作者感谢德国科学基金会资助这项工作 (泽 230/24-1)。

1. 单驱动冰粒子的合成
<ol><li>
安装设备 注: 用于微流控装置的所有材料均为高效液相色谱供应和商用。<ol>
<li>配备玻璃水浴盘 [直径 (D): 190 毫米, 连接: 两个29/24 地面玻璃连接法兰安装] 与两个隔膜。拉刀两个隔膜与一个锥, 以适应一个管与外径 (OD) 的1/16 英寸通过开口孔。</li>
		<li>将1/16 英寸外径油管和相应的套圈接头连接到聚四氟乙烯管 (1.1 管) 的末端;外径: 1/16 英寸, 内径 (ID): 0.17 毫米, 长度 (L): 5 厘米), 贴上聚酰亚胺涂层二氧化硅毛细管 (ID: 100 µm, 外径: 165 µm, L: 7 厘米) 的尖端 (ca. 1 厘米)。</li>
		<li>将管子拧到聚醚醚酮 (PEEK) T 接合处的一个对立臂上, 用于1/16 英寸外径管, 安装在一个小金属桌上。现在, 毛细管应该突出一些 centemeters 出 T 连接。 注: 最好用管子切割机切割聚四氟乙烯管。对于毛细血管, 最好使用劈裂石。</li>
		<li>将合适的管件和套圈连接到第二聚四氟乙烯管的末端 (管 1.2;外径: 1/16 英寸, ID: 0.75 毫米), 足够长的时间到达水浴外的注射器泵, 并将其拧到 T 形接头的侧臂上。</li>
		<li>粘第三聚四氟乙烯管 (管 1.3;外径: 1/16 英寸, ID: 0.17 毫米) 通过其中一个隔膜。管1.3 应足够长, 以连接第二注射器泵与管1.1 内的水浴。分别在1.1 和1.3 管的备用端添加两个女性鲁尔锁, 用于1/16 英寸外径油管。</li>
		<li>准备第四聚四氟乙烯管 (聚合管 1.4;外径: 1/16 英寸, ID: 0.75 毫米), 配有合适的加箍, 并通过第二隔膜粘贴。管1.4 应该足够长的时间离开水浴和通过一个精密加热板。连接管 1.4通过其拟合到 T 形接头的剩余臂上, 并将玻璃毛细管的末端置于管内。</li>
		<li>将水浴放在装有温度计的热板上, 用胶带固定在精密加热板顶部的1.4 管, 并将5毫升玻璃瓶连接到管1.4 的末端。将管1.2 的末端连接到充满连续相的注射器 (硅油; 粘度: 1.000 米2/秒), 将管1.3 连接到装有液压油的注射器, 用于单体相 (硅油; 粘度: 100 米2/秒) 和插头注射器泵。 注: 为了将管子连接到注射器, 用3/32 英寸的 ID 管鲁尔的钩头到女性的锁连接器最好使用。</li>
		<li>安装一个显微镜, 其重点是在毛细管的尖端设置, 以使观察液滴形成和安装紫外线光源 (e. g, 500 W 汞蒸气灯) 与光锥聚焦在管1.4。</li>
	</ol>
</li>
	<li>
单体混合物的制备
	<ol>
<li>要准备单体混合物40, 添加200毫克 (4-acryloyloxybutyl)-25-二 (4-butyloxybenzoyloxy) 苯甲酸为50毫升梨形烧瓶。</li>
		<li>加入7.2 毫克的 16-hexanediol 甲基丙烯酸酯 (10 (摩尔)) 和6.2 毫克的乙基 (24, 6-trimethylbenzoyl) 苯膦酸 (光, 3 w%) 的烧瓶。将混合物溶解在大约1毫升的二氯甲烷中。 注意: 从步骤1.2.2 开始, 所有步骤都应在 UV 无光条件下执行 (例如, 在黄灯下)。</li>
		<li>将溶剂完全清除在真空下 313 k, 并在油浴中将剩余固体熔化 383 k。</li>
		<li>用3/32 英寸的 ID 油管和连接四氟管 (管 1.5) 的鲁尔锁连接器准备注射器;外径: 1/8 英寸, 编号: 1.65 毫米)通过连接管 (外径: 1/16 英寸, id: 0.75 毫米)。在注射器的帮助下, 将单体混合物绘制到管1.5 中。 注: 单体用量不应少于70毫克. 否则, 很难将足够的单体混合物绘制成管1.5。协议可以在这里暂停。如果是这样, 把管子放在冰箱里。</li>
	</ol>
</li>
	<li>
微粒的准备
	<ol>
<li>将男性鲁尔锁固定在1/8 英寸外径油管两端的管 1.5, 其中包含单体混合物。然后, 连接两端的管1.5 与女性鲁尔锁在1.1 和1.3 管的两端。 注: 在合成前应用注射器泵提供的液体冲洗管子。</li>
		<li>将水浴的温度设置为 363 k, 将精密加热板的温度设置为 338 k。</li>
		<li>确保毛细管的尖端是在聚合管的中心 1.5, 不接触墙壁。 注意: 这里给出的温度对这种单体混合物进行了优化。一般情况下, 水浴的温度应足够高, 以熔化单体混合物, 加热板的温度应在液晶相的温度范围内。</li>
		<li>在单体混合物融化后, 将连续相位 (Qc) 的流速设置为介于1.5 和2.0 毫升/小时之间的值, 并选择 qc/Qd (qd = 液压油/单体相的流速) 之间的流速比20和200。 注: 对于 qc = 1.75 毫升/小时和 qd = 0.35 毫升/小时的流速, 将观察到具有 d 270 µm 的良好驱动粒子。</li>
		<li>在液滴形成开始后, 等待, 直到水滴都是相同的大小, 然后再打开 UV 光。对于所描述的单体混合物, 将 UV 源的1厘米以上的聚合管1.4 在精密加热板的右端。收集5毫升玻璃瓶中聚合粒子的不同分数, 在1.4 管末端。在紫外光动时 , 水滴的颜色应该由透明变为白色。 注意: 佩戴防紫外线护目镜以保护眼睛。</li>
		<li>在光源和水浴之间放置一个盾牌 (例如,一个纸盒), 以防止毛细血管堵塞。 注: 如果一个堵塞的聚合管, 它可能有助于加热堵塞部分与热枪。</li>
		<li>在所有单体被消耗后, 通过将丙酮注入1.3 管来清洁安装。</li>
	</ol>
</li>
</ol>2. 核壳冰粒子的合成
<ol><li>
设备安装
	<ol>
<li>按照步骤1.1.1。但用190毫米的水浴盘代替。</li>
		<li>将管件和套圈连接到氟化乙烯丙烯 (FEP) 油管套筒的两端 (ID: 395 µm, 外径: 1/16 英寸, L: 1.55 英寸), 分别。首先, 粘附熔融二氧化硅毛细管 (ID: 280 µm, 外径: 360 µm, L: 8 厘米) 通过套筒, 在这样的方式, 它突出约3毫米出一侧。然后贴一个更薄的毛细管 (ID: 100 µm, OD: 165 µm, L:11 厘米) 通过较大的一个, 使它突出了几毫米的更长的一面。</li>
