CAREER: in situ Polymer Gelation in Confined Flows

职业：受限流动中的原位聚合物凝胶化

• 批准号: 2239742
• 负责人: Sara Hashmi
• 金额: $ 55万
• 依托单位: Northeastern University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2023
• 资助国家: 美国
• 起止时间: 2023-05-01 至 2028-04-30
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2239742&HistoricalAwards=false
• 关键词: CAREER; situ; Polymer; Gelation; Confined

Polymer gels form in many natural and industrial flows: proteins gel in preparing foods like Jell-O or eggs; plastics can gel during 3D printing; blood proteins can crosslink to form clots in vessels. Flows become complex when polymer molecules crosslink, or gel, transforming the fluid into a soft solid. Crosslinking can result in intermittent flow or complete flow stoppage, resulting in clogging of small channels, nozzles, or vessels, and eventual failure of the system. The ability to predict flow regimes is key to assessing, controlling, and preventing intermittency and clogging. This award will advance our fundamental understanding of crosslinked polymer flows through small channels to enable such control. The outcome of this award could result in advances for a variety of applications including in bioprinting and 3D printing by enabling efficient printing of a wider variety of polymers. It will also help designing polymers to flow through small spaces, ranging from fluid fertilizers to biomedical and pharmaceutical products. Education and outreach activities are planned to engage and train high school, undergraduate, and graduate students in emerging topics in complex fluids. Curriculum development, engaging the general public, and supporting underrepresented populations in STEM are also planned.The goals of this award are twofold: (1) to understand the range of system parameters that lead to intermittency and clogging in crosslinking polymer flows through microchannels, and (2) to provide quantitative descriptions of intermittency and the rheological and material properties of intermittent flows. Video microscopy and in situ rheology combined with theoretical transport models will be employed for this purpose. Polymers can be crosslinked by chemical or physical methods, both of which are found in bioprinting. In chemical crosslinking, gelation proceeds quickly, as in alginate crosslinked by calcium. Gelation rate is controllable in physical crosslinking, as in gelatin crosslinked by lowering temperature. Both types of gelation will be investigated to determine the importance of reaction rate and mechanism. Dependence of flow regimes on chemical concentrations and flow rates will be studied. The outcome will provide parameters to predict and control flow regimes in a broad range of crosslinking polymer systems. The intermittent flow regime will be investigated by in situ rheological measurements to determine gel strength and viscoelasticity in flow, which will be compared to bulk rheological characterization of comparable systems. This will facilitate strategies to prevent and overcome intermittent flows in practical systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.

聚合物凝胶在许多自然和工业流程中形成：蛋白质在制备果冻或鸡蛋等食品时凝胶；塑料在 3D 打印过程中会凝胶化；血液蛋白质可以交联在血管中形成凝块。当聚合物分子交联或凝胶时，流动变得复杂，将流体转变为柔软的固体。交联可能导致间歇流动或完全流动停止，导致小通道、喷嘴或容器堵塞，并最终导致系统故障。预测流动状态的能力是评估、控制和防止间歇性和堵塞的关键。该奖项将增进我们对通过小通道的交联聚合物流动的基本理解，以实现这种控制。该奖项的成果可能会通过实现更广泛的聚合物的高效打印来促进包括生物打印和 3D 打印在内的各种应用的进步。它还将有助于设计可流经狭小空间的聚合物，范围从液体肥料到生物医学和药品。计划开展教育和外展活动，吸引和培训高中生、本科生和研究生，了解复杂流体的新兴主题。还计划开发课程、吸引公众参与并支持 STEM 中代表性不足的人群。该奖项的目标有两个：(1) 了解导致交联聚合物流通过微通道的间歇性和堵塞的系统参数范围，以及(2) 提供间歇性以及间歇流的流变学和材料特性的定量描述。为此目的，将采用视频显微镜和原位流变学与理论传输模型相结合。聚合物可以通过化学或物理方法交联，这两种方法都存在于生物打印中。在化学交联中，凝胶化进行得很快，就像通过钙交联的藻酸盐一样。物理交联中的凝胶化速率是可控的，如通过降低温度交联的明胶。将研究这两种类型的凝胶化以确定反应速率和机制的重要性。将研究流动状态对化学浓度和流速的依赖性。结果将提供参数来预测和控制各种交联聚合物系统中的流动状态。将通过原位流变测量来研究间歇流动状态，以确定流动中的凝胶强度和粘弹性，并将其与可比较系统的本体流变特性进行比较。这将有助于制定预防和克服实际系统中间歇性流动的策略。该奖项反映了 NSF 的法定使命，并通过使用基金会的智力优点和更广泛的影响审查标准进行评估，被认为值得支持。