Hydrogel two-phase flows: hydrodynamics and applications

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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.