		<li>将套筒拧到1/16 英寸外径管 (T 型接头 1) 的 PEEK T 形接头的一个对立臂上, 它安装在一个小金属桌上, 而更短的毛细管端伸到 T 形接合处。</li>
		<li>贴一聚四氟乙烯管 (管 2.1;外径: 1/16 英寸, ID: 0.17 毫米), 这是足够长的连接注射器泵与 T 连接1通过一个水浴的隔膜。将管件和套圈连接到水浴内的管端, 将其与 T 连接1的自由侧臂相连, 并将较薄的毛细管插在管内2.1 内。</li>
		<li>准备第二聚四氟乙烯管 (管 2.2;外径: 1/16 英寸, ID: 0.5 毫米), 配有管件和套圈, 并将其连接到 T 型接线1的备用臂上。粘另一聚四氟乙烯管 (管 2.3;外径: 1/16 寸, ID: 0.5 毫米) 通过第二个孔在间隔在管子2.1 旁边。管2.3 应该足够长, 以连接另一个注射器泵与管2.2。</li>
		<li>将两个女性鲁尔锁分别添加到水浴内2.2 和2.3 管的自由端1/16 英寸外径油管上。</li>
		<li>将套筒的自由端连接到第二个 PEEK t 形连接线 (t 连接 2) 的另一臂上, 它也安装在小金属桌上。准备第四聚四氟乙烯管 (管 2.4;外径: 1/16 英寸, ID: 0.75 毫米), 配有管件加箍。管2.4 是足够长的时间到达第三个注射器泵外的水浴, 并连接到侧臂的 T 连接2。</li>
		<li>准备第五聚四氟乙烯管 (聚合管 2.5;外径: 1/16 英寸, ID: 0.75 毫米), 配有合适的加箍, 并通过其他隔膜粘贴。管2.5 应该足够长的时间离开水浴和通过一个高精度的加热板。将管2.5 的管件与 T 形接头的剩余臂连接。现在, 玻璃毛细血管的小贴士应该位于管2.5 内。</li>
		<li>将水浴放在装有温度计的热板上, 用胶带固定在精密加热板顶部的2.5 管, 并将5毫升玻璃瓶连接到管端。将管2.1 的末端连接到用甘油 (内相) 填充的注射器上, 将管2.3 连接至装有液压油的注射器, 用于单体相 (硅油; 粘度: 100 米2/秒), 连接管2.4 到用连续相填充的注射器 (硅油;粘度: 1.000 米2/秒), 并将所有注射器插入注射器泵中。</li>
		<li>按照步骤 1.1.7, 但读管2.5 而不是管1.4。</li>
	</ol>
</li>
	<li>
单体混合物的制备
	<ol>
<li>执行所有步骤1.2。</li>
	</ol>
</li>
	<li>
核壳颗粒的制备
	<ol>
<li>将1/8 英寸外径管的雄性鲁尔锁分别连接在包含单体混合物的管两端。之后, 连接这管两端的女性鲁尔锁在管的两端2.2 和2.3。</li>
		<li>按照步骤 1.3. 2-1. 3.4。</li>
		<li>观察液滴形成通过立体显微镜。</li>
	</ol>
</li>
</ol>3、双面冰颗粒的合成
<ol><li>
设备安装
	<ol>
<li>按照步骤1.1.1。</li>
		<li>将管件和套圈连接到 FEP 油管套筒的两端 (ID: 395 µm, 外径: 1/16 英寸, L: 1.55 英寸), 分别。粘接两个平行排列的熔融二氧化硅毛细管 (ID: 100 µm, 外径: 165 µm, l1: 8 厘米, l2:11 厘米) 通过套筒。短毛细管凸出约3毫米从一侧的袖子。在袖子的另一侧, 两个毛细血管的长度相同。</li>
		<li>将一些胶水粘在袖子的一端, 然后等到固化后再用胶水把毛细血管粘起来。</li>
		<li>将两个 PEEK 的 T 形连接, 分别拧紧在一个对立的手臂上, 并安装在一个小的金属表上。</li>
		<li>按照步骤 2.1. 4-2. 1.7。</li>
		<li>准备第五聚四氟乙烯管 (管 3.5;外径: 1/16 英寸, ID: 0.75 毫米, L: 5 厘米), 配有管件加插箍, 并将其与 T 形结2的剩余臂连接。玻璃毛细血管的两个小贴士位于管3.5 内。</li>
		<li>粘另一聚四氟乙烯管 (管 3.6;外径: 1/16 英寸, ID: 0.5 毫米) 通过其他隔膜。管2.6 应该足够长的时间离开水浴和通过一个精密加热板。连接管3.5 和 3.6通过管件系统的1/16 英寸 OD 油管。</li>
		<li>将水浴放在装有温度计的热板上, 用胶带固定在精密加热板顶部的3.6 管, 并将5毫升玻璃瓶连接到管端。将管3.1 的末端连接到充满水单体混合物的注射器 (蒽醌. 单体相), 将管3.3 连接至装有液压油的注射器, 用于 LC 单体相 (硅油; 粘度: 100 米2/秒), 将管3.4 连接至填充的注射器与连续相 (硅油; 粘度: 1.000 米2/秒), 并将所有注射器插入注射器泵中。</li>
		<li>跟随步骤 1.1.8, 但读管3.6 而不是管1.4。</li>
	</ol>
</li>
	<li>
液晶 (LC) 单体混合物的制备
	<ol>
<li>执行所有步骤1.2。</li>
	</ol>
</li>
	<li>
水中单体混合物的制备
	<ol>
<li>在蒸馏水中制备 40 wt% 丙烯酰胺溶液。添加 10 (摩尔) 的交联剂 n、n '-methylenebis (丙烯酰胺) 和 2 wt% 的引发剂 2-羟基 2-methylpropiophenone 到溶液中。(这两种量都是关于丙烯酰胺的。 注: 为了提高水中单体混合物的粘度, 可以添加聚丙烯酰胺。</li>
		<li>在 RT 中搅拌24小时的混合物, 然后将其填充到1毫升注射器中。</li>
	</ol>
</li>
	<li>
双面粒子的制备
	<ol>
<li>分别在包含 LC 单体混合物的管两端上附加一个雄性鲁尔锁, 用于1/8 英寸外径管。然后, 连接这管两端的女性鲁尔锁在3.2 和3.3 管的两端。</li>
		<li>按照步骤 1.3. 2-1. 3.4。</li>
		<li>观察液滴形成通过立体显微镜。</li>
	</ol>
</li>
</ol>4. 对微粒的分析
<ol><li>将粒子放在一个热级的光学显微镜下, 用成像软件连接到计算机上。为了分析粒子的驱动, 在温度高于和低于其相变温度的情况下拍照, 并测量它们的 D。 注: 一滴硅油可以防止微粒粘在物体的滑动上。</li>
	<li>为了估计粒子的清除温度, 确定粒子在偏振光学显微镜 (POM) 下失去双折射的温度。</li>
</ol>

