Passive Flow Control in Microchannels using Diblock Copolymer Brushes

使用二嵌段共聚物刷进行微通道中的被动流量控制

• 批准号: 0423786
• 负责人: William Brittain
• 金额: $ 31万
• 依托单位: University of Akron
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2004
• 资助国家: 美国
• 起止时间: 2004-08-01 至 2008-01-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0423786&HistoricalAwards=false
• 关键词: Passive; Flow; Control; Microchannels; using

Tailoring materials to spontaneously undergo changes in surface properties is a developing area of research. These stimuli-responsive films can undergo surface changes that include wettability, adhesion, interaction with cells or proteins and membrane permeability. There has been extensive study on stimuli-responsive films based on diblock copolymer brushes. These diblock brushes can undergo compositional changes at the surface in response to solvent, temperature, pH and ionic strength. These reversible changes in surface composition have considerable potential in the field of separation technology. Passive flow control of diblock copolymer brushes in microchannels will be studied. The literature contains several reports where the responsive behavior of grafted polyacrylamides has been used to control flow in microfluidic devices. The reversible rearrangement of diblock copolymer brushes should offer an alternative responsive system where, depending on the composition of the fluid stream, the surface can change its affinity for different solutes, alter flow rate or adjust flow between competing microchannels. The focus of this proposal is on the application of polymer brush synthesis and characterization to microchannels. Several simple testing platforms are described to assess the effectiveness of diblock brush rearrangement on passive flow control. Specifically, silane-based initiators for atom transfer radical polymerization will be used to prepare diblock copolymer brushes on the interior of glass capillaries or on the surface of flat glass substrates. The testing platforms all rely on pressure-driven flow using commercially available micropumps. Flow will be determined using liquid mass flow meters, which have nL/min flow sensitivity. Preliminary flow studies will be conducted with polyelectrolyte homopolymers. Three specific testing platforms are proposed. Initial screening of the polyelectrolyte homopolymers and diblock rearrangement will be conducted using a single glass capillary with one pump and one flow meter. In the second testing platform, a simple T-pattern will be created in PDMS using soft lithography. The PDMS mold will be combined with a glass substrate that has patterned brush chemistry so that the two channels possess different diblock brush compositions on the glass portion of the microchannel. Relative flow output will be monitored by liquid mass flow meters. The third testing platform is a simple split capillary system where competitive flow will again be monitored. Because most microfluidic analyses use aqueous streams, we will concentrate on hydrophobic/hydrophilic diblock brush systems where the hydrophilic block is a cationic or anionic polyelectrolyte. A wide variety of additional block compositions can be envisioned based on results from our prior support. Variables in the flow streams that will be examined include: pH, ionic strength, concentration of solutes, and polarity of the medium.The intellectual merit of the proposed research is that this is first study to explore the application of diblock brush rearrangement as a flow control element in microchannels. To date, the use of surface-immobilized polymers in microchannels has focused on relatively primitive polymer systems. This study will employ state-of-the-art techniques in polymer synthesis to create stimuli-responsive coatings on the interior of microchannels. Successful control of flow in microchannels that is induced by compositional changes in the analyte stream will have a potentially large impact on the field of microfluidics and separation technology. The broader impact of the proposed research is a multidisciplinary project that will train graduate students, including one woman, in organic, polymer and physical chemistry. Undergraduate students may also participate through an REU summer supplement, with mentoring by graduate students. Participants will present their results at ACS and Gordon Research conferences. Students will learn how to use dry box techniques, NMR, GPC, FTIR, TGA, ellipsometry and tensiometry during the course of their research. This work will contribute to general field of microfluidics by testing and assessing the hypothesis that diblock brush rearrangement can be used for passive flow control in microchannels.

调整材料以自发的表面特性发生变化是研究的发展领域。 这些刺激反应膜可以发生表面变化，包括润湿性，粘附性，与细胞或蛋白质的相互作用以及膜渗透性。 已经对基于二嵌段共聚物刷的刺激响应膜进行了广泛的研究。 这些二嵌段刷可以响应溶剂，温度，pH和离子强度，在表面发生组成变化。 这些表面组成的可逆变化在分离技术领域具有巨大的潜力。 将研究微通道中二嵌段共聚物刷的被动流控制。 文献包含几个报道，其中已使用移植聚丙烯酰胺的响应行为来控制微流体设备中的流动。 二嵌段共聚物刷的可逆重排应该提供一个替代的响应系统，根据流体流的组成，表面可以改变其对不同溶质的亲和力，更改流速或调整竞争微通道之间的流量。 该建议的重点是将聚合物刷合成和表征应用于微通道。 描述了几个简单的测试平台，以评估被动流控制对二嵌段刷重排的有效性。 具体而言，原子转移自由基聚合的基于硅烷的启动器将用于在玻璃毛细管内部或扁平玻璃底物的表面上制备二嵌段共聚物刷。 测试平台都依赖于使用市售的微型聚会的压力驱动流动。 流量将使用具有NL/min流动敏感性的液体质量流量计确定。 将使用聚电解质均聚物进行初步流动研究。 提出了三个特定的测试平台。 将使用带有一个泵和一个流量计的单个玻璃毛细管对聚电解质均聚物和二嵌段重排的初始筛选。在第二个测试平台中，将使用软光刻在PDM中创建一个简单的T-Pattern。 PDMS模具将与具有图案化刷化学的玻璃基板结合使用，以便两个通道在微通道的玻璃部分上具有不同的二嵌段刷成分。 相对流量输出将通过液体质量流量计监测。 第三个测试平台是一个简单的毛细管系统，将再次监视竞争流程。 由于大多数微流体分析都使用水流，因此我们将集中于疏水/亲水二嵌段刷系统，其中亲水性块是阳离子或阴离子多电解质。 可以根据我们先前的支持的结果来设想各种各样的其他块组成。 流量流中将要检查的变量包括：pH，离子强度，溶质的浓度和培养基的极性。拟议的研究的智力优点是，这是探索二嵌段刷重新排列作为流程的首次研究微通道中的控制元件。 迄今为止，在微通道中使用表面弹性聚合物的使用已集中在相对原始的聚合物系统上。 这项研究将在聚合物合成中采用最新技术，以在微通道内部产生刺激性反应性涂层。 通过分析物流的组成变化引起的微通道中流量的成功控制将对微流体和分离技术领域产生很大的影响。拟议研究的更广泛的影响是一个多学科项目，该项目将在有机，聚合物和物理化学方面培训包括一名女性的研究生。 本科生也可以通过REU夏季补充剂来参加研究生的指导。 参与者将在ACS和Gordon研究会议上介绍其结果。 在研究过程中，学生将学习如何使用干盒技术，NMR，GPC，FTIR，TGA，TGA，椭圆法和张力仪。 这项工作将通过测试和评估二嵌段刷重排的假设来有助于微流体的一般领域，可用于微通道中的被动流量控制。