Name: fabricating high-viscosity droplets using microfluidic capillary device with phase-inversion co-flow structure
Uploaded: 2018-04-17T14:00:00.000+00:00
Duration: 8 min 2 s
Description: Watch this Scientific Journal Video about Fabricating High-viscosity Droplets using Microfluidic Capillary Device with Phase-inversion Co-flow Structure at JoVE.com

这项工作得到了中国国家自然科学基金 (51420105006 和51322501号) 的支持。我们感谢丹尼尔对高粘度思想的有益讨论。

1. 生产一种相反转的共流毛细管装置, 用于观察含直径为500微米的高粘度水滴的生成过程。
注: 此处使用的方形外管用于拍摄高粘度水滴的生成过程的图像。如果不需要拍摄图像, 则可以根据协议步骤2对设备进行简化版本。
<ol><li>
为毛细管装置的组装准备三个不同尺寸的玻璃管。
	<ol>
<li>取一个方形的玻璃管, 内部尺寸为1.05 毫米, 并切割一条管子的长度为4厘米。这将是设备的外管。</li>
		<li>取一圆玻璃管, 内径为580微米, 外径 (外径) 为1毫米, 并切割一条管子的长度为3厘米。这将是设备的中间管。</li>
		<li>取一圆玻璃管与身份证 = 200 微米和外径 = 330 微米, 并且切开管子的片断 ~ 2 cm 长度。这将是设备的内管。</li>
	</ol>
</li>
	<li>
修改中间管一端的表面润湿性为疏水性。
	<ol>
<li>取一个1毫升的玻璃瓶, 并添加0.3 毫升的氯 () 硅烷 (升) 到玻璃瓶。</li>
		<li>把中间管与身份证 = 580 微米准备在协议步骤 1.1.2, 并把它的一端浸入玻璃瓶中的十年代。</li>
		<li>取出中间管, 用氮气从未处理的末端冲洗管子。</li>
	</ol>
</li>
	<li>
为毛细管装置的入口准备针头。
	<ol>
<li>采取一个20G 钝尖配药针, 并削减一个插槽与0.5 毫米 x 0.5 毫米的边缘, 塑料鲁尔轮毂与刀片。 注: 此针可作为低粘度油相的入口。</li>
		<li>再拿一个20G 钝尖配药针, 在塑料鲁尔中心的边缘切两个插槽。将两个插槽与通过鲁尔集线器直径的直线对齐。 注: 一个插槽的尺寸为0.5 毫米 x 0.5 毫米, 而另一个插槽的尺寸为1.0 毫米 x 1.0 毫米。该针可作为高粘度水相的入口。</li>
		<li>再拿一个20G 钝尖配药针, 在塑料鲁尔中心的边缘切两个插槽。将两个插槽与通过鲁尔集线器直径的直线对齐。 注: 一个插槽的尺寸为1.5 毫米 x 1.5 毫米;而另一个插槽的尺寸为1.0 毫米 x 1.0 毫米。此针可作为清洗用的入口。</li>
	</ol>
</li>
	<li>
按下装配玻璃管图 1A。<ol>
<li>以常规的7.62 厘米 x 2.54 厘米的玻璃幻灯片作为毛细管装置的基板。</li>
		<li>把外管与 id = 1.05 毫米, 准备在协议步骤 1.1.1, 在玻璃幻灯片与〜1厘米挤出玻璃滑动的短边缘。</li>
		<li>带 id 为580微米的中间管, 在协议步骤1.2 中制备, 并将中间管的疏水端插入玻璃滑动端的外管, 并将中间管的1厘米保持在外管外。</li>
		<li>取内径为200微米的内管, 在协议步骤1.1.3 中制备, 并将内管一端插入中间管, 并将内管的1厘米保持在中间管外。</li>
		<li>使用环氧树脂胶固定在玻璃滑块中心位置的三管。然后等待 ~ 5 分钟或更长的胶水完全凝固。</li>
	</ol>
</li>
	<li>
在毛细管装置上装配入口。
	<ol>
<li>采取在协议步骤1.3.1 中制备的低粘度油相的入口针, 并让鲁尔集线器覆盖基体上的内管末端, 然后使用环氧树脂胶固定基板上的鲁尔轮毂。</li>
		<li>采用进口针为高粘度水相, 在协议步骤1.3.2 中制备, 并让鲁尔集线器覆盖内管和中间管之间的连接, 然后用环氧树脂胶将鲁尔轮毂固定到基体上。</li>
		<li>取入口针, 准备在协议步骤 1.3.3, 并为清洗, 让鲁尔枢纽覆盖中间管和外管之间的连接, 然后使用环氧树脂胶固定在基板上的鲁尔集线器。</li>
		<li>等待 ~ 5 分钟或更长的胶水完全凝固。</li>
		<li>使用环氧树脂胶封在基板上的针鲁尔集线器。</li>
	</ol>
</li>
	<li>等待 ~ 30 分钟或更长的胶水完全凝固, 然后设备准备使用。</li>
</ol>2. 制作一种相反转、共流毛细管装置, 用于制造直径为500微米的水性高粘度水滴。
注意: 此处所做的设备是协议步骤1中设备的简化版本。
<ol><li>
为毛细管装置的组装准备两个不同尺寸的玻璃管。
	<ol>
<li>取一圆玻璃管与身份证 = 580 微米和外径 = 1 毫米, 并且切开一条管子与 3 cm 长度。这将是设备的中间管。</li>
		<li>取一圆玻璃管与身份证 = 200 微米和外径 = 330 微米, 并且切开一条管子与 2 cm 长度。这将是设备的内管。</li>
	</ol>
</li>
	<li>
修改中间管一端的表面润湿性为疏水性。
	<ol>
<li>在1毫升的玻璃瓶中加入0.3 毫升的培养基。</li>
