理所需的聚合物的这一点至关重要。正如我们小组先前所描述的，聚合物溶液必须保持足够的:1）表面张力，使液体细丝的形成为微米/亚微米结构; 2）粘度承受毛细血管分手;和，3）的蒸发速率，以提高纤维凝固18。这些参数之间的协同作用是关键成功地生产纤维超过直径的特定范围。与此同时，不稳定性，在任何这些参数可防止微米/亚微米级纤维的形成。维持期间纤维制造这些参数之间的协同作用，以保证针和针阀后一个直写S被彻底清洁是非常重要的分裂国家，以防止:1）污染溶液; 2）在通过针将聚合物溶液流率的降低;和，3）过度增长在针的尖端的聚合物珠。此外，在加热器的温度控制器必须设置为所需的温度，以保持聚合物溶液的恒定蒸发速度。 分叉支路纤维为59％，41％和24％的直径大于该支撑结构在图6-8中，分别使用了24％的PMMA溶液。这主要是由于在该纤维被拉伸的距离。具体地，支撑结构跨过衬底的整个宽度绘制（10.0毫米X和Y方向;14.4毫米对角线）。其结果是，这些是整体悬挂结构的最长纤维。分叉的分支结构显著短，从7毫米最大长度下降到2.5毫米。这种短纤维拉丝长度确实没吨有效地诱导在纤维减薄过程所需的光纤应变以产生小直径的纤维。另一方面，大直径的电线被要求作为支撑纤维，以便有效地维持在分叉支路拉拔处理引起的拖拽和变形。作为分岔分支横跨支承纤维拉伸，支撑纤维几何形状的重塑可能是由于该图的力以及聚甲基丙烯酸甲酯聚合物在所述载体之间的界面的本地化溶解和支纤维从溶剂中存在的聚合物溶液。因此，在一些情况下，载体纤维可能需要被选自聚合物的较高浓度的，以产生更大的直径和机械强纤维的聚合物溶液制成。 有主要3种有效的方法，用于修改现有的协议，以产生一个更广泛的支持和支纤维直径:1）最初分配从较大针尖的聚合物（ 例如，25 G组; n = 254微米），以产生载体纤维，然后交换为一个较小的针尖（ 例如，32 G组; n = 101.6微米），以制造较小的分支纤维; 2）如上所述，使用多个聚合物浓度;和/或，3）调整进给速率， 即，在该阶段遍历，其中，增加进料速率产生较小直径的纤维和降低进给速率的速度产生较大的直径的纤维。到目前为止，我们已经能够成功地制造纤维小到90纳米;然而，纤维产量在这方面是低，由于毛细血管破裂。 自动直写方法的一个限制是，只有一个浓度的聚合物溶液可以同时被分配。这个限制也可以，而不必开发悬浮结构的复杂性的级别:1）添加第二分配阀的机器人;或者，2）删除现有的阀门和分配第二聚合物溶液，这需要更多的时间之前进行清理协议（第3.4节）。第二个限制是进料速率（或打印速度），其中，最大进料速率，该系统能够实现的为500毫米/秒。然而，有进料速率和纤维形成之间的折衷。具体地说，如果惯性力（由于进料速率的力）大于表面张力和将聚合物溶液的蒸发速率，纤维形成不会发生。另一方面，如果进料速率太低，纤维将断裂，由于之前和期间的伸长过程过度蒸发。第三，纤维和结构的尺寸被限制为在x，y和z方向上的工作范围内的机器人的阶段， 即200毫米，200毫米和25毫米（用10微米的位置精度），分别。然而，这一工艺的确使高纵横比的形成（纤维升ength:直径）纤维。战略上改变分配尖端尺寸和聚合物溶液浓度将允许更广泛的纤维直径范围，创建，以产生更高的复杂性自由悬挂结构的能力。 按照上述的协议，微米和亚微米直径的聚合物纤维可以具有空间控制高水平通过利用聚合物溶液的表面张力驱动流体力学，不能与任何其他湿，干的或静电纺丝的过程控制而生成的。从以前的工作8,19，我们知道，这种技术可用于制造复杂的微/亚微米流体装置19和生物工程支架8。这种廉价和简单的技术都有自己的优势在许多方面传统的刨床加工方法。

