Name: microbubble fabrication of concave-porosity pdms beads
Uploaded: 2015-12-15T14:00:00.000+00:00
Duration: 11 min 52 s
Description: Watch this Scientific Journal Video about Microbubble Fabrication of Concave-porosity PDMS Beads at JoVE.com

这项工作已经由科学与工程，包括从化学系和研究办公室（RCAP 13-8032）内部支持的西肯塔基大学的奥格登学院的支持。约翰·Andersland博士在WKU显微镜基金（SEM图像）和WKU研究所燃烧科学与工程（BET分析）副曹燕教授的援助是中央对开展这项工作。

1.准备乳液<ol><li>乳液内容<ol><li>质量盐适量，以产生10个毫升0.03-M的溶液。对于铂（IV），氯化度量0.101克，为锌（II）氯化物（ 氯化锌 ）度量0.032克和氯化钠（NaCl）中测量0.018克。 </li><li>在个别试管，溶解每种盐于10ml DI水中。预留以备以后使用。 </li><li>使用一个20毫升，可密封的玻璃小瓶中的内容整个过程。去皮的平衡向玻璃小瓶。 </li><li>慢慢浇过来一个搅拌棒和成玻璃小瓶搁在归零衡称重乙烯基聚二甲基硅氧烷终止。称取1.02的克（相当于1.080毫升）。 注:该聚合物的高粘度，使移液不切实际。 </li><li>吸管1.02的毫升正庚烷的小瓶。添加2滴非离子表面活性剂（山梨糖醇单油酸酯）的小瓶中。吸管0.3 ml的盐溶液和0.45毫升去离子水的小瓶中。 </li><li>通过拧紧盖子上加以密封的玻璃小瓶。剧烈摇晃60秒开始超声之前启动乳液。 </li></ol></li><li>水，水浴超声设备建设<ol><li>填写超声仪加水至最低填充线。加入250毫升的自来水中以一个400毫升烧杯中。填补400毫升烧杯中在冰冷，使得水位刚好在轮辋。 </li><li>将此烧杯水浴超声波仪内。检查的超声发生器的填充线，如果需要调整。放置一个环站直接在水浴超声波仪旁边。 </li><li>使用两个环站箍，定位，使臂延伸出来，垂直于该环站和另一个延伸朝向水浴使其朝下放入盛有冰水的烧杯中。附加其他夹持到环站有温度计在400毫升烧杯中的向下，以使温度可以在整个超声处理进行监测。 </li></ol></li><li>乳化剂ication过程<ol><li>放置含乳剂样品瓶，以便它是由固定其插入夹具突出下入烧杯完全浸没在400毫升烧杯中。 </li><li>确保包含PDMS的混合物的玻璃小瓶未​​接触到烧杯的两侧，以消除因摩擦热。 </li><li>打开超声波仪和设置声波处理时间7分钟。因为该乳液是非常热敏感，确保该烧杯中的温度在0至5℃，在整个超声处理。启动超声处理一旦烧杯中的温度是理想的。 </li><li>后超声处理7分钟，取出小瓶并轻轻摇动/涡流1分钟，保持小瓶的顶部，以消除可能形成乳液的任何团块。 </li><li>处置的烧杯中的内容。重新注入250ml水，并填充冰加至在1厘米的烧杯的顶部。 </li><li>将小瓶放回钳。淹没它在冰水resumË超声7分钟。 </li><li>重复步骤1.3.3至1.3.6的总共八个，7分钟超声处理期间，或直到超声处理似乎是同质的并且没有团块存在。存储在RT。 注意:乳化应稳定数天，但通过超声处理如上述在7分钟的间隔，直到它出现均匀可以恢复。存储在RT。 </li></ol></li></ol> 2.交联<ol><li>设置为加三乙氧基硅烷/表面活性剂溶液<ol><li>吸管5.4 ml的三乙氧基硅烷置于试管。放置在通风橱中以备后用下一个试管架上。 </li><li>填写一个400毫升的烧杯中，用冰水，并放置在引擎盖下。旁边的400毫升烧杯中代替环站在附夹具，直接延伸在烧杯的开口。