		<li>用 id 为580微米的中间管, 在协议步骤2.1.1 中准备, 并将它的一端浸入玻璃瓶中的 "十年代"。</li>
		<li>取出中间管, 然后用氮气从未处理的末端冲洗管子。</li>
	</ol>
</li>
	<li>
为毛细管装置的入口准备针头。
	<ol>
<li>准备一个20G 钝尖配药针, 这将成为低粘油阶段的入口。然后, 用刀片在塑料鲁尔集线器的边缘切割一个0.5 毫米 x 0.5 毫米的插槽。</li>
		<li>再拿一个20G 钝尖配药针, 在塑料鲁尔中心的边缘切两个插槽。将两个插槽与通过鲁尔集线器直径的直线对齐。 注: 一个插槽的尺寸为0.5 毫米 x 0.5 毫米, 而另一个插槽的尺寸为1.0 毫米 x 1.0 毫米。第二针将作为高粘度水相的入口。</li>
	</ol>
</li>
	<li>
按下装配玻璃管图 1A.
	<ol>
<li>以常规的7.62 厘米 x 2.54 厘米的玻璃幻灯片作为毛细管装置的基板。</li>
		<li>将中间管与 id = 580 微米, 准备在协议步骤 2.2, 在玻璃滑动与疏水性端挤出 ~ 1 厘米在玻璃滑梯的短边缘。</li>
		<li>取内径为200微米的内管, 在协议步骤2.1.2 中进行制备, 并将内管的一端插入到中间管中, 从玻璃滑块上未处理的端部, 并在中间管外保持1厘米的内管。</li>
		<li>使用环氧树脂胶固定在玻璃滑块中心位置的两个管。</li>
		<li>等待5分钟或更长的胶水完全凝固。</li>
	</ol>
</li>
	<li>
在毛细管装置上装配入口。
	<ol>
<li>采取在协议步骤2.3.1 中制备的低粘度油相的入口针, 并让鲁尔集线器覆盖基体上的内管末端, 然后使用环氧树脂胶固定基板上的鲁尔轮毂。</li>
		<li>采用进口针为高粘度水相, 在协议步骤2.3.2 中制备, 并让鲁尔轮毂覆盖内管和中间管之间的连接, 然后使用环氧树脂胶固定在基板上的鲁尔轮毂。 注: 中间管的另一端是装置的出口。</li>
		<li>等待 ~ 5 分钟或更长的胶水完全凝固。</li>
		<li>使用环氧树脂胶封在基板上的针鲁尔集线器。</li>
	</ol>
</li>
	<li>等待 ~ 30 分钟或更长的胶水完全凝固。</li>
	<li>将中间管的自由端与出口油管连接, i. e., 带 id 的聚乙烯油管长度为0.86 毫米和 ~ 20 毫米。 注意: 外部油管的轻微变形将确保连接的密封, 因此这里不需要胶水。出口油管作为一个更广泛的外管的相反转。此时, 设备可以使用。</li>
</ol>3. 制作相逆共流毛细管装置, 观察直径为200微米的高粘度水滴的生成过程。
注意: 此处所做的设备是协议步骤1的设备的较小版本, 可以制作更小的水滴。
<ol><li>
为毛细管装置的组装准备三个不同尺寸的玻璃管。
	<ol>
<li>取一个方形的玻璃管与身份证 = 400 微米, 并且切开管子的片断〜 4 cm 长度, 将是设备的外在管子。</li>
		<li>取一圆玻璃管与身份证 = 200 微米和外径 = 330 微米, 并且切开管子的片断 ~ 3 cm 长度, 将是设备的中间管子。</li>
		<li>取一圆玻璃管与身份证 = 100 微米和外径 = 170 微米, 并且切开管子的片断 ~ 2 cm 长度, 将是设备的内管。</li>
	</ol>
</li>
	<li>
修改中间管一端的表面润湿性为疏水性。
	<ol>
<li>拿一个1毫升的玻璃瓶, 并添加0.3 毫升的增加到玻璃瓶。</li>
		<li>用 id 为200微米的中间管, 在协议步骤3.1.2 中准备, 并将它的一端浸入玻璃瓶中的 "十年代"。</li>
		<li>取出中间管, 然后用氮气从未处理的末端冲洗管子。</li>
	</ol>
</li>
	<li>
为毛细管装置的入口准备针头。
	<ol>
<li>准备一个20G 钝尖配药针, 这将成为低粘油阶段的入口。然后, 用刀片, 切一个插槽〜0.2 毫米 x 0.2 毫米的边缘的塑料鲁尔枢纽。</li>
		<li>准备另一20G 钝尖配药针, 并削减两个插槽的边缘塑料鲁尔枢纽。将两个插槽与通过鲁尔集线器直径的直线对齐。 注: 一个插槽的尺寸为0.2 毫米 x 0.2 毫米, 而另一个插槽的尺寸为0.4 毫米 x 0.4 毫米。第二针将作为高粘度水相的入口。</li>
		<li>再拿一个20G 钝尖配药针, 在塑料鲁尔中心的边缘切两个插槽。两个插槽在通过鲁尔中心直径的线对齐。 注: 一个插槽的尺寸为0.8 毫米 x 0.8 毫米, 而另一个插槽的尺寸为0.4 毫米 x 0.4 毫米。这第三针将作为一个入口为清洁目的。</li>
	</ol>
</li>
	<li>按照协议步骤 1.4-1.6 完成该设备, 使用在协议步骤3.1 中编写的玻璃管, 而不是在协议步骤1.1 中编写的, 使用在协议步骤3.3 中编写的针, 而不是在协议步骤1.3 中编写的。</li>
</ol>4. 观察液体石蜡中甘油滴的产生
注: 为拍摄图1B 中显示的图像, 请使用在协议步骤1中编写的设备;要拍摄图 3中显示的图像, 请使用在协议步骤3中准备的设备。
<ol><li>
准备在实验中使用的解决方案。
	<ol>
<li>以甘油为高粘度水相, 并加0.5 的甲苯胺蓝 O 染成蓝色。</li>
		<li>采用液体石蜡作为低粘度油相, 并在其上加入1% 的 80, 作为表面活性剂。</li>
	</ol>
</li>
	<li>
准备三1毫升注射器和三注射器泵。 注: 三在议定书步骤4.1 中制备的液体用注射器: 一种用于注射在协议步骤4.1.1 中制备的高粘度甘油, 另两种用于注射低黏度液体石蜡, 分别在协议步骤4.1.2 中制备。<ol>