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作者没有什么可透露的。

我们描述了不同形貌的粒子的制造,通过微流控方法生产冰微执行器。为此, 建立了毛细管微流控装置, 允许液滴形成, 然后在规定的温度下聚合。
在这里, 成功合成的一个关键方面是安装的正确安装。必须正确修复单个部件之间的所有连接, 以防止液体泄漏, 并且在每次合成前必须清洁设备以防止堵塞。同样重要的是, 实验是在无紫外线条件下进行的, 因为, 否则, 单体混合物过早聚合, 从而再次堵塞的设置将是结果。
到今天, 这里描述的微流控方法是唯一能够产生驱动的冰粒子的方法。在此, 微流控过程同时满足两个要求。除了制造大量的同样大小的微型物体, 液晶控制器的方向在这些粒子中被诱导。此外, 这是一个相当简单的程序, 因为大量的执行器可以合成一个单一的步骤。应用其他方法, 液晶聚的方向通常需要一个额外的步骤, 如拉伸的样本或应用的照片对准层。此外, 这些过程是手动的, 这意味着许多执行器的生产是非常耗时的。此外, 冰形态是-在大多数情况下, 仅限于聚合物薄膜。微流控方法的缺点是颗粒尺寸的限制 (因为直径限制在200和400µm 之间的值), 堵塞毛细管的脆弱性, 以及在粒子制备过程中无紫外线条件的必要性。安装程序。
芯片上的系统经常被用于微流控粒子的制造, 因为它们可以很容易地产生, 只由一个片断组成。然而, 这些设置, 不仅缺乏必要的调节, 在流动的不同温度, 但也不够灵活, 以方便地交换堵塞或损坏的部分微反应器。因此, 我们使用的毛细管型设置更适合于冰执行器的合成, 因为它们满足了关键的要求。
除了我们所提出的驱动微型泵粒子和核壳的结果, 更复杂的驱动粒子具有新的性能, 可以在未来合成, 并打开新的可能性, 软执行器的应用。在对多响应粒子进行进一步的修饰时, 已经在进行中。因此, 我们的目标是引进第二温度反应聚合物除了驱动冰。进一步可能性为新的微粒设计也可能出现从使用液晶偶氮单体, 导致冰微粒的轻驱动的驱动力17,18。在这种情况下, 我们可以想到的是既包含温度响应, 也包括光驱动部分的两面粒子。光驱动的核壳颗粒或类似管道结构的合成提供了另一种可能的粒子设计, 这将导致光响应微型泵。我们上面提出的微流控原理的修正应该允许各种新的执行器。