这将是冰浴中加入三乙氧基硅烷。 </li><li>放置在热板上在环形支架的另一侧。填写一个800毫升的烧杯中，用约700毫升自来水。将其放在加热板上。 </li><li>开启热板，保持75℃至85℃的800毫升烧杯内。附加的夹紧用温度计环形底座以800毫升烧杯内的水的温度可以被监控。 </li><li>产生通过将0.5克十二烷基硫酸钠375毫升水（4.62毫摩尔）的表面活性剂溶液。再加上约10毫升的表面活性剂溶液到一个干净的空试管中。 </li><li>附加其他夹持到环站与表面活性剂试管罩下固定，使得其液面为800毫升烧杯内的水的表面之下。允许10分钟的热平衡。 </li><li>湿一张滤纸，并将其放置在一个小漏斗的顶部。放置一个250ml的锥形烧瓶内漏斗的干，并放置在引擎盖下的烧瓶中。 </li></ol></li><li>另外三乙氧基硅烷<ol><li>放置乳液小瓶在钳位在冰水喙呃在罩内。在夹紧位置与PDMS混合物中，使小瓶内容是水的表面之下。加入三乙氧基硅烷导致放热反应，使该乳液必须保持冷，以保持其结构。 </li><li>从玻璃小瓶移除盖，以避免气体积聚。 </li><li>历时约10秒（大约0.5毫升/秒）慢慢倒入含有试管三乙氧基到玻璃小瓶中的连续流。 注意:除了三乙氧基硅烷开始放热反应，苛性氯化氢（HCl）气体的释放。小瓶会变得非常热，有毒气体将发展从混合物。不要搅拌的内容，同时增加了三乙氧基硅烷。 </li><li>完全加入三乙氧基硅烷后，轻轻搅拌用玻璃搅拌棒的内容，但戴防热手套。等待2分钟或直到气体停止从瓶中发展。 </li><li> FOLL由于交联，没有相分离的试样中可见。如果团块存在，密封小瓶，并摇晃严格，持续20秒，同时保持瓶的盖子。 </li></ol></li><li>珠生产<ol><li>使用干净的玻璃巴斯德吸管从玻璃小瓶绘制交联乳液。加交联的乳液滴至表面活性剂溶液（其应保持在75和85℃）放入试管以尽可能少的时间尽可能在液滴之间。 </li><li> 30秒到1在加入乳剂后分，表面活性剂溶液将开始慢慢演变气体作为固体开始形成的试管内。 </li><li>虽然穿着热防护手套，取试管出钳，其全部内容倒在引擎盖下的过滤装置。过滤5分钟。从过滤器中取出滤纸。 </li><li>下的H传输滤出的固体上表玻璃和单独的珠O / N干燥洪水。珠清洁可无限期推迟。商店干燥珠在室温在密封的玻璃小瓶中直到需要，清洁前立即使用。 </li></ol></li><li>珠清洗<ol><li>创建罩下另过滤装置，并放置在漏斗内的干燥珠在滤纸的上面。 </li><li>用塑料洗瓶装满离子水冲洗珠轻轻的，移动起来稍微，以确保所有的珠子冲洗。 </li><li>让珠通过将它们放置在引擎盖下表玻璃干燥1小时。使用的洗涤瓶填充用己烷冲洗使用相同的方法的珠用水漂洗。 </li><li>将珠子上的表玻璃。放置皿，在引擎盖下的珠粒干燥。 </li><li>后珠粒完全干燥后，将它们放置在一个小的可密封的玻璃小瓶中并储存在室温下供将来使用。 </li></ol></li><li>安装珠的SEM分析SEM设置<ol><li>将做一个带在其上的珠子会被安装在短线的顶部uble双面碳导电胶带。用剪刀修剪周围的存根，以确保没有带笼罩着边缘。 </li><li>放置存根下一张滤纸在一个平面上。从带去除顶层，使得粘合剂底面露出。 </li><li>轻轻倒入珠在存根。有些珠将坚持到磁带上，但大多数人会弹开和土地在滤纸上。倾这些放回小瓶如果他们停留在滤纸上。必要时重复进行，任何清洗珠（根据2.4.2至2.4.5），其被污染。 </li><li>为确保珠的存根安全，使用球形注射器轻轻密切吹存根表面。在存根倾多珠如果只有几个粘到带上。确保所有的珠子都将存根到SEM室和疏散前的安全。 </li><li>一旦样品已安装正确，他们现在已经准备好进行SEM肛门ysis 15。在低洼VAC模式的图像在15千电子伏，优化的珠的表面特征的分辨率。 </li></ol></li></ol>

