(2df) Advancing Health and Sustainability through Multiscale Computational Modeling of Soft Materials

Research Interests

My long-term research goal is to develop multiscale computational modeling tools in soft materials to advance human health and environmental sustainability. Specifically, my research will focus on two main topics: (1) blood fluid and (2) vitrimer polymer network. In the first topic, I aim to establish a quantitative relationship between blood rheology and its pathological compositional variations in different diseases through multistage modeling and spatiotemporal characterizations. In the second topic, my objective is to develop a multiscale modeling framework to establish a structure-characterization-processing-property relationship for vitrimers, thereby advancing their applications in industry as low-cost and recyclable polymer materials.

As a step towards this goal, I have devoted my career to computer simulations of soft materials intending to create novel multiscale molecular dynamics (MD) simulation models, characterization tools and theoretical methods to study cellular and polymer systems. During my doctoral studies, I focused on nano-bio interfaces within the context of nanomedicine. Notably, I developed innovative simulation methods to explore how the size, shape, stiffness, and surface chemistry of nanoparticles influence their cellular uptake. My works contribute to a better understanding for controversial experimental results in this field. Expanding my expertise, I have also focused on spatiotemporal characterization techniques. I proposed novel frameworks for scattering analysis, enabling the identification of new polymer physics in both equilibrium and non-equilibrium states. Currently, I am undergoing training in theoretical modeling, with a focus on constructing rheology and kinetic models for polymer flows and crystallization during the film-blowing process. Our model facilitates the connection between polymer configuration information and product properties through multi-state optimizations of polymerization reactions, rheology, and crystallization. I have published 34 journal articles, serving as the lead author for 18 of them. These papers have been featured in prestigious journals such as Physical Review Letters, ACS Nano, Macromolecules, and Nanoscale.

1: Multistage modeling of blood diseases: from biophysics to clinical diagnosis

Blood, a vital organ crucial for our body's normal functioning, consists of red blood cells (RBCs) (40%-45% of total volume), white cells, platelets, and proteins. It behaves as a complex fluid, exhibiting diverse rheological behaviors under flow conditions. Pathological changes in blood compositions, such as lipids and proteins, can disrupt cellular function, leading to alterations in blood rheology and transportation. These changes are associated with a wide variety of blood disorders, including blood cancers, platelet disorders, anemia, diabetes, and hypertension. To advance potential medical treatments and clinical diagnoses, it is crucial to establish molecular understandings of different diseases and their relationships with cellular functions and blood flow properties. However, the quantitative understanding linking blood rheology to compositions and pathological variations remains lacking due to research difficulties at different scales:

1. At the molecular level, the complex nature of lipids and proteins poses challenges in establishing the relationship between molecular composition and the properties and behaviors of RBCs. For instance, the RBC membrane stands out with its highest cholesterol/phospholipid ratio compared to other cells. However, the role of cholesterol in determining the mechanical properties and gas permeability of the multicomponent membrane remains poorly understood.

2. At the single-cell level, though the deformability of RBCs is recognized as a crucial indicator for various diseases, available reports on healthy and pathological RBCs are limited and often lack well-defined mechanical parameters. This research gap poses challenges in integration of these findings into the fundamental understanding of blood flow and hinders the translating this knowledge into clinical applications, particularly for establishing relationships between membrane defects and the clinical status of patients.

3. At the blood flow level, quantitative measurements of intravascular microscopic dynamics in vivo are crucial for understanding the flow behaviors. However, the accuracy and reliability of light scattering-based spectroscopy, an important non-invasive intravascular technique, is hindered by inaccuracy of assumptions in the contrast-to-blood flow relationship derivation.

I will develop multiscale modeling framework and characterization approaches to fill the research gaps as mentioned above. More importantly, through multiscale simulations techniques, I will link all the knowledge at different levels and establish a quantitative relation between the blood rheology and blood compositions in different diseases.

2: Computational modeling of vitrimer for greener future: from polymer physics to industrial processing.