微流控合成已成为最近几年制造液晶弹性体 (冰) 驱动器的著名方法1,2,3。这种方法不仅使生产大量的良好的驱动粒子, 而且还允许制造的形状和形貌, 这是不可用的其他方法。因为在微型机器人中, 冰执行器是一个应用人造肌肉的候选者, 所以合成这种粒子的新方法对于未来的技术4是非常重要的。
在 LCEs 中, 液晶 (LC) 的液晶聚连接到弹性体网络的聚合物链 5, 6, 7, 8.液晶聚与聚合物链的联系可以以侧链、主链或联合 LC 聚合物9、10、11的形式出现.交联点之间的距离应该足够远, 允许在中间的聚合物链的自由重新定向 (事实上, 这是真实的任何弹性体, 区分他们从 "热固性")。因此, 交联可以是永久性的或可逆的, 因为强的非共价键相互作用12,13,14。这种材料结合了两种特性, 即液晶的各向异性行为与弹性体的熵弹性。在液晶相的温度范围内, 聚合物链采用了由液晶相的各向异性引起的 (或多或少) 拉伸构象, 这是由向列序参量量化的。当样品被带到正向向各向同性相变温度以上时, 各向异性消失, 网络松弛到大力偏爱的随机线圈构象。这导致一个宏观变形, 从而驱动5,15。除了加热的样品, 这种相变也可能诱发其他刺激, 如光或溶剂扩散在 LCEs16,17,18,19。
为了获得强烈的变形, 在交联步骤20期间, 样本必须形成一个 monodomain 或特征至少是单个域控制器的首选方向。对于冰膜的生产, 这通常是通过拉伸预聚合样品,通过在电场或磁场中的域方向, 借助照片对齐层或通过3 d 打印21 ,22,23,24,25,26。
另一种方法是用毛细管微流控液滴发生器连续制备冰微粒。液晶单体水滴分散在高度粘性的连续相, 流动在水滴周围, 并在水滴表面应用剪切速率。因此, 在单体液滴内循环观察, 导致液晶相的整体对准27。因此, 在水滴上作用的剪切速率的大小对液滴的形状和大小, 以及液晶控制器的方向有很大的影响。这些良好的液滴可以在微流控装置的下游进一步聚合。因此, 使用不同形状 (例如、粒子和纤维) 和更复杂的形貌 (如核壳和双面粒子) 的驱动器的制备是可能的28,29,30,31。它甚至可以制备扁颗粒, 沿其对称轴和高度扁, 纤维状粒子, 在相变收缩。这两种粒子都可以用同一种微流控装置进行, 只需改变剪切速率27。在此, 我们提出了如何在自制毛细管微流控装置上生产不同形貌的冰执行器的协议。
除了基团对冰液的影响, 以及不同形状的聚合物的可达性, 微流控方法还有进一步的优势。比其他微粒制造方法象降雨雪在非溶剂或悬浮聚合32 (导致微粒以宽广的大小分布), 单分散微粒 (微粒大小的变动系数是 < 5%) 可以使用微流体 33, 34 来合成.另外, 通过流动可以很容易地打破水滴的球体对称性。因此, 具有圆柱对称性的大粒子是可访问的, 这是执行器所需要的。这与悬浮聚合32所做的 LC 粒子不同。此外, 粒子的大小是很好的可调的微流体在一个范围从几微米到上百个微米, 和添加剂可以很容易地被带入颗粒或在其表面。这就是为什么微流控微粒制剂经常用于诸如药物传递35或化妆品36的制造等主题。
本文中使用的微流控装置由塞拉et介绍。33,37,38.这些都是自制的, 由高效液相色谱 (HPLC) 聚四氟乙烯 (PTFE) 管和 T 连接, 以及提供单相的熔融二氧化硅毛细血管组成。因此, 设置可以很容易地修改, 单件可以简单地交换, 因为它们是商业可用。在单体混合物中加入一个光, 使适当的光源能够在它们离开毛细管后, 在飞行中诱导液滴的聚合。除毛细血管外的照射是必要的, 以防止堵塞的设置。其他类型的聚合仅在液滴离开毛细管 (例如, 与基于氧化还原过程的启动器)39之后才开始聚合。然而, 由于光诱导交联聚合的速度和远程控制能力, 引发是最有利的一种。
由于冰的单体混合物在室温下是结晶的, 因此需要对整个微流控装置进行仔细的温度控制。因此, 产生液滴形成的部分设置放在水浴中。在这里, 水滴是在高温下形成的混合物的各向同性熔融。对于定向, 水滴必须冷却成液晶相。因此, 聚合管放置在热板上, 设置为 LC 阶段的较低温度范围 (图 1)。
在这里, 我们描述了一个灵活和直接的方法, 制造的冰执行器在一个流动。该协议提供了在几分钟内为合成单个粒子以及双面和核壳粒子建立微流控装置所需的步骤。接下来, 我们描述了如何运行一个综合, 并显示了典型的结果, 以及驱动粒子的性质。最后, 我们讨论了这种方法的优点, 以及为什么我们认为它可能会给冰执行器领域带来进展。

<table><tbody><tr><td>NanoTight fitting for 1/16&#039;&#039; OD tubings</td><td>Postnova_IDEX</td><td>F-333N</td><td></td></tr><tr><td>NanoTight ferrule for 1/16&#039;&#039; OD tubings</td><td>Postnova_IDEX</td><td>F-142N</td><td></td></tr><tr><td>PEEK Tee for 1/16&amp;rdquo; OD Tubing</td><td>Postnova_IDEX</td><td>P-728</td><td>T-junction</td></tr><tr><td>Female Fitting for 1/16&amp;rdquo; OD Tubing</td><td>Postnova_IDEX</td><td>P-835</td><td>female luer-lock</td></tr><tr><td>Male Fitting for 1/8&amp;rdquo; OD Tubing</td><td>Postnova_IDEX</td><td>P-831</td><td>male luer-lock</td></tr><tr><td>Female Luer Connectors for use with 3/32&amp;rdquo; ID tubings</td><td>Postnova_IDEX</td><td>P-858</td><td>for the syrringe&#039;s tip</td></tr><tr><td>NanoTight FEP tubing sleeve ID: 395 &amp;micro;m OD: 1/16&#039;&#039;</td><td>Postnova_IDEX</td><td>F-185</td><td></td></tr><tr><td>Fused Silica Capillary Tubing ID: 100 &amp;micro;m OD: 165 &amp;micro;m</td><td>Postnova</td><td>Z-FSS-100165</td><td>glass capillary</td></tr><tr><td>Fused Silica Capillary Tubing ID: 280 &amp;micro;m OD: 360 &amp;micro;m</td><td>Postnova</td><td>Z-FSS-280360</td><td>glass capillary</td></tr><tr><td>&amp;lsquo;&amp;lsquo;Pump 33&amp;rsquo;&amp;rsquo; DDS</td><td>Harvard Apparatus</td><td>70-3333</td><td>syringe pump</td></tr><tr><td>Precision hot plate</td><td>Harry Gestigkeit GmbH</td><td>PZ 28-2</td><td></td></tr><tr><td>Stereomicroscope stemi 2000-C</td><td>Carl Zeiss Microscopy GmbH</td><td>455106-9010-000</td><td></td></tr><tr><td>Mercury vapor lamp Oriel LSH302</td><td>LOT</td><td></td><td>Intensity: 500 W</td></tr><tr><td>Teflon Kapillare, 1/16&#039;&#039; x 0,75mm</td><td>WICOM</td><td>WIC 33104</td><td>teflon tube</td></tr><tr><td>Teflon Kapillare, 1/16&#039;&#039; x 0,50mm</td><td>WICOM</td><td>WIC 33102</td><td>teflon tube</td></tr><tr><td>Teflon Kapillare, 1/16&#039;&#039; x 0,17mm</td><td>WICOM</td><td>WIC 33101</td><td>teflon tube</td></tr><tr><td>Silicion oil 1.000 cSt</td><td>Sigma Aldrich</td><td>378399</td><td></td></tr><tr><td>Silicion oil 100 cSt</td><td>Sigma Aldrich</td><td>378364</td><td></td></tr><tr><td>1,6-hexanediol dimethacrylate</td><td>Sigma Aldrich</td><td>246816</td><td>Crosslinker</td></tr><tr><td>Lucirin TPO</td><td>Sigma Aldrich</td><td>415952</td><td>Initiator</td></tr><tr><td>Polarized optical microscope BX51</td><td>Olympus</td><td></td><td>For analysis</td></tr><tr><td>Hotstage TMS 94</td><td>Linkam</td><td></td><td>For analysis</td></tr><tr><td>Imaging software Cell^D</td><td>Olympus</td><td></td><td>For analysis</td></tr></tbody></table>