在过去的几十年中，各种的制造技术，如湿纺，干纺和静电，已经被用来产生新的聚合物的纤维结构具有不同和健壮的生物，化学，电和机械性能1-12。虽然这些纺丝技术是能够产生悬浮三维纤维，他们在他们的精确控制纤维取向在三维空间中，因为通过这些过程纤维沉积是随机的能力是有限的。此外，这些技术被限制在其尺寸范围为纤维制造;具体地，通过湿纺和干纺生产的纤维变化的直径从几十到几百微米，而电纺丝收率纤维直径从数十纳米到单个微米13。 提供的纤维取向更精确地控制在3-D空间，我们小组开发出了自-assemble或"直写"光纤制造工艺直接弹出一个聚合材料出一个中空毛细管，然后绘制其薄且固化成可预测的纤维直径通过利用表面张力驱动的流体力学14根单丝。我们的用于提高光纤位置和直径的控制水平初始直接写入系统包括附连到由超高精度微细铣削机（ 图1）的自定义的头部的定制制造的弹簧加载的注射器分配系统。所述UHPMM有阶段与在X和Y方向1.25纳米和在被编程控制，以创建微米和亚微米尺度线和结构在Z方向20纳米的定位分辨率。这个特定的直写系统中的一个限制是缺乏通过针尖的聚合物溶液的流控制。虽然弹簧加载分配系统成功产生恒定的FLO瓦特通过末端，聚合物溶液连续扩张的球形珠在注射器尖端，在尺寸和容积变化取决于环境条件的出口被创建。 <img alt="图1" src="/files/ftp_upload/52834/52834fig1.jpg" /> 图超高精度微细铣削机1.图像:在制作微米/亚微米尺度结构采用的首次直接写入系统 <a href="https://www.jove.com/files/ftp_upload/52834/52834fig1large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> 这个源珠的不一致影响了系统的重复制造一个规定直径的线的能力。虽然，用这种直接写入处理成功产生的结构，增强了过程通过增加聚合物溶液的流动的控制将允许更多PRECI本身，通过珠尺寸的调节在注射器尖端规定的纤维直径。因此，该工作描述了一个3轴自动分配系统与气动分配器阀来精确控制来创建规定的聚合物溶液流速和尖珠尺寸，微米/亚微米悬浮结构的实施。

<table><tbody><tr><td>ROBOT DR2203N 3 AXES 200MM X 200MM</td><td>Nordson EFD</td><td>7023145</td><td>3-Axis Robot</td></tr><tr><td>CONTROLLER 7100, DISPENSE VALVE</td><td>Nordson EFD</td><td>7015340</td><td>Valve Controller</td></tr><tr><td>MICRODOT VALVE</td><td>Nordson EFD</td><td>7021233</td><td>Microdot Valve</td></tr><tr><td>ROBOT ACC FIXTURE PLATE 200MM</td><td>Nordson EFD</td><td>7028276</td><td>Fixture Platen</td></tr><tr><td>ROBOT ACC DRN / DSRN POINTS SOFTWAR</td><td>Nordson EFD</td><td>7023144</td><td>JR-C Software</td></tr><tr><td>ROBOT MOUNT VALVE UNIVERSAL</td><td>Nordson EFD</td><td>7028273</td><td>Microdot Valve Mount</td></tr><tr><td>15 PSI BARREL PRESS. REGULATOR</td><td>Nordson EFD</td><td>7020585</td><td>Barrel Regulator</td></tr><tr><td>KIT O BRL/PIST 5CC CL/WH 40</td><td>Nordson EFD</td><td>7012096</td><td>5CC Barrels with Pistons</td></tr><tr><td>ADAPTER ASM O 5CC BL</td><td>Nordson EFD</td><td>7012054</td><td>Pneumatic Barrel Adapter</td></tr><tr><td>TIP 30GA .006X.25 LAVNDR 50PC</td><td>Nordson EFD</td><td>7018424</td><td>30 gauge Needle Tip (0.250&quot; length)</td></tr><tr><td>Electric Baseboard Heater (500&amp;nbsp;W, 30&quot; length)</td><td>Cadet</td><td>2F500</td><td>Heater</td></tr><tr><td>Temperature Controller with Timer</td><td>Control Company</td><td>130726596</td><td>Temperature Controller</td></tr><tr><td>eScope USB Microscope</td><td>OiTez</td><td>DP-M02</td><td>200X USB Microscope</td></tr><tr><td>Poly(methyl methacrylate)</td><td>Aldrich</td><td>182265-500G</td><td>PMMA Powder</td></tr><tr><td>Chlorobenzene</td><td>Sigma Aldrich</td><td>284513</td><td>Solvent to dissolve PMMA</td></tr></tbody></table>

prescribed 3-d direct writing of suspended micron/sub-micron scale fiber structures via a robotic dispensing system