Plastics, the most widely used man-made materials, reached a global production of 390 million tons in 2021. However, the prevalent use of single-use plastics leads to costly disposal and environmental contamination. It is crucial to address this issue by designing polymer systems that can replace current plastics with renewable and degradable alternatives. Vitrimer, a promising solution, incorporates dynamic covalent bonds (DCBs) into polymeric materials to form reversible polymer networks. These networks exhibit permanent crosslinking at service temperatures while displaying thermoplastic-like flow at elevated temperatures. By introducing DCBs into low-recycling-rate commodity plastics like polyethylene (PE), polypropylene (PP), and polystyrene (PS), we can transform them into dynamic, low-cost recyclable polymers, facilitating a greener future without significant changes to processing equipment and production speed. Although numerous DCBs are available in the form of small molecules, such as boronic esters, transesterification, and disulfide exchange, there is a significant gap between DCB small molecular design and the development of reversible network for (re)processing and achieving desired product performance. Vitrimer polymer network research is still in its early stages, and various challenges persist in different areas:

1. The transition from DCB small molecular design to polymer network design poses challenges. While numerous DCBs exist at the small molecular level, replicating their programmability in polymer networks is complex due to the large number of combinatorial sequences within the chains. Currently, selecting DCBs for desired network properties relies on a trial-and-error approach.

2. Polymer chains in vitrimer have intricate structures and dynamics due to their interactions with DBCs, expressing rich phase behavior and rheology performance at wide range of different scales. There is a need for advanced polymer network characterization techniques that lag behind in capturing these behaviors at both spatial and temporal scales.

3. The industrial applications of vitrimer involve complex (re)processing and service conditions, including varying temperature histories, flow fields, and loading conditions. To meet these demands, vitrimer must strike a balance between dimensional stability at working temperature and rapid stress relaxation during (re)processing temperature.

4. The complexities involved in characterization and (re)processing hinder our comprehensive understanding of vitrimer in various aspects, including rheology, self-healing, crystallization, and mechanical properties. To advance our knowledge in these areas, new physical models are required.

Our group aims to develop multiscale modeling approaches to advance knowledge in each area and establish connections between them. By encompassing chemical structure, characterization, processing conditions, and product properties, we strive to build a comprehensive understanding of vitrimer.

Teaching Interests

My aspiration to become a professor in engineering is driven not only by my passion for cutting-edge research but also by my deep enthusiasm for teaching. Having personally benefited from the guidance and support of my teachers and mentors, which enabled me to overcome the challenges of growing up in a low-income family and become a first-generation graduate, I am determined to pass on this spirit of empowerment to my students. Through teaching, I aim to make a meaningful impact on their lives and equip them with the necessary skills for successful careers. I have had the opportunity to gain valuable teaching experience in various roles, including as a teaching assistant (TA), guest lecturer, and mentor for undergraduates. As an assistant professor in the future, I eagerly anticipate teaching a diverse range of undergraduate courses, with a particular focus on subjects such as polymers, mechanics, and computational modeling.

My initial teaching experience dates to 2012 when I volunteered as a lecturer for a group of high school students. During this time, I taught both math and physics, and it was inspiring to witness the students' keen interest when I emphasized the connections between physical and mathematical concepts. As a TA for the Computational Mechanics course, which had approximately 100 undergraduate students, my responsibilities included grading assignments, holding weekly office hours, and delivering lectures when the professor was unavailable. Additionally, I had the privilege of serving as the coordinator for REU students. One aspect of this role that I thoroughly enjoyed was hosting weekly group meetings, where I would address topics based on their specific needs, such as efficient literature review techniques, and lead engaging group discussions. During my graduate studies, I had the opportunity to mentor a small research team comprising undergraduate students, namely Jason Yang, Alessandro Fisher, William Baker, and Jeffery Ge. Through our collaboration, each of them published at least one paper alongside me, and I am proud to see them embark on successful career paths. For instance, Jason is currently pursuing his Ph.D. degree at Caltech with an NSF Graduate Research Fellowship, while Jeffery has found success as an engineer at Amazon.

In summary, my teaching interests stem from a genuine desire to impart knowledge, inspire curiosity, and support the personal and professional growth of my students. I am committed to creating an engaging learning environment and fostering a collaborative spirit that enables students to thrive academically and pursue rewarding careers.