microfluidic preparation of liquid crystalline elastomer actuators

本文重点研究了微流控过程 (及其参数), 从液晶弹性体中制备驱动粒子。制备通常包括在高温下形成含有低摩尔质量液晶的水滴。随后, 这些粒子前体在毛细管的流场中定向, 通过交联聚合固化, 产生最终的驱动粒子。该工艺的优化是为了获得驱动粒子和工艺参数 (温度和流速) 的适当变化, 并允许大小和形状的变化 (从扁球形到强扁形貌), 以及驱动的大小。此外, 也有可能改变驱动从伸长到收缩的类型, 这取决于在毛细管中流体中诱导的液滴的导演剖面, 这又取决于微流控过程及其参数。此外, 还可以通过调整设置来制备更复杂形状的粒子, 如核壳结构或双面粒子。通过液晶弹性体的化学结构和交联 (凝固) 方式的变化, 也可以制备由热或紫外辐照引发的驱动粒子。

在本协议中, 我们提出了用微流控法对不同形貌的冰粒子进行合成的方法 (通过)。用于制造单核壳和双面粒子的微流控装置, 如图 129、38、41所示。连续流动生产的一个好处是对微粒的大小和形状的非常好控制。图 2a说明了单滴设置的优点: 一个非常窄的大小分布, 所有粒子具有相同的形状41。因此, 通过改变不同相的流速比, 可以很容易地调整球体的大小。按照该协议, 在200和400µm 之间的粒子直径可以通过选择流量比率来进行控制, 如图 2b1所示。对于1.5 至2.0 毫升/小时之间的连续相位 (Qc) 的流速和 qc/Qd (qd = 单体相的流速) 在20和200之间的流速比率, 获得最佳结果。例如, 对于 qc = 1.75 毫升/小时和 qd = 0.35 毫升/小时的流速, 有270µm 直径的良好驱动粒子被观察到。如果选择较高的比值 Qc/Qd , 则雾滴的形成受到较少的控制, 颗粒的尺寸分布变得更加广阔。对于较低的比值, 粒子不再是球形的。除流量调整外, UV 灯与聚合管的距离以及精密热板的左、右端之间的位置可以改变冰粒的驱动特性, 如聚合动力学变化的原因选择单体混合物的成分或应用聚合温度不同于这里描述的价值。
图 3a显示在加热超过其相变温度时拉长70% 的驱动粒子, 这证明了在聚合之前诱导液晶控制器定向的要求。液晶聚的这种对准是由于高粘性连续相和单体水滴表面之间的剪切而产生的。如果使用较低粘度的硅油, 则减少了粒子的驱动。
此外, 微流控装置允许对不同类型的驱动模式进行控制, 例如在相变过程中的伸长或收缩, 通过改变聚合过程中水滴作用的剪切速率。采用不同的聚合管内径, 可以很容易地在连续相的恒定流速下处理。图 3a显示一个扁形状的粒子, 它沿其旋转轴拉长, 在更宽的聚合管中以较低的剪切速率合成 (ID: 0.75 毫米)。在这种情况下, 液晶分子 (液晶聚) 沿同心控制器场对齐。在另一侧, 杆状粒子 (如图 3b中所示) 的特点是在相变过程中收缩, 液晶聚 "控制器" 字段的双极对准。该粒子是在更薄的聚合管中以较高的剪切速率产生的 (ID: 0.5 毫米)。
该协议描述了微流控过程的另一个优点。除单一粒子外, 还可以合成更复杂形貌的样品。图 3c显示一个驱动内核 shell 粒子和图 3d , 这两个粒子都是在协议29、30的2和3部分之后产生的。
如果协议的所有步骤都正确完成, 则应获得图 4中显示的属性的粒子341。在图 4a中, 绘制了在不同流速下合成的单个粒子的加热和冷却曲线。通过加热粒子的室温, 液晶的顺序是-在第一次减少一点点, 导致小变形的粒子。然而, 接近相变温度, 所有方向突然消失, 粒子显示一个强大的伸长只是通过加热它的几个程度。通过冷却颗粒向下, 可以观察到滞后现象, 并获得原始形状。此过程在许多驱动周期中是可逆的, 如图 4b所示。
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/57715/57715fig1.jpg"> 图 1: 微流控设置.(a) 一般设置包括三注射器, 其中包含液压硅油 (1)、水单体混合物 (3) 和连续相硅油 (4)。液晶单体混合物 (2) 放在水浴 (5) 在 363 K, 加热液晶到各向同性状态。该液滴的聚合是在热板 (6) 上开始的, 在 338 K 的液晶的向列状态的紫外线照射 (7)。(单一粒子设置等于一般设置, 但缺少第二毛细管, 注射器 (3) 和第二 T 连接)。(b) 此面板显示一个安装程序, 其中包含两个毛细血管并排, 从而允许双面熔滴形成。(c) 核心外壳设置由毛细管组成, 缩短为更宽的第二毛细管。<a href="/files/ftp_upload/57715/57715fig1large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/57715/57715fig2.jpg"> 图 2:微流控单粒子设置中获得的代表性粒子。(a) 此面板显示了微流控单粒子设置中制备的分散的冰粒子的显微图像。刻度条 = 200 µm. (b) 此面板显示了粒子直径与油的流速 (qc) 与单体混合物的流速 (qd) 的比值的依赖性。得到的粒子的大小只取决于两个阶段的速度比, 而不是它们的绝对值。(此数字已从欧姆、弗莱希曼天文、克劳斯、塞拉和 Zentel 1 和欧姆、塞拉和 Zentel 41 中进行了修改. <a href="/files/ftp_upload/57715/57715fig2large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/57715/57715fig3.jpg"> 图 3: 四种不同粒子形貌的光学显微图像 (在 353 k) 和在各向同性状态下的相变 (413 k)。这些面板显示 (a) 一个扁形的冰粒子 (同心控制器场) 的伸长, (b) 一个棒状的冰-粒子 (双极控制器场) 的收缩, (c) 扁形核壳的伸长率粒子和 (d) 收缩的扁形的双面粒子 (左部分: 冰, 右部分: 丙烯酰胺水凝胶)。刻度条 = 100 µm.<a href="/files/ftp_upload/57715/57715fig3large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/57715/57715fig4.jpg"> 图 4: 具有代表性的单个粒子的驱动属性。(a) 此面板显示了在连续相的不同流速下, 在单粒子微流控装置中制备的冰粒子的加热和冷却曲线。在最高流速下制备的粒子表现出最强的驱动 (约 70%), 两条曲线分别形成迟滞。(b) 这是一个图10个驱动循环的冰粒子显示没有减少其驱动的周期数。这证明了粒子是交联的, 驱动是完全可逆的。注: 此图是为一个由主链冰系统制成的粒子绘制的, 但与本文使用的冰系统看起来是一样的。(此数字已从欧姆、塞拉和 Zentel41中进行了修改。<a href="/files/ftp_upload/57715/57715fig4large.jpg" target="_blank">请单击此处查看此图的较大版本.</a>