A 3-axis dispensing system is utilized to control the initiating and terminating fiber positions and trajectory via the dispensing software. The polymer fiber length and orientation is defined by the spatial positioning of the dispensing system 3-axis stages. The fiber diameter is defined by the prescribed dispense time of the dispensing system valve, the feed rate (the speed at which the stage traverses from an initiating to a terminating position), the gauge diameter of the dispensing tip, the viscosity and surface tension of the polymer solution, and the programmed drawing length. The stage feed rate affects the polymer solution&#8217;s evaporation rate and capillary breakup of the filaments. The dispensing system consists of a pneumatic valve controller, a droplet-dispensing valve and a dispensing tip. Characterization of the direct write process to determine the optimum combination of factors leads to repeatedly acquiring the desired range of fiber diameters. The advantage of this robotic dispensing system is the ease of obtaining a precise range of micron/sub-micron fibers onto a desired, programmed location via automated process control. Here, the discussed self-assembled micron/sub-micron scale 3D structures have been employed to fabricate suspended structures to create micron/sub-micron fluidic devices and bioengineered scaffolds.

通过为每个在图3-5A＆B如上所定义的相应的设计和JR的C-点算法的3轴的机器人和直写方法产生的实际结构的图像分别示于图6A，7A和8A所示 。如可在所产生的图像中可以看出，三维的，自由悬挂纤维已通过精确操纵分配器触头到规定的空间位置包括所述发起/终止点以及交叉点成功"写入"一直到基片上。这些数字的插图放大交点悬浮的纤维，这表明该系统的精确控制纤维取向（ 图6B，7B和8B）在3-D空间的能力的点。 <img alt="图6" src="/files/ftp_upload/52834/52834fig6.jpg" /> 图6（A）欧普<html> （;比例尺=1毫米15X光学倍率），单光纤分叉（289X放大倍率（二）SEM图像;捏造"四"有2支纤维（对角线）和12支岔PMMA纤维悬浮网结构蒂卡尔图像比例酒吧= 100微米）。 <a href="https://www.jove.com/files/ftp_upload/52834/52834fig6large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <img alt="图7" src="/files/ftp_upload/52834/52834fig7.jpg" /> 图7（A）制造的"对称"暂停网，它具有1支持光纤（水平）和11支岔PMMA纤维结构的光学图像;单一分叉（15X光学放大倍率比例尺= 1毫米），（B）SEM图像纤维（107X放大;比例尺= 100微米）。52834fig7large.jpg"目标="_空白"&gt;点击此处查看该图的放大版本。 <img alt="图8" src="/files/ftp_upload/52834/52834fig8.jpg" /> 图8（A）的制备"双V形"光学影像悬浮有1支持光纤（水平）和22支岔PMMA纤维网状结构（15X光学放大倍数;比例尺= 1毫米），（B）单的SEM图像分叉纤维（80X放大;比例尺= 100微米） <a href="https://www.jove.com/files/ftp_upload/52834/52834fig8large.jpg" target="_blank">请点击这里查看这个数字的放大版本。</a> 图9显示特写视图纤维制造的连续点至点顺序在该3轴机器人和分送系统可以生成自由悬浮幅状结构。在P<html>用数字显示olymer接触点对应于编程发起和终止点在图3B中引用上述JR-C软件。箭头代表机器人的运动轨迹。 图10显示了微米和亚微米级聚合物纤维，这表明直接写入系统的制作不同大小的导线能力。 <img alt="图9" src="/files/ftp_upload/52834/52834fig9.jpg" /> 图9. SEM图像说明用于绘制微米和亚微米级的聚合物纤维（29X放大倍数;比例尺= 200微米）的连续点至点的制造订单。 <a href="https://www.jove.com/files/ftp_upload/52834/52834fig9large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> 2834 / 52834fig10.jpg"/&gt; 图10. SEM微米（6.5微米）和亚微米（555纳米）用20％浓度的PMMA聚合物溶液拉伸纤维的形象。（2,270X放大;比例尺= 2微米）， <a href="https://www.jove.com/files/ftp_upload/52834/52834fig10large.jpg" target="_blank">请点击此处查看大图这个数字。</a> 聚合物纤维长度和直径分别使用扫描电子显微镜测定。 表1示出的平均金属丝直径为每个独特的结构之上对应于分叉支路纤维和支撑纤维示于图6-8。表2显示测定该聚合物的参数从被用于制造如上所述的结构，其中24％的PMMA的解决方案。 <table border="0" cellpadding="0" cellspacing="0"><tbody><tr><td></td><td>结构的直径在图6中</td><td>结构的直径在图7中</td><td>结构的直径在图8中</td></tr><tr><td> 支撑纤维 </td><td> 8.65±1.43微米</td><td> 9.39±1.23微米</td><td> 9.31±1.65微米</td></tr><tr><td> 分支光纤 </td><td> 20.96±3.35微米</td><td> 15.92±1.44微米</td><td> 12.24±5.42微米</td></tr></tbody></table> 暂停支持和分支光纤的表1的平均直径在图6-8为24％PMMA解决方案如图所示。 <table border="0" cellpadding="0" cellspacing="0"><tbody><tr><td></td><td> 24％的PMMA </td></tr><tr><td> 粘度（帕·秒） </td><td> 35.19 </td></tr><tr><td> 表面张力（达因/厘米） </td><td> 262.01 </td></tr><tr><tD&gt; 传质系数（米/秒） </td><td> 8.59×10 -8 </td></tr></tbody></table> 被用于制造在这项工作中提出的纤维结构，其在24％的PMMA溶液表2聚合物的参数。