<li>将含有甘油的注射器连接到中间管。</li>
		<li>将含有液体石蜡的注射器连接到内胎的入口, 同时将其连接到入口以进行清洗。</li>
	</ol>
</li>
	<li>将在1号协议步骤中准备的设备放置在倒置显微镜下, 并将一块 Kimwipe 置于外管的出口处, 以吸收泄漏的液体。 注意: 不要让流体在 Kimwipe 区域外泄漏。</li>
	<li>
设置注射器泵的流速。 注: 当中间管出口周围有陷泡或水滴时, 使用与外管连接的注射器泵进行清洗。否则, 就把水泵停了。<ol>
<li>将甘油的流速设置为Qw = 10 ul/分钟的中间管。</li>
		<li>设置向Qo = 30 ul/分钟内管注入液体石蜡的流速。</li>
		<li>运行两个泵产生甘油滴。</li>
	</ol>
</li>
	<li>等待0.5 分钟, 直到流量稳定, 甘油滴在中间管出口均匀生成。然后, 拍下水滴生成过程的视频或图像。 注意: 图1B 中的图像可以使用在协议步骤1中编写的设备, 而图 3A中的图像可以使用在协议步骤3中编写的设备进行。一旦拍摄完视频或图像, 立即停止所有的水泵, 立即将设备从显微镜上取出。</li>
	<li>
准备收集高粘度的水滴。
	<ol>
<li>将设备放在垂直平面上, 并将插座指向下方, 并将培养皿放在插座下。使用胶带修复设备与出口〜2毫米以上的培养皿底部。</li>
		<li>将在协议步骤4.1.2 中制备的液体石蜡倒入培养皿中, 然后浸入装置的出口。</li>
	</ol>
</li>
	<li>再次运行两个注射器泵在Qw = 10 ul/分钟和Qo = 30 ul/分钟, 并收集在培养皿中的甘油滴。 注: 等待 ~ 1 分钟, 直到流量稳定, 甘油滴在外管出口均匀生成, 可以采取培养皿中的水滴的图像, 如图 1D中所示的协议1中编写的设备, 或者是在协议步骤3中准备的设备的图 3B 。</li>
</ol>5. 用步骤2中制备的简化装置在液体石蜡中生成和收集甘油滴。
注: 这是为了拍摄在不同流速比的Qo/Qw生成的甘油水滴的图像, 并测量图 2中数据点的相应大小变化。
<ol><li>按照协议步骤 4.1, 准备在实验中使用的解决方案。</li>
	<li>
准备两个1毫升注射器和两个注射器泵。 注: 在协议步骤4.1 中制备的液体用两个注射器: 一种注射高粘度甘油, 在协议步骤4.1.1 中制备, 另一种用于注射低黏度液体石蜡, 分别在协议步骤4.1.2 中制备。<ol>
<li>将含有0.8 毫升甘油的注射器连接到中间管的入口。</li>
		<li>将含有0.8 毫升液体石蜡的注射器连接到内胎的入口。</li>
	</ol>
</li>
	<li>
准备收集高粘度的水滴。
	<ol>
<li>将设备放在垂直平面上, 并将插座指向下方, 并将35毫米的培养皿放在插座下。使用胶带修复设备与出口〜2毫米以上的培养皿底部。</li>
		<li>将在协议步骤4.1.2 中制备的液体石蜡倒入培养皿中, 然后浸入装置的出口。</li>
	</ol>
</li>
	<li>
设置注射器泵的流速。 注: 对于图 2中的每个流量比率, 请固定甘油qw = 2 ul/分钟的流量, 同时根据所需的 q 的流速比率增加液体石蜡Qo到不同值的流量. o/Qw。对于每个流速比, 等待 ~ 1 分钟, 直到流稳定和均匀甘油滴在培养皿中收集, 然后采取水滴的图像。<ol>
<li>设置在Qw = 2 ul/分钟的中间管中注入的甘油的流速。</li>
		<li>设置在Qo = 6 ul/分钟内管中注入的液体石蜡的流速。</li>
		<li>运行两个泵产生甘油滴。 注: 水滴的产生过程可以用手机相机直接观察到, 或者是安装在三脚架上的数码相机。</li>
	</ol>
</li>
	<li>等待 ~ 1 分钟, 直到流量稳定, 并改变一个新的培养皿收集均匀甘油滴。</li>
</ol>6. 采用相倒置共流装置, 在液体石蜡中产生其它高粘度滴。
注意: 这是为图 4中的图像提供的。实验中使用的低粘度油相与协议步骤4.1.2 中所用的方法相同。
<ol><li>使用纯蜂蜜作为图 4A的高粘度水相。</li>
	<li>为图 4B准备 6% 的淀粉溶液。 注意: 使用适当的高温玻璃介质瓶和高温帽。佩戴耐热手套。<ol>
<li>在100毫升的玻璃介质瓶中添加47克水, 并在瓶子里放一个搅拌棒。</li>
		<li>把瓶子放在水浴中, 把温度设置为100摄氏度。</li>
		<li>水浴达到100摄氏度后, 将3克淀粉粉加入热水中。</li>
		<li>盖子的瓶盖, 并保持搅拌4小时, 直到解决方案是明确的。</li>
		<li>等到溶液冷却到室温, 然后再使用。</li>
	</ol>
</li>
	<li>为图 4C准备 10 PVA-124% 的解决方案。 注意: 使用适当的高温玻璃介质瓶和高温帽。佩戴耐热手套。<ol>
<li>在100毫升的玻璃介质瓶中添加45克水, 并在瓶子里放一个搅拌棒。</li>
		<li>把瓶子放在水浴中, 把温度设置为70摄氏度。</li>
		<li>在水浴达到70摄氏度后, 在瓶子中加入5克 PVA-124 粉。</li>
		<li>盖子的瓶盖, 并保持搅拌1小时, 直到解决方案是明确的。</li>
		<li>等到溶液冷却到室温, 然后再使用。</li>
	</ol>
</li>
	<li>
在液体石蜡中产生高粘度滴。
	<ol>
<li>使用步骤 6.1-6.3 中准备的高粘度流体, 而不是在协议步骤5中的甘油, 遵循协议步骤5。</li>
		<li>使用Qw = 1 ul/分钟的流速设置, Qo = 5 ul/分钟图 4。</li>
	</ol>
</li>
</ol>

