Hydrogel two-phase flows: hydrodynamics and applications

水凝胶是一种柔软的可变形材料，对许多新兴技术非常重要。由于它们的柔软和无毒，它们经常被用在小型芯片上的器官装置中，以容纳和培养能够成长为功能性组织和器官的细胞。另一个应用是在石油和天然气行业。气井和油井的钻井和密封需要向井中泵入更稠密、更坚硬的液体，以驱替水。水凝胶是这种液体的一个很好的候选者，因为它是一种柔软的固体，在泵送时会变成流动的液体。因此，它的液-固二元性在这些应用中具有独特的作用。为了设计和优化这类技术，我们需要了解水凝胶如何流动以及它们如何熔化和固化。由于其复杂的内部结构，其物理过程被证明是复杂的。水凝胶是由链状分子组成的，这种分子被称为聚合物，它们被交联在一起形成网络，并在水中膨胀。根据外力、温度和化学试剂的作用，凝胶可以可逆地熔化或固化。此外，在大多数应用中，水凝胶是使用液体展开的，因此产生了水凝胶-液体分层流动的场景。例如，凝胶溶液可以在凝胶化之前被泵入适当的位置，或者固体凝胶可以由另一种液体携带到所需的位置。水凝胶如何与流动的液体机械地相互作用？流动如何影响凝胶的膨胀/收缩和融化？如何利用液体流动来控制凝胶-流体界面？这样的问题很少被提出，实际应用大多是通过反复试验进行的。这些问题的答案不仅是促进我们对这些迷人材料的科学理解的关键，而且对上述技术应用也很重要。我们建议建立一个理论框架来描述和预测这种高度复杂的水凝胶-液体材料。此外，我们的目标是开发计算方法和软件，工程师可以使用它们来预测水凝胶-液体混合物体系的流量和结构。这项工作的性质将主要是数学和计算；它将量化我们对这些复杂流体的理解，并将这些知识与新兴技术的应用联系起来。这项研究可能会在生物医学工程和药物输送领域产生最大的社会影响。基于水凝胶的芯片上器官装置可以用于复制关键的组织和器官功能；这可以使药物测试和组织工程取得突破，甚至可能导致可植入装置。使用凝胶包裹药物颗粒为我们提供了一种新的方法，可以将药物输送到人体的靶区，并在很长一段时间内控制药物的释放。因此，拟议的工作不仅将推进一个科学研究领域，而且对加拿大和其他地区也有深远的好处。

Hydrogels are soft deformable materials important to many emerging technologies. Because of their softness and lack of toxicity, they are often used in small "organ-on-chip" devices to hold and nurture cells that can grow into functional tissues and organs. Another application is in the oil and gas industry. The drilling and sealing of gas and oil wells require pumping a thicker and stiffer liquid into the well to displace water. Hydrogel is a good candidate for such a liquid, as it is a soft solid that becomes a flowing liquid when pumped. Thus, its liquid-solid duality serves a unique role in these applications. For the design and optimization of such technologies, we need to understand how hydrogels flow and how they melt and solidify. The physics of this turns out to be complex thanks to their complex inner structure. Hydrogels are made of chain-like molecules, called polymers, that are cross-linked together into a network, and swollen with water. Depending on external forcing, temperature and chemical agents, a gel can melt or solidify reversibly. Besides, in most applications, hydrogels are deployed using liquids, thus generating a hydrogel-liquid layered flow scenario. For example, a gel solution may be pumped into place before gelation, or solid gels may be carried by another liquid into desirable locations. How does a hydrogel interact mechanically with a flowing liquid? How does flow influence the swelling/shrinking and melting of the gel? How to use liquid flow to control the gel-fluid interface? Such questions have rarely been raised, and practical applications mostly proceed through trial and error. The answers to these questions will not only be key to advancing our scientific understanding of these fascinating materials, but also important to the technological applications mentioned above. We propose to establish a theoretical framework for describing and predicting this highly complex hydrogel-liquid material. Moreover, we aim to develop computational methods and software that engineers can use to predict the flow and the structure of the hydrogel-liquid mixture system. The nature of this work will be mostly mathematical and computational; it will quantify our understanding of these complex fluids and link that knowledge to applications in emerging technologies. The research will likely have its greatest societal impact in the fields of biomedical engineering and drug delivery. Hydrogel-based organ-on-chip devices can be used to reproduce key tissue and organ functions; these can enable breakthroughs in drug testing and tissue engineering, and may even lead to implantable devices. Using gels to encapsulate drug particles gives us a new way to deliver drugs into target areas in the human body and to control the release of the drugs over a long period of time. Therefore, the proposed work will not only advance an area of scientific research, but also have far-reaching benefits for Canada and beyond.