Watch this Scientific Journal Video about Prescribed 3-D Direct Writing of Suspended Micron/Sub-micron Scale Fiber Structures via a Robotic Dispensing System at JoVE.com

Prescribed 3-D Direct Writing of Suspended Micron/Sub-micron Scale Fiber Structures via a Robotic Dispensing System

在这里，我们提出了一个协议，以制造自由悬浮，微米/亚微米尺度的聚合物通过自动化的直接写入过程由一个3轴分配系统的装置产生的纤维和"网状"结构。

暂停规定微米/亚微米尺度的纤维结构的3-D直写经全自动点胶系统

A 3-axis dispensing system is utilized to control the initiating and terminating fiber positions and trajectory via the dispensing software. The polymer ...

prescribed-3-d-direct-writing-suspended-micronsub-micron-scale-fiber

Research

JoVE Journal

Engineering

8.0K 次观看.  University of Louisville. 在这里，我们提出了一个协议，以制造自由悬浮，微米/亚微米尺度的聚合物通过自动化的直接写入过程由一个3轴分配系统的装置产生的纤维和"网状"结构。 

视频: Prescribed 3-D Direct Writing of Suspended Micron/Sub-micron Scale Fiber Structures via a Robotic Dispensing System

Fabrication, Densification, and Replica Molding of 3D Carbon Nanotube Microstructures