<ol>
	<li>Pedraza, E., Brady, A. C., Fraker, C. A., Stabler, C. L. <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+macroporous+poly(dimethylsiloxane)+scaffolds+for+tissue+engineering+applications.">Synthesis of macroporous poly(dimethylsiloxane) scaffolds for tissue engineering applications.</a> J. Biomater. Sci., Polym. Ed. 24 (9), 1041-1056 (2013).</li><li>Ratner, B. D., Bryant, S. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Biomaterials:+Where+we+have+been+and+where+we+are+going.">Biomaterials: Where we have been and where we are going.</a> Annu. Rev. Biomed. Eng. 6, 41-75 (2004).</li><li>B&#233;langer, M. C., Marois, Y. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Hemocompatibility,+biocompatibility,+inflammatory+and+in+vivo+studies+of+primary+reference+materials+low-density+polyethylene+and+polydimethylsiloxane:+A+review.">Hemocompatibility, biocompatibility, inflammatory and in vivo studies of primary reference materials low-density polyethylene and polydimethylsiloxane: A review.</a> J. Biomed. Mater. 58 (5), 467-477 (2001).</li><li>Kobayashi, T., Saitoh, H., Fujii, N., Hoshino, Y., Takanashi, M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Porous+membrane+of+polydimethylsiloxane+by+hydrosilylation+cure:+characteristics+of+membranes+having+pores+formed+by+hydrogen+foams.">Porous membrane of polydimethylsiloxane by hydrosilylation cure: characteristics of membranes having pores formed by hydrogen foams.</a> J. Appl. Polym. Sci. 50 (6), 971-979 (1993).</li><li>Yager, P., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Microfluidic+diagnostic+technologies+for+global+public+health.">Microfluidic diagnostic technologies for global public health.</a> Nature. 442 (7101), 412-418 (2006).</li><li>Yu, P., Lu, C. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=PDMS+used+in+microfluidic+devices:+principles,+devices+and+technologies.">PDMS used in microfluidic devices: principles, devices and technologies.</a> Adv. Mater. Sci. Res. 11, 443-450 (2011).</li><li>Zhou, J., Khodakov, D. A., Ellis, A. V., Voelcker, N. H. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Surface+modification+for+PDMS-based+microfluidic+devices.">Surface modification for PDMS-based microfluidic devices.</a> Electrophoresis. 33 (1), 89-104 (2012).</li><li>Spietelun, A., Pilarczyk, M., Kloskowski, A., Namie&#347;nik, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Polyethylene+glycol-coated+solid-phase+microextraction+fibres+for+the+extraction+of+polar+analytes&#8212;A+review.">Polyethylene glycol-coated solid-phase microextraction fibres for the extraction of polar analytes&#8212;A review.</a> Talanta. 87, 1-7 (2011).</li><li>Vas, G., V&#233;key, K. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Solid-phase+microextraction:+a+powerful+sample+preparation+tool+prior+to+mass+spectrometric+analysis.">Solid-phase microextraction: a powerful sample preparation tool prior to mass spectrometric analysis.</a> J. Mass Spectrom. 39 (3), 233-254 (2004).</li><li>Odziemkowski, M., Koziel, J. A., Irish, D. E., Pawliszyn, J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Sampling+and+Raman+confocal+microspectroscopic+analysis+of+airborne+particulate+matter+using+poly(dimethylsiloxane)+solid+phase+microextraction+fibers.">Sampling and Raman confocal microspectroscopic analysis of airborne particulate matter using poly(dimethylsiloxane) solid phase microextraction fibers.</a> Anal. Chem. 73 (13), 3131-3139 (2001).</li><li>Grosse, M. T., Lamotte, M., Birot, M., Deleuze, H. <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+microcellular+polysiloxane+monoliths.">Preparation of microcellular polysiloxane monoliths.</a> J. Polym. Sci., Part A: Polym. Chem. 46 (1), 21-32 (2007).</li><li>Sun, W., Yan, X., Zhu, X. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Synthesis,+porous+structure,+and+underwater+acoustic+properties+of+macroporous+cross-linked+copolymer+beads.">Synthesis, porous structure, and underwater acoustic properties of macroporous cross-linked copolymer beads.</a> Colloid Polym. Sci. 290 (1), 73-80 (2012).</li><li>Dufaud, O., Favre, E., Sadtler, V. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Porous+elastomeric+beads+from+crosslinked+emulsions.">Porous elastomeric beads from crosslinked emulsions.</a> J. Appl. Polym. Sci. 83 (5), 967-971 (2002).</li><li>Farmer, B. C., Mason, M., Nee, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Concave+porosity+non-polar+beads+by+a+modified+microbubble+fabrication.">Concave porosity non-polar beads by a modified microbubble fabrication.</a> Mater. Lett. 98, 105-107 (2013).</li><li>Flegler, S. L., Heckman, J. W., Klomparens, K. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=.">.</a> Scanning and Transmission Electron Microscopy: An Introduction. , 151-155 (1995).</li><li>Brunauer, S., Emmett, P. H., Teller, E. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Adsorption+of+Gases+in+Multimolecular+Layers.">Adsorption of Gases in Multimolecular Layers.</a> J. Am. Chem. Soc. 60 (2), 309-319 (1938).</li><li>Sing, K. S. W. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Characterization+of+porous+materials:+past,+present+and+future.">Characterization of porous materials: past, present and future.</a> Colloids Surf. A. 241 (1), 3-7 (2004).</li></ol>