<ol>
	<li>Shah, R. K., Shum, H. C., Rowat, A. C., Lee, D., Agresti, J. J., Utada, A. S., Chu, L. Y., Kim, J. W., Fernandez-Nieves, A., Martinez, C. J., Weitz, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Designer+emulsions+using+microfluidics.">Designer emulsions using microfluidics.</a> Mater. Today. 11, 18-27 (2008).</li><li>Park, J. I., Saffari, A., Kumar, S., G&#252;nther, A., Kumacheva, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+synthesis+of+polymer+and+inorganic+particulate+materials.">Microfluidic synthesis of polymer and inorganic particulate materials.</a> Annu. Rev. Mater. Res. 40, 415-443 (2010).</li><li>Heath, J. R., Ribas, A., Mischel, P. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Single-cell+analysis+tools+for+drug+discovery+and+development.">Single-cell analysis tools for drug discovery and development.</a> Nat. Rev. Drug Discovery. 15, 204-216 (2016).</li><li>Murphy, S. V., Atala, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=3D+Bioprinting+of+tissues+and+organs.">3D Bioprinting of tissues and organs.</a> Nat. Biotechnol. 32, 773-785 (2014).</li><li>Du, G., Fang, Q., den Toonder, J. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidics+for+cell-based+high+throughput+screening+platforms-a+review.">Microfluidics for cell-based high throughput screening platforms-a review.</a> Anal. Chim. Acta. 903, 36-50 (2016).</li><li>Ushikubo, F. Y., Oliveira, D. R. B., Michelon, M., Cunha, R. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Designing+food+structure+using+microfluidics.">Designing food structure using microfluidics.</a> Food Eng. Rev. 7, 393-416 (2015).</li><li>Xu, J. H., Li, S. W., Tan, J., Wang, Y. J., Luo, G. S. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Preparation+of+highly+monodisperse+droplet+in+a+T-junction+microfluidic+device.">Preparation of highly monodisperse droplet in a T-junction microfluidic device.</a> AIChE Journal. 52, 3005-3010 (2006).</li><li>van Steijn, V., Kleijn, C. R., Kreutzer, M. T. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Flows+around+confined+bubbles+and+their+importance+in+triggering+pinch-off.">Flows around confined bubbles and their importance in triggering pinch-off.</a> Phys. Rev. Lett. 103, 214501 (2009).</li><li>Utada, A. S., Fernandez-Nieves, A., Stone, H. A., Weitz, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dripping+to+jetting+transitions+in+coflowing+liquid+streams.">Dripping to jetting transitions in coflowing liquid streams.</a> Phys. Rev. Lett. 99, 094502 (2007).</li><li>Anna, S. L., Bontoux, N., Stone, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Formation+of+dispersions+using+&amp;#34;flow+focusing&amp;#34;+in+microchannels.">Formation of dispersions using &amp;#34;flow focusing&amp;#34; in microchannels.</a> Appl. phys. lett. 82, 364-366 (2003).</li><li>Utada, A. S., Lorenceau, E., Link, D. R., Kaplan, P. D., Stone, H. A., Weitz, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Monodisperse+double+emulsions+generated+from+a+microcapillary+device.">Monodisperse double emulsions generated from a microcapillary device.</a> Science. 308, 537-541 (2005).</li><li>Teh, S. Y., Lin, R., Hung, L. H., Lee, A. P. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Droplet+microfluidics.">Droplet microfluidics.</a> Lab Chip. 8, 198-220 (2008).</li><li>Nunes, J. K., Tsai, S. S. H., Wan, J., Stone, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Dripping+and+jetting+in+microfluidic+multiphase+flows+applied+to+particle+and+fiber+synthesis.">Dripping and jetting in microfluidic multiphase flows applied to particle and fiber synthesis.</a> J. Phys. D: Appl. Phys. 46, 114002 (2013).</li><li>Cubaud, T., Mason, T. G. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Capillary+threads+and+viscous+droplets+in+square+microchannels.">Capillary threads and viscous droplets in square microchannels.</a> Phys. Fluids. 20, 053302 (2008).</li><li>Shestopalov, I., Tice, J. D., Ismagilov, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Multi-step+synthesis+of+nanoparticles+performed+on+millisecond+time+scale+in+a+microfluidic+droplet-based+system.">Multi-step synthesis of nanoparticles performed on millisecond time scale in a microfluidic droplet-based system.</a> Lab Chip. 4, 316-321 (2004).</li><li>Zheng, B., Roach, L. S., Ismagilov, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Screening+of+protein+crystallization+conditions+on+a+microfluidic+chip+using+nanoliter-size+droplets.">Screening of protein crystallization conditions on a microfluidic chip using nanoliter-size droplets.</a> J. Am. Chem. Soc. 125, 11170-11171 (2003).</li><li>Nie, Z. H., Xu, S. Q., Seo, M., Lewis, P. C., Kumacheva, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+production+of+biopolymer+microcapsules+with+controlled+morphology.">Microfluidic production of biopolymer microcapsules with controlled morphology.</a> J. Am. Chem. Soc. 127, 8058-8063 (2005).</li><li>Abate, A. R., Kutsovsky, M., Seiffert, S., Windbergs, M., Pinto, L. F., Rotem, A., Utada, A. S., Weitz, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis+of+monodisperse+microparticles+from+non-Newtonian+polymer+solutions+with+microfluidic+devices.">Synthesis of monodisperse microparticles from non-Newtonian polymer solutions with microfluidic devices.</a> Adv. Mater. 23, 1757-1760 (2011).</li><li>Seo, M., Nie, Z., Xu, S., Mok, M., Lewis, P. C., Graham, R., Kumacheva, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Continuous+microfluidic+reactors+for+polymer+particles.">Continuous microfluidic reactors for polymer particles.</a> Langmuir. 21, 11614-11622 (2005).</li><li>Duncanson, W. J., Lin, T., Abate, A. R., Seiffert, S., Shah, R. K., Weitz, D. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+synthesis+of+advanced+microparticles+for+encapsulation+and+controlled+release.">Microfluidic synthesis of advanced microparticles for encapsulation and controlled release.</a> Lab Chip. 12, 2135-2145 (2012).</li><li>Song, H., Chen, D. L., Ismagilov, R. F. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactions+in+droplets+in+microfluidic+channels.">Reactions in droplets in microfluidic channels.</a> Angew. Chem. Int. Ed. 45, 7336-7356 (2006).</li><li>Chen, H., Zhao, Y., Li, J., Guo, M., Wan, J., Weitz, D. A., Stone, H. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Reactions+in+double+emulsions+by+flow-controlled+coalescence+of+encapsulated+drops.">Reactions in double emulsions by flow-controlled coalescence of encapsulated drops.</a> Lab Chip. 11, 2312-2315 (2011).</li><li>Wang, P., Li, J., Nunes, J., Hao, S., Liu, B., Chen, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Droplet+micro-reactor+for+internal+gelation+to+fabricate+ZrO2+ceramic+microspheres.">Droplet micro-reactor for internal gelation to fabricate ZrO2 ceramic microspheres.</a> J. Am. Ceram. Soc. 100, 41-48 (2017).</li><li>Chen, H., Man, J., Li, Z., Li, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+generation+of+high-viscosity+droplets+by+surface-controlled+breakup+of+segment+flow.">Microfluidic generation of high-viscosity droplets by surface-controlled breakup of segment flow.</a> ACS Appl. Mater. Interfaces. 9, 21059-21064 (2017).</li><li>Man, J., Li, Z., Li, J., Chen, H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Phase+inversion+of+slug+flow+on+step+surface+to+form+high+viscosity+droplets+in+microchannel.">Phase inversion of slug flow on step surface to form high viscosity droplets in microchannel.</a> Appl. Phys. Lett. 110, 181601 (2017).</li></ol>