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip devices, and their applications. In particular, capabilities for cost-effective fabrication of polymer microstructures were transformed by the advent of soft lithography and other micromolding techniques 1, 2, and this led a revolution in applications of microfabrication to biomedical engineering and biology. Nevertheless, it remains challenging to fabricate microstructures with well-defined nanoscale surface textures, and to fabricate arbitrary 3D shapes at the micro-scale. Robustness of master molds and maintenance of shape integrity is especially important to achieve high fidelity replication of complex structures and preserving their nanoscale surface texture. The combination of hierarchical textures, and heterogeneous shapes, is a profound challenge to existing microfabrication methods that largely rely upon top-down etching using fixed mask templates. On the other hand, the bottom-up synthesis of nanostructures such as nanotubes and nanowires can offer new capabilities to microfabrication, in particular by taking advantage of the collective self-organization of nanostructures, and local control of their growth behavior with respect to microfabricated patterns. 
Our goal is to introduce vertically aligned carbon nanotubes (CNTs), which we refer to as CNT "forests", as a new microfabrication material. We present details of a suite of related methods recently developed by our group: fabrication of CNT forest microstructures by thermal CVD from lithographically patterned catalyst thin films; self-directed elastocapillary densification of CNT microstructures; and replica molding of polymer microstructures using CNT composite master molds. In particular, our work shows that self-directed capillary densification ("capillary forming"), which is performed by condensation of a solvent onto the substrate with CNT microstructures, significantly increases the packing density of CNTs. This process enables directed transformation of vertical CNT microstructures into straight, inclined, and twisted shapes, which have robust mechanical properties exceeding those of typical microfabrication polymers. This in turn enables formation of nanocomposite CNT master molds by capillary-driven infiltration of polymers. The replica structures exhibit the anisotropic nanoscale texture of the aligned CNTs, and can have walls with sub-micron thickness and aspect ratios exceeding 50:1. Integration of CNT microstructures in fabrication offers further opportunity to exploit the electrical and thermal properties of CNTs, and diverse capabilities for chemical and biochemical functionalization 3.

We present methods for fabrication of patterned microstructures of vertically aligned carbon nanotubes (CNTs), and their use as master molds for production of polymer microstructures with organized nanoscale surface texture. The CNT forests are densified by condensation of solvent onto the substrate, which significantly increases their packing density and enables self-directed formation of 3D shapes.

制备，致密，副本三维碳纳米管微结构成型

The introduction of new materials and processes to microfabrication has, in large part, enabled many important advances in microsystems, lab-on-a-chip ...

科研

工程学

A Method to Fabricate Disconnected Silver Nanostructures in 3D

The standard nanofabrication toolkit includes techniques primarily aimed at creating 2D patterns in dielectric media. Creating metal patterns on a submicron scale requires a combination of nanofabrication tools and several material processing steps. For example, steps to create planar metal structures using ultraviolet photolithography and electron-beam lithography can include sample exposure, sample development, metal deposition, and metal liftoff. To create 3D metal structures, the sequence is repeated multiple times. The complexity and difficulty of stacking and aligning multiple layers limits practical implementations of 3D metal structuring using standard nanofabrication tools. Femtosecond-laser direct-writing has emerged as a pre-eminent technique for 3D nanofabrication.1,2 Femtosecond lasers are frequently used to create 3D patterns in polymers and glasses.3-7 However, 3D metal direct-writing remains a challenge. Here, we describe a method to fabricate silver nanostructures embedded inside a polymer matrix using a femtosecond laser centered at 800 nm. The method enables the fabrication of patterns not feasible using other techniques, such as 3D arrays of disconnected silver voxels.8 Disconnected 3D metal patterns are useful for metamaterials where unit cells are not in contact with each other,9 such as coupled metal dot10,11or coupled metal rod12,13 resonators. Potential applications include negative index metamaterials, invisibility cloaks, and perfect lenses.
In femtosecond-laser direct-writing, the laser wavelength is chosen such that photons are not linearly absorbed in the target medium. When the laser pulse duration is compressed to the femtosecond time scale and the radiation is tightly focused inside the target, the extremely high intensity induces nonlinear absorption. Multiple photons are absorbed simultaneously to cause electronic transitions that lead to material modification within the focused region. Using this approach, one can form structures in the bulk of a material rather than on its surface.
Most work on 3D direct metal writing has focused on creating self-supported metal structures.14-16 The method described here yields sub-micrometer silver structures that do not need to be self-supported because they are embedded inside a matrix. A doped polymer matrix is prepared using a mixture of silver nitrate (AgNO3), polyvinylpyrrolidone (PVP) and water (H2O). Samples are then patterned by irradiation with an 11-MHz femtosecond laser producing 50-fs pulses. During irradiation, photoreduction of silver ions is induced through nonlinear absorption, creating an aggregate of silver nanoparticles in the focal region. Using this approach we create silver patterns embedded in a doped PVP matrix. Adding 3D translation of the sample extends the patterning to three dimensions.

Femtosecond-laser direct-writing is frequently used to create three-dimensional (3D) patterns in polymers and glasses. However, patterning metals in 3D remains a challenge. We describe a method for fabricating silver nanostructures embedded inside a polymer matrix using a femtosecond laser centered at 800 nm.