The authors have nothing to disclose.

使用此协议（以及通过调节电解质浓度和同一性）中产生的小珠与那些用低离子强度的乳液产生根本的不同，所看到的图1A的比较的其他SEM图像在图1中。我们最初的报告中使用PTCL 4的进一步催化聚合交联在水性脂族接口 14的意图。在该报告中，大凹压痕进行观察。由于该报告中，我们已经改进我们的程序来优化SAV的比例。无需水洗珠，扫描电镜图像中域的元素分析表明，铂发现几乎全部被找到整个圈结构的凹孔中。因为这个铂通过搅拌珠在水中容易地除去，我们得出的结论在我们的原始报告中指出，铂只是上残留的PDMS表面上，而不是即incorporated到聚合物中。这意味着在固化过程中的铂催化剂的作用。在图1所示的珠粒的特点是球形子结构，大致凸状的外观，但那些具有补充电解液产生还包含凹的球面区域诸如图1B的圆圈部分。电解质的存在似乎降低乳液中的微气泡的大小。详细的图像表明，基于所述球面子的大小，在乳液中的气泡的直径与氯化锌 0.2至2μm的量级上，但更常用的1-10微米的直径，而不电解质（具有一致以前的工作由DuFaud， 等人13）。 这里提供的数据表明，更便宜，更大地丰富的金属可以使用，而不是原来PTCL 4:凹孔隙珠无论在ident都产金属离子的，两者均用，虽然到显著不同程度。使用的ZnCl 2的提供急剧增加，在SAV比率，六倍高达为PTCL 4，和大约30倍高的控制程序，其中不包含电解质。的BET结果与SEM图像良好的协议:为氯化锌 ，许多凹穴，在直径为几微米，被认为在整个结构分布。在图2B的详细的图像还表明，有一个相当多的内部空间，当珠粒生产中的ZnCl 2的存在。这两项功能位点用于增加可用表面积为吸附，一种特性，它是用于分离，其中PDMS用作固定相高度期望的。 为进行测试，以日，所有电解质，有盐的最佳浓度，一个最大化珠的表面孔隙率生产的，一第二它似乎是0.012微米的总浓度，而不管该金属反离子的。下面和上面这个最佳浓度，该SAV比小于最大值，而显得单调从最大在任一方向减小。这对盐浓度的依赖性，而不是仅基于催化活性金属离子在溶液中的存在，表明电解质上微泡制造的效果是改变乳剂的性能。不添加盐的含量，所述乳液最好被描述为脂族（即，含有聚合物的）相的空腔嵌入到更连续的水相。当盐加入时，表面张力被改变以这样的方式，该脂族相是在一些地方连续的，与分散的水的气泡。当乳剂是在表面活性剂浴突然加热，滴保留了这一结构的PDMS固化。这导致具有较少球形的形状，但有IM珠层状与由于含水口袋的存在孔，即使对于钠的金属氯化物，其预期不会有实质性的催化作用。虽然任何水溶性盐应该工作在原则来实现这种效果，我们注意到，存在最小的金属离子的身份的最佳浓度的依赖性，有一个明显的优势，以已知催化有机碳 - 碳偶联反应的金属。这表明，虽然在离子强度的改变是必要的，以使相位反转，初级决定因素在调整SAV比是金属充当催化剂的交联个别聚合物链的能力，引导其发生优先在含水/脂肪族接口。 我们的协议的最关键方面是，超声处理过程并增加三乙氧基硅烷的可既产生大量的热如果不仔细控制。这种热量能引起索利双链形成过早，这将使得所期望的珠的生成是不可能的。超声处理问题已通过使用浴式超声波仪的主要处理，而且在浴中加入冰，以帮助调节该温度。 7分钟超声处理期间被发现是最佳的在减少乳液的不希望的聚集，这部分是因为之后大约7分钟超声处理，大部分在浴中冰已经融化。另外三乙氧基硅烷必须与活性搅拌和浸没在冰浴中的混合物来完成。 比起原来报告产生凸孔隙PDMS珠，我们的协议说明了在产物的SAV比的显著优势。我们已经证明，添加即使便宜的盐的在多孔聚合物珠粒微泡制造中所使用的乳液的水相可导致到底材料的形态剧变。虽然任何盐的存在似乎结果在乳液，其中脂肪相可以成为连续的，仅通过加入催化活性的金属离子的是SAV比率虽然我们没有测试此协议的任何其它聚合物增加了30倍，我们预期，任何聚合物是交联和热固化（我们的协议的限制）可与该方法可以用于产生凹孔隙微结构化珠。在这样的扩展，它很可能是该特定的电解质浓度将需要优化所用的乳液，以确保该脂族相是连续的，并且将水相是离散的。

Polydimethylsiloxane (PDMS) is one of the most widely used silicone compounds. Its biocompatibility has led to widespread use in implant and other biomedical engineering structures1,2. It is trivially cross-linked into elastic structures using an organosilyl compound (such as triethoxysilane), a simple and reliable procedure which has made it useful for cast polymer applications where some flexibility is required3. Once cross-linked, PDMS is largely inert, particularly in biological conditions, and is therefore useful for a variety of food and medical applications4,5. Ease of casting, chemical inertness, and hydrophobicity have made it a natural choice for microfluidic devices6,7. Its affinity for non-halogenated, non-polar organic compounds has made it a popular stationary phase in separations chemistry8-10. 
Recently, microbubble fabrications have been used to generate porous beads for use as catalyst structural substrates or in chemical separations11,12. In both applications, ideal materials will have a maximized surface-area-to-volume (SAV) ratio for best efficiency. In a microbubble fabrication process, microstructuring of materials is typically accomplished by isolating the polymer in aliphatic &#8220;microbubbles&#8221; by emulsification in an aqueous continuous phase. The initial report of microporous PDMS beads produced them by mechanical emulsification of two phases (aliphatic and aqueous)13. The stock PDMS liquid (and its cross-linking agent) is dissolved into the aliphatic phase, which is structured into microscopic beads by being forced to cavitate within the (continuous) aqueous phase. The emulsification is stabilized by the addition of a non-ionic surfactant. When the emulsion is added dropwise to a heated bath, solid beads form by agglomeration of the microbubbles into clusters of tiny spheres of cross-linked PDMS. Our goal in this protocol is to modify this procedure to develop beads with an inverted porosity to improve the SAV ratio of the material.
As reported previously, control of the beads can be directed to some extent by the aliphatic:aqueous ratios in the emulsion. However, we have reported recently that addition of platinum(IV) chloride (PtCl4) inverts the porosity: materials are formed in which the PDMS is riddled with concave pores14. This indicates that the aqueous layer cavitates inside the aliphatic one, despite having similar aliphatic:aqueous ratios to those published in the original work13. The primary advantage of our method is that this concave porosity should naturally result in an increased SAV ratio, and thus, improved efficiency for analytical chemistry applications. While we are continuing to explore the specific effects of the addition of the platinum compound, we show here that the same effect can be accomplished using any aqueously soluble ionic compound, though perhaps to a reduced extent. Because our techniques also differ in some key aspects from what has been previously reported, we present our protocols here as a video to encourage others to extend our methods. Most notably, we use a common bath sonicator of the type used to clean glassware or other equipment, rather than the (considerably more expensive) probe sonicator often used in microbubble fabrication. This adjusted approach to the microbubble fabrication procedure could potentially be extended for the production of large quantities of bulk materials as well, creating porous sheets or slabs which could have applications for biomedical devices, aerospace and automotive industry, or substrates for chemical catalysis. Users seeking to generate high-SAV-ratio, microstructured materials using other similar polymers for such analyses may find that our protocols can be extended to any polymer for which the microbubble emulsion technique can be applied.

