(4cm) Rheology-Assisted Modeling, Design and Optimization of Bioprinting with Enhanced Architectural Complexity

My research experience during the graduate study at MIT centers around the development of advanced rheological techniques (including a customized capillary thinning extensional rheometer) for the modeling and characterization of graphene-derived nanocomposites, with an especial focus on the non-linear rheological response in strong shear and extensional flows. The toolkit I developed has been applied to create rheology-assisted strategies for rapid structural analysis and improved nanofiller dispersion for the nanocomposite systems. In addition, this toolkit is combined with rheo-optic techniques and has been developed into an in-situ technique to characterize and optimize the wet-spinning process for bio-degradable polymers. With these projects ultimately extending my research interests to the fabrication of biological constructs, I am now a postdoctoral researcher at Stanford University working on the development of rheology-inspired bioprinting strategies.

Research Interests

My primary research interest will focus on rheology-assisted modeling, design and optimization of bioprinting with enhanced architectural complexity and cell viability. The proposed research plan is comprised of two aspects:

(1) Advanced rheological characterizations are to be performed to novel bioinks with increased rheological complexity. The concepts of viscoelasticity and yield stress have been implemented recently to these material systems to provide broad guidelines for material selection. However, a systematic rheological study in the non-linear region is still absent, hampering an accurate modeling of their flow response during the fabrication process as well as the resulting printing performance. Techniques such as Large Amplitude Oscillatory Shear (LAOS) and capillary thinning extensional rheometry will be implemented, and a robust constitutive framework will be constructed to obtain a profound understanding of the bioink dynamics.

(2) The aforementioned rheological characterizations will become the fundamentals to explore the manufacturing of more complex hierarchical biological constructs. A broader range of fabrication methods based on the fluid dynamics and instabilities will be implemented to create more refined structures beyond the capability of additive manufacturing with increased efficiency and less amount of fabrication resources. In the long term, this rheology-assisted bioprinting strategy is aimed to bridge the gap towards the future applications in clinical therapies.

Selected Publications

1. Jianyi Du, Hiroko Ohtani, Crystal E. Owens, Lenan Zhang, Kevin Ellwood, Gareth H. McKinley. “An improved Capillary Breakup Extensional Rheometer to characterize weakly rate-thickening fluids: Applications in synthetic automotive oils”. Non-Newtonian. Fluid. Mech. 291:104496, 2021.
2. Jianyi Du, Hiroko Ohtani, Kevin Ellwood, Gareth H. McKinley. “Capillarity-driven thinning and breakup of weakly rate-thickening fluids”. Non-Newtonian. Fluid. Mech. In prep.
3. Jianyi Du, Hiroko Ohtani, Kevin Ellwood, Gareth H. McKinley. “Capillarity-driven thinning dynamics of entangled polymer solutions”. ACS Macromol. In prep.
4. Youzhi Liang*, Jianyi Du*, Irmgard Bischofberger, Anette E. Hosoi. “Particle-induced reduction of Saffman-Taylor instability”. Commun. In prep. (*contributed equally)
5. Pablo B. Sánchez. Crystal E. Owens, Jianyi Du, Gareth H. McKinley­­­­. “Understanding dynamics of cellulose dissolved in an ionic solvent under shear and extensional flow”. In prep.

Teaching Interests

My teaching experience is primarily twofold: (1) I became a mentor in the Undergraduate Research Opportunities Program (UROP) during my graduate study at MIT. In this program, I worked with an MIT undergraduate student, helped him define a research problem, construct a research plan, and promote the research output. (2) In 2019, I participated in the Kaufman Teaching Certificate Program (KTCP) offered by MIT Teaching and Learning Lab to obtain systematic training in teaching practices and to prepare my teaching philosophy statement.

Based on my background, I will set my primary teaching interests in Fluid Mechanics and Dynamics. I would also like to develop a course that focuses on interactive teaching of Fundamental Rheology (with additional topics in the rheology of food and biomaterials), which is aimed at introducing rheology of soft materials to the students with a background in biology. The course will include lab sessions for the students to learn and practice rheological techniques to characterize a number of natural and synthetic biomaterials, and to develop a constitutive model to describe the complex material systems.