一个断开连接的银纳米结构的方法来制作的3D

The standard nanofabrication toolkit includes  techniques primarily aimed at creating 2D patterns in dielectric media. Creating  metal patterns on a ...

Process of Making Three-dimensional Microstructures using Vaporization of a Sacrificial Component

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material fabrication techniques are able to mimic the complexity of these structures while maintaining scalability. The Vaporization of a Sacrificial Component (VaSC) process is able to do so. This process uses sacrificial fibers as a template to form hollow, cylindrical microchannels embedded within a matrix. Tin (II) oxalate (SnOx) is embedded within poly(lactic) acid (PLA) fibers which facilitates the use of this process. The SnOx catalyzes the depolymerization of the PLA fibers at lower temperatures. The lactic acid monomers are gaseous at these temperatures and can be removed from the embedded matrix at temperatures that do not damage the matrix. Here we show a method for aligning these fibers using micromachined plates and a tensioning device to create complex patterns of three-dimensionally arrayed microchannels. The process allows the exploration of virtually any arrangement of fiber topologies and structures.

The Vaporization of a Sacrificial Component (VaSC) process is used to fabricate microvascular structures. This procedure uses sacrificial poly(lactic) acid fibers to form hollow microchannels with precise 3D geometric positioning provided by laser micromachined guide plates.

制作三维微结构，用牺牲部分汽化过程

Vascular structures in natural systems are able to provide high mass transport through high surface areas and optimized structure. Few synthetic material ...

Planar and Three-Dimensional Printing of Conductive Inks

Printed electronics rely on low-cost, large-area fabrication routes to create flexible or multidimensional electronic, optoelectronic, and biomedical devices1-3. In this paper, we focus on one- (1D), two- (2D), and three-dimensional (3D) printing of conductive metallic inks in the form of flexible, stretchable, and spanning microelectrodes.
Direct-write assembly4,5 is a 1-to-3D printing technique that enables the fabrication of features ranging from simple lines to complex structures by the deposition of concentrated inks through fine nozzles (~0.1 - 250 &mu;m). This printing method consists of a computer-controlled 3-axis translation stage, an ink reservoir and nozzle, and 10x telescopic lens for visualization. Unlike inkjet printing, a droplet-based process, direct-write assembly involves the extrusion of ink filaments either in- or out-of-plane. The printed filaments typically conform to the nozzle size. Hence, microscale features (&lt; 1 &mu;m) can be patterned and assembled into larger arrays and multidimensional architectures.
In this paper, we first synthesize a highly concentrated silver nanoparticle ink for planar and 3D printing via direct-write assembly. Next, a standard protocol for printing microelectrodes in multidimensional motifs is demonstrated. Finally, applications of printed microelectrodes for electrically small antennas, solar cells, and light-emitting diodes are highlighted.

Planar and three-dimensional printing of conductive metallic inks is described. Our approach provides new avenues for fabricating printed electronic, optoelectronic, and biomedical devices in unusual layouts at the microscale.

平面和立体印刷的导电油墨

Printed electronics rely on low-cost, large-area fabrication routes to create flexible or multidimensional electronic, optoelectronic, and biomedical ...

生物工程

Manufacturing of Three-dimensionally Microstructured Nanocomposites through Microfluidic Infiltration

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite in&#64257;ltration of 3D interconnected microfluidic networks. The manufacturing of the reinforced beams begins with the fabrication of microfluidic networks, which involves layer-by-layer deposition of fugitive ink filaments using a dispensing robot, filling the empty space between filaments using a low viscosity resin, curing the resin and finally removing the ink.&#160;Self-supported 3D structures with other geometries and many layers (e.g.&#160;a few hundreds layers) could be built using this method. The resulting tubular micro&#64258;uidic networks are then infiltrated with thermosetting nanocomposite suspensions containing nanofillers (e.g.&#160;single-walled carbon nanotubes), and subsequently cured. The infiltration is done by applying a pressure gradient between two ends of the empty network (either by applying a vacuum or vacuum-assisted microinjection). Prior to the infiltration, the nanocomposite suspensions are prepared by dispersing nanofillers into polymer matrices using ultrasonication and three-roll mixing methods. The nanocomposites (i.e.&#160;materials infiltrated) are then solidified under UV exposure/heat cure, resulting in a 3D-reinforced composite structure. The technique presented here enables the design of functional nanocomposite macroscopic products for microengineering applications such as actuators and sensors.