<table><tbody><tr><td>Poly(dimethylsiloxane), vinyl terminated</td><td>Sigma-Aldrich</td><td>68083-19-2</td><td></td></tr><tr><td>n-Heptane</td><td>Sigma-Aldrich</td><td>142-82-5</td><td>Flammable</td></tr><tr><td>Triethoxysilane</td><td>Sigma-Aldrich</td><td>998-30-1</td><td>Flammable, Accutely Toxic</td></tr><tr><td>Sorbitan Monoleate (Span-80)</td><td>Fluker</td><td>1338-43-8</td><td></td></tr><tr><td>Platinum(IV) Chloride</td><td>Sigma-Aldrich</td><td>13454-96-1</td><td>Accutely Toxic</td></tr><tr><td>Zinc(II) Chloride</td><td>Sigma-Aldrich</td><td>7646-85-7</td><td></td></tr><tr><td>Sodium Chloride</td><td>Sigma-Aldrich</td><td>7647-14-5</td><td></td></tr><tr><td>2.8 L Water Bath Sonicator</td><td>VWR</td><td>97043-964</td><td></td></tr></tbody></table>

microbubble fabrication of concave-porosity pdms beads

Microbubble fabrication (by use of a fine emulsion) provides a means of increasing the surface-area-to-volume (SAV) ratio of polymer materials, which is particularly useful for separations applications. Porous polydimethylsiloxane (PDMS) beads can be produced by heat-curing such an emulsion, allowing the interface between the aqueous and aliphatic phases to mold the morphology of the polymer. In the procedures described here, both polymer and crosslinker (triethoxysilane) are sonicated together in a cold-bath sonicator. Following a period of cross-linking, emulsions are added dropwise to a hot surfactant solution, allowing the aqueous phase of the emulsion to separate, and forming porous polymer beads. We demonstrate that this method can be tuned, and the SAV ratio optimized, by adjusting the electrolyte content of the aqueous phase in the emulsion. Beads produced in this way are imaged with scanning electron microscopy, and representative SAV ratios are determined using Brunauer&#8211;Emmett&#8211;Teller (BET) analysis. Considerable variability with the electrolyte identity is observed, but the general trend is consistent: there is a maximum in SAV obtained at a specific concentration, after which porosity decreases markedly.

从乳液具有不同的电解质条件所引起珠的代表性SEM图像示于图1。图1A示出类似于由DuFaud获得， 等人 13的胎圈，制作使用我们的程序，不加入任何的电解质。 如图1B-D珠，从而导致不同的形态为每个金属离子。对于所示的所有图像，300微升0.03-M的电解质溶液代替300微升去离子水中的水相，使用，得到0.012 M在该相中的电解质浓度。更高分辨率的图像示于的无电解质（一）中，用氯化锌制备珠粒图2。 布鲁诺尔-埃米特-特勒（BET）的分析的珠16,17是用氮气等温线在五个不同的压力下进行。在图1所示的珠吨<html>从相同批次的用于在每种情况下的BET分析材料AKEN。的BET分析得到的表面积定量值与体积之比，在表1中列出 。 <img alt="图1" src="/files/ftp_upload/53440/53440fig1.jpg" /> 整个珠图1的SEM图像由这里所描述的微泡制造技术生产的硅橡胶珠的SEM图像。不加入任何电解质到水层中（A）的制备珠粒完全凸面孔隙率。长度尺度对所有图像是由在图中的比例尺给出。那些与0.012摩尔金属浓度为PTCL 4（B）的ZnCl 2（C），和NaCl（D）中的净浓度产生表现出不同的形态，包括大量的除由于微泡的形成凹孔，如在圆圈指示区。LES / ftp_upload / 53440 / 53440fig1large.jpg"目标="_空白"&gt;点击此处查看该图的放大版本。 <img alt="图2" src="/files/ftp_upload/53440/53440fig2.jpg" /> 图2.详细的SEM图像的产生无电解质中加入（A）的小珠更紧密SEM图像，并用的ZnCl 2（B）中。不添加电解质的，球形子结构一般较大，更紧密堆积比与另外的ZnCl 2，其显著的增加表面面积与体积之比的贡献的。尺度的所有图像都通过在图中的比例尺定。 <a href="https://www-jove-com.remotexs.ntu.edu.sg/files/ftp_upload/53440/53440fig2large.jpg" target="_blank">请点击此处查看该图的放大版本。</a> <table border="0"><tbody><tr><td> 食盐添加 </td><td> BET SAV比率（厘米2 /厘米3） </stroNG&gt; </td><td> SAV改进（相对于对照） </td></tr><tr><td>无（对照） </td><td> 361.6 </td><td> 1 </td></tr><tr><td> PTCL 4 </td><td> 1849 </td><td> 5.1 </td></tr><tr><td> 氯化锌 </td><td> 11060 </td><td> 30.6 </td></tr><tr><td>氯化钠</td><td> 298.9 </td><td> 0.83 </td></tr></tbody></table> 表1的BET分析。表面面积对体积（SAV）的比率的材料，由布鲁诺尔-埃米特-特勒（BET）等温线分析测定，使用产生的水相具有不同电解质的0.012-M的水溶液。第一列字母表示相应的图像面板在图1中。SAV比率均基于每单位质量的总表面积，所述样品的质量，和样品的总冷自由空间。