Watch this Scientific Journal Video about Microfluidic Preparation of Liquid Crystalline Elastomer Actuators at JoVE.com

Microfluidic Preparation of Liquid Crystalline Elastomer Actuators

液晶弹性体致动器的微流控制备

本文介绍了微流控工艺和参数, 以准备从液晶弹性体的驱动粒子。这一过程允许制备的驱动粒子和其大小和形状的变化 (从扁球形到强扁, 核壳, 和双面形貌) 以及驱动的大小。

This paper focuses on the microfluidic process (and its parameters) to prepare actuating particles from liquid crystalline elastomers. The preparation ...

microfluidic-preparation-of-liquid-crystalline-elastomer-actuators

Research

JoVE Journal

Chemistry

8.9K 次观看.  Johannes Gutenberg University. 本文介绍了微流控工艺和参数, 以准备从液晶弹性体的驱动粒子。这一过程允许制备的驱动粒子和其大小和形状的变化 (从扁球形到强扁, 核壳, 和双面形貌) 以及驱动的大小。

视频: Microfluidic Preparation of Liquid Crystalline Elastomer Actuators

Microfluidic Chips Controlled with Elastomeric Microvalve Arrays

Miniaturized microfluidic systems provide simple and effective solutions for low-cost point-of-care diagnostics and high-throughput biomedical assays. Robust flow control and precise fluidic volumes are two critical requirements for these applications. We have developed microfluidic chips featuring elastomeric polydimethylsiloxane (PDMS) microvalve arrays that: 1) need no extra energy source to close the fluidic path, hence the loaded device is highly portable; and 2) allow for microfabricating deep (up to 1 mm) channels with vertical sidewalls and resulting in very precise features.

The PDMS microvalves-based devices consist of three layers: a fluidic layer containing fluidic paths and microchambers of various sizes, a control layer containing the microchannels necessary to actuate the fluidic path with microvalves, and a middle thin PDMS membrane that is bound to the control layer. Fluidic layer and control layers are made by replica molding of PDMS from SU-8 photoresist masters, and the thin PDMS membrane is made by spinning PDMS at specified heights. The control layer is bonded to the thin PDMS membrane after oxygen activation of both, and then assembled with the fluidic layer. The microvalves are closed at rest and can be opened by applying negative pressure (e.g., house vacuum). Microvalve closure and opening are automated via solenoid valves controlled by computer software.

Here, we demonstrate two microvalve-based microfluidic chips for two different applications. The first chip allows for storing and mixing precise sub-nanoliter volumes of aqueous solutions at various mixing ratios. The second chip allows for computer-controlled perfusion of microfluidic cell cultures.

The devices are easy to fabricate and simple to control. Due to the biocompatibility of PDMS, these microchips could have broad applications in miniaturized diagnostic assays as well as basic cell biology studies.

We demonstrate protocols for manufacturing and automating elastomeric polydimethylsiloxane (PDMS)-based microvalve arrays that need no extra energy to close and feature photolithographically defined precise volumes. A parallel subnanoliter-volume mixer and an integrated microfluidic perfusion system are presented.

微流控芯片控制，弹性微阀阵列

Miniaturized microfluidic systems provide simple and effective solutions for low-cost point-of-care diagnostics and high-throughput biomedical assays.  ...

科研

生物学

Synthesis of Programmable Main-chain Liquid-crystalline Elastomers Using a Two-stage Thiol-acrylate Reaction

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline elastomers (LCEs) with facile control over network structure and programming of an aligned monodomain. Tailored LCE networks were synthesized using routine mixing of commercially available starting materials and pouring monomer solutions into molds to cure. An initial polydomain LCE network is formed via a self-limiting thiol-acrylate Michael-addition reaction. Strain-to-failure and glass transition behavior were investigated as a function of crosslinking monomer, pentaerythritol tetrakis(3-mercaptopropionate) (PETMP). An example non-stoichiometric system of 15 mol% PETMP thiol groups and an excess of 15 mol% acrylate groups was used to demonstrate the robust nature of the material. The LCE formed an aligned and transparent monodomain when stretched, with a maximum failure strain over 600%. Stretched LCE samples were able to demonstrate both stress-driven thermal actuation when held under a constant bias stress or the shape-memory effect when stretched and unloaded. A permanently programmed monodomain was achieved via a second-stage photopolymerization reaction of the excess acrylate groups when the sample was in the stretched state. LCE samples were photo-cured and programmed at 100%, 200%, 300%, and 400% strain, with all samples demonstrating over 90% shape fixity when unloaded. The magnitude of total stress-free actuation increased from 35% to 115% with increased programming strain. Overall, the two-stage TAMAP methodology is presented as a powerful tool to prepare main-chain LCE systems and explore structure-property-performance relationships in these fascinating stimuli-sensitive materials.