Three-dimensional (3D) microstructured composite beams are fabricated through the directed and localized infiltration of nanocomposites into 3D porous microfluidic networks. The flexibility of this manufacturing method enables the utilization of different thermosetting materials and nanofillers in order to achieve a variety of functional 3D reinforced nanocomposite macroscopic products.

通过微流体渗透制备三维微结构纳米复合材料的制造

Microstructured composite beams reinforced with complex three-dimensionally (3D) patterned nanocomposite microfilaments are fabricated via nanocomposite ...

化学

Laser-induced Forward Transfer of Ag Nanopaste

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of these processes such as inkjet3 and laser-induced forward transfer (LIFT)4 have become increasingly popular as interest in printable electronics and maskless patterning has grown. These additive manufacturing processes are inexpensive, environmentally friendly, and well suited for rapid prototyping, when compared to more traditional semiconductor processing techniques. While most direct-write processes are confined to two-dimensional structures and cannot handle materials with high viscosity (particularly inkjet), LIFT can transcend both constraints if performed properly. Congruent transfer of three dimensional pixels (called voxels), also referred to as laser decal transfer (LDT)5-9, has recently been demonstrated with the LIFT technique using highly viscous Ag nanopastes to fabricate freestanding interconnects, complex voxel shapes, and high-aspect-ratio structures. In this paper, we demonstrate a simple yet versatile process for fabricating a variety of micro- and macroscale Ag structures. Structures include simple shapes for patterning electrical contacts, bridging and cantilever structures, high-aspect-ratio structures, and single-shot, large area transfers using a commercial digital micromirror device (DMD) chip.

We demonstrate the use of the Laser-induced forward transfer technique (LIFT) for the printing of high-viscosity Ag paste. This technique offers a simple, low temperature, robust process for non-lithographically printing microscale 2D and 3D structures.

银纳米糊膏的激光诱导正向传输

Over the past decade, there has been much development of non-lithographic methods1-3 for printing metallic inks or other functional materials. Many of ...

Microfluidic Fabrication of Polymeric and Biohybrid Fibers with Predesigned Size and Shape

A &#8220;sheath&#8221; fluid passing through a microfluidic channel at low Reynolds number can be directed around another &#8220;core&#8221; stream and used to dictate the shape as well as the diameter of a core stream.&#160;Grooves in the top and bottom of a microfluidic channel were designed to direct the sheath fluid and shape the core fluid.&#160;By matching the viscosity and hydrophilicity of the sheath and core fluids, the interfacial effects are minimized and complex fluid shapes can be formed.&#160;Controlling the relative flow rates of the sheath and core fluids determines the cross-sectional area of the core fluid.&#160;Fibers have been produced with sizes ranging from 300 nm to ~1 mm, and fiber cross-sections can be round, flat, square, or complex as in the case with double anchor fibers. Polymerization of the core fluid downstream from the shaping region solidifies the fibers.&#160;Photoinitiated click chemistries are well suited for rapid polymerization of the core fluid by irradiation with ultraviolet light.&#160;Fibers with a wide variety of shapes have been produced from a list of polymers including liquid crystals, poly(methylmethacrylate), thiol-ene and thiol-yne resins, polyethylene glycol, and hydrogel derivatives. Minimal shear during the shaping process and mild polymerization conditions also makes the fabrication process well suited for encapsulation of cells and other biological components.

Two adjacent fluids passing through a grooved microfluidic channel can be directed to form a sheath around a prepolymer core; thereby&#160;determining both shape and cross-section. Photoinitiated polymerization, such as thiol click chemistry, is well suited for rapidly solidifying the core fluid into a microfiber with predetermined size and shape.

预设计尺寸和形状的聚合物纤维和生物贿赂纤维的微流体制造

A &#8220;sheath&#8221; fluid passing through a microfluidic channel at low Reynolds number can be directed around another &#8220;core&#8221; stream and ...