作者没有什么可透露的。

反相共流装置提供了一种简单、直接的方法, 能产生单分散高粘度水滴。该装置与普通共流装置具有相似的结构, 因为基本的共流结构由插入在中间管中的内管组成, 其出口与出口油管相连。然而, 相逆共流装置与普通共流装置之间存在两个主要区别, 即产生粘度为η > 1 Pa·s 的高粘度水滴。
首先, 在常用的共流装置中, 采用锥形尖端的内管, 而直内管可用于相倒置的共流装...

水滴的产生正在成为各种应用的关键技术, 如药物输送, 材料合成, 3D 生物打印, 细胞化验, 食品工程 1, 2, 3, 4,5,6. 带 T 形连接7、8、co 流1、9或流聚焦10、11结构的微流控设备广泛用于生成单分散单乳液滴。选择一个更粘性的连续相将有助于形成水滴12, 并且连续和分散的流体的粘度通常低于 0.1 Pas 在液滴微流体 13.然而, 在许多应用中, 分散相的粘度可能比水高几倍, 例如甘油14、含有纳米粒子15、蛋白质16或聚合物17的溶液。,18,19, 而在微流控设备中, 很难直接从稳定的滴水状态11中的高粘度流体中实现单分散液滴, 特别是对于具有η > 1 Pa·s14的粘度的流体.,17,18,19。此外, 还报告了13、18 , 认为液滴形成的典型微流控方法要求流体具有相对较低的粘度和适度的界面张力, 形成稳定滴水中的均匀水滴。政权。
对于具有稍大于 0.1 Pas 的粘度的分散相位, 有几种可能的方法可以通过典型的 T 连接、共流或流聚焦微流控装置来促进液滴的形成: (1) 降低分散的粘度在挥发性溶剂11,20中稀释它的相位;(2) 通过增加连续相位1,11的粘度, 减少分散到连续的粘度比;(3) 将分散相的流速降低到极低的值, 同时保持高连续到分散的流量比率14,19。但是, 这些方法对于粘度高得多的流体来说是不切实际的, 因为它们会显著降低生产速率, 同时显著提高挥发性溶剂或连续相的消耗。在百货商店, 据报道, 一些高粘度聚合物溶液与η > 1 Pa·s 仍然没有分解成水滴与上述方法17,19。
还有几种改进的微流控装置的设计, 将第三阶段的流体引入到系统中, 从而促进了高粘度滴的产生。创新包括: 引入气泡将喷射螺纹切割成水滴21, 一种具有中等粘度的不溶做伴流体, 引入 dipsersed 相和连续相18之间的中间相, 并微反应器介绍了从两个低粘度前体生成高粘度的小水滴 21, 22, 23.然而, 随着这个过程中的一个流体越来越多, 这个系统变得更加复杂, 而这些装置通常在比生成单乳液滴的典型装置更窄的流动机制中工作。
为了直接从高粘度流体中产生单分散液滴与η > 1 Pa·s, 研究了表面控相反演方法的24。由于低黏度水滴的产生比高粘度水滴容易得多12, 高粘度连续相的细长低黏度水滴首先使用典型的共流结构产生, 然后被分解为在共流结构的下游表面润湿性的变化。释放的低粘度流体将下游高粘度流体封装成水滴, 从而完成了相位反演。根据相变机理, 单分散高粘度液滴可根据典型的共流装置产生, 而该共流装置的出口被处理为由低粘度流体润湿, 然后连接到更宽的管24 ,25。

<table><tbody><tr><td>VitroTubes Glass Tubing</td><td>VitroCom</td><td>8240</td><td>Square - Miniature Hollow Glass Tubing, I.D.=0.4mm, OD=0.8mm</td></tr><tr><td>VitroTubes Glass Tubing</td><td>VitroCom</td><td>CV2033</td><td>Round - Miniature Hollow Glass Tubing, I.D.=0.2mm, O.D.=0.33mm</td></tr><tr><td>VitroTubes Glass Tubing</td><td>VitroCom</td><td>CV1017</td><td>Round - Miniature Hollow Glass Tubing, I.D.=0.1mm, O.D.=0.17mm</td></tr><tr><td>VitroTubes Glass Tubing</td><td>VitroCom</td><td>Q14606</td><td>Square - Miniature Hollow Glass Tubing, I.D.=1.05mm+0.1/-0, OD=1.5mm</td></tr><tr><td>Standard Glass Capillaries</td><td>WPI</td><td>1B100-6</td><td>Round - Glass Tubing, I.D.=0.58mm, O.D.=1.00mm</td></tr><tr><td>Glycerol</td><td>Sinopharm Chemical Reagent Beijing</td><td>10010618</td><td></td></tr><tr><td>Paraffin Liquid</td><td>Sinopharm Chemical Reagent Beijing</td><td>30139828</td><td></td></tr><tr><td>Poly(vinyl alcohol), PVA-124</td><td>Sinopharm Chemical Reagent Beijing</td><td>30153084</td><td></td></tr><tr><td>Span 80</td><td>Sigma-Aldrich</td><td>85548</td><td></td></tr><tr><td>Starch</td><td>Sigma-Aldrich</td><td>S9765</td><td></td></tr><tr><td>Trichloro(octadecyl)silane</td><td>Sigma-Aldrich</td><td>104817</td><td></td></tr><tr><td>Toluidine Blue O</td><td>Sigma-Aldrich</td><td>T3260</td><td></td></tr><tr><td>Honey</td><td></td><td></td><td>Chaste tree honey, common food product purchased from supermarket</td></tr><tr><td>DEVCON 5 Minute Epoxy</td><td>ITW&amp;nbsp;</td><td></td><td>Epoxy glue</td></tr><tr><td>Blunt Tip Stainless Steel Dispensing Needles (Luer Lock)</td><td>Suzhou Lanbo Needle, China</td><td>LTA820050</td><td>20G x 1/2&quot;&amp;nbsp;</td></tr><tr><td>Tungsten/Carbide Scriber</td><td>Ullman</td><td>1830</td><td>For cutting glass tubing</td></tr><tr><td>Microscope Slides</td><td>Sail Brand</td><td>7101</td><td>76.2 mm x 25.4 mm, Thickness 1 - 1.2 mm</td></tr><tr><td>Polyethylene Tubing</td><td>Scientific Commodities</td><td>BB31695-PE/5</td><td>I.D. = 0.86 mm, O.D. = 1.32 mm</td></tr><tr><td>Syringe Pumps</td><td>Longer Pump, China</td><td>LSP01-1A</td><td>3 pumps needed for the experiments</td></tr></tbody></table>

fabricating high-viscosity droplets using microfluidic capillary device with phase-inversion co-flow structure

高粘度的单分散液滴的产生一直是液滴微流体的挑战。在这里, 我们演示了一个相逆共流装置, 以产生均匀的高粘度液滴在低粘度流体。微流控毛细管装置有一个共同的共流结构, 其出口连接到一个更宽的管。低粘度流体的细长滴液首先由高粘度流体在共流结构中封装。当细长的低粘度水滴流过出口时, 被低粘度流体所润湿, 然后通过低粘度水滴与出口尖端的粘附来诱导相反转, 从而导致随后的反高粘度流体的封装。通过将低粘度流体的流速比转化为高粘度流体, 可以调节产生的高粘度水滴的大小。我们展示了几个典型的例子, 产生高粘度的水滴, 粘度高达 11.9 Pas, 如甘油, 蜂蜜, 淀粉和聚合物溶液。该方法提供了一种简单而直接的方法来生成单分散高粘度滴, 可用于各种液滴的应用, 如材料合成, 药物输送, 细胞化验, 生物工程和食品工程。

采用相反转、共流结构的微流控毛细管装置, 设计成单分散水性高粘度水滴, 如图 1A所示。在图 1中, 高粘度水相是甘油, 其黏度为ηw = 1.4 Pas;低粘度油相为液体石蜡, 其粘度为ηo = 0.029 Pas;两个阶段之间的表面张力为γ = 27.7 锰/米。在中间管, 拉长的油滴可以由甘油封装在一个良好控制的滴水模式<sup cla...