Watch this Scientific Journal Video about Microbubble Fabrication of Concave-porosity PDMS Beads at JoVE.com

Microbubble Fabrication of Concave-porosity PDMS Beads

Procedures used to generate microstructured concave-porosity polydimethylsiloxane beads are presented. Effects of electrolyte concentration and identity within the aqueous phase are particularly emphasized.

的凹孔隙PDMS珠微泡制作

Microbubble fabrication (by use of a fine emulsion) provides a means of increasing the surface-area-to-volume (SAV) ratio of polymer materials, which is ...

microbubble-fabrication-of-concave-porosity-pdms-beads

Nanyang Technological University

Research

JoVE Journal

Chemistry

8.3K 次观看.  Western Kentucky University. Procedures used to generate microstructured concave-porosity polydimethylsiloxane beads are presented. Effects of electrolyte concentration and identity within the aqueous phase are particularly emphasized. 

视频: Microbubble Fabrication of Concave-porosity PDMS Beads

Micropunching Lithography for Generating Micro- and Submicron-patterns on Polymer Substrates

Conducting polymers have attracted great attention since the discovery of high conductivity in doped polyacetylene in 19771. They offer the advantages of low weight, easy tailoring of properties and a wide spectrum of applications2,3. Due to sensitivity of conducting polymers to environmental conditions (e.g., air, oxygen, moisture, high temperature and chemical solutions), lithographic techniques present significant technical challenges when working with these materials4. For example, current photolithographic methods, such as ultra-violet (UV), are unsuitable for patterning the conducting polymers due to the involvement of wet and/or dry etching processes in these methods. In addition, current micro/nanosystems mainly have a planar form5,6. One layer of structures is built on the top surfaces of another layer of fabricated features. Multiple layers of these structures are stacked together to form numerous devices on a common substrate. The sidewall surfaces of the microstructures have not been used in constructing devices. On the other hand, sidewall patterns could be used, for example, to build 3-D circuits, modify fluidic channels and direct horizontal growth of nanowires and nanotubes.
A macropunching method has been applied in the manufacturing industry to create macropatterns in a sheet metal for over a hundred years. Motivated by this approach, we have developed a micropunching lithography method (MPL) to overcome the obstacles of patterning conducting polymers and generating sidewall patterns. Like the macropunching method, the MPL also includes two operations (Fig. 1): (i) cutting; and (ii) drawing. The "cutting" operation was applied to pattern three conducting polymers4, polypyrrole (PPy), Poly(3,4-ethylenedioxythiophen)-poly(4-styrenesulphonate) (PEDOT) and polyaniline (PANI). It was also employed to create Al microstructures7. The fabricated microstructures of conducting polymers have been used as humidity8, chemical8, and glucose sensors9. Combined microstructures of Al and conducting polymers have been employed to fabricate capacitors and various heterojunctions9,10,11. The "cutting" operation was also applied to generate submicron-patterns, such as 100- and 500-nm-wide PPy lines as well as 100-nm-wide Au wires. The "drawing" operation was employed for two applications: (i) produce Au sidewall patterns on high density polyethylene (HDPE) channels which could be used for building 3D microsystems12,13,14, and (ii) fabricate polydimethylsiloxane (PDMS) micropillars on HDPE substrates to increase the contact angle of the channel15.

A micropunching lithography approach is developed to generate micro- and submicron-patterns on top, sidewall and bottom surfaces of polymer substrates. It overcomes the obstacles of patterning conducting polymers and generating sidewall patterns. This method allows rapid fabrication of multiple features and is free of aggressive chemistry.

Micropunching为微型和亚微米模式聚合物基板上生成的光刻

Conducting polymers have attracted great attention since the discovery of high conductivity in doped polyacetylene in 19771. They offer the advantages of ...