A novel methodology is presented to synthesize and program main-chain liquid-crystalline elastomers using commercially available starting monomers. A wide range of thermomechanical properties was tailored by adjusting the amount of crosslinker, while the actuation performance was dependent on the amount of applied strain during programming.

的可编程主链液晶性弹性体用双级硫醇丙烯酸酯反应合成

This study presents a novel two-stage thiol-acrylate Michael addition-photopolymerization (TAMAP) reaction to prepare main-chain liquid-crystalline ...

化学

Fabrication Process of Silicone-based Dielectric Elastomer Actuators

This contribution demonstrates the fabrication process of dielectric elastomer transducers (DETs). DETs are stretchable capacitors consisting of an elastomeric dielectric membrane sandwiched between two compliant electrodes. The large actuation strains of these transducers when used as actuators (over 300% area strain) and their soft and compliant nature has been exploited for a wide range of applications, including electrically tunable optics, haptic feedback devices, wave-energy harvesting, deformable cell-culture devices, compliant grippers, and propulsion of a bio-inspired fish-like airship. In most cases, DETs are made with a commercial proprietary acrylic elastomer and with hand-applied electrodes of carbon powder or carbon grease. This combination leads to non-reproducible and slow actuators exhibiting viscoelastic creep and a short lifetime. We present here a complete process flow for the reproducible fabrication of DETs based on thin elastomeric silicone films, including casting of thin silicone membranes, membrane release and prestretching, patterning of robust compliant electrodes, assembly and testing. The membranes are cast on flexible polyethylene terephthalate (PET) substrates coated with a water-soluble sacrificial layer for ease of release. The electrodes consist of carbon black particles dispersed into a silicone matrix and patterned using a stamping technique, which leads to precisely-defined compliant electrodes that present a high adhesion to the dielectric membrane on which they are applied.

This manuscript shows the fabrication process for the manufacture of dielectric elastomer soft actuators based on silicone membranes. The three key stages of production are presented in detail: blade casting of thin silicone membranes; pad printing of compliant electrodes; and the assembly of all the components.

有机硅为基础的介电弹性体致动器的制作工艺

This contribution demonstrates the fabrication process of dielectric elastomer transducers (DETs). DETs are stretchable capacitors consisting of an ...

工程学

Microfluidic Pneumatic Cages: A Novel Approach for In-chip Crystal Trapping, Manipulation and Controlled Chemical Treatment

The precise localization and controlled chemical treatment of structures on a surface are significant challenges for common laboratory technologies. Herein, we introduce a microfluidic-based technology, employing a double-layer microfluidic device, which can trap and localize in situ and ex situ synthesized structures on microfluidic channel surfaces. Crucially, we show how such a device can be used to conduct controlled chemical reactions onto on-chip trapped structures and we demonstrate how the synthetic pathway of a crystalline molecular material and its positioning inside a microfluidic channel can be precisely modified with this technology. This approach provides new opportunities for the controlled assembly of structures on surface and for their subsequent treatment.

Herein, we describe the fabrication and operation of a double-layer microfluidic system made of polydimethylsiloxane (PDMS). We demonstrate the potential of this device for trapping, directing the coordination pathway of a crystalline molecular material and controlling chemical reactions onto on-chip trapped structures.

微流控气动笼:在芯片水晶捕获，处理的新方法和控制化学处理

The precise localization and controlled chemical treatment of structures on a surface are significant challenges for common laboratory technologies. ...

Free-form Light Actuators &#8212; Fabrication and Control of Actuation in Microscopic Scale

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted researchers&#39; attention in many fields. Most of the studies focused on macroscopic LCE structures (films, fibers) and their miniaturization is still in its infancy. Recently developed lithography techniques, e.g., mask exposure and replica molding, only allow for creating 2D structures on LCE thin films. Direct laser writing (DLW) opens access to truly 3D fabrication in the microscopic scale. However, controlling the actuation topology and dynamics at the same length scale remains a challenge.
In this paper we report on a method to control the liquid crystal (LC) molecular alignment in the LCE microstructures of arbitrary three-dimensional shape. This was made possible by a combination of direct laser writing for both the LCE structures as well as for micrograting patterns inducing local LC alignment. Several types of grating patterns were used to introduce different LC alignments, which can be subsequently patterned into the LCE structures. This protocol allows one to obtain LCE microstructures with engineered alignments able to perform multiple opto-mechanical actuation, thus being capable of multiple functionalities. Applications can be foreseen in the fields of tunable photonics, micro-robotics, lab-on-chip technology and others.

Here, we fabricate 3D polymeric micro/nano structures in which both the shape and the molecular alignment can be engineered with nanometer scale accuracy by the use of direct laser writing. Light induced deformation of several types of liquid crystalline elastomer microstructures can be controlled in the microscopic scale.

自由形式的光驱动器 - 制作和开动控制在微观尺度

Liquid crystalline elastomers (LCEs) are smart materials capable of reversible shape-change in response to external stimuli, and have attracted ...

A Microfluidic Platform to Study Bioclogging in Porous Media

Bacterial biofilms are found in several environmental and industrial porous media, including soils and filtration membranes. Biofilms grow under certain flow conditions and can clog pores, thereby redirecting the local fluid flow. The ability of biofilms to clog pores, the so-called bioclogging, can have a tremendous effect on the local permeability of the porous medium, creating a pressure buildup in the system, and impacting the mass flow through it. To understand the interplay between biofilm growth and fluid flow under different physical conditions (e.g., at different flow velocities and pore sizes), in the present study, a microfluidic platform is developed to visualize biofilm development using a microscope under externally-imposed, controlled physical conditions. The biofilm-induced pressure buildup in the porous medium can be measured simultaneously using pressure sensors and, later, correlated with the surface coverage of the biofilm. The presented platform provides a baseline for a systematic approach to investigate bioclogging caused by biofilms in porous media under flow conditions and can be adapted to studying environmental isolates or multispecies biofilms.

The present protocol describes a microfluidic platform to study biofilm development in quasi-2D porous media by combining high-resolution microscopy imaging with simultaneous pressure difference measurements. The platform quantifies the influence of pore size and fluid flow rates in porous media on bioclogging.

研究多孔介质中生物堵塞的微流体平台

Bacterial biofilms are found in several environmental and industrial porous media, including soils and filtration membranes. Biofilms grow under certain ...