Watch this Scientific Journal Video about Fabricating High-viscosity Droplets using Microfluidic Capillary Device with Phase-inversion Co-flow Structure at JoVE.com

Fabricating High-viscosity Droplets using Microfluidic Capillary Device with Phase-inversion Co-flow Structure

反相共流微流控毛细管装置制备高粘度水滴的方法

本文展示了一种反相共流装置, 以产生单分散高粘度在 1 Pas 以上的液滴, 在液滴微流体中难以实现。

The generation of monodisperse droplets with high viscosity has always been a challenge in droplet microfluidics. Here, we demonstrate a phase-inversion ...

fabricating-high-viscosity-droplets-using-microfluidic-capillary

Research

Education

JoVE Journal

JoVE Core

Chemistry

Liquids, Solids, and Intermolecular Forces

SCIENTISTS IN ACTION

10.3K 次观看.  University of Science and Technology Beijing. 本文展示了一种反相共流装置, 以产生单分散高粘度在 1 Pas 以上的液滴, 在液滴微流体中难以实现。

视频: Fabricating High-viscosity Droplets using Microfluidic Capillary Device with Phase-inversion Co-flow Structure

Fluorescence detection methods for microfluidic droplet platforms

The development of microfluidic platforms for performing chemistry and biology has in large part been driven by a range of potential benefits that accompany system miniaturisation. Advantages include the ability to efficiently process nano- to femoto- liter volumes of sample, facile integration of functional components, an intrinsic predisposition towards large-scale multiplexing, enhanced analytical throughput, improved control and reduced instrumental footprints.1
In recent years much interest has focussed on the development of droplet-based (or segmented flow) microfluidic systems and their potential as platforms in high-throughput experimentation.2-4 Here water-in-oil emulsions are made to spontaneously form in microfluidic channels as a result of capillary instabilities between the two immiscible phases. Importantly, microdroplets of precisely defined volumes and compositions can be generated at frequencies of several kHz. Furthermore, by encapsulating reagents of interest within isolated compartments separated by a continuous immiscible phase, both sample cross-talk and dispersion (diffusion- and Taylor-based) can be eliminated, which leads to minimal cross-contamination and the ability to time analytical processes with great accuracy. Additionally, since there is no contact between the contents of the droplets and the channel walls (which are wetted by the continuous phase) absorption and loss of reagents on the channel walls is prevented.
Once droplets of this kind have been generated and processed, it is necessary to extract the required analytical information. In this respect the detection method of choice should be rapid, provide high-sensitivity and low limits of detection, be applicable to a range of molecular species, be non-destructive and be able to be integrated with microfluidic devices in a facile manner. To address this need we have developed a suite of experimental tools and protocols that enable the extraction of large amounts of photophysical information from small-volume environments, and are applicable to the analysis of a wide range of physical, chemical and biological parameters. Herein two examples of these methods are presented and applied to the detection of single cells and the mapping of mixing processes inside picoliter-volume droplets. We report the entire experimental process including microfluidic chip fabrication, the optical setup and the process of droplet generation and detection.

Droplet-based microfluidic platforms are promising candidates for high throughput experimentation since they are able to generate picoliter, self-compartmentalized vessels inexpensively at kHz rates. Through integration with fast, sensitive and high resolution fluorescence spectroscopic methods, the large amounts of information generated within these systems can be efficiently extracted, harnessed and utilized.

荧光检测方法，为微流体液滴平台

The development of microfluidic platforms for performing chemistry and biology has in large part been driven by a range of potential benefits that ...