科研

工程学

Fabrication of a Microfluidic Device for the Compartmentalization of Neuron Soma and Axons

In this video, we demonstrate the technique of soft lithography with polydimethyl siloxane (PDMS) which we use to fabricate a microfluidic device for culturing neurons. Previously, a silicon wafer was patterned with the design for the neuron microfluidic device using SU-8 and photolithography to create a master mold, or what we simply refer to as a "master". Next, we pour the silicon polymer PDMS on top of the master which is then cured by heating the PDMS to 80&deg;C for 1 hour. The PDMS forms a negative mold of the device. The PDMS is then carefully cut and lifted away from the master. Holes are punched where the reservoirs will be and the excess PDMS trimmed away from the device. Nitrogen is used to blow away any excess debris from the device. At this point the devices are now ready for use and can either bonded to corning No. 1 cover glass with a plasma sterilizer/cleaner or can be reversibly bound to the cover glass by simply placing the device on top of the cover glass. The reversible bonding of the device to glass is covered in a separate video and requires first that the device be sterilized either with 70% ethanol or by autoclaving. Plasma treating sterilizes the devices so no further treatment is necessary. It is, however, important, when plasma-treating the devices, to add liquid to the devices within 10 minutes of the plasma treatment while the surfaces are still hydrophilic. Waiting longer than 10 minutes to add liquid to the device makes it difficult for the liquid to enter the device. The neuron devices are typically plasma-bound to cover glass and 0.5 mg/ml poly-L-lysine (PLL) in pH 8.5 borate buffer is immediately added to the device. After a minimum of 3 hours incubating with PLL, the devices are washed with dH2O water a minimum of 3 times with at least 15 minutes between each wash. Next, the water is removed and fresh media is added to the device. At this point the device is ready for use. It is important to remember at this point to never remove all the media from the device. Always leave media in the main channel.

In this video we demonstrate the technique of soft lithography with polydimethyl siloxane (PDMS) which we use to farbricate a microfluidic device for culturing neurons.

条块索玛的神经元和轴突的一个微流体设备制造

In this video, we demonstrate the technique of soft lithography with polydimethyl siloxane (PDMS) which we use to fabricate a microfluidic device for ...

生物学

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.  ...

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 ...

生物工程

Creating Sub-50 Nm Nanofluidic Junctions in PDMS Microfluidic Chip via Self-Assembly Process of Colloidal Particles

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its transparency. Due to the softness of the PDMS material, however, it is challenging to use PDMS for building nanochannels. The channels tend to collapse easily during plasma bonding. In this paper, we present an evaporation-driven self-assembly method of silica colloidal nanoparticles to create nanofluidic junctions with sub-50 nm pores between two microchannels. The pore size as well as the surface charge of the nanofluidic junction is tunable simply by changing the colloidal silica bead size and surface functionalization outside of the assembled microfluidic device in a vial before the self-assembly process. Using the self-assembly of nanoparticles with a bead size of 300 nm, 500 nm, and 900 nm, it was possible to fabricate a porous membrane with a pore size of ~45 nm, ~75 nm and ~135 nm, respectively. Under electrical potential, this nanoporous membrane initiated ion concentration polarization (ICP) acting as a cation-selective membrane to concentrate DNA by ~1,700 times within 15 min. This non-lithographic nanofabrication process opens up a new opportunity to build a tunable nanofluidic junction for the study of nanoscale transport processes of ions and molecules inside a PDMS microfluidic chip.

We propose a simple self-assembly technique of silica colloidal nanoparticles to create a nanofluidic junction between two microchannels in polydimethylsiloxane (PDMS). Using this technique, a nanoporous bead membrane with a pore size down to ~45 nm was built inside a microchannel and applied to electrokinetic preconcentration of DNA samples.

通过胶体粒子自组装过程创建在PDMS微流控芯片分50纳米的纳米流体结

Polydimethylsiloxane (PDMS) is the prevailing building material to make microfluidic devices due to its ease of molding and bonding as well as its ...

A Microfluidic Technique to Probe Cell Deformability

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an efficient manner. Typically, data for ~102 cells can be acquired within a 1 hr experiment. An automated image analysis program enables efficient post-experiment analysis of image data, enabling processing to be complete within a few hours. Our device geometry is unique in that cells must deform through a series of micron-scale constrictions, thereby enabling the initial deformation and time-dependent relaxation of individual cells to be assayed. The applicability of this method to human promyelocytic leukemia (HL-60) cells is demonstrated. Driving cells to deform through micron-scale constrictions using pressure-driven flow, we observe that human promyelocytic (HL-60) cells momentarily occlude the first constriction for a median time of 9.3 msec before passaging more quickly through the subsequent constrictions with a median transit time of 4.0 msec per constriction. By contrast, all-trans retinoic acid-treated (neutrophil-type) HL-60 cells occlude the first constriction for only 4.3 msec before passaging through the subsequent constrictions with a median transit time of 3.3 msec. This method can provide insight into the viscoelastic nature of cells, and ultimately reveal the molecular origins of this behavior.

We demonstrate a microfluidics-based assay to measure the timescale for cells to transit through a sequence of micron-scale constrictions.

微流体技术，探讨细胞变形

Here we detail the design, fabrication, and use of a microfluidic device to evaluate the deformability of a large number of individual cells in an ...