Microfluidic Dry-spinning and Characterization of Regenerated Silk Fibroin Fibers

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables the silk proteins to be compact and ordered by shearing and elongation forces. Here, a biomimetic microfluidic channel was designed to mimic the specific geometry of the spinning duct of the silkworm. Regenerated silk fibroin (RSF) spinning doped with high concentration, was extruded through the microchannel to dry-spin fibers at ambient temperature and pressure. In the post-treated process, the as-spun fibers were drawn and stored in ethanol aqueous solution. Synchrotron radiation wide-angle X-ray diffraction (SR-WAXD) technology was used to investigate the microstructure of single RSF fibers, which were fixed to a sample holder with the RSF fiber axis normal to the microbeam of the X-ray. The crystallinity, crystallite size, and crystalline orientation of the fiber were calculated from the WAXD data. The diffraction arcs near the equator of the two-dimensional WAXD pattern indicate that the post-treated RSF fiber has a high orientation degree.

A protocol for the microfluidic spinning and microstructure characterization of regenerated silk fibroin monofilament is presented.

微流控干纺及再生丝素纤维的表征

The protocol demonstrates a method for mimicking the spinning process of silkworm. In the native spinning process, the contracting spinning duct enables ...

Automated Robotic Dispensing Technique for Surface Guidance and Bioprinting of Cells

This manuscript describes the introduction of cell guidance features followed by the direct delivery of cells to these features in a hydrogel bioink using an automated robotic dispensing system. The particular bioink was selected as it allows cells to sediment towards and sense the features. The dispensing system bioprints viable cells in hydrogel bioinks using a backpressure assisted print head. However, by replacing the print head with a sharpened stylus or scalpel, the dispensing system can also be employed to create topographical cues through surface etching. The stylus movement can be programmed in steps of 10 &#181;m in the X, Y and Z directions. The patterned grooves were able to orientate mesenchymal stem cells, influencing them to adopt an elongated morphology in alignment with the grooves&#39; direction. The patterning could be designed using plotting software in straight lines, concentric circles, and sinusoidal waves. In a subsequent procedure, fibroblasts and mesenchymal stem cells were suspended in a 2% gelatin bioink, for bioprinting in a backpressure driven extrusion printhead. The cell bearing bioink was then printed using the same programmed coordinates used for the etching. The bioprinted cells were able to sense and react to the etched features as demonstrated by their elongated orientation along the direction of the etched grooves.

This protocol describes a bioprinting methodology using an automated robotic depositing system that incorporates etched topographical guidance cues with the precision deposition of a cell bearing hydrogel bioink. The printed cells are directly delivered to the etched features and are able to sense and orientate with them.

自动点胶机器人技术在细胞表面和指导生物印刷

This manuscript describes the introduction of cell guidance features followed by the direct delivery of cells to these features in a hydrogel bioink using ...

Melt Electrospinning Writing of Three-dimensional Poly(&#949;-caprolactone) Scaffolds with Controllable Morphologies for Tissue Engineering Applications

This tutorial reflects on the fundamental principles and guidelines for electrospinning writing with polymer melts, an additive manufacturing technology with great potential for biomedical applications. The technique facilitates the direct deposition of biocompatible polymer fibers to fabricate well-ordered scaffolds in the sub-micron to micro scale range. The establishment of a stable, viscoelastic, polymer jet between a spinneret and a collector is achieved using an applied voltage and can be direct-written. A significant benefit of a typical porous scaffold is a high surface-to-volume ratio which provides increased effective adhesion sites for cell attachment and growth. Controlling the printing process by fine-tuning the system parameters enables high reproducibility in the quality of the printed scaffolds. It also provides a flexible manufacturing platform for users to tailor the morphological structures of the scaffolds to their specific requirements. For this purpose, we present a protocol to obtain different fiber diameters using melt electrospinning writing (MEW) with a guided amendment of the parameters, including flow rate, voltage and collection speed. Furthermore, we demonstrate how to optimize the jet, discuss often experienced technical challenges, explain troubleshooting techniques and showcase a wide range of printable scaffold architectures.

This protocol serves as a comprehensive guideline to fabricate scaffolds via electrospinning with polymer melts in a direct writing mode. We systematically outline the process and define the appropriate parameter settings for achieving targeted scaffold architectures.

用于组织工程应用的三维聚 (ε-内) 支架的熔体静电纺丝

This tutorial reflects on the fundamental principles and guidelines for electrospinning writing with polymer melts, an additive manufacturing technology ...