科研

生物工程

High Throughput Single-cell and Multiple-cell Micro-encapsulation

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement from a bulk fluid environment with applications in high throughput screening, cytometry, and mass spectrometry. We describe a method to not only encapsulate single cells, but to repeatedly capture a set number of cells (here we demonstrate one- and two-cell encapsulation) to study both isolation and the interactions between cells in groups of controlled sizes. By combining drop generation techniques with cell and particle ordering, we demonstrate controlled encapsulation of cell-sized particles for efficient, continuous encapsulation. Using an aqueous particle suspension and immiscible fluorocarbon oil, we generate aqueous drops in oil with a flow focusing nozzle. The aqueous flow rate is sufficiently high to create ordering of particles which reach the nozzle at integer multiple frequencies of the drop generation frequency, encapsulating a controlled number of cells in each drop. For representative results, 9.9 &mu;m polystyrene particles are used as cell surrogates. This study shows a single-particle encapsulation efficiency Pk=1 of 83.7% and a double-particle encapsulation efficiency Pk=2 of 79.5% as compared to their respective Poisson efficiencies of 39.3% and 33.3%, respectively. The effect of consistent cell and particle concentration is demonstrated to be of major importance for efficient encapsulation, and dripping to jetting transitions are also addressed. 
Introduction 
Continuous media aqueous cell suspensions share a common fluid environment which allows cells to interact in parallel and also homogenizes the effects of specific cells in measurements from the media. High-throughput encapsulation of cells into picoliter-scale drops confines the samples to protect drops from cross-contamination, enable a measure of cellular diversity within samples, prevent dilution of reagents and expressed biomarkers, and amplify signals from bioreactor products. Drops also provide the ability to re-merge drops into larger aqueous samples or with other drops for intercellular signaling studies.1,2 The reduction in dilution implies stronger detection signals for higher accuracy measurements as well as the ability to reduce potentially costly sample and reagent volumes.3 Encapsulation of cells in drops has been utilized to improve detection of protein expression,4 antibodies,5,6 enzymes,7 and metabolic activity8 for high throughput screening, and could be used to improve high throughput cytometry.9 Additional studies present applications in bio-electrospraying of cell containing drops for mass spectrometry10 and targeted surface cell coatings.11 Some applications, however, have been limited by the lack of ability to control the number of cells encapsulated in drops. Here we present a method of ordered encapsulation12 which increases the demonstrated encapsulation efficiencies for one and two cells and may be extrapolated for encapsulation of a larger number of cells.
To achieve monodisperse drop generation, microfluidic "flow focusing" enables the creation of controllable-size drops of one fluid (an aqueous cell mixture) within another (a continuous oil phase) by using a nozzle at which the streams converge.13 For a given nozzle geometry, the drop generation frequency f and drop size can be altered by adjusting oil and aqueous flow rates Qoil and Qaq. As the flow rates increase, the flows may transition from drop generation to unstable jetting of aqueous fluid from the nozzle.14 
When the aqueous solution contains suspended particles, particles become encapsulated and isolated from one another at the nozzle. For drop generation using a randomly distributed aqueous cell suspension, the average fraction of drops Dk containing k cells is dictated by Poisson statistics, where Dk = &lambda;k exp(-&lambda;)/(k!) and &lambda; is the average number of cells per drop. The fraction of cells which end up in the "correctly" encapsulated drops is calculated using Pk = (k x Dk)/&Sigma;(k' x Dk'). The subtle difference between the two metrics is that Dk relates to the utilization of aqueous fluid and the amount of drop sorting that must be completed following encapsulation, and Pk relates to the utilization of the cell sample. As an example, one could use a dilute cell suspension (low &lambda;) to encapsulate drops where most drops containing cells would contain just one cell. While the efficiency metric Pk would be high, the majority of drops would be empty (low Dk), thus requiring a sorting mechanism to remove empty drops, also reducing throughput.15
Combining drop generation with inertial ordering provides the ability to encapsulate drops with more predictable numbers of cells per drop and higher throughputs than random encapsulation. Inertial focusing was first discovered by Segre and Silberberg16 and refers to the tendency of finite-sized particles to migrate to lateral equilibrium positions in channel flow. Inertial ordering refers to the tendency of the particles and cells to passively organize into equally spaced, staggered, constant velocity trains. Both focusing and ordering require sufficiently high flow rates (high Reynolds number) and particle sizes (high Particle Reynolds number).17,18 Here, the Reynolds number Re =uDh/&nu; and particle Reynolds number Rep =Re(a/Dh)2, where u is a characteristic flow velocity, Dh [=2wh/(w+h)] is the hydraulic diameter, &nu; is the kinematic viscosity, a is the particle diameter, w is the channel width, and h is the channel height. Empirically, the length required to achieve fully ordered trains decreases as Re and Rep increase. Note that the high Re and Rep requirements (for this study on the order of 5 and 0.5, respectively) may conflict with the need to keep aqueous flow rates low to avoid jetting at the drop generation nozzle. Additionally, high flow rates lead to higher shear stresses on cells, which are not addressed in this protocol. The previous ordered encapsulation study demonstrated that over 90% of singly encapsulated HL60 cells under similar flow conditions to those in this study maintained cell membrane integrity.12 However, the effect of the magnitude and time scales of shear stresses will need to be carefully considered when extrapolating to different cell types and flow parameters. The overlapping of the cell ordering, drop generation, and cell viability aqueous flow rate constraints provides an ideal operational regime for controlled encapsulation of single and multiple cells.
Because very few studies address inter-particle train spacing,19,20 determining the spacing is most easily done empirically and will depend on channel geometry, flow rate, particle size, and particle concentration. Nonetheless, the equal lateral spacing between trains implies that cells arrive at predictable, consistent time intervals. When drop generation occurs at the same rate at which ordered cells arrive at the nozzle, the cells become encapsulated within the drop in a controlled manner. This technique has been utilized to encapsulate single cells with throughputs on the order of 15 kHz,12 a significant improvement over previous studies reporting encapsulation rates on the order of 60-160 Hz.4,15 In the controlled encapsulation work, over 80% of drops contained one and only one cell, a significant efficiency improvement over Poisson (random) statistics, which predicts less than 40% efficiency on average.12
In previous controlled encapsulation work,12 the average number of particles per drop &lambda; was tuned to provide single-cell encapsulation. We hypothesize that through tuning of flow rates, we can efficiently encapsulate any number of cells per drop when &lambda; is equal or close to the number of desired cells per drop. While single-cell encapsulation is valuable in determining individual cell responses from stimuli, multiple-cell encapsulation provides information relating to the interaction of controlled numbers and types of cells. Here we present a protocol, representative results using polystyrene microspheres, and discussion for controlled encapsulation of multiple cells using a passive inertial ordering channel and drop generation nozzle.

Combining monodisperse drop generation with inertial ordering of cells and particles, we describe a method to encapsulate a desired number of cells or particles in a single drop at kHz rates. We demonstrate efficiencies twice exceeding those of unordered encapsulation for single- and double-particle drops.

高吞吐量的单细胞和多细胞微胶囊

Microfluidic encapsulation methods have been previously utilized to capture cells in picoliter-scale aqueous, monodisperse drops, providing confinement ...

Capillary-based Centrifugal Microfluidic Device for Size-controllable Formation of Monodisperse Microdroplets

Here, we demonstrate a simple method for the rapid production of size-controllable, monodisperse, W/O microdroplets using a capillary-based centrifugal microfluidic device. W/O microdroplets have recently been used in powerful methods that enable miniaturized chemical experiments. Therefore, developing a versatile method to yield monodisperse W/O microdroplets is needed. We have developed a method for generating monodisperse W/O microdroplets based on a capillary-based centrifugal axisymmetric co-flowing microfluidic device. We succeeded in controlling the size of microdroplets by adjusting the capillary orifice. Our method requires equipment that is easier-to-use than with other microfluidic techniques, requires only a small volume (0.1-1 &#181;l) of sample solution for encapsulation, and enables the production of hundreds of thousands number of W/O microdroplets per second. We expect this method will assist biological studies that require precious biological samples by conserving the volume of the samples for rapid quantitative analysis biochemical and biological studies.

Here, we demonstrate a simple production method for size-controllable, monodisperse, water-in-oil (W/O) microdroplets using a capillary-based centrifugal microfluidic device. This method requires only a small sample volume and enables high-yield production. We expect this method will be useful for rapid biochemical and cellular analyses.

基于毛细管的离心微流体装置单分散微滴的大小可控的形成

Here, we demonstrate a simple method for the rapid production of size-controllable, monodisperse, W/O microdroplets using a capillary-based centrifugal ...

工程学

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. ...

High Speed Droplet-based Delivery System for Passive Pumping in Microfluidic Devices

A novel microfluidic system has been developed that uses the phenomenon of passive pumping along with a user controlled droplet based fluid delivery system. Passive pumping is the phenomenon by which surface tension induced pressure differences drive fluid movement in closed channels. The automated fluid delivery system consists of a set of voltage controlled valves with micro-nozzles connected to a fluid reservoir and a control system. These voltage controlled valves offer a volumetrically precise way to deliver fluid droplets to the inlet of a microfluidic device in a high frequency manner. Based on the  dimensions demonstrated in the current study example, the system is capable of flowing 4 milliliters per minute (through a 2.2mm by 260um cross-sectional channel). Based on these same channel dimensions, fluid exchange of a point inside the channel can be achieved in as little as eight milliseconds. It is observed that there is interplay between momentum of the system (imparted by a combination of the droplets created by the valves and the fluid velocity in the channel), and the surface tension of the liquid. Where momentum provides velocity to the fluid flow (or vice-versa), equilibration of surface tension at the inlet provides a sudden stop to any flow. This sudden stop allows the user to control the flow characteristics of the channel and opens the door for a variety of biological applications, ranging anywhere from reagent delivery to drug-cell studies. It is also observed that when nozzles are aimed at the inlet at shallow angles, the droplet momentum can cause additional interesting fluid phenomena, such as mixing of multiple droplets in the inlet.