Fabrication of Refractive-index-matched Devices for Biomedical Microfluidics

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices can be implemented as part of a robust platform capable of making simultaneous complementary measurements. The primary challenge created by the combination of these two techniques is the mismatch in refractive index between the materials traditionally used to make microfluidic devices and the aqueous solutions typically used in biomedicine. This mismatch can create optical artifacts near the channel or device edges. One solution is to reduce the refractive index of the material used to fabricate the device by using a fluorinated polymer such as MY133-V2000 whose refractive index is similar to that of water (n = 1.33). Here, the construction of a microfluidic device made out of MY133-V2000 using soft lithography techniques is demonstrated, using O2 plasma in conjunction with an acrylic holder to increase the adhesion between the MY133-V2000 fabricated device and the polydimethylsiloxane (PDMS) substrate. The device is then tested by incubating it filled with cell culture media for 24 h to demonstrate the ability of the device to maintain cell culture conditions during the course of a typical imaging experiment. Finally, quantitative phase microscopy (QPM) is used to measure the distribution of mass within the live adherent cells in the microchannel. This way, the increased precision, enabled by fabricating the device from a low index of refraction polymer such as MY133-V2000 in lieu of traditional soft lithography materials such as PDMS, is demonstrated. Overall, this approach for fabricating microfluidic devices can be readily integrated into existing soft lithography workflows in order to reduce optical artifacts and increase measurement precision.

This protocol describes the fabrication of microfluidic devices from MY133-V2000 to eliminate artifacts that often arise in microchannels due to the mismatching refractive indices between microchannel structures and an aqueous solution. This protocol uses an acrylic holder to compress the encapsulated device, improving adhesion both chemically and mechanically.

生物医学微流体折射率匹配器件的研制

The use of microfluidic devices has emerged as a defining tool for biomedical applications. When combined with modern microscopy techniques, these devices ...

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 ...

Window on a Microworld: Simple Microfluidic Systems for Studying Microbial Transport in Porous Media

Microbial growth and transport in porous media have important implications for the quality of groundwater and surface water, the recycling of nutrients in the environment, as well as directly for the transmission of pathogens to drinking water supplies. Natural porous media is composed of an intricate physical topology, varied surface chemistries, dynamic gradients of nutrients and electron acceptors, and a patchy distribution of microbes. These features vary substantially over a length scale of microns, making the results of macro-scale investigations of microbial transport difficult to interpret, and the validation of mechanistic models challenging. Here we demonstrate how simple microfluidic devices can be used to visualize microbial interactions with micro-structured habitats, to identify key processes influencing the observed phenomena, and to systematically validate predictive models. Simple, easy-to-use flow cells were constructed out of the transparent, biocompatible and oxygen-permeable material poly(dimethyl siloxane). Standard methods of photolithography were used to make micro-structured masters, and replica molding was used to cast micro-structured flow cells from the masters. The physical design of the flow cell chamber is adaptable to the experimental requirements: microchannels can vary from simple linear connections to complex topologies with feature sizes as small as 2 &mu;m. Our modular EcoChip flow cell array features dozens of identical chambers and flow control by a gravity-driven flow module. We demonstrate that through use of EcoChip devices, physical structures and pressure heads can be held constant or varied systematically while the influence of surface chemistry, fluid properties, or the characteristics of the microbial population is investigated. Through transport experiments using a non-pathogenic, green fluorescent protein-expressing Vibrio bacterial strain, we illustrate the importance of habitat structure, flow conditions, and inoculums size on fundamental transport phenomena, and with real-time particle-scale observations, demonstrate that microfluidics offer a compelling view of a hidden world.

Microfluidic devices can be used to visualize complex natural processes in real time and at the appropriate physical scales. We have developed a simple microfluidic device that mimics key features of natural porous media for studying growth and transport of bacteria in the subsurface.

窗口上的一个微观世界：简单的微流体系统为研究多孔介质中的微生物运输

Microbial growth and transport in porous media have important implications for the quality of groundwater and surface water, the recycling of nutrients in ...

A Paired Bead and Magnet Array for Molding Microwells with Variable Concave Geometries

A spheroid culture is a useful tool for understanding cellular behavior in that it provides an in vivo-like three-dimensional environment. Various spheroid production methods such as non-adhesive surfaces, spinner flasks, hanging drops, and microwells have been used in studies of cell-to-cell interaction, immune-activation, drug screening, stem cell differentiation, and organoid generation. Among these methods, microwells with a three-dimensional concave geometry have gained the attention of scientists and engineers, given their advantages of uniform-sized spheroid generation and the ease with which the responses of individual spheroids can be monitored. Even though cost-effective methods such as the use of flexible membranes and ice lithography have been proposed, these techniques incur serious drawbacks such as difficulty in controlling the pattern sizes, achievement of high aspect ratios, and production of larger areas of microwells. To overcome these problems, we propose a robust method for fabricating concave microwells without the need for complex high-cost facilities. This method utilizes a 30 x 30 through-hole array, several hundred micrometer-order steel beads, and magnetic force to fabricate 900 microwells in a 3 cm x 3 cm polydimethylsiloxane (PDMS) substrate. To demonstrate the applicability of our method to cell biological applications, we cultured adipose stem cells for 3 days and successfully produced spheroids using our microwell platform. In addition, we performed a magnetostatic simulation to investigate the mechanism, whereby magnetic force was used to trap the steel beads in the through-holes. We believe that the proposed microwell fabrication method could be applied to many spheroid-based cellular studies such as drug screening, tissue regeneration, stem cell differentiation, and cancer metastasis.

This manuscript introduces a robust method of fabricating concave microwells without the need for complex high-cost facilities. Using magnetic force, steel beads, and a through-hole array, several hundred microwells were formed in a 3 cm x 3 cm polydimethylsiloxane (PDMS) substrate.