环境科学

Double Emulsion Generation Using a Polydimethylsiloxane (PDMS) Co-axial Flow Focus Device

Double emulsions are useful in a number of biological and industrial applications in which it is important to have an aqueous carrier fluid. This paper presents a polydimethylsiloxane (PDMS) microfluidic device capable of generating water/oil/water double emulsions using a coaxial flow focusing geometry that can be fabricated entirely using soft lithography. Similar to emulsion devices using glass capillaries, double emulsions can be formed in channels with uniform wettability and with dimensions much smaller than the channel sizes. Three dimensional flow focusing geometry is achieved by casting a pair of PDMS slabs using two layer soft lithography, then mating the slabs together in a clamshell configuration. Complementary locking features molded into the PDMS slabs enable the accurate registration of features on each of the slab surfaces. Device testing demonstrates formation of double emulsions from 14 &#181;m to 50 &#181;m in diameter while using large channels that are robust against fouling and clogging.

Double Emulsion Generation Using a Polydimethylsiloxane PDMS Co-axial Flow Focus Device

Microfluidic double emulsions generation typically involves devices with patterned wettability or custom-fabricated glass components. Here we describe the fabrication and testing of an all polydimethylsiloxane (PDMS) double emulsion generator that does not require surface treatment or complicated fabrication processes, and is capable of producing double emulsions down to 14 &#181;m.

复乳代使用聚二甲基硅氧烷（PDMS）同轴流量聚焦设备

Double emulsions are useful in a number of biological and industrial applications in which it is important to have an aqueous carrier fluid. This paper ...

生物工程

Preparation of Monodomain Liquid Crystal Elastomers and Liquid Crystal Elastomer Nanocomposites

LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and as soft robots. Here, we demonstrate the preparation of shape-responsive liquid crystal elastomers (LCEs) and LCE nanocomposites along with characterization of their shape-responsiveness, mechanical properties, and microstructure. Two types of LCEs &#8212; polysiloxane-based and epoxy-based &#8212; are synthesized, aligned, and characterized. Polysiloxane-based LCEs are prepared through two crosslinking steps, the second under an applied load, resulting in monodomain LCEs. Polysiloxane LCE nanocomposites are prepared through the addition of conductive carbon black nanoparticles, both throughout the bulk of the LCE and to the LCE surface. Epoxy-based LCEs are prepared through a reversible esterification reaction. Epoxy-based LCEs are aligned through the application of a uniaxial load at elevated (160 &#176;C) temperatures. Aligned LCEs and LCE nanocomposites are characterized with respect to reversible strain, mechanical stiffness, and liquid crystal ordering using a combination of imaging, two-dimensional X-ray diffraction measurements, differential scanning calorimetry, and dynamic mechanical analysis. LCEs and LCE nanocomposites can be stimulated with heat and/or electrical potential to controllably generate strains in cell culture media, and we demonstrate the application of LCEs as shape-responsive substrates for cell culture using a custom-made apparatus.

We demonstrate the preparation of siloxane-based and epoxy-based liquid crystal elastomers (LCEs) and LCE nanocomposites. The LCEs are characterized with respect to reversible strain, liquid crystal ordering, and stiffness. As a potential application, we demonstrate their use as shape-responsive substrates in a custom device for active cell culture.

单域液晶的弹性体和液晶橡胶纳米复合材料的制备

LCEs are shape-responsive materials with fully reversible shape change and potential applications in medicine, tissue engineering, artificial muscles, and ...

Fabrication of Carbon-Based Ionic Electromechanically Active Soft Actuators

Ionic electromechanically active capacitive laminates are a type of smart material that move in response to electrical stimulation. Due to the soft, compliant and biomimetic nature of this deformation, actuators made of the laminate have received increasing interest in soft robotics and (bio)medical applications. However, methods to easily fabricate the active material in large (even industrial) quantities and with a high batch-to-batch and within-batch repeatability are needed to transfer the knowledge from laboratory to industry. This protocol describes a simple, industrially scalable and reproducible method for the fabrication of ionic carbon-based electromechanically active capacitive laminates and the preparation of actuators made thereof. The inclusion of a passive and chemically inert (insoluble) middle layer (e.g., a textile-reinforced polymer network or microporous Teflon) distinguishes the method from others. The protocol is divided into five steps: membrane preparation, electrode preparation, current collector attachment, cutting and shaping, and actuation. Following the protocol results in an active material that can, for example, compliantly grasp and hold a randomly shaped object as demonstrated in the article.

This article describes a fast and simple manufacturing process of ionic electromechanically active composite materials for actuators in biomedical, biomimetic and soft robotics applications. The key fabrication steps, their importance for the actuators&#39; final properties, and some of the main characterization techniques are described in detail.

碳基离子机电活性软执行器的制造

Ionic electromechanically active capacitive laminates are a type of smart material that move in response to electrical stimulation. Due to the soft, ...

Microfluidic Synthesis of Microgel Building Blocks for Microporous Annealed Particle Scaffold

The microporous annealed particle (MAP) scaffold platform is a subclass of granular hydrogels. It is composed of an injectable slurry of microgels that can form a structurally stable scaffold with cell-scale porosity in situ following a secondary light-based chemical crosslinking step (i.e.,&#160;annealing). MAP scaffold has shown success in a variety of regenerative medicine applications, including dermal wound healing, vocal fold augmentation, and stem cell delivery. This paper describes the methods for synthesis and characterization of poly(ethylene glycol) (PEG) microgels as the building blocks to form a MAP scaffold. These methods include the synthesis of a custom annealing macromer (MethMAL), determination of microgel precursor gelation kinetics, microfluidic device fabrication, microfluidic generation of microgels, microgel purification, and basic scaffold characterization, including microgel sizing and scaffold annealing. Specifically, the high-throughput microfluidic methods described herein can produce large volumes of microgels that can be used to generate MAP scaffolds for any desired application, especially in the field of regenerative medicine.

This protocol describes a set of methods for synthesizing the microgel building blocks for microporous annealed particle scaffold, which can be used for a variety of regenerative medicine applications.

微流体合成微孔退火粒子支架用微凝胶构建块

The microporous annealed particle (MAP) scaffold platform is a subclass of granular hydrogels. It is composed of an injectable slurry of microgels that ...