A novel microfluidic system has been developed using the phenomenon of passive pumping and a user controlled fluid delivery system. This microfluidic system has the potential to be used in a wide variety of biological applications given its low cost, ease of use, volumetric precision, high speed, repeatability and automation.

基于液滴在微流体装置的被动抽水高速输送系统

A novel microfluidic system has been developed that uses the phenomenon of passive pumping along with a user controlled droplet based fluid delivery ...

生物学

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 ...

Fabricating Degradable Thermoresponsive Hydrogels on Multiple Length Scales via Reactive Extrusion, Microfluidics, Self-assembly, and Electrospinning

While various smart materials have been explored for a variety of biomedical applications (e.g., drug delivery, tissue engineering, bioimaging, etc.), their ultimate clinical use has been hampered by the lack of biologically-relevant degradation observed for most smart materials. This is particularly true for temperature-responsive hydrogels, which are almost uniformly based on polymers that are functionally non-degradable (e.g., poly(N-isopropylacrylamide) (PNIPAM) or poly(oligoethylene glycol methacrylate) (POEGMA)). As such, to effectively translate the potential of thermoresponsive hydrogels to the challenges of remote-controlled or metabolism-regulated drug delivery, cell scaffolds with tunable cell-material interactions, theranostic materials with the potential for both imaging and drug delivery, and other such applications, a method is required to render the hydrogels (if not fully degradable) at least capable of renal clearance following the required lifetime of the material. To that end, this protocol describes the preparation of hydrolytically-degradable hydrazone-crosslinked hydrogels on multiple length scales based on the reaction between hydrazide and aldehyde-functionalized PNIPAM or POEGMA oligomers with molecular weights below the renal filtration limit. Specifically, methods to fabricate degradable thermoresponsive bulk hydrogels (using a double barrel syringe technique), hydrogel particles (on both the microscale through the use of a microfluidics platform facilitating simultaneous mixing and emulsification of the precursor polymers and the nanoscale through the use of a thermally-driven self-assembly and cross-linking method), and hydrogel nanofibers (using a reactive electrospinning strategy) are described. In each case, hydrogels with temperature-responsive properties similar to those achieved via conventional free radical cross-linking processes can be achieved, but the hydrazone cross-linked network can be degraded over time to re-form the oligomeric precursor polymers and enable clearance. As such, we anticipate these methods (which may be generically applied to any synthetic water-soluble polymer, not just smart materials) will enable easier translation of synthetic smart materials to clinical applications.

Protocols are described for the fabrication of degradable thermoresponsive hydrogels based on hydrazone cross-linking of polymeric oligomers on the bulk scale, microscale, and nanoscale, the latter for preparation of both gel nanoparticles and nanofibers.

通过反应挤出、微流体、自组装和电纺丝制备多长尺度可降解 Thermoresponsive 水凝胶

While various smart materials have been explored for a variety of biomedical applications (e.g., drug delivery, tissue engineering, bioimaging, etc.), ...

Glass-Based Devices to Generate Drops and Emulsions

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

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

基于玻璃的设备，用于产生液滴和乳液

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

Multi-step Variable Height Photolithography for Valved Multilayer Microfluidic Devices

Microfluidic systems have enabled powerful new approaches to high-throughput biochemical and biological analysis. However, there remains a barrier to entry for non-specialists who would benefit greatly from the ability to develop their own microfluidic devices to address research questions. Particularly lacking has been the open dissemination of protocols related to photolithography, a key step in the development of a replica mold for the manufacture of polydimethylsiloxane (PDMS) devices. While the fabrication of single height silicon masters has been explored extensively in literature, fabrication steps for more complicated photolithography features necessary for many interesting device functionalities (such as feature rounding to make valve structures, multi-height single-mold patterning, or high aspect ratio definition) are often not explicitly outlined. 
Here, we provide a complete protocol for making multilayer microfluidic devices with valves and complex multi-height geometries, tunable for any application. These fabrication procedures are presented in the context of a microfluidic hydrogel bead synthesizer and demonstrate the production of droplets containing polyethylene glycol (PEG diacrylate) and a photoinitiator that can be polymerized into solid beads. This protocol and accompanying discussion provide a foundation of design principles and fabrication methods that enables development of a wide variety of microfluidic devices. The details included here should allow non-specialists to design and fabricate novel devices, thereby bringing a host of recently developed technologies to their most exciting applications in biological laboratories.

Multilayer microfluidic devices often involve the fabrication of master molds with complex geometries for functionality. This article presents a complete protocol for multi-step photolithography with valves and variable height features tunable to any application. As a demonstration, we fabricate a microfluidic droplet generator capable of producing hydrogel beads.

多级可变高度的光刻多层带瓣微流体装置

Microfluidic systems have enabled powerful new approaches to high-throughput biochemical and biological analysis. However, there remains a barrier to ...

用于组合插头生产的微流体装置的设置

Bilayer Microfluidic Device for Combinatorial Plug Production

Droplet microfluidics is a versatile tool that allows the execution of a large number of reactions in chemically distinct nanoliter compartments. Such systems have been used to encapsulate a variety of biochemical reactions - from incubation of single cells to implementation of PCR reactions, from genomics to chemical synthesis. Coupling the microfluidic channels with regulatory valves allows control over their opening and closing, thereby enabling the rapid production of large-scale combinatorial libraries consisting of a population of droplets with unique compositions. In this paper, protocols for the fabrication and operation of a pressure-driven, PDMS-based bilayer microfluidic device that can be utilized to generate combinatorial libraries of water-in-oil emulsions called plugs are presented. By incorporating software programs and microfluidic hardware, the flow of desired fluids in the device can be controlled and manipulated to generate combinatorial plug libraries and to control the composition and quantity of constituent plug populations. These protocols will expedite the process of generating combinatorial screens, particularly to study drug response in cells from cancer patient biopsies.

作者聚焦：在精准肿瘤学中整合计算和实验方法

The fabrication of a polydimethylsiloxane (PDMS)-based bilayer device for the production of combinatorial libraries in water-in-oil emulsions (plugs) is presented here. The necessary hardware and software required to automate plug production are detailed in the protocol, and the production of a quantitative library of fluorescent plugs is also demonstrated.

用于组合塞生产的双层微流控装置

Droplet microfluidics is a versatile tool that allows the execution of a large number of reactions in chemically distinct nanoliter compartments. Such ...